Friday. ... actually, Sunday.
1209.6055
Mid-infrared selection of active galactic nuclei with the wide-field infrared survey explorer. II. Properties of WISE-selected active galactic nuclei in the NDWFS Bo\"otes field
Assef, Stern, Kochanek, ... Brown, Jannuzi, ... et al
Simple criterion of W1(3.4 microns) - W2(4.6 microns) >=0.8 provides a highly reliable and complete AGN sample for W2<15.05: extend study with a wider field, deeper WISE observations than COSMOS field. Find that the simple color cut loses reliability at fainter fluxes. Define new selection criterion based on both color and magnitude. Detection biased towards objects where the AGN dominates the bolometric luminosity output, and can identify highly obscured AGN. Dust obscuration distribution depend strongly on AGN luminosity: at L~3e44 erg/s, 30% are type 1, while at 4e45 erg/s, the fraction os 65%. Distribution of obscuration values suggests that dust in the torus is present as both a diffuse medium and in optically thick clouds.
1209.6069
The inhomogeneous reionization of the inter-galactic medium by metal-oor globular clusters
Griffen et al
Reionization by metal-poor globular clusters: GC formation suppressed if local gas is ionized. Possible for metal-poor GCs to have formed via DM halo formation, with truncation at z=10. Contributions to reioinziation could be as high as 90-98%; in the photon-poorest model, 60-65%. The surviving clusters in all models have a narrow age range (13.34 Gyr) consistent with curent ages estimates of the MW metal-poor globular clusters. 60% of all metal-poor globular clusters formed at high-z have since been destroyed via tidal interactions with the host galaxy.
1209.6130
Growth of a localized seed magnetic field in a turbulent medium
Cho, Yoo
Study amplification of localized seed B-fields in a turbulent medium; assume driving scale of turbulence comparable to the size of medium. Find: (1) turbulence can amplify localized seed B-field very efficiently. (2) Localized seed B-field disperses and fills the whole system very fast. (3) Growth and turbulence diffusion of a localized seed magnetic field are also fast in high magnetic Prandtl number turbulence [?]. (4) even in decaying turbulence, a localized seed B-field can ultimately fill the whole system.
1209.6135
Solar Cycle 24: is the peak coming?
Sello
The current solar cycle 24 appeared unusual: an unusually extended minimum period, and a global low activity compared to those of the previous 3 or 4 cycles. ....
1209.6181
Testing homogeneity with the galaxy fossil record
Hoyle, .. Heavens, et al
Homogeneity must be proved inside our past lightcone, while observations take place on the light cone. The SFH in galaxy fossil record provides a novel way: stack 10 z bin slices of LRG spectra in 12 equal contiguous area; use SFH in a time period which samples the history of the Universe between 11.5 to 13.4 Gyrs (0.2<z<0.5) as a proxy for homogeneity, calculate the posterior distribution for the excess large-scale variance due to inhomogeneity. Most likely solution is no extra variance at all.
1209.6220
Fitting functions for dark matter density profiles
An, Zhao
Present a unified parameterization of the fitting functions of density profiles of DM haloes or elliptical galaxies. Notable: classical Einasto profile appears naturally as the continuous limiting case of the cored subfamily amongst the double power-law profiles of Zhao (1996). There is basically no qualitative difference between halo models well-fitted by the Einasto profile and NFW model.
1209.6231
Revealing a strongly reddened, faint active galactic nucleus population by stacking deep co-added images
Varga, Csabai, Dobos
More than 50% of radio objects have not been detected by wide-field optical surveys. Aim: detect optical emission from unresolved, isolated radio sources of VLA faint images of FIRST survey have no identified optical counterparts in SDSS stripe 82. 2116 such radio point sources selected; cut-out images from stripe 82 generated; then stacked again to obtain images of high S/N ratio, in the hope that optical emission from radio sources would become detectable. Resulting stacked images show central peaks similar to point sources, have very red colors with steep optical spectral energy distributions. Total integration time: ~300h, with corresponding 5 sig detection limit at r = 26.6 mag,vprobably mostly from the central regions of dust-reddenedd Type 1 active galactic nuclei.
