Thursday. Karnaval! (Not going.)
1402.6319
A globular cluster toward M87 with a radial velocity < -1000 km/s: the first hypervelocity cluster
Caldwell, Strader, Romanowsky, Brodie, Moore, Diemand, Martizzi
An object near M87 in the Virgo Cluster with offset of >2300 km/s from systemic velocity (blueshift of 1025 km/s). Photometric and spectroscopic data provide strong evidence that this object is a distant massive globular cluster ("HVGC-1"). Disfavor system of stars bound to a recoiling BH. The odds of observing an outlier as extreme as HVGC-1 in a virialized distribution of intracluster objects are small; it appears more likely that the cluster was (or is being) ejected from Virgo following a 3-body interaction. The nature of the interaction is unclear, and could involve either a sub halo or a binary SMBH at the center of M87.
1402.6325
Grain physics and IR dust emission in AGN environments
Hensley, Ostriker, Ciotti
Study effects of dust physics on the properties and evolution of early type galaxies containing central BHs, as determined by AGN feedback. Find that during cooling flow episodes, radiation pressure on the dust in and interior to infalling shells of cold gas can greatly impact the amount of gas able to be accreted and therefore the frequency of AGN bursts. However, the overall hydrodynamic evolution of all models, including mass budget, is relatively robust to the assumptions on dust. The most detailed models find that the dust to metals ratio is reduced by factors of 1e-1 to 1e-2 relative to MW abundances, and in quiescent phases the dust content of the galaxy would result in ~0.03 magnitudes of extinction to the center of the galaxy. Find that IR re-emission from hot dust can dominate the bolometric luminosity of the galaxy during the early stages of an AGN burst, reaching values in excess of 1e46 erg/s. The AGN-emitted UV is largely absorbed, but the optical depth in the IR does not exceed unity, so the radiation momentum input never exceeds L_BH/c. Constrain the viability of the models by comparing the energy output in each band, AGN duty cycle, FIR emission, dust mass and opacity, BH mass, and other model predictions to current observations. These constraints force models wherein the destruction of dust in hot gas by sputtering and the competing growth of dust in cold gas results in depletion at the 1e-2 level, and only models with a dynamic dust to gas ratio are able to produce both quiescent galaxies consistent with observations and high obscured fractions during AGN "on" phases. During AGN outbursts, predict that a large fraction of the FIR luminosity can be attributed to warm dust emission (~100K) from dense dusty gas within <1kpc reradiating the AGN UV emission.
1402.6326
Characterizing the best cosmic telescopes with the millennium simulations
French, … Zabludoff, Keeton, … et al
Characterize LoS which maximize the number of lensed z~10 galaxies with "entendue" sigma_mu, the area in the source plane magnified over some threshold mu. Use sims to determine the frequency of high sigma_mu beams on the sky, their properties, and efficient selection criteria. Define the best beams as having sigma_{mu>3}>2000 arcsec^2, for a z~10 source plane, and predict 477pm21 such beams on the sky. The total mass in the beam and sigma_{mu>3} are strongly correlated. After controlling for total mass, find a significant residual correlation between sigma_{mu>3} and the number of cluster-scale haloes (1e14 Msun/h) in the beam. Beams with sigma_{mu>3}>2000 arcsec^2 are 10x more likely to contain multiple cluster-scale halos than a single cluster-scale halo. Beams containing A1689-like massive cluster halo often have additional structures along the LoS, including at least one additional cluster-scale (M200>1e14 Msun/h) halo 28% of the time. Selecting beams with multiple, massive structures will lead to enhanced detection of the most distant and intrinsically faint galaxies.
1402.6335
A submillimeter galaxy illuminating its circumgalactic medium: Ly-alpha scattering in a cold, clumpy outflow
Geach et al
A 100kpc-scale radio-quiet emission-line nebula at z=3.1 (a "Lyman alpha blob"). Flux density of source implies the presence of a galaxy (or a group of galaxies) with L~1e12 L_sun. The position of an active source at the center of a ~50kpc-radius ring of linearly polarized Lya emission detected suggests that the central source is leaking Lya photons preferentially in the plane of the sky, which undergo scattering in HI clouds at large galactocentric radius. The Lya morphology around the sub millimeter detection is reminiscent of biconical outflow, and the average Lya line profiles of the two lobes are dominated by a red peak, expected for a resonant line emerging from a medium with a bulk velocity gradient that is outflowing relative to the line center. Taken together, these observations provide compelling evidence that the central active galaxy (or galaxies) is responsible for a large fraction of the extended Lya emission and morphology. Less clear is the history of the cold gas in the circumgalactic medium being traced by Lya: is it mainly pristine material accreting into the halo that has not yet been processed through an ISM, now being blown back as it encounters an outflow, or does it mainly comprise gas that has been sept-up within the ISM and expelled from the galaxy?
1402.6470
Structure and morphology of X-ray selected AGN hosts at 1<z<3 in CANDELS-COSMOS field
Fan et al
35 X-ray selected AGNs at z~2 in COSMOS; compare to 350 control sample galaxies. GALFIT on surface brightness profile show that the distribution of Sersic index n of AGN hosts does not show a statistical difference from that of the control sample. All distributions of other structural parameters (asymmetry index, Gini coefficient, concentration index and M20 index) are consistent with those on the control sample. No significant difference in the distortion fractions between the AGN host sample and control sample. Conclude that the morphologies of X-ray selected AGN hosts are similar to those of nonactive galaxies and most AGN activity is not triggered by major merger.
Thursday, February 27, 2014
Wednesday, February 26, 2014
Day 597
Wednesday.
1402.5490
A large lunar impact blast on September 11th 2013
Madiedo et al
As the title says. Equivalent of 15 tones of TNT.
1402.5963
A constrained trasport scheme for MHD on unstructured static and moving meshes
Mocz, Vogelsberger, Hernquist
B-fields play an important role in many astrophysical systems and a detailed understanding of their impact on the gas dynamics requires robust numerical simulations. Present a new method to evolve the ideal MHD equations on unstructured static and moving meshes that preserves the B-field divergence-free constraint to machine precision. The method overcomes the major problems of using a cleaning scheme on the B-fields instead, which is non-conserative, not fully Galilean invariant, does not eliminate divergence errors completely, and may produce incorrect jumps across shocks. The new method is a generalization of the constrained transport (CT) algorithm used to enforce the divergence(B)=0 condition on fixed Cartesian grids. Preserving this at the discretized level is necessary to maintain the orthogonality between the Lorenz force and B. The possibility of performing CT on a moving mesh provides several advantage over static mesh methods due to the quasi-Lagrangian nature of the former (i.e., the mesh generating points move with the flow), such as making the simulation automatically adaptive and significantly reducing advection errors. Method preserves B-fields and fluid quantities in pure advection exactly.
1402.5964
From haloes to galaxies - I: the dynamics of the gas regulator model and the implied cosmic sSFR-history
Peng, Maiolino
Explore the basic parameters that drive the evolution of the fundamental properties of SF galaxies within the gas regulator model, or bathtub-model. Derive the general analytic form of the evolution of the key galaxy properties, i.e. gas mass, SFR, stellar mass, sSFR, gas fraction, gas phase metallicity and stellar metallicity, without assuming that galaxies live in the equilibrium state. Find that the timescale required to reach equilibrium, tau_eq, which is determined by the product of SF efficiency and mass-loading factor, is the central parameter in the gas regulator model that is essentially in control of the evolution of all key galaxy properties. The scatters in most of the key scaling relations are primarily governed by tau_eq. Most strikingly, the predicted sSFR evolution is controlled solely by tau_eq (apart from the cosmic time). Although the precise evolution of the sSFR depends on tau_eq, the sSFR history is largely insensitive to different values of tau_eq. The difference between the minimum and maximum sSFR at any epoch is less than a factor of four. The shape of the predicted sSFR history simply mimics that of the specific mass increase rate of the dark matter haloes (sMIR_DM) with the typical value of the sSFR around 2*sMIR_DM. The predicted sSFR from the gas regulator model is in good agreement with typical SAMs, but both are fundamentally different from the observed sSFR history. This clearly implies that some key process is missing in both typical SAMs and gas regulator model, and so hint at some possible culprit. Emphasize the critical role of tau_eq in controlling the evolution of the galaxy population, especially for gas rich low mass galaxies that are very unlikely to live around the equilibrium state at any epoch; this has been largely ignored in many similar studies.
1402.5975
Detecting floating black holes as they traverse the gas disk of the Milky Way
Wang, Loeb
A population of intermediate-mass BHs is predicted to be freely floating n the MW halo, due to gravitational wave recoil, ejection from triple BH systems, or tidal stripping in the dwarf galaxies that merged to make the MW. As these BHs traverse the MW disk, a bow shock forms, producing detectable radio synchrotron emission from accelerated electrons. Calculate the synchrotron flux to be ~0.01-10 mJy at GHz frequency, detected by JVLA, and ~0.1-1 uJy in the IR, detectable by HST and JWST. The discovery of the floating BH population will provide insights on the formation and merger history of the MW as well as on the evolution of massive BHs in the early Universe.
1402.5976
Spectral energy distributions of QSOs at z>5: common AGN-heated dust and occasionally strong star-formation
Leipski, … Rix, et al
Present SEDs of 69 QSOs at z>5. The detection rate of the QSOs with Spitzer is very high, but drops towards the Herschel bands with 30% detected in PACS (MIR in rest-frame) and 15% in SPIRE (FIR in rest-frame). Perform multi-component SED fits for Herschel-detected objects and confirm that to match the observed SEDs, a clumpy torus model needs to be complemented by a hot (~1300K) component and, in cases with prominent FIR emission, also by a cold (~50K) component. In the FIR detected cases, the luminosity of the cold component is on the order of 1e13 Lsun which is likely heated by SF. From the SED fits, also determine that the AGN dust-to-accretion disk luminosity ratio declines with UV/optical luminosity. Emission from hot (~1300K) dust is common in the sample, showing that nuclear dust is ubiquitous in luminous QSOs out to z=6. However, about 15% of the objects appear under-luminous in the NIR compared to their optical emission and seem to be deficient in (but not devoid of) hot dust. Within the full sample, the QSOs detected with Herschel are found at the high luminosity end in L_UV/opt and L_NIR and show low EWs in Halpha and Lya. In the distribution of H_alpha EWs, as determined from the Spitzer photometry, the high-z WSOs show little different to low z AGN.
1402.6101
Effects of center offset and noise on weak-lensing derived concentraion-mass relation of dark matter halos.
Du, Fan
From the halo catalog of the Millennium Sims, analyze WL density profiles for clusters. c-M relation can be biased by the center offset, selection effect and shape noise from intrinsic ellipticities of BG galaxies. Different methods for finding cluster center employed. Find: for intermediate z clusters, the highest peak from the two-scale smoothing method applied to the reconstructed convergence field, first with a smoothing scale of 2 arcmin and then 0.5 arcmin, corresponds the best to the true center. Assuming the parameterized NFW profile, fit the reduced tangential shear signals around different centers. It is shown that for the ensemble median values, a center offset larger than one scale radius r_s can bias the derived mass and concentration significantly lower than the true values especially for low mass haloes. However, the existence of noise can compensate the offset effect and reduce the systematic bias although the scatters of mass and concentration get considerably larger. Statistically, the bias effect of center offset on the c-M relation is insignificant if an appropriate center finding method is adopted. On the other hand, noise from intrinsic ellipticities can bias the c-M relation derived from a sample of WL analyzed clusters if a simple chisq fitting method is used. To account for the scatters and covariance between c and M properly, apply a Bayesian method to improve the statistical analysis on the c-M relation. It is show that this new method allows us to derive the c-M relation with significantly reduced biases.
1402.6212
Cosmology and astrophysics from related galaxy clusters II: cosmological constraints
Mantz, Allen, Morris, Rapetti, Applegate, Kelly, von der Linden, Schmidt
Present cosmo constraints from f_gas for massive, dynamically relaxed galaxy clusters. 40 such clusters from Chandra, some with WL data. Incorporating a robust gravitational lensing calibration of the X-ray mass estimates, and restricting measurements to the most self-similar and accurately measured regions of clusters, significantly reduces systematic uncertainties compared to previous work. Data constrain intrinsic scatter in f_gas: 7.4pm2.3% in a spherical shell at radii 0.8-1.2 r_2500, consistent with the expected variation in gas depletion and non-thermal pressure for relaxed clusters. From the lowest-z data in the sample, obtain a constraint on a combination of the Hubble parameter and cosmic baryon fraction h^3/2 Omega_b/Omega_m = 0.089pm0.012, that is insensitive to the nature of DE. Combined with standard priors on h and Omega_b h^2, this provides a tight constraint on the cosmic matter density, Omega_m=0.27pm0.04, which is similarly insensitive to DE. Using the entire cluster sample, extending to z>1, obtain consistent results for Omega_m and interesting constraints on DE: Omega_Lambda = 0.65pm0.2 for non-flat LCDM models, and w=-0.98pm0.26 for flat constant-w models. Results are both competitive and consistent with those from recent CMB, SNIa and BAO data. Present constraints on models of evolving DE from the combination of f_gas data with these external data sets, and comment on the possibilities for improved f_gas constraints using current and next-generationg X-ray observatories and lensing data.
1402.5490
A large lunar impact blast on September 11th 2013
Madiedo et al
As the title says. Equivalent of 15 tones of TNT.
1402.5963
A constrained trasport scheme for MHD on unstructured static and moving meshes
Mocz, Vogelsberger, Hernquist
B-fields play an important role in many astrophysical systems and a detailed understanding of their impact on the gas dynamics requires robust numerical simulations. Present a new method to evolve the ideal MHD equations on unstructured static and moving meshes that preserves the B-field divergence-free constraint to machine precision. The method overcomes the major problems of using a cleaning scheme on the B-fields instead, which is non-conserative, not fully Galilean invariant, does not eliminate divergence errors completely, and may produce incorrect jumps across shocks. The new method is a generalization of the constrained transport (CT) algorithm used to enforce the divergence(B)=0 condition on fixed Cartesian grids. Preserving this at the discretized level is necessary to maintain the orthogonality between the Lorenz force and B. The possibility of performing CT on a moving mesh provides several advantage over static mesh methods due to the quasi-Lagrangian nature of the former (i.e., the mesh generating points move with the flow), such as making the simulation automatically adaptive and significantly reducing advection errors. Method preserves B-fields and fluid quantities in pure advection exactly.
1402.5964
From haloes to galaxies - I: the dynamics of the gas regulator model and the implied cosmic sSFR-history
Peng, Maiolino
Explore the basic parameters that drive the evolution of the fundamental properties of SF galaxies within the gas regulator model, or bathtub-model. Derive the general analytic form of the evolution of the key galaxy properties, i.e. gas mass, SFR, stellar mass, sSFR, gas fraction, gas phase metallicity and stellar metallicity, without assuming that galaxies live in the equilibrium state. Find that the timescale required to reach equilibrium, tau_eq, which is determined by the product of SF efficiency and mass-loading factor, is the central parameter in the gas regulator model that is essentially in control of the evolution of all key galaxy properties. The scatters in most of the key scaling relations are primarily governed by tau_eq. Most strikingly, the predicted sSFR evolution is controlled solely by tau_eq (apart from the cosmic time). Although the precise evolution of the sSFR depends on tau_eq, the sSFR history is largely insensitive to different values of tau_eq. The difference between the minimum and maximum sSFR at any epoch is less than a factor of four. The shape of the predicted sSFR history simply mimics that of the specific mass increase rate of the dark matter haloes (sMIR_DM) with the typical value of the sSFR around 2*sMIR_DM. The predicted sSFR from the gas regulator model is in good agreement with typical SAMs, but both are fundamentally different from the observed sSFR history. This clearly implies that some key process is missing in both typical SAMs and gas regulator model, and so hint at some possible culprit. Emphasize the critical role of tau_eq in controlling the evolution of the galaxy population, especially for gas rich low mass galaxies that are very unlikely to live around the equilibrium state at any epoch; this has been largely ignored in many similar studies.
1402.5975
Detecting floating black holes as they traverse the gas disk of the Milky Way
Wang, Loeb
A population of intermediate-mass BHs is predicted to be freely floating n the MW halo, due to gravitational wave recoil, ejection from triple BH systems, or tidal stripping in the dwarf galaxies that merged to make the MW. As these BHs traverse the MW disk, a bow shock forms, producing detectable radio synchrotron emission from accelerated electrons. Calculate the synchrotron flux to be ~0.01-10 mJy at GHz frequency, detected by JVLA, and ~0.1-1 uJy in the IR, detectable by HST and JWST. The discovery of the floating BH population will provide insights on the formation and merger history of the MW as well as on the evolution of massive BHs in the early Universe.
1402.5976
Spectral energy distributions of QSOs at z>5: common AGN-heated dust and occasionally strong star-formation
Leipski, … Rix, et al
Present SEDs of 69 QSOs at z>5. The detection rate of the QSOs with Spitzer is very high, but drops towards the Herschel bands with 30% detected in PACS (MIR in rest-frame) and 15% in SPIRE (FIR in rest-frame). Perform multi-component SED fits for Herschel-detected objects and confirm that to match the observed SEDs, a clumpy torus model needs to be complemented by a hot (~1300K) component and, in cases with prominent FIR emission, also by a cold (~50K) component. In the FIR detected cases, the luminosity of the cold component is on the order of 1e13 Lsun which is likely heated by SF. From the SED fits, also determine that the AGN dust-to-accretion disk luminosity ratio declines with UV/optical luminosity. Emission from hot (~1300K) dust is common in the sample, showing that nuclear dust is ubiquitous in luminous QSOs out to z=6. However, about 15% of the objects appear under-luminous in the NIR compared to their optical emission and seem to be deficient in (but not devoid of) hot dust. Within the full sample, the QSOs detected with Herschel are found at the high luminosity end in L_UV/opt and L_NIR and show low EWs in Halpha and Lya. In the distribution of H_alpha EWs, as determined from the Spitzer photometry, the high-z WSOs show little different to low z AGN.
1402.6101
Effects of center offset and noise on weak-lensing derived concentraion-mass relation of dark matter halos.
Du, Fan
From the halo catalog of the Millennium Sims, analyze WL density profiles for clusters. c-M relation can be biased by the center offset, selection effect and shape noise from intrinsic ellipticities of BG galaxies. Different methods for finding cluster center employed. Find: for intermediate z clusters, the highest peak from the two-scale smoothing method applied to the reconstructed convergence field, first with a smoothing scale of 2 arcmin and then 0.5 arcmin, corresponds the best to the true center. Assuming the parameterized NFW profile, fit the reduced tangential shear signals around different centers. It is shown that for the ensemble median values, a center offset larger than one scale radius r_s can bias the derived mass and concentration significantly lower than the true values especially for low mass haloes. However, the existence of noise can compensate the offset effect and reduce the systematic bias although the scatters of mass and concentration get considerably larger. Statistically, the bias effect of center offset on the c-M relation is insignificant if an appropriate center finding method is adopted. On the other hand, noise from intrinsic ellipticities can bias the c-M relation derived from a sample of WL analyzed clusters if a simple chisq fitting method is used. To account for the scatters and covariance between c and M properly, apply a Bayesian method to improve the statistical analysis on the c-M relation. It is show that this new method allows us to derive the c-M relation with significantly reduced biases.
1402.6212
Cosmology and astrophysics from related galaxy clusters II: cosmological constraints
Mantz, Allen, Morris, Rapetti, Applegate, Kelly, von der Linden, Schmidt
Present cosmo constraints from f_gas for massive, dynamically relaxed galaxy clusters. 40 such clusters from Chandra, some with WL data. Incorporating a robust gravitational lensing calibration of the X-ray mass estimates, and restricting measurements to the most self-similar and accurately measured regions of clusters, significantly reduces systematic uncertainties compared to previous work. Data constrain intrinsic scatter in f_gas: 7.4pm2.3% in a spherical shell at radii 0.8-1.2 r_2500, consistent with the expected variation in gas depletion and non-thermal pressure for relaxed clusters. From the lowest-z data in the sample, obtain a constraint on a combination of the Hubble parameter and cosmic baryon fraction h^3/2 Omega_b/Omega_m = 0.089pm0.012, that is insensitive to the nature of DE. Combined with standard priors on h and Omega_b h^2, this provides a tight constraint on the cosmic matter density, Omega_m=0.27pm0.04, which is similarly insensitive to DE. Using the entire cluster sample, extending to z>1, obtain consistent results for Omega_m and interesting constraints on DE: Omega_Lambda = 0.65pm0.2 for non-flat LCDM models, and w=-0.98pm0.26 for flat constant-w models. Results are both competitive and consistent with those from recent CMB, SNIa and BAO data. Present constraints on models of evolving DE from the combination of f_gas data with these external data sets, and comment on the possibilities for improved f_gas constraints using current and next-generationg X-ray observatories and lensing data.
Tuesday, February 25, 2014
Day 596
Tuesday.
1402.5412
The pulsar spin-down luminosity: simulations in general relativity
Ruiz, Paschalidis, Shapiro
Method of matching general relativistic, ideal MHD to its force-free limit [?], perform the first systematic simulations of force-free pulsar magnetospheres in GR. Endow the NS with a GR dipole B-field, model the interior with ideal MHD, and adopt force-free electrodynamics in the exterior. Comparing the spin-down luminosity to its corresponding Minkowski value, find that GR effects give rise to a modest enhancement: the maximum enhancement for n=1 prolytropes is ~23%. Evolving a rapidly rotating n=0.5 polytrope, find an even greater enhancement of ~35%. Using simulation, derive fitting formulae for the pulsar spin-down luminosity as a function of the NS compaction, angular speed, and dipole B moment. Expect stiffer EoS and more rapidly spinning NSs to lead to even larger enhancements in the spin-down luminosity. [no, i don't understand what's going on.]
1402.5420
A UV to Mid-IR study of AGN selection
Chung, Kochanek, … Stern, Jannuzi, Gonzalez, et al
Classify SEDs of 431k sources in NDWFS (9 sq deg). Up to 17 bands of data available, from UV, optical, NIR, and MIR, as well as 20k spectroscopic redshifts, primarily from the AGN and Galaxy Evolution Survey (AGES). Fit galaxy, AGN, stellar, and brown dwarf templates to the observed SEDs, which yield spectral classes for the Galactic sources and photometric redshifts and galaxy/AGN luminosities for the extragalactic sources. The photo-z precision of the galaxy and AGN samples are sigma/(1+z)=0.040 and 0.169, respectively, with the worst 5% outliers excluded. Based on the reduced chi-squared of the SED fit for each SED model, able to distinguish between Galactic and extragalactic sources for sources brighter than I=23.5. Compare the SED fits for a galaxy-only model and galaxy+AGN model. Using known X-ray and spectroscopic AGN samples, confirm that SED fitting can be successfully used as a method to identify large populations of AGN, including spatially resolved AGN with significant contributions from the host galaxy and objects with the emission line ratios of "composite" spectra. Also use results to compare the X-ray, MIR, optical color and emission line ratio selection techniques. For an F-ratio threshold of F>10, find 16k AGN candidates brighter than I=23.5 and a surface density of ~1900 AGN / deg^2.
1402.5454
Spot scan probe of lateral field effects in a thick fully-depleted CCD
O'Connor
Flat-field images with thick, fully-depleted CCDs exhibit response variations near the edges of the chip and at other locations, such as the regions bordering mid-frame blooming stop implants. Two possible origins for these response variations have been suggested: either photometric response (quantum efficiency) or effective pixel area is modified in these regions. In the latter case, source position and shape distortions would be expected in these regions, with consequent impact on astrometric and WL measurements. As an experimental check to distinguish between the two effects and to gauge the magnitude of distortion, perform a measurement scanning an artificial star image across the affected region of one device.
1402.5526
Effects of the environment on galaxies in the catalog of isolated galaxies: physical satellites and large scale structure
Argudo-Fernández et al
Aim to identify and quantify the effects of the satellite distribution around a sample of galaxies in CIG, as well as the effects of the LSS using SDSS-DR9. To recover the physically bound galaxies, focus on the satellites which are within the escape speed of each CIG galaxy [using spectra of the satellite for LoS velocity?]. Also propose a more conservative method using the stacked Gaussian distribution of the velocity difference of the neighbors. The tidal strengths affecting the primary galaxy are estimated to quantify the effects of the local and LSS environments. Also define the projected number density parameter at the 5th nearest neighbor to characters the LSS around the CIG galaxies. Out of the 386 CIG galaxies considered, at least 340 have no physically linked satellite. Out of the 386 CIG galaxies, 327 have no physical companion within a projected distance of 0.3 Mpc. The CIG galaxies are distributed following the LSS of the local Universe, although presenting a large heterogeneity in their degree of connection with it. A clear segregation appears between early-type CIG galaxies with companions and isolated late-type CIG galaxies. Isolated galaxies are in general bluer, with likely younger stellar populations and rather high SF with respect to older, redder CIG galaxies with companions. Reciprocally, the satellites are redder and with an older stellar populations around massive early-type CIG galaxies, while they have a younger stellar content around massive late-type CIG galaxies. This suggests that the CIG is composed of a heterogeneous population of galaxies, sampling from old to more recent, dynamical systems of galaxies.
1402.5545
Study of dust and ionized gas in early-type galaxies
Kulkarni et al
Observations of 40 nearby early-type galaxies. The morphology and extend of ionized gas is found similar to those of dust, indicating possible coexistence of dust and ionized gas in these galaxies. The absence of any apparent correlation between blue luminosity and normalized IRAS dust mass is suggestive of merger related origin of dust and gas in these galaxies.
1402.5654
Galaxy and mass assembly (GAMA): the evolution of bias in the radio source population to z~1.5
Lindsay, et al
Large scale clustering analysis of radio galaxies in GAMA survey area, limited to S1.4 GHz > 1 mJy with r<19.8 (spec-z) and r<22 (photo-z). For the GAMA spec-z matches, present the z-space and projected correlation functions, the latter of which yielding a correlation length r0~8.2 Mpc/h and linear bias of ~1.9 at z~0.34. Furthermore, use the angular 2-pt correlation function w(theta) to determine spatial clustering properties at higher z. Find r0 [correlation length] to increase from ~6 to ~14 Mpc/h between z=0.3 and 1.55, with the corresponding bias increasing from ~2 to ~10 over the same range [as you go to higher z, the intrinsic radio luminosity must become brighter, and hence more bias]. Results consistent with the bias prescription implemented in the SKADS simulations at low z, but exceed these predictions at z>1. This is indicative of an increasing (rather the fixed) halo mass and/or AGN fraction at higher z or a larger typical halo mass for the more abundant FRI sources.
1402.5752
The evolution of galaxy size and morphology at z~0.5-3.0 in the GOODS-N region with HST/WFC3 data
Morishita, Ichikawa, Kajisawa
Study the formation and evolution of Quiescent galaxies (QGs) with Sersic profiles of 299 QGs and 1k SFGs at z~0.5-3.0; find the evolution of re and n of M*>1e10.5 Msun QGs while weaker evolution of SFGs and less massive (M*<1e10.5Msun) QGs. The regression of the size evolution of massive QGs follows re~(1+z)-alpha re [? not an exponent?] with alpha re = 1.06 (a factor of ~2.2 increase from z~2.5 to 0.5) which is consistent with the general picture of the significant size growth. For the further understanding of the evolution scenario, study the evolution of Sersic index, n, and find that of massive QGs to significantly evolve as n~(1+z)-apha n with alpha n = 0.74 (n~1 to 4 at z~2.5 to 0.5, respectively), while those of the other populations are unchanged (n~1) over the redshift range. The results in the present day are consistent with both of observation and numerical simulations, where gas-poor minor merger is believed to be the main evolution scenario. By taking account of the connection with less massive QGs and SFGs, discuss the formation and evolution of the massive QGs over "Cosmic High Noon", or the peak of SF in the universe.
1402.5412
The pulsar spin-down luminosity: simulations in general relativity
Ruiz, Paschalidis, Shapiro
Method of matching general relativistic, ideal MHD to its force-free limit [?], perform the first systematic simulations of force-free pulsar magnetospheres in GR. Endow the NS with a GR dipole B-field, model the interior with ideal MHD, and adopt force-free electrodynamics in the exterior. Comparing the spin-down luminosity to its corresponding Minkowski value, find that GR effects give rise to a modest enhancement: the maximum enhancement for n=1 prolytropes is ~23%. Evolving a rapidly rotating n=0.5 polytrope, find an even greater enhancement of ~35%. Using simulation, derive fitting formulae for the pulsar spin-down luminosity as a function of the NS compaction, angular speed, and dipole B moment. Expect stiffer EoS and more rapidly spinning NSs to lead to even larger enhancements in the spin-down luminosity. [no, i don't understand what's going on.]
1402.5420
A UV to Mid-IR study of AGN selection
Chung, Kochanek, … Stern, Jannuzi, Gonzalez, et al
Classify SEDs of 431k sources in NDWFS (9 sq deg). Up to 17 bands of data available, from UV, optical, NIR, and MIR, as well as 20k spectroscopic redshifts, primarily from the AGN and Galaxy Evolution Survey (AGES). Fit galaxy, AGN, stellar, and brown dwarf templates to the observed SEDs, which yield spectral classes for the Galactic sources and photometric redshifts and galaxy/AGN luminosities for the extragalactic sources. The photo-z precision of the galaxy and AGN samples are sigma/(1+z)=0.040 and 0.169, respectively, with the worst 5% outliers excluded. Based on the reduced chi-squared of the SED fit for each SED model, able to distinguish between Galactic and extragalactic sources for sources brighter than I=23.5. Compare the SED fits for a galaxy-only model and galaxy+AGN model. Using known X-ray and spectroscopic AGN samples, confirm that SED fitting can be successfully used as a method to identify large populations of AGN, including spatially resolved AGN with significant contributions from the host galaxy and objects with the emission line ratios of "composite" spectra. Also use results to compare the X-ray, MIR, optical color and emission line ratio selection techniques. For an F-ratio threshold of F>10, find 16k AGN candidates brighter than I=23.5 and a surface density of ~1900 AGN / deg^2.
1402.5454
Spot scan probe of lateral field effects in a thick fully-depleted CCD
O'Connor
Flat-field images with thick, fully-depleted CCDs exhibit response variations near the edges of the chip and at other locations, such as the regions bordering mid-frame blooming stop implants. Two possible origins for these response variations have been suggested: either photometric response (quantum efficiency) or effective pixel area is modified in these regions. In the latter case, source position and shape distortions would be expected in these regions, with consequent impact on astrometric and WL measurements. As an experimental check to distinguish between the two effects and to gauge the magnitude of distortion, perform a measurement scanning an artificial star image across the affected region of one device.
1402.5526
Effects of the environment on galaxies in the catalog of isolated galaxies: physical satellites and large scale structure
Argudo-Fernández et al
Aim to identify and quantify the effects of the satellite distribution around a sample of galaxies in CIG, as well as the effects of the LSS using SDSS-DR9. To recover the physically bound galaxies, focus on the satellites which are within the escape speed of each CIG galaxy [using spectra of the satellite for LoS velocity?]. Also propose a more conservative method using the stacked Gaussian distribution of the velocity difference of the neighbors. The tidal strengths affecting the primary galaxy are estimated to quantify the effects of the local and LSS environments. Also define the projected number density parameter at the 5th nearest neighbor to characters the LSS around the CIG galaxies. Out of the 386 CIG galaxies considered, at least 340 have no physically linked satellite. Out of the 386 CIG galaxies, 327 have no physical companion within a projected distance of 0.3 Mpc. The CIG galaxies are distributed following the LSS of the local Universe, although presenting a large heterogeneity in their degree of connection with it. A clear segregation appears between early-type CIG galaxies with companions and isolated late-type CIG galaxies. Isolated galaxies are in general bluer, with likely younger stellar populations and rather high SF with respect to older, redder CIG galaxies with companions. Reciprocally, the satellites are redder and with an older stellar populations around massive early-type CIG galaxies, while they have a younger stellar content around massive late-type CIG galaxies. This suggests that the CIG is composed of a heterogeneous population of galaxies, sampling from old to more recent, dynamical systems of galaxies.
1402.5545
Study of dust and ionized gas in early-type galaxies
Kulkarni et al
Observations of 40 nearby early-type galaxies. The morphology and extend of ionized gas is found similar to those of dust, indicating possible coexistence of dust and ionized gas in these galaxies. The absence of any apparent correlation between blue luminosity and normalized IRAS dust mass is suggestive of merger related origin of dust and gas in these galaxies.
1402.5654
Galaxy and mass assembly (GAMA): the evolution of bias in the radio source population to z~1.5
Lindsay, et al
Large scale clustering analysis of radio galaxies in GAMA survey area, limited to S1.4 GHz > 1 mJy with r<19.8 (spec-z) and r<22 (photo-z). For the GAMA spec-z matches, present the z-space and projected correlation functions, the latter of which yielding a correlation length r0~8.2 Mpc/h and linear bias of ~1.9 at z~0.34. Furthermore, use the angular 2-pt correlation function w(theta) to determine spatial clustering properties at higher z. Find r0 [correlation length] to increase from ~6 to ~14 Mpc/h between z=0.3 and 1.55, with the corresponding bias increasing from ~2 to ~10 over the same range [as you go to higher z, the intrinsic radio luminosity must become brighter, and hence more bias]. Results consistent with the bias prescription implemented in the SKADS simulations at low z, but exceed these predictions at z>1. This is indicative of an increasing (rather the fixed) halo mass and/or AGN fraction at higher z or a larger typical halo mass for the more abundant FRI sources.
1402.5752
The evolution of galaxy size and morphology at z~0.5-3.0 in the GOODS-N region with HST/WFC3 data
Morishita, Ichikawa, Kajisawa
Study the formation and evolution of Quiescent galaxies (QGs) with Sersic profiles of 299 QGs and 1k SFGs at z~0.5-3.0; find the evolution of re and n of M*>1e10.5 Msun QGs while weaker evolution of SFGs and less massive (M*<1e10.5Msun) QGs. The regression of the size evolution of massive QGs follows re~(1+z)-alpha re [? not an exponent?] with alpha re = 1.06 (a factor of ~2.2 increase from z~2.5 to 0.5) which is consistent with the general picture of the significant size growth. For the further understanding of the evolution scenario, study the evolution of Sersic index, n, and find that of massive QGs to significantly evolve as n~(1+z)-apha n with alpha n = 0.74 (n~1 to 4 at z~2.5 to 0.5, respectively), while those of the other populations are unchanged (n~1) over the redshift range. The results in the present day are consistent with both of observation and numerical simulations, where gas-poor minor merger is believed to be the main evolution scenario. By taking account of the connection with less massive QGs and SFGs, discuss the formation and evolution of the massive QGs over "Cosmic High Noon", or the peak of SF in the universe.
Monday, February 24, 2014
Day 595
Sunday. Monday.
1402.0510
Physical properties of emission-line galaxies at z~2 from near-infrared spectroscopy with Magellan FIRE
Masters et al
Results from NIR spectroscopy of 26 emission-line galaxies at z~2, selected from WISP survey, which uses the NIR grism of HST WFC3 to detect emission-line galaxies over 0.3<z<2.3. The FIRE follow-up spectroscopy (R~5000) over 1.0-2.5 micron permits detailed measurements of physical properties of the z~2 emission-line galaxies. Dust-corrected SFRs for the sample range from ~5-100 Msun/yr. Derive a median metallicity for the sample of ~0.45 Z_sun, and the estimated stellar masses range from ~1e8.5-9.5 Msun. The average ionization parameters measured for the sample are typically much higher than what is found for local SF galaxies. Derive composite spectra from the FIRE sample, from which typical nebular electron densities of ~100-400 cm^-3 is implied. Based on the location of the galaxies and composite spectra on BPT diagrams, do not find evidence for significant AGN activity in the sample. Most of the galaxies as well as the composites are offset in the BPT diagram toward higher [OIII]/H-beta at a given [NII]/H-alpha, in agreement with other observations of z>1 SF galaxies, but composite spectra derived from the sample do not show an appreciable offset from the local SF sequence on the [OIII]/H-beta versus [SII]/H-alpha diagram. Infer a high nitrogen-to-oxygen abundance ratio from the composite spectrum, which may contribute to the offset of the high-redshift galaxies from the local SF sequence in the [OIII]/H-beta versus [NII]/H-alpha diagram. Speculate that the elevated nitrogen abundance could result from substantial numbers of WR stars in star bursting galaxies at z~2.
1402.5145
The nebular emission of star-forming galaxies in a hierarchical universe
Orsi, et al
Predict nebular emission from SF galaxies within a cosmological galaxy formation model. Computed by combining the SAM SAG with the photo-ionization code MAPPINGS-III. Characterize the ISM of galaxies by relating the ionization parameter of gas in galaxies to their cold gas metallicity. Model is in reasonable agreement with the observed H-alpha, [OII] and [OIII] LFs. Also, the model reproduces the SF sequence of the BPT diagram for local galaxies and the observed H-alpha to [OII] line ratios at high z. The average ionization parameter predicted for galaxies is found to increase in galaxies with low SFRs and also towards higher redshifts, in agreement with recent observational results. Study the relation between the SFR of galaxies and their emission line luminosities as a function of z, finding strong correlation between different emission lines and their SFRs. Present scaling relations that can be used to infer the SFR using only single line luminosities. Model predicts that high z emission line galaxies have modest clustering bias, and thus reside in by DM haloes of masses below M<1e12 Msun/h, consistent with observational estimates of the clustering of emission lines. Present predictions for the number of SF galaxies that can be detected at z up to ~10 by targeting different FIR emission lines with sub millimeter facilities such as ALMA. Discuss the limitations of modeling technique and the possible ways to extend it.
1402.5151
Simulated galaxy interactions as probes of merger spectral energy distributions
Lanz, … Hernquist, et al
First systematic comparison of UV-millimeter SEDs of observed and simulated interacting galaxies. Sample drawn from from Spitzer Interactive Galaxy Survey, and probes a range of galaxy interaction parameters. Use 31 galaxies in 14 systems which have been observed with Herschel, Spitzer, GALEX, and 2MASS. Create a suite of GADGET-3 hydrodynamic simulations of isolated and interacting galaxies with stellar masses comparable to those in the sample of interacting galaxies. Photometry for the simulated systems is then calculated with the SUNRISE radiative transfer code for comparison with the observed systems. For most of the observed systems, one or more of the simulated SEDs match reasonably well. The best matches recover the IR luminosity and the SFR of the observed systems, and the more massive systems preferentially match SEDs from simulations of more massive galaxies. The most morphologically distorted systems in the sample are best matched to simulated SEDs close to coalescence, while less evolved systems match well with SEDs over a wide range of interaction stages, suggesting that an SED alone is insufficient to identify interaction stage except during the most active phases in strongly interacting systems. This result is supported by findings that the SEDs calculated for simulated systems vary little over the interaction sequence.
1402.5219
Galaxies in HI 21-cm absorption at z<3.5
Gupta et al
21-cm observation to trace the evolution of cold gas in galaxies, using ~130 sight lines. Find that within the the measurement uncertainty, the 21-cm detection rate in strong MgII systems is constant over 0.5<z<1.5. Since stellar feedback processes are expected to diminish the filling factor of CNM over 0.5<z<1, this lack of evolution in the 21-cm detection rate in MgII absorbers is intriguing. Further, find that if the majority of 21-cm absorbers arise from DLAs then the cross-section of 21-cm absorbing gas i.e., cold neutral medium amongst DLAs has increased from z=3.5 to z=0.5. In a samples of 13 z>2 DLAs with both 21-cm and H2 absorption measurements, report two new H2 detections and find that in 8/13 cases neither 21-cm nor H2 is detected. This confirms that the HI gas in z>2 DLAs is predominantly warm. There are 2 cases where 21cm absorption is not detected despite the presence of H2 with evidence for the presence of cold gas. This can be explained if H2 components seen in DLA are compact (15 pc) and contain <10% of the total N(HI). Briefly discuss results from ongoing survey to identify 21-cm absorbers at low-z to establish connection between 21-cm absorbers and galaxies, and constrain the extent of absorbing gas.
1402.5333
The phases of water ice in the solar nebula
Ciesla
Show that amorphous ice formed more readily than previously recognized, with formation temperatures <70 K being possible under protoplanetary disk conditions. Further argue that photodesorption and freeze-out of water molecules near the surface layers of the solar nebular would have provided the conditions needed for amorphous ice to form. This processing would be a natural consequence of ice dynamics, and would allow for the trapping of noble gases and other volatiles in water ice in the outer solar nebula.
1402.0510
Physical properties of emission-line galaxies at z~2 from near-infrared spectroscopy with Magellan FIRE
Masters et al
Results from NIR spectroscopy of 26 emission-line galaxies at z~2, selected from WISP survey, which uses the NIR grism of HST WFC3 to detect emission-line galaxies over 0.3<z<2.3. The FIRE follow-up spectroscopy (R~5000) over 1.0-2.5 micron permits detailed measurements of physical properties of the z~2 emission-line galaxies. Dust-corrected SFRs for the sample range from ~5-100 Msun/yr. Derive a median metallicity for the sample of ~0.45 Z_sun, and the estimated stellar masses range from ~1e8.5-9.5 Msun. The average ionization parameters measured for the sample are typically much higher than what is found for local SF galaxies. Derive composite spectra from the FIRE sample, from which typical nebular electron densities of ~100-400 cm^-3 is implied. Based on the location of the galaxies and composite spectra on BPT diagrams, do not find evidence for significant AGN activity in the sample. Most of the galaxies as well as the composites are offset in the BPT diagram toward higher [OIII]/H-beta at a given [NII]/H-alpha, in agreement with other observations of z>1 SF galaxies, but composite spectra derived from the sample do not show an appreciable offset from the local SF sequence on the [OIII]/H-beta versus [SII]/H-alpha diagram. Infer a high nitrogen-to-oxygen abundance ratio from the composite spectrum, which may contribute to the offset of the high-redshift galaxies from the local SF sequence in the [OIII]/H-beta versus [NII]/H-alpha diagram. Speculate that the elevated nitrogen abundance could result from substantial numbers of WR stars in star bursting galaxies at z~2.
1402.5145
The nebular emission of star-forming galaxies in a hierarchical universe
Orsi, et al
Predict nebular emission from SF galaxies within a cosmological galaxy formation model. Computed by combining the SAM SAG with the photo-ionization code MAPPINGS-III. Characterize the ISM of galaxies by relating the ionization parameter of gas in galaxies to their cold gas metallicity. Model is in reasonable agreement with the observed H-alpha, [OII] and [OIII] LFs. Also, the model reproduces the SF sequence of the BPT diagram for local galaxies and the observed H-alpha to [OII] line ratios at high z. The average ionization parameter predicted for galaxies is found to increase in galaxies with low SFRs and also towards higher redshifts, in agreement with recent observational results. Study the relation between the SFR of galaxies and their emission line luminosities as a function of z, finding strong correlation between different emission lines and their SFRs. Present scaling relations that can be used to infer the SFR using only single line luminosities. Model predicts that high z emission line galaxies have modest clustering bias, and thus reside in by DM haloes of masses below M<1e12 Msun/h, consistent with observational estimates of the clustering of emission lines. Present predictions for the number of SF galaxies that can be detected at z up to ~10 by targeting different FIR emission lines with sub millimeter facilities such as ALMA. Discuss the limitations of modeling technique and the possible ways to extend it.
1402.5151
Simulated galaxy interactions as probes of merger spectral energy distributions
Lanz, … Hernquist, et al
First systematic comparison of UV-millimeter SEDs of observed and simulated interacting galaxies. Sample drawn from from Spitzer Interactive Galaxy Survey, and probes a range of galaxy interaction parameters. Use 31 galaxies in 14 systems which have been observed with Herschel, Spitzer, GALEX, and 2MASS. Create a suite of GADGET-3 hydrodynamic simulations of isolated and interacting galaxies with stellar masses comparable to those in the sample of interacting galaxies. Photometry for the simulated systems is then calculated with the SUNRISE radiative transfer code for comparison with the observed systems. For most of the observed systems, one or more of the simulated SEDs match reasonably well. The best matches recover the IR luminosity and the SFR of the observed systems, and the more massive systems preferentially match SEDs from simulations of more massive galaxies. The most morphologically distorted systems in the sample are best matched to simulated SEDs close to coalescence, while less evolved systems match well with SEDs over a wide range of interaction stages, suggesting that an SED alone is insufficient to identify interaction stage except during the most active phases in strongly interacting systems. This result is supported by findings that the SEDs calculated for simulated systems vary little over the interaction sequence.
1402.5219
Galaxies in HI 21-cm absorption at z<3.5
Gupta et al
21-cm observation to trace the evolution of cold gas in galaxies, using ~130 sight lines. Find that within the the measurement uncertainty, the 21-cm detection rate in strong MgII systems is constant over 0.5<z<1.5. Since stellar feedback processes are expected to diminish the filling factor of CNM over 0.5<z<1, this lack of evolution in the 21-cm detection rate in MgII absorbers is intriguing. Further, find that if the majority of 21-cm absorbers arise from DLAs then the cross-section of 21-cm absorbing gas i.e., cold neutral medium amongst DLAs has increased from z=3.5 to z=0.5. In a samples of 13 z>2 DLAs with both 21-cm and H2 absorption measurements, report two new H2 detections and find that in 8/13 cases neither 21-cm nor H2 is detected. This confirms that the HI gas in z>2 DLAs is predominantly warm. There are 2 cases where 21cm absorption is not detected despite the presence of H2 with evidence for the presence of cold gas. This can be explained if H2 components seen in DLA are compact (15 pc) and contain <10% of the total N(HI). Briefly discuss results from ongoing survey to identify 21-cm absorbers at low-z to establish connection between 21-cm absorbers and galaxies, and constrain the extent of absorbing gas.
1402.5333
The phases of water ice in the solar nebula
Ciesla
Show that amorphous ice formed more readily than previously recognized, with formation temperatures <70 K being possible under protoplanetary disk conditions. Further argue that photodesorption and freeze-out of water molecules near the surface layers of the solar nebular would have provided the conditions needed for amorphous ice to form. This processing would be a natural consequence of ice dynamics, and would allow for the trapping of noble gases and other volatiles in water ice in the outer solar nebula.
Sunday, February 23, 2014
Day 594
Saturday.
1402.4803
Red or blue? A potential kilo nova imprint of the delay until black hole formation flooding a neutron star merger
Metzger, Fernández
Mergers of binary NSs usually result in the formation of a hypermassive neutron star (HMNS). Whether and when this remnant collapses to a BH depends primarily on the EoS and on angular momentum transport processes, both of which are uncertain. Show that the lifetime of the merger remnant may be directly imprinted in the radioactively powered kilo nova emission following the merger. Employ axisymmetric, time-dependent hydrodynamic simulations of remnant accretion disks orbiting a HMNS of variable lifetime, and characterize the effect of this delay to BH formation on the disk wind ejecta. Models follow the system solution over several seconds, and include the effect of nuclear recombination, viscous heating, and neutrino irradiation by both the HMNS and the disk. When BH formation is relatively prompt (<100 ms), outflows from the disk are sufficiently neutron rich to form heavy r-process elements with mass number A>140, resulting in ~week-long emission with a spectral peak in the NIR, similar to that produced by the dynamical ejecta. In contrast, delayed BH formation allows neutrinos from the HMNS to raise the electron fraction in the polar direction to values such that potentially Lanthanide-free outflows (A<140) are generated. The lower opacity would produce a brighter, bluer, and shorter-lived ~day-long emission (a `blue bump') prior to the late NIR peak from the dynamical ejecta and equatorial wind. A long-lived HMNS also increases the eject mass significantly compared to the prompt BH case. Work motivates effects to obtain early (~day) optical follow-up of mergers detected by Advanced LIG/Virgo. This new diagnostic of BH formation should be useful for events with a signal to noise lower than that required for direct detection of gravitational waveform signatures.
1402.4812
Dust formation by failed supernovae
Kochanek
Consider dust formation during the ejection of the hydrogen envelope of a red supergiant during a failed supernova (SN) crating a black hole. While the dense, slow moving eject are very efficient at forming dust, only the very last phases of the predicted visual transient will be obscured. The net grain production consists of ~0.01 solar masses of very large grains (10 to 1000 microns). This means that failed SNe could be the source of the very large extrasolar dust grains identified by Ulysses, Galileo and radar studies of meteoroid re-entry trails rather than their coming from an ejection process associated with protoplanetary or other disks.
1402.4814
The green valley is a red herring: Galaxy Zoo reveals two evolutionary pathways towards quenching of star formation in early- and late-type galaxies
Schawinski et al
Use SDSS+GALEX+Galaxy Zoo data to study the quenching of SF in low-redshift galaxies. Show that the green valley between the blue cloud of SF galaxies and the red sequence of quiescent galaxies in the color-mass diagram is not a single transitional state through which most blue galaxies evolve into red galaxies. Rather, an analysis that takes morphology into account makes clear that only a small population of blue early-type galaxies move rapidly across the green valley after the morphologies are transformed from disk to spheroid and SF is quenched rapidly. In contrast, the majority of blue SF galaxies have significant disks, and they retain their late-type morphologies as their SF rates decline very slowly. Summarize a range of observations that lead to these conclusions, including UV-opitcal colors and halo masses, which both show a striking dependence on morphological type. Interpret these results in terms of the evolution of cosmic gas supply and gas reservoirs. Conclude that late-type galaxies are consistent with a scenario where the cosmic supply of gas is shut off, perhaps at a critical halo mass, followed by a slow exhaustion of the remaining gas over several Gyr, driven by secular and/or environmental processes. In contrast, early-type galaxies require a scenario where the gas supply and gas reservoir are destroyed virtually instantaneously, which rapid quenching accompanied by a morphological transformation disk to spheroid. This gas reservoir destruction could be the consequence of a major merger, which in most cases transforms galaxies from disk to elliptical morphology, and mergers could pay a role in inducing black hole accretion and possibly AGN feedback.
1402.4815
Measurement of the halo bias from stacked shear profiles of galaxy clusters
Covone, Sereno, Kilbinger, Cardone
Observational evidence of the 2-halo term in the stacked shear profile of a sample of ~1200 optically selected galaxy clusters based on imaging data and the public shear catalog from the CFHTLenS. Find that the halo bias, a measure of the correlated distribution of matter around galaxy clusters, has amplitude and correlation with galaxy cluster mass in very good agreement with the predictions based on the LCDM standard cosmological model. The mass-concentration relation is flat but higher than theoretical predictions. Also confirm the close scaling relation between the optical richness of galaxy clusters and their mass.
1402.4828
The ages of stellar populations in a warm dark matter universe
Calura, Menci, Gallazzi
By SAM, show how the local observed relation between age and galactic stellar mass is affected by assuming a DM PS with a small-scale cutoff. Compare results obtained by means of both a LCDM and LWDM PS -- suppressed with respect to the LCDM at scales below ~ 1Mpc. Show that, within a LWDM cosmology with a thermal relic particle mass of 0.75 KeV, both the mass-weighted and the luminosity-weighted age-mass relations are steeper than those obtained within a LCDM universe, in better agreement with the observed relations. Moreover, both the observed differential and cumulative age distributions are better reproduced within a LWDM cosmology. In such a scenario, SF appears globally delayed with respect to the LCDM, in particular in low-mass galaxies. The difficulty of obtaining a full agreement between model results and observations is to be ascribed to our present poor understanding of baryonic physics. [the SAM used may not be correct either?]
1402.4856
A small, rapid optical-IR response gamma-ray burst space observatory
Grossan, Kumar, Perley, Smoot
Propose a new GRB mission: Next Generation rapid-response GRB observatory (NGRG). GRB initial location determined from a coded-mask X-ray camera (similar to Swift). Two new features above Swift: a beam steering system to begin optical observations within ~ 1s after location; second, a NIR camera viewing the same sky, for sensitivity to extinguished bursts. These features allow measurement of the rise phase of GRB optical-NIR emission. Thus far, the rise time and transition between prompt and afterglow in the optical and NIR are rarely measured. Rapid-response measurements explore many science topics including optical emission mechanisms (synchrotron vs. SSC, photospheric emission) and jet characteristics (reverse vs. forward shock emission, baryon-dominated vs. magnetic dominated). Rapid optical-NIR response can measure dynamic evolution of extinction due to vaporization of dust, and separate star system and galaxy dust extinction. Discuss these measurements, giving reliable detection rate estimate from analysis of Swift data and scaled Swift performance. Te NGRG will explore optical/NIR emission measured earlier than ever before, and potentially fainter, more extinguish GRBs than ever before. Costs are important: the proposed modest NGRG can still produce new GRB science, while providing rapid GRB alerts for the entire community for post-Swift GRB science. Show that an X-ray instrument barely 1/5 the area of Swift BAT will yield a significant fraction of Swift's detection rate: more than 65 X-ray, and with a 30cm optical-IR telescope and modern cameras, more than 19 NIR and 14 optical detections each year. In addition, active feedback control of the beam-steering would remove the need for arc sec stabilization of the spacecraft, for a substantial cost saving.
1402.5101
Impact of chromatic effects on galaxy shape measurements
Meyers, Burchat
Current and future imaging surveys will measure cosmic shear with a statistical precision that demands a deeper understanding of potential systematic biases in galaxy shape measurements than has been achieved to date. Investigate the effects of using the PSF measured with stars to determine the shape of a galaxy that has a different SED than the star. Demonstrate that a wavelength dependent PSF size, for example as may originate from atmospheric seeing or the diffraction limit of the primary aperture, can introduce significant shape measurement biases. This analysis shows that even small wavelength dependencies in the PSF may introduce biases, and hence that achieving the ultimate precision for WL from current and future imaging surveys will require a detailed understanding of the wavelength dependence of the PSF from all sources, including the CCD sensors.
1402.4803
Red or blue? A potential kilo nova imprint of the delay until black hole formation flooding a neutron star merger
Metzger, Fernández
Mergers of binary NSs usually result in the formation of a hypermassive neutron star (HMNS). Whether and when this remnant collapses to a BH depends primarily on the EoS and on angular momentum transport processes, both of which are uncertain. Show that the lifetime of the merger remnant may be directly imprinted in the radioactively powered kilo nova emission following the merger. Employ axisymmetric, time-dependent hydrodynamic simulations of remnant accretion disks orbiting a HMNS of variable lifetime, and characterize the effect of this delay to BH formation on the disk wind ejecta. Models follow the system solution over several seconds, and include the effect of nuclear recombination, viscous heating, and neutrino irradiation by both the HMNS and the disk. When BH formation is relatively prompt (<100 ms), outflows from the disk are sufficiently neutron rich to form heavy r-process elements with mass number A>140, resulting in ~week-long emission with a spectral peak in the NIR, similar to that produced by the dynamical ejecta. In contrast, delayed BH formation allows neutrinos from the HMNS to raise the electron fraction in the polar direction to values such that potentially Lanthanide-free outflows (A<140) are generated. The lower opacity would produce a brighter, bluer, and shorter-lived ~day-long emission (a `blue bump') prior to the late NIR peak from the dynamical ejecta and equatorial wind. A long-lived HMNS also increases the eject mass significantly compared to the prompt BH case. Work motivates effects to obtain early (~day) optical follow-up of mergers detected by Advanced LIG/Virgo. This new diagnostic of BH formation should be useful for events with a signal to noise lower than that required for direct detection of gravitational waveform signatures.
1402.4812
Dust formation by failed supernovae
Kochanek
Consider dust formation during the ejection of the hydrogen envelope of a red supergiant during a failed supernova (SN) crating a black hole. While the dense, slow moving eject are very efficient at forming dust, only the very last phases of the predicted visual transient will be obscured. The net grain production consists of ~0.01 solar masses of very large grains (10 to 1000 microns). This means that failed SNe could be the source of the very large extrasolar dust grains identified by Ulysses, Galileo and radar studies of meteoroid re-entry trails rather than their coming from an ejection process associated with protoplanetary or other disks.
1402.4814
The green valley is a red herring: Galaxy Zoo reveals two evolutionary pathways towards quenching of star formation in early- and late-type galaxies
Schawinski et al
Use SDSS+GALEX+Galaxy Zoo data to study the quenching of SF in low-redshift galaxies. Show that the green valley between the blue cloud of SF galaxies and the red sequence of quiescent galaxies in the color-mass diagram is not a single transitional state through which most blue galaxies evolve into red galaxies. Rather, an analysis that takes morphology into account makes clear that only a small population of blue early-type galaxies move rapidly across the green valley after the morphologies are transformed from disk to spheroid and SF is quenched rapidly. In contrast, the majority of blue SF galaxies have significant disks, and they retain their late-type morphologies as their SF rates decline very slowly. Summarize a range of observations that lead to these conclusions, including UV-opitcal colors and halo masses, which both show a striking dependence on morphological type. Interpret these results in terms of the evolution of cosmic gas supply and gas reservoirs. Conclude that late-type galaxies are consistent with a scenario where the cosmic supply of gas is shut off, perhaps at a critical halo mass, followed by a slow exhaustion of the remaining gas over several Gyr, driven by secular and/or environmental processes. In contrast, early-type galaxies require a scenario where the gas supply and gas reservoir are destroyed virtually instantaneously, which rapid quenching accompanied by a morphological transformation disk to spheroid. This gas reservoir destruction could be the consequence of a major merger, which in most cases transforms galaxies from disk to elliptical morphology, and mergers could pay a role in inducing black hole accretion and possibly AGN feedback.
1402.4815
Measurement of the halo bias from stacked shear profiles of galaxy clusters
Covone, Sereno, Kilbinger, Cardone
Observational evidence of the 2-halo term in the stacked shear profile of a sample of ~1200 optically selected galaxy clusters based on imaging data and the public shear catalog from the CFHTLenS. Find that the halo bias, a measure of the correlated distribution of matter around galaxy clusters, has amplitude and correlation with galaxy cluster mass in very good agreement with the predictions based on the LCDM standard cosmological model. The mass-concentration relation is flat but higher than theoretical predictions. Also confirm the close scaling relation between the optical richness of galaxy clusters and their mass.
1402.4828
The ages of stellar populations in a warm dark matter universe
Calura, Menci, Gallazzi
By SAM, show how the local observed relation between age and galactic stellar mass is affected by assuming a DM PS with a small-scale cutoff. Compare results obtained by means of both a LCDM and LWDM PS -- suppressed with respect to the LCDM at scales below ~ 1Mpc. Show that, within a LWDM cosmology with a thermal relic particle mass of 0.75 KeV, both the mass-weighted and the luminosity-weighted age-mass relations are steeper than those obtained within a LCDM universe, in better agreement with the observed relations. Moreover, both the observed differential and cumulative age distributions are better reproduced within a LWDM cosmology. In such a scenario, SF appears globally delayed with respect to the LCDM, in particular in low-mass galaxies. The difficulty of obtaining a full agreement between model results and observations is to be ascribed to our present poor understanding of baryonic physics. [the SAM used may not be correct either?]
1402.4856
A small, rapid optical-IR response gamma-ray burst space observatory
Grossan, Kumar, Perley, Smoot
Propose a new GRB mission: Next Generation rapid-response GRB observatory (NGRG). GRB initial location determined from a coded-mask X-ray camera (similar to Swift). Two new features above Swift: a beam steering system to begin optical observations within ~ 1s after location; second, a NIR camera viewing the same sky, for sensitivity to extinguished bursts. These features allow measurement of the rise phase of GRB optical-NIR emission. Thus far, the rise time and transition between prompt and afterglow in the optical and NIR are rarely measured. Rapid-response measurements explore many science topics including optical emission mechanisms (synchrotron vs. SSC, photospheric emission) and jet characteristics (reverse vs. forward shock emission, baryon-dominated vs. magnetic dominated). Rapid optical-NIR response can measure dynamic evolution of extinction due to vaporization of dust, and separate star system and galaxy dust extinction. Discuss these measurements, giving reliable detection rate estimate from analysis of Swift data and scaled Swift performance. Te NGRG will explore optical/NIR emission measured earlier than ever before, and potentially fainter, more extinguish GRBs than ever before. Costs are important: the proposed modest NGRG can still produce new GRB science, while providing rapid GRB alerts for the entire community for post-Swift GRB science. Show that an X-ray instrument barely 1/5 the area of Swift BAT will yield a significant fraction of Swift's detection rate: more than 65 X-ray, and with a 30cm optical-IR telescope and modern cameras, more than 19 NIR and 14 optical detections each year. In addition, active feedback control of the beam-steering would remove the need for arc sec stabilization of the spacecraft, for a substantial cost saving.
1402.5101
Impact of chromatic effects on galaxy shape measurements
Meyers, Burchat
Current and future imaging surveys will measure cosmic shear with a statistical precision that demands a deeper understanding of potential systematic biases in galaxy shape measurements than has been achieved to date. Investigate the effects of using the PSF measured with stars to determine the shape of a galaxy that has a different SED than the star. Demonstrate that a wavelength dependent PSF size, for example as may originate from atmospheric seeing or the diffraction limit of the primary aperture, can introduce significant shape measurement biases. This analysis shows that even small wavelength dependencies in the PSF may introduce biases, and hence that achieving the ultimate precision for WL from current and future imaging surveys will require a detailed understanding of the wavelength dependence of the PSF from all sources, including the CCD sensors.
Friday, February 21, 2014
Day 593
Thursday.
1402.4480
The effect of gravitational tides on dwarf spheroidal galaxies
Nichols, Revaz, Jablonka
From simulation, study from both dynamical and chemical point of view. Find: tidal effects quench the SF even inside gas-endowed dwarfs. Such quenching may produce the radial distribution of dwarf spheroidals from the orbits seen within large cosmological simulations. Also find that the metallicity gradient within a dwarf is gradually erased through tidal interactions as stellar orbits move to higher radii. The model dwarfs also shift to higher <[Fe/H]>/L ratios, but only when losing >20% of stellar mass.
1402.4482
AGN-driven outflows without quenching in simulations of high-redshift disk galaxies
Gabor, Bournaud
Study AGNs using high-res sims of idealized z=2 isolated disk galaxies. Episodic accretion events lead to outflows with velocities >1000 km/s and mass outflow rates up to the SFR (several tens of Msun/yr). Outflowing winds escape perpendicular to the disk with wide opening angles, and are typically asymmetric (i.e., unipolar) because dense gas above or below the AGN in the resolved disk inhibits outflow. Owing to rapid variability in the accretion rates, outflowing gas may be detectable even when the AGN is effectively "off". The highest velocity outflows are concentrated within 2-3 kpc of the galactic center during the peak accretion. With the purely thermal AGN feedback model -- standard in previous literature -- the outflowing material is mostly hot (1e6K) and diffuse (nH<1e-2 cm^-3), but includes a cold component entrained in the hot wind. Despite the powerful bursts and outflow rates near the SFR, AGN feedback has little effect on the dense gas in the galaxy disk.
1402.4484
The X-ray properties of weak lensing selected galaxy clusters
Giles, … Hamana, Miyazaki, … Ellis, Massey
X-ray follow-up targeting 10 WL-selected clusters from Subaru WL survey. 8 clusters studied with Chandra, remaining 2 from archival X-ray data. The WL clusters appear to fit the same scaling relation between X-ray luminosity and temperature as X-ray selected clusters. However, when L-M relation considered, the WL selected clusters appear under luminous by a factor 3.8pm0.9 (or more massive by 2.9pm0.2), compared to X-ray selected clusters. Only by considering various observational effects that could potentially bias WL mass, can this difference be reconciled. Used X-ray imaging data to quantify the dynamical state of the clusters and found that one of the clusters appears dynamically relaxed, and two of the clusters host a cool core, consistent with SZ-selected clusters. Results suggest that regular, cool core clusters may be over-represented in X-ray selected samples. [what was the WL cluster selection criteria? WL mass? Then more "massive" clusters may be preferred with WL selection.]
1402.4766
Giant sparks at cosmological distances?
Kulkarni, et al
Millisecond duration bright radio pulses in the 1.4 GHz band and with inferred dispersion measures (DM) well in excess of galactic values have been reported by Lorimer et al. and Thornton et al. The all-sky rate of these events is large, ~1e4 per day above ~1 Jy. To add to the mystery, there now exists "Perytons" -- also pulsed and dispersed sources but most certainly of local (artificial or atmospheric) origin. The suggested models now range from sources originating in the Earth's atmosphere, in stellar coronae, in other galaxies and at even cosmological distances. Using a series of physically motivated assumptions combined with the observed properties of these bursts, explore possible constraints on sites or processes that can account for such high DMs. In the analysis, focus on the first such reported event by Lorimer+: a 30 Jy, 5-ms duration burst with a dispersion measure of 375 cm^-3 pc and exhibiting a steep frequency-dependent pulse width ("the Sparker"). Assuming that the DM of the Sparker is produced by propagation through a cold plasma and using all available observations, constrain its distance to be greater than 300 kpc. A similar analysis on the 4 other reported events (all with larger DMs) would lead to a stronger conclusion, namely these Fast Radio Bursts (FRBs) are of extragalactic origin, provided that the inferred DM arises due to propagation through cold plasma. Explore proposed extra-galactic as well as stellar coronal models for FRBs and find most of them either unable to account for the high daily rate or have difficulty in having an ultra-clean explosion site (essential to the production of high brightness temperature pulse) or suffer from free-free absorption on length scales beyond the immediate production of the radio pulses.
1402.4480
The effect of gravitational tides on dwarf spheroidal galaxies
Nichols, Revaz, Jablonka
From simulation, study from both dynamical and chemical point of view. Find: tidal effects quench the SF even inside gas-endowed dwarfs. Such quenching may produce the radial distribution of dwarf spheroidals from the orbits seen within large cosmological simulations. Also find that the metallicity gradient within a dwarf is gradually erased through tidal interactions as stellar orbits move to higher radii. The model dwarfs also shift to higher <[Fe/H]>/L ratios, but only when losing >20% of stellar mass.
1402.4482
AGN-driven outflows without quenching in simulations of high-redshift disk galaxies
Gabor, Bournaud
Study AGNs using high-res sims of idealized z=2 isolated disk galaxies. Episodic accretion events lead to outflows with velocities >1000 km/s and mass outflow rates up to the SFR (several tens of Msun/yr). Outflowing winds escape perpendicular to the disk with wide opening angles, and are typically asymmetric (i.e., unipolar) because dense gas above or below the AGN in the resolved disk inhibits outflow. Owing to rapid variability in the accretion rates, outflowing gas may be detectable even when the AGN is effectively "off". The highest velocity outflows are concentrated within 2-3 kpc of the galactic center during the peak accretion. With the purely thermal AGN feedback model -- standard in previous literature -- the outflowing material is mostly hot (1e6K) and diffuse (nH<1e-2 cm^-3), but includes a cold component entrained in the hot wind. Despite the powerful bursts and outflow rates near the SFR, AGN feedback has little effect on the dense gas in the galaxy disk.
1402.4484
The X-ray properties of weak lensing selected galaxy clusters
Giles, … Hamana, Miyazaki, … Ellis, Massey
X-ray follow-up targeting 10 WL-selected clusters from Subaru WL survey. 8 clusters studied with Chandra, remaining 2 from archival X-ray data. The WL clusters appear to fit the same scaling relation between X-ray luminosity and temperature as X-ray selected clusters. However, when L-M relation considered, the WL selected clusters appear under luminous by a factor 3.8pm0.9 (or more massive by 2.9pm0.2), compared to X-ray selected clusters. Only by considering various observational effects that could potentially bias WL mass, can this difference be reconciled. Used X-ray imaging data to quantify the dynamical state of the clusters and found that one of the clusters appears dynamically relaxed, and two of the clusters host a cool core, consistent with SZ-selected clusters. Results suggest that regular, cool core clusters may be over-represented in X-ray selected samples. [what was the WL cluster selection criteria? WL mass? Then more "massive" clusters may be preferred with WL selection.]
1402.4766
Giant sparks at cosmological distances?
Kulkarni, et al
Millisecond duration bright radio pulses in the 1.4 GHz band and with inferred dispersion measures (DM) well in excess of galactic values have been reported by Lorimer et al. and Thornton et al. The all-sky rate of these events is large, ~1e4 per day above ~1 Jy. To add to the mystery, there now exists "Perytons" -- also pulsed and dispersed sources but most certainly of local (artificial or atmospheric) origin. The suggested models now range from sources originating in the Earth's atmosphere, in stellar coronae, in other galaxies and at even cosmological distances. Using a series of physically motivated assumptions combined with the observed properties of these bursts, explore possible constraints on sites or processes that can account for such high DMs. In the analysis, focus on the first such reported event by Lorimer+: a 30 Jy, 5-ms duration burst with a dispersion measure of 375 cm^-3 pc and exhibiting a steep frequency-dependent pulse width ("the Sparker"). Assuming that the DM of the Sparker is produced by propagation through a cold plasma and using all available observations, constrain its distance to be greater than 300 kpc. A similar analysis on the 4 other reported events (all with larger DMs) would lead to a stronger conclusion, namely these Fast Radio Bursts (FRBs) are of extragalactic origin, provided that the inferred DM arises due to propagation through cold plasma. Explore proposed extra-galactic as well as stellar coronal models for FRBs and find most of them either unable to account for the high daily rate or have difficulty in having an ultra-clean explosion site (essential to the production of high brightness temperature pulse) or suffer from free-free absorption on length scales beyond the immediate production of the radio pulses.
Wednesday, February 19, 2014
Day 592
Wednesday.
1402.4129
The luminosity function at z~8 from 97 Y-band dropouts: inferences about reionization
Schmidt, Treu, et al
BoRG (Brightest of Reionizing Galaxies) survey with 350 arcmin^2 of HST V-, Y-, J- and H-bands: largest search to dat for z~8 LBGs; total of 38 BoRG LBGs (z~8 candidates). Estimate LF in Bayesian formalism, including a likelihood based on the correct binomial distribution instead of Poisson. 97 galaxies when including a fainter sample from Bouwens+2012 from HUDF and ERS. Show that z~8 LF well described by Schechter function with M*=-20.15, faint end slope of alpha=-1.87, and a number density of log_10 phi*=-3.24. Integrated down to M=-17.7, this LF yields a luminosity density log_10 epsilon [erg/s/Hz/Mpc^3] = 25.52. The LF analysis is consistent with previous values. Implications: assuming priors on the clumping factor and the photon escape fraction, show that the UV LF from galaxy samples down to M=-17.7 can ionize only 10-50% of the neutral hydrogen at z~8. Full reionization would require extending the LF down to M=-15. [but there is no observations there, right?]
1402.4139
Galaxy And Mass Assembly (GAMA): testing galaxy formation models through the most massive galaxies in the Universe
Oliva-Altamirano, … et al
883 GGGs and GCGs in GAMA: compare stellar mass of BGGs and BCGs in groups and clusters of similar dynamical masses, find no significant growth [in stellar mass?] between z=0.27 and z=0.09. Also examine the number of BGGs/BCGs that have line emission, finding that approximately 65% of BGGs/BCGs show Ha in emission. From the galaxies where the necessary spectroscopic lines were accurately recovered (54% of the sample), find that half of this harbor on-going SF with rates up to 10 Msun/yr, and the other half have an AGN at the center [is it because of the SF that the lines exist?]. BGGs are more likely to have ongoing SF, while BCGs show a higher fraction of AGN activity. By examining the position of the BGGs/BCGs with respect to their host DM halo, find that around 13% of them do not lie at the center of the DM halo. This could be an indicator of recent cluster-cluster mergers. Conclude that BGGs and BCGs acquired their stellar mass rapidly at higher redshifts as predicted by SAMs, mildly slowing down at low redshifts.
1402.4170
A free-form lensing grid solution for A1689 with new multiple images
Diego, Broadhurst, Benitez, Umetsu, Coe, … et al
Many SL in A1689, resolving substructures ~25 kpc across. Examine A1689 non-parametrically, combining SL images and WL from wider imaging, and incorporate member galaxies to improve the lens solution. Strongly lensed galaxies are often locally affected by member galaxies, however, these perturbations cannot be recovered in grid based reconstructions because the lensing information is too spares to resolve member galaxies. By adding luminosity-scaled member galaxy deflections to the smooth grid, can derive meaningful solutions with sufficient accuracy to permit the identification of the strongly lensed images, so the model becomes self consistent. Identify 11 new multiply lensed system candidates and clarify previously ambiguous cases, and the deepest optical and NIR data from Hubble and Subaru. Improved spatial resolution brings up new features and not seen when the weak and strong lensing effects are used separately, including clumps and filamentary DM around the main halo. This treatment allows an objective mass ratio between the cluster and galaxy components, for examining the extent of tidal stripping of the luminous member galaxies. FInd a typical M/L_B=21 inside the r<1 arc minute region that drops to M/L_B=17 inside the r<40 arc second [isn't that smaller than 1 arcrminute?] region. Model independence means objectively evaluating the competitiveness of stacking cluster lenses for defining the geometric lensing-distance-redshift relation in a model independent way.
1402.4217
Mass-galaxy offsets in Abell 3827, 2218 and 1689: intrinsic properties or line-of-sight substructures?
Mohammed, Liesenborgs, Saha, Williams
Mass mass of 3 clusters to test for mass-light offsets. Use GRALE for minimum assumptions [on mass distribution] independent of light distribution. In 3827 and 2218, find local mass peaks in the central regions that are displaced form the nearby galaxies to a few to several kpc, which appear to be intrinsic. For A1689, see no significant offsets in the central region, but do detect a possible LoS structure: it appears only when sources at z>3 are used for reconstructing the mass. Discuss possible origins of the mass-galaxy offsets in A3827 and 2218: these include pure gravitational effects like dynamical friction, but also non-standard mechanisms like self-interacting DM.
1402.4429
The origin and optical depth of ionizing photons in the Green Pea galaxies
Jaskot, Oey
GP galaxies are similar to high-z galaxies in their morphologies and SFRs and are tools for probing the generation and transmission of ionizing photons. The GPs contain massive star clusters that emit copious amounts of high-energy radiation, as indicated by intense [OIII] 5007 and HeII 4686 emission. Focus on 6 GP galaxies with high ratios of [OIII]/[OII]>~10. Such high ratios indicate gas with a high ionization parameter or a low optical depth. The GP line ratios and ages point to chemically homogeneous massive stars, WR stars, or shock ionization as the most likely sources of the HeII emission. Models including shock ionization suggest that the GPs may have low optical depths, consistent with a scenario in which ionizing photons escape along passageways created by recent SNe. The GPs and similar galaxies can shed new light on cosmic reionization by revealing how ionizing photons propagate from massive star clusters to the IGM.
1402.4461
The impact of galaxy formation on the total mass, profiles and abundance of haloes
Velliscig, van Daalen, Schaye, McCarthy, Cacciato, LeBrun, Vecchia
Use cosmo hydro-sims to investigate how the inclusion of physical processes relevant to galaxy formation (SF, metal-line cooling, stellar winds, SNe and feedback from AGN) change the properties of haloes, over 4 orders of magnitude in mass. Find that gas expulsion and the associated DM expansion induced by SN-driven winds are important for halos with M200<1e13 Msun, lowering their masses by up to 20% relative to DM-only model. AGN feedback, which is required to prevent overcooling, has a significant impact on halo masses all the way up to cluster scales (M200~1e15 Msun). Baryonic physics changes the total mass profiles of haloes out to several times the virial radius, a modification that cannot be captured by a change in the halo concentration. The decrease in the total halo mass causes a decrease in the halo MF of about 20%. This effect can have important consequences for abundance matching technique as well as for most SAM of galaxy formation. Provide analytic fitting formulae, derived from simulations that reproduce the observed baryon fractions, to correct halo masses and mass functions from DM-only simulations. The effect of baryonic physics (AGN feedback in particular) on cluster member counts is about as large as changing the cosmology from WMAP7 to Planck, even when a moderately high mass limit of M500~1e14 Msun is adopted. Thus, for precision cosmology the effects of baryons must be accounted for.
1402.4129
The luminosity function at z~8 from 97 Y-band dropouts: inferences about reionization
Schmidt, Treu, et al
BoRG (Brightest of Reionizing Galaxies) survey with 350 arcmin^2 of HST V-, Y-, J- and H-bands: largest search to dat for z~8 LBGs; total of 38 BoRG LBGs (z~8 candidates). Estimate LF in Bayesian formalism, including a likelihood based on the correct binomial distribution instead of Poisson. 97 galaxies when including a fainter sample from Bouwens+2012 from HUDF and ERS. Show that z~8 LF well described by Schechter function with M*=-20.15, faint end slope of alpha=-1.87, and a number density of log_10 phi*=-3.24. Integrated down to M=-17.7, this LF yields a luminosity density log_10 epsilon [erg/s/Hz/Mpc^3] = 25.52. The LF analysis is consistent with previous values. Implications: assuming priors on the clumping factor and the photon escape fraction, show that the UV LF from galaxy samples down to M=-17.7 can ionize only 10-50% of the neutral hydrogen at z~8. Full reionization would require extending the LF down to M=-15. [but there is no observations there, right?]
1402.4139
Galaxy And Mass Assembly (GAMA): testing galaxy formation models through the most massive galaxies in the Universe
Oliva-Altamirano, … et al
883 GGGs and GCGs in GAMA: compare stellar mass of BGGs and BCGs in groups and clusters of similar dynamical masses, find no significant growth [in stellar mass?] between z=0.27 and z=0.09. Also examine the number of BGGs/BCGs that have line emission, finding that approximately 65% of BGGs/BCGs show Ha in emission. From the galaxies where the necessary spectroscopic lines were accurately recovered (54% of the sample), find that half of this harbor on-going SF with rates up to 10 Msun/yr, and the other half have an AGN at the center [is it because of the SF that the lines exist?]. BGGs are more likely to have ongoing SF, while BCGs show a higher fraction of AGN activity. By examining the position of the BGGs/BCGs with respect to their host DM halo, find that around 13% of them do not lie at the center of the DM halo. This could be an indicator of recent cluster-cluster mergers. Conclude that BGGs and BCGs acquired their stellar mass rapidly at higher redshifts as predicted by SAMs, mildly slowing down at low redshifts.
1402.4170
A free-form lensing grid solution for A1689 with new multiple images
Diego, Broadhurst, Benitez, Umetsu, Coe, … et al
Many SL in A1689, resolving substructures ~25 kpc across. Examine A1689 non-parametrically, combining SL images and WL from wider imaging, and incorporate member galaxies to improve the lens solution. Strongly lensed galaxies are often locally affected by member galaxies, however, these perturbations cannot be recovered in grid based reconstructions because the lensing information is too spares to resolve member galaxies. By adding luminosity-scaled member galaxy deflections to the smooth grid, can derive meaningful solutions with sufficient accuracy to permit the identification of the strongly lensed images, so the model becomes self consistent. Identify 11 new multiply lensed system candidates and clarify previously ambiguous cases, and the deepest optical and NIR data from Hubble and Subaru. Improved spatial resolution brings up new features and not seen when the weak and strong lensing effects are used separately, including clumps and filamentary DM around the main halo. This treatment allows an objective mass ratio between the cluster and galaxy components, for examining the extent of tidal stripping of the luminous member galaxies. FInd a typical M/L_B=21 inside the r<1 arc minute region that drops to M/L_B=17 inside the r<40 arc second [isn't that smaller than 1 arcrminute?] region. Model independence means objectively evaluating the competitiveness of stacking cluster lenses for defining the geometric lensing-distance-redshift relation in a model independent way.
1402.4217
Mass-galaxy offsets in Abell 3827, 2218 and 1689: intrinsic properties or line-of-sight substructures?
Mohammed, Liesenborgs, Saha, Williams
Mass mass of 3 clusters to test for mass-light offsets. Use GRALE for minimum assumptions [on mass distribution] independent of light distribution. In 3827 and 2218, find local mass peaks in the central regions that are displaced form the nearby galaxies to a few to several kpc, which appear to be intrinsic. For A1689, see no significant offsets in the central region, but do detect a possible LoS structure: it appears only when sources at z>3 are used for reconstructing the mass. Discuss possible origins of the mass-galaxy offsets in A3827 and 2218: these include pure gravitational effects like dynamical friction, but also non-standard mechanisms like self-interacting DM.
1402.4429
The origin and optical depth of ionizing photons in the Green Pea galaxies
Jaskot, Oey
GP galaxies are similar to high-z galaxies in their morphologies and SFRs and are tools for probing the generation and transmission of ionizing photons. The GPs contain massive star clusters that emit copious amounts of high-energy radiation, as indicated by intense [OIII] 5007 and HeII 4686 emission. Focus on 6 GP galaxies with high ratios of [OIII]/[OII]>~10. Such high ratios indicate gas with a high ionization parameter or a low optical depth. The GP line ratios and ages point to chemically homogeneous massive stars, WR stars, or shock ionization as the most likely sources of the HeII emission. Models including shock ionization suggest that the GPs may have low optical depths, consistent with a scenario in which ionizing photons escape along passageways created by recent SNe. The GPs and similar galaxies can shed new light on cosmic reionization by revealing how ionizing photons propagate from massive star clusters to the IGM.
1402.4461
The impact of galaxy formation on the total mass, profiles and abundance of haloes
Velliscig, van Daalen, Schaye, McCarthy, Cacciato, LeBrun, Vecchia
Use cosmo hydro-sims to investigate how the inclusion of physical processes relevant to galaxy formation (SF, metal-line cooling, stellar winds, SNe and feedback from AGN) change the properties of haloes, over 4 orders of magnitude in mass. Find that gas expulsion and the associated DM expansion induced by SN-driven winds are important for halos with M200<1e13 Msun, lowering their masses by up to 20% relative to DM-only model. AGN feedback, which is required to prevent overcooling, has a significant impact on halo masses all the way up to cluster scales (M200~1e15 Msun). Baryonic physics changes the total mass profiles of haloes out to several times the virial radius, a modification that cannot be captured by a change in the halo concentration. The decrease in the total halo mass causes a decrease in the halo MF of about 20%. This effect can have important consequences for abundance matching technique as well as for most SAM of galaxy formation. Provide analytic fitting formulae, derived from simulations that reproduce the observed baryon fractions, to correct halo masses and mass functions from DM-only simulations. The effect of baryonic physics (AGN feedback in particular) on cluster member counts is about as large as changing the cosmology from WMAP7 to Planck, even when a moderately high mass limit of M500~1e14 Msun is adopted. Thus, for precision cosmology the effects of baryons must be accounted for.
Tuesday, February 18, 2014
Day 591
Tuesday.
1402.3590
Clustering tomography: measuring cosmological distances through angular clustering in thin redshift shells
Salazar-Alboronoz, Sánchez, Padilla, Baugh
Test the cosmological implications of studying galaxy clustering using a tomographic approach, by computing the galaxy 2pt angular correlation function w(theta) in thin redshift shells using a spectroscopic-redshift galaxy survey. The advantages of this procedure are that it is not necessary to assume a fiducial cosmology in order to convert measured angular positions and redshifts into distances, and that it give several (less accurate) measurements of the angular diameter distance D_A(z) instead of only one (more precise) measurement of the effective average distance D_V(z), which results in better constraints on the expansion history of the Universe. Test model for w(theta) and its covariance matrix against a set of mock galaxy catalogues and show that this technique is able to extract unbiased cosmological constraints. Also, assuming the best-fit LCDM cosmology from the CMB measurements from the Planck satellite, forecast the result of applying this tomographic approach to the final BOSS catalog in combination with Planck for 3 flat cosmological models, and compare them with the expected results of the isotropic BAO measurements post-reconstrunction on the same galaxy catalogue combined with Planck. While BAOs are more accurate for constraining cosmological parameters of the standard LCDM model, the tomographic technique gives better results when we allow the DE EoS w_DE deviate from -1, resulting in a performance similar to BAOs in the case of a constant value of w_DE, and a significant improvement of the case of time-dependent value of w_DE, increasing the value of the FoM in the w0-wa plane by a factor of 1.4.
1402.3594
Galaxy properties in clusters. II. Backsplash galaxies
Muriel, Coenda
Explore properties of galaxies on the outskirts of clusters and their dependence on recent dynamical history in order to understand the real impact that the cluster core has on the evolution of galaxies. >1000 galaxies M_0.1r<-19.6 on outskirts of 90 clusters (1<r/rvir<2) in 0.05<z<0.10. Use LoS velocity, select high and low velocity subsamples. Theoretical predictions indicate that a significant fraction of the first subsample should be backsplash galaxies, that is, objects that have already orbited near the cluster center. A significant proportion of the sample of high relative velocity HV galaxies seems to be composed of in falling objects. Results suggest that, at fixed stellar mass, late type galaxies in the low velocity LV sample are systematically older, refer and have formed fewer stars ruling the last 3 Gyrs than galaxies in the HV sample. This result is consistent with models that assume that the central regions of clusters are effective in quenching the SF by means of processes such as ram pressure stripping or strangulation. At fixed stellar mass, LV galaxies show some evidence of having higher surface brightness and smaller size than HV galaxies. These results are consistent with the scenario where galaxies that have orbited the central regions of clusters are more likely to suffer tidal effect, producing loss of mass as well as redistribution of matter towards more compact configurations. Finally, found a higher fraction of ET galaxies in the LV sample, supporting the idea that the central region of clusters of galaxies may contribute to the transformation of morphological types towards earlier types.
1402.3674
New results on the exotic galaxy `Speca' and discovering many more Specas with RAD@home network
Hota et al
A citizen-science research lab built on free web-services (Facebook, Google, Skype, …). Present 10 newly found candidate episodic radio galaxies, and 10 more interesting cases which includes bent-lobe radio galaxies located in new M-c-scale filaments, likely tracing cosmological cluster accretion from the cosmic web. The new Speca-like rare spiral-host large radio galaxies also been reported. Early analysis from follow-up observations revealed that Speca is likely a new entry to the cluster and its a fast rotating, extremely massive SF disk galaxy. Speca-like massive galaxies with giant radio lobes are possibly remnants of luminous quasars in the early Universe or of first SMBHs with in first massive galaxies [?]. As discoveries of Speca-like galaxies did not require new data from big telescopes, but free archival radio-optical data, these early results demonstrate the potential of RAD@home and how it can help resource-rich professionals, as well as demonstrate a model of academic-growth for resource-poor people in the underdeveloped regions via Internet.
1402.3823
r-Java 2.0: the nuclear physics
Kostka et al
A nucleosynthesis code for open use that performs r-process calculations as well as a suite of other analysis tools. With GUI, it is capable of: simulating nuclear statistical equilibrium (NSE), calculating r-process abundances for a wide range of input parameters and astrophysical environments, computing the mass fragmentation from neutron-induced fission as well as the study of individual nucleosynthesis processes. New feature: ability to solve the full reaction network. 3 fission channels (beta-delayed, neutron-induced and spontaneous fission) as well as computation of the mass fragmentation; compared to the upper limit on mass fission approximation. The effects of including beta-delayed neutron emission on r-process yield is studied. The role of coulomb interactions in NSE abundances is shown to be significant, supporting previous foundlings. Comparative analysis undertaken, producing results in literature: high-entroy wind around a proto-neutron star, the ejecta from a NS merger or the relativistic ejecta from a quark nova.
1402.3824
r-Java 2.0: the astrophysics
Kostka et al
Astrophysics incorporated into the software described. Survey of the available parameters for each astrophysical site is undertaken and the effect on final r-process abundance is compared. Resulting abundances for each site are also compared to solar observations both independently and in concert. R-Java 2.0 available for download.
1402.0506
Scale-dependent bias in the BAO-scale intergalactic neutral hydrogen
Pontzen
Show that HI density of the z~2.3 IGM's relation to cosmic overdensity is strongly scale-dependent. This behavior arises from a linearized version of the well-known "proximity effect", in which bright sources suppress atomic hydrogen density. Demonstrate how HI density consequently anti-correlates with total matter density when averaged on scales exceeding the Ly-limint mean-free-path. The radiative transfer thumbprint is highly distinctive and should be measurable in the Lya forest. Effects extend to sufficiently small scales to generate significant distortion of the correlation function shape around the BAO peak, although the peak location shifts only by 1.2 % for a mean source bias of b_j=3. The distortion changes significantly with b_j and other astrophysical parameters; measuring it should provide a helpful observational constrain on the nature of ionizing photon sources in the near future.
1402.3590
Clustering tomography: measuring cosmological distances through angular clustering in thin redshift shells
Salazar-Alboronoz, Sánchez, Padilla, Baugh
Test the cosmological implications of studying galaxy clustering using a tomographic approach, by computing the galaxy 2pt angular correlation function w(theta) in thin redshift shells using a spectroscopic-redshift galaxy survey. The advantages of this procedure are that it is not necessary to assume a fiducial cosmology in order to convert measured angular positions and redshifts into distances, and that it give several (less accurate) measurements of the angular diameter distance D_A(z) instead of only one (more precise) measurement of the effective average distance D_V(z), which results in better constraints on the expansion history of the Universe. Test model for w(theta) and its covariance matrix against a set of mock galaxy catalogues and show that this technique is able to extract unbiased cosmological constraints. Also, assuming the best-fit LCDM cosmology from the CMB measurements from the Planck satellite, forecast the result of applying this tomographic approach to the final BOSS catalog in combination with Planck for 3 flat cosmological models, and compare them with the expected results of the isotropic BAO measurements post-reconstrunction on the same galaxy catalogue combined with Planck. While BAOs are more accurate for constraining cosmological parameters of the standard LCDM model, the tomographic technique gives better results when we allow the DE EoS w_DE deviate from -1, resulting in a performance similar to BAOs in the case of a constant value of w_DE, and a significant improvement of the case of time-dependent value of w_DE, increasing the value of the FoM in the w0-wa plane by a factor of 1.4.
1402.3594
Galaxy properties in clusters. II. Backsplash galaxies
Muriel, Coenda
Explore properties of galaxies on the outskirts of clusters and their dependence on recent dynamical history in order to understand the real impact that the cluster core has on the evolution of galaxies. >1000 galaxies M_0.1r<-19.6 on outskirts of 90 clusters (1<r/rvir<2) in 0.05<z<0.10. Use LoS velocity, select high and low velocity subsamples. Theoretical predictions indicate that a significant fraction of the first subsample should be backsplash galaxies, that is, objects that have already orbited near the cluster center. A significant proportion of the sample of high relative velocity HV galaxies seems to be composed of in falling objects. Results suggest that, at fixed stellar mass, late type galaxies in the low velocity LV sample are systematically older, refer and have formed fewer stars ruling the last 3 Gyrs than galaxies in the HV sample. This result is consistent with models that assume that the central regions of clusters are effective in quenching the SF by means of processes such as ram pressure stripping or strangulation. At fixed stellar mass, LV galaxies show some evidence of having higher surface brightness and smaller size than HV galaxies. These results are consistent with the scenario where galaxies that have orbited the central regions of clusters are more likely to suffer tidal effect, producing loss of mass as well as redistribution of matter towards more compact configurations. Finally, found a higher fraction of ET galaxies in the LV sample, supporting the idea that the central region of clusters of galaxies may contribute to the transformation of morphological types towards earlier types.
1402.3674
New results on the exotic galaxy `Speca' and discovering many more Specas with RAD@home network
Hota et al
A citizen-science research lab built on free web-services (Facebook, Google, Skype, …). Present 10 newly found candidate episodic radio galaxies, and 10 more interesting cases which includes bent-lobe radio galaxies located in new M-c-scale filaments, likely tracing cosmological cluster accretion from the cosmic web. The new Speca-like rare spiral-host large radio galaxies also been reported. Early analysis from follow-up observations revealed that Speca is likely a new entry to the cluster and its a fast rotating, extremely massive SF disk galaxy. Speca-like massive galaxies with giant radio lobes are possibly remnants of luminous quasars in the early Universe or of first SMBHs with in first massive galaxies [?]. As discoveries of Speca-like galaxies did not require new data from big telescopes, but free archival radio-optical data, these early results demonstrate the potential of RAD@home and how it can help resource-rich professionals, as well as demonstrate a model of academic-growth for resource-poor people in the underdeveloped regions via Internet.
1402.3823
r-Java 2.0: the nuclear physics
Kostka et al
A nucleosynthesis code for open use that performs r-process calculations as well as a suite of other analysis tools. With GUI, it is capable of: simulating nuclear statistical equilibrium (NSE), calculating r-process abundances for a wide range of input parameters and astrophysical environments, computing the mass fragmentation from neutron-induced fission as well as the study of individual nucleosynthesis processes. New feature: ability to solve the full reaction network. 3 fission channels (beta-delayed, neutron-induced and spontaneous fission) as well as computation of the mass fragmentation; compared to the upper limit on mass fission approximation. The effects of including beta-delayed neutron emission on r-process yield is studied. The role of coulomb interactions in NSE abundances is shown to be significant, supporting previous foundlings. Comparative analysis undertaken, producing results in literature: high-entroy wind around a proto-neutron star, the ejecta from a NS merger or the relativistic ejecta from a quark nova.
1402.3824
r-Java 2.0: the astrophysics
Kostka et al
Astrophysics incorporated into the software described. Survey of the available parameters for each astrophysical site is undertaken and the effect on final r-process abundance is compared. Resulting abundances for each site are also compared to solar observations both independently and in concert. R-Java 2.0 available for download.
1402.0506
Scale-dependent bias in the BAO-scale intergalactic neutral hydrogen
Pontzen
Show that HI density of the z~2.3 IGM's relation to cosmic overdensity is strongly scale-dependent. This behavior arises from a linearized version of the well-known "proximity effect", in which bright sources suppress atomic hydrogen density. Demonstrate how HI density consequently anti-correlates with total matter density when averaged on scales exceeding the Ly-limint mean-free-path. The radiative transfer thumbprint is highly distinctive and should be measurable in the Lya forest. Effects extend to sufficiently small scales to generate significant distortion of the correlation function shape around the BAO peak, although the peak location shifts only by 1.2 % for a mean source bias of b_j=3. The distortion changes significantly with b_j and other astrophysical parameters; measuring it should provide a helpful observational constrain on the nature of ionizing photon sources in the near future.
Monday, February 17, 2014
Day 590
Sunday. Monday.
1402.0037
Formation of the Moon: a new mechanism
Gupta
Understanding the Moon's formation mechanism is necessary for studying not only the Moon itself, but also the evolution, formation, habitability, and structure of other planets and the moons in the Solar system and in extrasolar planetary systems. In this paper, suggest a mechanism of the Moon formation: form at the time of planet formation in a parallel and simultaneous process, and the new moons cannot form in a grown up Solar system. [This is different from the current theory of Moon formation…]
1402.0075
Galaxy luminosity function and its cosmological evolution: testing a new feedback model depending n galaxy-scale dust opacity
Makiya, Totani, et al
New SAM incorporating a SF law with a feedback depending on the galaxy-scale mean dust opacity and metallicity, motivated by recent observations of SF in nearby galaxies and theoretical considerations. This new model is used to investigate the effect of such a feedback on shaping the galaxy LF and its evolution. SF activity is significantly suppressed in dwarf galaxies by the new feedback effect, and the faint-end slope of local LFs can be reproduced with a reasonable strength of SN feedback, which is in contrast to the previous models that require a rather extreme strength of SN feedback. Model can also reproduce the early appearance of massive galaxy manifested in the bright-end of high z K-band LFs. Though some of the previous models also succeeded in reproducing this, they assumed a SF law depending on the galaxy-scale dynamical time, which is not supported by observations. Argue that the feedback depending on dust opacity (or metal column density) is essential, rather than that simply depending on gas column density, to get these results.
1402.0466
Molecular excitations: a new way to detect Dark matter
Va'vra
Possibility that DAMA observes the WIMP via molecular excitations of OH-molecules, left in the NaI(TI) material as an impurity. Independently of the outcome of this particular investigation, think that the DM shear should be expanded into a domain of detectors sensitive to molecular excitations, and therefore make searches more sensitive. In this paper, investigate the fused silica material with large content of OH-molecules, which are intentionally loaded into this material to improve the radiation hardness and to reduce the UV sensitivity. Also looked at a possibility to use simple pure water to detect vibrations of water molecule and conclude that it is worthwhile to pursue further. Presently, we do not have suitable IR detectors to observe long wavelengths, however, some OH-molecular excitations extend to visible and UV wavelengths, and can be measured by Bialkali photocathodes. There are many other chemical substances with diatomic molecules, which could be investigated along these lines as well.
1402.3293
Testing the equal-time angular-averaged consistency relation of the gravitational dynamics in N-body simulations
Nishimichi, Valegeas
Test the equal-time consistency relation [?] between the angular-averaged bispectrum and the PS of the matter density field, employing a large suite of cosmological N-body simulations. This is the lowest-order version of the relations between (ell+n)-point and n-point polyspectra, where one averages over the angles of ell soft modes. This relation depends on two wave numbers, k' in the soft domain and k in the hard domain [what's a soft and hard domain?]. Show that it holds up to a good accuracy, when k'/k << 1 and k' is in the linear regime, while the hard mode k goes from linear (0.1 h/Mpc) to nonlinear (1.0 h/Mpc) scales. On scales k<0.4 h/Mpc, conform the relation within a ~5% accuracy, even though the bispectrm can already deviate from leading-order perturbation theory by more than 30 %. Further show that the relation extends up to NL scales, k~1.0 h/Mpc, within an accuracy of ~10%.
1402.3302
Detection of stacked filament lensing between SDSS luminous red galaxies
Clampitt, Jain, Takada
Search for the lensing signal of massive filaments between 220,000 pairs of LRGs from the SDSS. Use a nulling technique to remove the contribution of the LRG halos, resulting in a 10 sigma detection of the filament lensing signal. Compare the measurements with halo model predictions based on a calculation of 3pt halo-halo-mass correlations. Comparing the "thick" halo model filament to a "thin" string of halos, thick filaments larger than a Mpc in width are clearly preferred by the data.
1402.3394
The connection between galaxy structure and quenching efficiency
Omand, Balogh, Poggianti
From SDSS DR7 with structural measurements from GIM2D, show how the fraction of quiescent galaxies depends on galaxy stellar mass M*, effective radius R_e, fraction of r-band light in the bulge, B/T, and their status as a central or satellite galaxy at 0.01<z<0.2. For central galaxies, confirm that the quiescent fraction depends not only on stellar mass, but also on R_e. The dependence is particularly strong as a function of M*/R_e^alpha, with alpha ~ 1.5. This appears to be driven by a simple dependence on B/T per the mass range 9<log(M*/Msun)<11.5, and is qualitatively similar even if galaxies with B/T>0.3 are excluded. For satellite galaxies, the quiescent fraction is always larger than that of central galaxies, for any combination of M*, R_e and B/T. The quenching efficiency is not constant, but reaches a maximum of ~0.7 for galaxies with 9<log(M*/Msun)<9.5 and R_e<1 kpc. This is the same region of parameter space in which the satellite fraction itself reaches its maximum value, suggesting that the transformation from an active central galaxy to a quiescent satellite is associated with a reduction in R_e due to an increase in dominance of a bulge component.
1402.0037
Formation of the Moon: a new mechanism
Gupta
Understanding the Moon's formation mechanism is necessary for studying not only the Moon itself, but also the evolution, formation, habitability, and structure of other planets and the moons in the Solar system and in extrasolar planetary systems. In this paper, suggest a mechanism of the Moon formation: form at the time of planet formation in a parallel and simultaneous process, and the new moons cannot form in a grown up Solar system. [This is different from the current theory of Moon formation…]
1402.0075
Galaxy luminosity function and its cosmological evolution: testing a new feedback model depending n galaxy-scale dust opacity
Makiya, Totani, et al
New SAM incorporating a SF law with a feedback depending on the galaxy-scale mean dust opacity and metallicity, motivated by recent observations of SF in nearby galaxies and theoretical considerations. This new model is used to investigate the effect of such a feedback on shaping the galaxy LF and its evolution. SF activity is significantly suppressed in dwarf galaxies by the new feedback effect, and the faint-end slope of local LFs can be reproduced with a reasonable strength of SN feedback, which is in contrast to the previous models that require a rather extreme strength of SN feedback. Model can also reproduce the early appearance of massive galaxy manifested in the bright-end of high z K-band LFs. Though some of the previous models also succeeded in reproducing this, they assumed a SF law depending on the galaxy-scale dynamical time, which is not supported by observations. Argue that the feedback depending on dust opacity (or metal column density) is essential, rather than that simply depending on gas column density, to get these results.
1402.0466
Molecular excitations: a new way to detect Dark matter
Va'vra
Possibility that DAMA observes the WIMP via molecular excitations of OH-molecules, left in the NaI(TI) material as an impurity. Independently of the outcome of this particular investigation, think that the DM shear should be expanded into a domain of detectors sensitive to molecular excitations, and therefore make searches more sensitive. In this paper, investigate the fused silica material with large content of OH-molecules, which are intentionally loaded into this material to improve the radiation hardness and to reduce the UV sensitivity. Also looked at a possibility to use simple pure water to detect vibrations of water molecule and conclude that it is worthwhile to pursue further. Presently, we do not have suitable IR detectors to observe long wavelengths, however, some OH-molecular excitations extend to visible and UV wavelengths, and can be measured by Bialkali photocathodes. There are many other chemical substances with diatomic molecules, which could be investigated along these lines as well.
1402.3293
Testing the equal-time angular-averaged consistency relation of the gravitational dynamics in N-body simulations
Nishimichi, Valegeas
Test the equal-time consistency relation [?] between the angular-averaged bispectrum and the PS of the matter density field, employing a large suite of cosmological N-body simulations. This is the lowest-order version of the relations between (ell+n)-point and n-point polyspectra, where one averages over the angles of ell soft modes. This relation depends on two wave numbers, k' in the soft domain and k in the hard domain [what's a soft and hard domain?]. Show that it holds up to a good accuracy, when k'/k << 1 and k' is in the linear regime, while the hard mode k goes from linear (0.1 h/Mpc) to nonlinear (1.0 h/Mpc) scales. On scales k<0.4 h/Mpc, conform the relation within a ~5% accuracy, even though the bispectrm can already deviate from leading-order perturbation theory by more than 30 %. Further show that the relation extends up to NL scales, k~1.0 h/Mpc, within an accuracy of ~10%.
1402.3302
Detection of stacked filament lensing between SDSS luminous red galaxies
Clampitt, Jain, Takada
Search for the lensing signal of massive filaments between 220,000 pairs of LRGs from the SDSS. Use a nulling technique to remove the contribution of the LRG halos, resulting in a 10 sigma detection of the filament lensing signal. Compare the measurements with halo model predictions based on a calculation of 3pt halo-halo-mass correlations. Comparing the "thick" halo model filament to a "thin" string of halos, thick filaments larger than a Mpc in width are clearly preferred by the data.
1402.3394
The connection between galaxy structure and quenching efficiency
Omand, Balogh, Poggianti
From SDSS DR7 with structural measurements from GIM2D, show how the fraction of quiescent galaxies depends on galaxy stellar mass M*, effective radius R_e, fraction of r-band light in the bulge, B/T, and their status as a central or satellite galaxy at 0.01<z<0.2. For central galaxies, confirm that the quiescent fraction depends not only on stellar mass, but also on R_e. The dependence is particularly strong as a function of M*/R_e^alpha, with alpha ~ 1.5. This appears to be driven by a simple dependence on B/T per the mass range 9<log(M*/Msun)<11.5, and is qualitatively similar even if galaxies with B/T>0.3 are excluded. For satellite galaxies, the quiescent fraction is always larger than that of central galaxies, for any combination of M*, R_e and B/T. The quenching efficiency is not constant, but reaches a maximum of ~0.7 for galaxies with 9<log(M*/Msun)<9.5 and R_e<1 kpc. This is the same region of parameter space in which the satellite fraction itself reaches its maximum value, suggesting that the transformation from an active central galaxy to a quiescent satellite is associated with a reduction in R_e due to an increase in dominance of a bulge component.
Saturday, February 15, 2014
Day 589
Friday. Saturday.
1402.2976
On the universality of void density profiles
Riccardelli, Quilis, Varela
Show: void density profile is insensitive to the void radius both in a catalogue of observed voids and in voids from a large cosmological simulation. However, the observed and simulated voids display different profile shapes, with the former having much steeper profiles than the latter. Sparsity canon be the main reason for this discrepancy. The observed profile shows a significant dependence on the galaxy sample used to trace the matter distribution. Samples including low-mass galaxies lead to shallower profiles wrt the samples where only massive galaxies are used, as faint galaxies live closer to the void center. Argue that galaxies are biased tracers when used to probe the matter distribution within voids.
1402.3267
The 400d galaxy cluster survey weak lensing programme: III: evidence for consistent WL and X-ray masses at $z\approx 0.5$
Israel, Reiprich, Erben, Massey, Sarazin, Schneider, Vikhlinin
Extend calibration of WL-X-ray mass scaling down to 1e14 Msun in a sample representative of z~0.4-0.5 population, in 8 clusters (0.39<z<0.80). Overall find good agreement between WL and X-ray masses, with different mass bias estimators consistent with zero. Subdividing the sample, find the high-mass subsample to show no significant mass bias while for the low-mass subsample, there is a bias towards overestimated X-ray masses at the ~2sigma level for some mass proxies. Overall scatter in the relation is low. Do not find evidence for a strong (~40%) underestimate in the X-ray masses, as suggested to reconcile PLanck cluster counts and cosmological constraints. For high-mass clusters, measurements are consistent with studies in the literature. The mass dependent bias, significant at ~2sigma, may hit at a physically different cluster population (less relaxed clusters with more substructure and mergers); or it may be due to small number statistics.
1402.0003
The progenitors of local ultra-massive galaxies across cosmic time: from dusty star-bursting to quiescent stellar populations
Marchesini, Muzzin, … et al
Using the UltraVISTA catalogs, investigate the evolution in the 11.4 Gyr since z=3 of the progenitors of local ultra-massive galaxies log(M*/Msun)~11.8 (UMGs), providing a complete and consistent picture of how the most massive galaxies at z=0 have assembled. Select progenitors with a SAM approach using abundance matching; infer growth in stellar mass of 0.56 / 0.45 / 0.27 dex from z=3/2/1, respectively, to z=0. At z<1, the progenitors of UMGs constitute a homogeneous population of only quiescent galaxies with old stellar populations. At z>1, the contribution from SF galaxies progressively increases, with the progenitors at 2<z<3 being dominated by massive (M*~2e11 Msun), dusty (A_V~1-2.2 mag), SF (SFR~100-400 Msun/yr) galaxies with a large range in stellar ages. At z=2.75, ~15% of the progenitors are quiescent, with properties typical of post-starburst galaxies with little dust extinction and strong Balmer break, and showing a large scatter in color. Findings indicate that local UMGs have been mostly assembled between z=3 and z=1.5. Most of the quenching of the SF progenitors happened between z=2.75 and z=1.25, in good agreement with the typical formation redshift and scatter in age of z=0 UMGs as derived from their fossil records. Show that the progenitors of local UMGs, including the SF ones, have never lived on the blue cloud since z=3, challenging previously proposed pictures for the formation of local massive spheroids; propose an alternative path for the formation of local UMGs consistent with findings.
1402.0006
The total infrared luminosity may significantly overestimate the star formation rate of recently quenched galaxies
Hayward et al
The total IR luminosity is very useful for estimating the SFR of galaxies, but converting the IR luminosity into an SFR relies on assumptions that do not hold for all galaxies. Test the effectiveness of the IR luminosity as an SFR indicator by applying it to synthetic SEDs generated from 3d hydro-sims of isolated disk galaxies and galaxy mergers. In general, the SFR inferred from the IR luminosity agrees well with the true instantaneous SFR of the simulated galaxies. However, for the major mergers in which a strong starburst is induced, the SFR inferred from the IR luminosity can overestimate the instantaneous SFR during the post-starburst phase by greater than two orders of magnitude. Even though the instantaneous SFR decreases rapidly after the starburst, the stars that were formed in the starburst remain dust-obscured and thus produce significant IR luminosity. Consequently, use of the IR luminosity as an SFR indicator may cause one to conclude that post-starburst galaxies are still star-forming, whereas in reality, SF was recently quenched.
1402.0021
Kinematic structure of massive star-forming regions - I. Accretion along filaments
Trackenberg et al
MIR and FIR view on high-mass star formation has shed light on many aspects of massive SF, but these continuum studies lack kinematic information. Study the kinematics of the molecular gas in high-mass SF regions. Complement PACS and SPIRE FIR data on 16 high-mass SF regions from the Herschel key project EPoS with N2H+ molecular line data from the MOPRA and Nobeyama 45m telescope. Using the full N2H+ hyperfine structure, produce column density, velocity, and line width maps. These were correlated with PACS 70 um images and PACS point sources. Additionally searched for velocity gradients. For several regions, the data suggest that the line width on the scale of clumps is dominated by outflows or unresolved velocity gradients. 2 objects show two velocity components along several LoS. Find that all regions with a diameter larger than 1pc show either velocity gradients or fragment into independent structures with distinct velocities. The velocity profiles of 3 regions with a smooth gradient are consistent with gas flows along the filament, suggesting accretion flows onto the densest regions. Show that the kinematics of several regions have a significant and complex velocity structure. For 3 filaments, suggest that gas flows toward the more massive clumps are present.
1402.2976
On the universality of void density profiles
Riccardelli, Quilis, Varela
Show: void density profile is insensitive to the void radius both in a catalogue of observed voids and in voids from a large cosmological simulation. However, the observed and simulated voids display different profile shapes, with the former having much steeper profiles than the latter. Sparsity canon be the main reason for this discrepancy. The observed profile shows a significant dependence on the galaxy sample used to trace the matter distribution. Samples including low-mass galaxies lead to shallower profiles wrt the samples where only massive galaxies are used, as faint galaxies live closer to the void center. Argue that galaxies are biased tracers when used to probe the matter distribution within voids.
1402.3267
The 400d galaxy cluster survey weak lensing programme: III: evidence for consistent WL and X-ray masses at $z\approx 0.5$
Israel, Reiprich, Erben, Massey, Sarazin, Schneider, Vikhlinin
Extend calibration of WL-X-ray mass scaling down to 1e14 Msun in a sample representative of z~0.4-0.5 population, in 8 clusters (0.39<z<0.80). Overall find good agreement between WL and X-ray masses, with different mass bias estimators consistent with zero. Subdividing the sample, find the high-mass subsample to show no significant mass bias while for the low-mass subsample, there is a bias towards overestimated X-ray masses at the ~2sigma level for some mass proxies. Overall scatter in the relation is low. Do not find evidence for a strong (~40%) underestimate in the X-ray masses, as suggested to reconcile PLanck cluster counts and cosmological constraints. For high-mass clusters, measurements are consistent with studies in the literature. The mass dependent bias, significant at ~2sigma, may hit at a physically different cluster population (less relaxed clusters with more substructure and mergers); or it may be due to small number statistics.
1402.0003
The progenitors of local ultra-massive galaxies across cosmic time: from dusty star-bursting to quiescent stellar populations
Marchesini, Muzzin, … et al
Using the UltraVISTA catalogs, investigate the evolution in the 11.4 Gyr since z=3 of the progenitors of local ultra-massive galaxies log(M*/Msun)~11.8 (UMGs), providing a complete and consistent picture of how the most massive galaxies at z=0 have assembled. Select progenitors with a SAM approach using abundance matching; infer growth in stellar mass of 0.56 / 0.45 / 0.27 dex from z=3/2/1, respectively, to z=0. At z<1, the progenitors of UMGs constitute a homogeneous population of only quiescent galaxies with old stellar populations. At z>1, the contribution from SF galaxies progressively increases, with the progenitors at 2<z<3 being dominated by massive (M*~2e11 Msun), dusty (A_V~1-2.2 mag), SF (SFR~100-400 Msun/yr) galaxies with a large range in stellar ages. At z=2.75, ~15% of the progenitors are quiescent, with properties typical of post-starburst galaxies with little dust extinction and strong Balmer break, and showing a large scatter in color. Findings indicate that local UMGs have been mostly assembled between z=3 and z=1.5. Most of the quenching of the SF progenitors happened between z=2.75 and z=1.25, in good agreement with the typical formation redshift and scatter in age of z=0 UMGs as derived from their fossil records. Show that the progenitors of local UMGs, including the SF ones, have never lived on the blue cloud since z=3, challenging previously proposed pictures for the formation of local massive spheroids; propose an alternative path for the formation of local UMGs consistent with findings.
1402.0006
The total infrared luminosity may significantly overestimate the star formation rate of recently quenched galaxies
Hayward et al
The total IR luminosity is very useful for estimating the SFR of galaxies, but converting the IR luminosity into an SFR relies on assumptions that do not hold for all galaxies. Test the effectiveness of the IR luminosity as an SFR indicator by applying it to synthetic SEDs generated from 3d hydro-sims of isolated disk galaxies and galaxy mergers. In general, the SFR inferred from the IR luminosity agrees well with the true instantaneous SFR of the simulated galaxies. However, for the major mergers in which a strong starburst is induced, the SFR inferred from the IR luminosity can overestimate the instantaneous SFR during the post-starburst phase by greater than two orders of magnitude. Even though the instantaneous SFR decreases rapidly after the starburst, the stars that were formed in the starburst remain dust-obscured and thus produce significant IR luminosity. Consequently, use of the IR luminosity as an SFR indicator may cause one to conclude that post-starburst galaxies are still star-forming, whereas in reality, SF was recently quenched.
1402.0021
Kinematic structure of massive star-forming regions - I. Accretion along filaments
Trackenberg et al
MIR and FIR view on high-mass star formation has shed light on many aspects of massive SF, but these continuum studies lack kinematic information. Study the kinematics of the molecular gas in high-mass SF regions. Complement PACS and SPIRE FIR data on 16 high-mass SF regions from the Herschel key project EPoS with N2H+ molecular line data from the MOPRA and Nobeyama 45m telescope. Using the full N2H+ hyperfine structure, produce column density, velocity, and line width maps. These were correlated with PACS 70 um images and PACS point sources. Additionally searched for velocity gradients. For several regions, the data suggest that the line width on the scale of clumps is dominated by outflows or unresolved velocity gradients. 2 objects show two velocity components along several LoS. Find that all regions with a diameter larger than 1pc show either velocity gradients or fragment into independent structures with distinct velocities. The velocity profiles of 3 regions with a smooth gradient are consistent with gas flows along the filament, suggesting accretion flows onto the densest regions. Show that the kinematics of several regions have a significant and complex velocity structure. For 3 filaments, suggest that gas flows toward the more massive clumps are present.
Thursday, February 13, 2014
Day 588
Thursday.
1402.2650
The scientific case for a mission to the ice giant planets with twin spacecraft to unveil the history of our Solar System
Turrini et al
Exploration of ice giant planets Uranus and Neptune---"a timely milestone, fully appropriate for an L class mission" (Cosmic Vision 2015-2025). Explore both planets and satellites in the framework of a single L-class mission. Goals: comparatively studying these two similar yet extremely different systems, sheds new light on the ancient past of the SS and on the processes that shaped its formation and evolution. This would reveal whether the SS and the very diverse extrasolar systems discovered so far all share a common origin or if different environments and mechanisms were responsible for their formation. Also open up the possibility to use Uranus and Neptune as templates in the study of one of the most abundant type of extrasolar planets in the galaxy. Also allow a detailed study of the interplanetary and gravitational environments at a range of distances from the Sun poorly covered by direct exploration, improving the constraints on the fundamental theories of gravitation and the behavior of the solar wind and the interplanetary B-field.
1402.2655
An HST/COS survey of the low-redshift IGM. I. Survey, methodology, & overall results
Danforth et al
Spectra of 75 bright AGNs at z<0.85, get 4369 individual absorption lines. The column-density distribution of HI systems is seen to evolve both in amplitude and slope at z<0.47. Observe 985 metal lines in 354 systems, and find that the fraction of absorbers detected in metals is strongly dependent on HI column density. OVI absorbers appear to evolve in the same sense as the Lya forest. A velocity-space 2-pt correlation function shows substantial clustering of HI absorbers on scales of Delta nu=50-300 km/s with no significant clustering at larger Delta nu. Most of the clustering signal comes from the stronger (N_HI>1e13.5 cm^-2) absorbers particularly those with metal absorption. The full catalog of absorption lines and fully-reduced spectra is available via MAST as a high-level science product at archive.stsci.edu/prepds/igm/.
1402.2670
Robust weak-lensing mass calibration of Planck galaxy clusters
von der Linden, Mantz, Allen, Applegate, et al
Tension between Planck SZ cluster sounds and CMB temperature anisotropies: compare Planck cluster mass estimates with robust, WL mass measurements from Weighting the Giants (WtG) project. For the 22 clusters in common, find overall mass ratio of <M_Planck/M_WtG>=0.688pm0.072. Extending those not used in Planck cosmology analysis yields similar values, for the 38 clusters in common. Identifying the WL masses as process for the true cluster mass (on average), these ratios are ~1.6 sigma lower than the default mass bias of 0.8 assumed in the Planck cluster analysis. Adopting the WtG WL-based mass calibration would substantially reduce the tension found between the Planck cluster count cosmology results and those from CMB temperature anisotropies. Also find modest evidence (95% CL) for a mass dependence of the calibration ratio and discuss its potential origin in light of systematic uncertainties in the temperature calibration of the X-ray measurements used to calibrate the Planck cluster masses. Results exemplify the critical role that robust absolute mass calibration plays in cluster cosmology, and the invaluable role of accurate WL mass measurements.
1402.2650
The scientific case for a mission to the ice giant planets with twin spacecraft to unveil the history of our Solar System
Turrini et al
Exploration of ice giant planets Uranus and Neptune---"a timely milestone, fully appropriate for an L class mission" (Cosmic Vision 2015-2025). Explore both planets and satellites in the framework of a single L-class mission. Goals: comparatively studying these two similar yet extremely different systems, sheds new light on the ancient past of the SS and on the processes that shaped its formation and evolution. This would reveal whether the SS and the very diverse extrasolar systems discovered so far all share a common origin or if different environments and mechanisms were responsible for their formation. Also open up the possibility to use Uranus and Neptune as templates in the study of one of the most abundant type of extrasolar planets in the galaxy. Also allow a detailed study of the interplanetary and gravitational environments at a range of distances from the Sun poorly covered by direct exploration, improving the constraints on the fundamental theories of gravitation and the behavior of the solar wind and the interplanetary B-field.
1402.2655
An HST/COS survey of the low-redshift IGM. I. Survey, methodology, & overall results
Danforth et al
Spectra of 75 bright AGNs at z<0.85, get 4369 individual absorption lines. The column-density distribution of HI systems is seen to evolve both in amplitude and slope at z<0.47. Observe 985 metal lines in 354 systems, and find that the fraction of absorbers detected in metals is strongly dependent on HI column density. OVI absorbers appear to evolve in the same sense as the Lya forest. A velocity-space 2-pt correlation function shows substantial clustering of HI absorbers on scales of Delta nu=50-300 km/s with no significant clustering at larger Delta nu. Most of the clustering signal comes from the stronger (N_HI>1e13.5 cm^-2) absorbers particularly those with metal absorption. The full catalog of absorption lines and fully-reduced spectra is available via MAST as a high-level science product at archive.stsci.edu/prepds/igm/.
1402.2670
Robust weak-lensing mass calibration of Planck galaxy clusters
von der Linden, Mantz, Allen, Applegate, et al
Tension between Planck SZ cluster sounds and CMB temperature anisotropies: compare Planck cluster mass estimates with robust, WL mass measurements from Weighting the Giants (WtG) project. For the 22 clusters in common, find overall mass ratio of <M_Planck/M_WtG>=0.688pm0.072. Extending those not used in Planck cosmology analysis yields similar values, for the 38 clusters in common. Identifying the WL masses as process for the true cluster mass (on average), these ratios are ~1.6 sigma lower than the default mass bias of 0.8 assumed in the Planck cluster analysis. Adopting the WtG WL-based mass calibration would substantially reduce the tension found between the Planck cluster count cosmology results and those from CMB temperature anisotropies. Also find modest evidence (95% CL) for a mass dependence of the calibration ratio and discuss its potential origin in light of systematic uncertainties in the temperature calibration of the X-ray measurements used to calibrate the Planck cluster masses. Results exemplify the critical role that robust absolute mass calibration plays in cluster cosmology, and the invaluable role of accurate WL mass measurements.
Subscribe to:
Posts (Atom)