Sunday, September 30, 2012
Thursday, September 27, 2012
Day 306
Thursday.
1209.5745
Numerical simulations of the dark universe: state of the art and the next decade
Kuhlen, Vogelsberger, Angulo
Review of the current state of the art of cosmological dark matter simulations, with particular emphasis on the implications for dark matter detection efforts and studies of dark energy. Cosmo simulations are massive, requires supercomputing centers. Limitations of cold and collisionless DM-only approach; some efforts to include different particle physics as well as baryonic physics in galaxy formation simulations, including a discussion of recent results highlighting how the distribution of DM in haloes may be altered.
1209.5752
The cosmology of atomic dark matter
Cyr-Racine, Sigurdson
DM kinematically decouples from standard model plasma early on; it can remain coupled to a bath of "dark radiation" until a relatively late epoch. Atomic Dark Matter model, form neutral atom-like bound states and form gravitationally-bound structures. Necessarily includes an extra dark radiation component.
1209.5753
Gaia and the dynamics of the galaxy
Famaey
Gaia mission will answer: rotation curve of the outer Galaxy, departure from axisymmetry and equilibrium of the Galaxy, hierarchical formation and secular evolution in shaping the Galaxy and its various components, properties of the Galaxy in accordance with expectations from the standard model of cosmology. Dynamics of the MW, gravitational potential and mass distribution, including DM component.
1209.5842
Escape of Lyman-alpha and continuum photons from star-formng galaxies
Yajima, Li, Zhu, Abel, Gronwall, Ciardullo
Ionizing photos from LAEs alone are not sufficient to ionize IGM at z>6, but they can maintain the ionization of IGM at 0<z<5.
1209.5930
The distribution of faint satellites around central galaxies in the CFHT legacy survey
Jiang, Jing, Li
Radial number density profile and abundance distribution of faint satellites around central galaxies in the low-z universe. 3 magnitude bins of centrals; projected radial number density of satellites obeys a power law form with the slope of -1.05, independent of central galaxy luminosity and satellite luminosity. Projected cross correlation function between central and satellite galaxies exhibits a non-monotonic trend with satellite luminosity. Decreasing trend of clustering amplitude with satellite luminosity is reversed when satellites are fainter than central galaxies by more than 2 magnitudes. Comparison with the satellite luminosity function is MW and M31: MW and M31 have 2x as many satellites as around a typical central galaxy of similar luminosity.
1209.5938
Richness-mass relation self-calibration for galaxy clusters
Anderon, Berge
(1) Derive richness-mass scaling in local universe from 53 clusters (slope and scatter). (2) Show in photo-z in 250 clusters of 0.06<z<0.9 (mostly z<0.3) with red-sequence photo-z of delta-z < 0.02. (3) Compute predicted prior of the richness-mass scaling to forecast the capabilities of future wide-field-area surveys of galaxy clusters to constrain cosmological parameters. Better knowledge of scaling parameter likely has a strong impact on the relative importance of the different probes used to constrain cosmological parameters.
1209.6021
Constraints on primordial black holes as dark matter candidates from star formation
Capela, Pshirkov, Tinyakov
Estimate amount of DM trapped in stars, considering adiabatic contraction of the DM during star formation. If DM consists partly of primordial BHs (PBHs), they will be trapped together with the rest of the DM and will be finally inherited by a star compact remnant (WD or NS), which they will destroy in a short time. Observations of WDs and NSs thus impose constraints on the abundance of PBH. Best constraints: Omega_PBH/Omega_DM < 1e-5.
1209.5745
Numerical simulations of the dark universe: state of the art and the next decade
Kuhlen, Vogelsberger, Angulo
Review of the current state of the art of cosmological dark matter simulations, with particular emphasis on the implications for dark matter detection efforts and studies of dark energy. Cosmo simulations are massive, requires supercomputing centers. Limitations of cold and collisionless DM-only approach; some efforts to include different particle physics as well as baryonic physics in galaxy formation simulations, including a discussion of recent results highlighting how the distribution of DM in haloes may be altered.
1209.5752
The cosmology of atomic dark matter
Cyr-Racine, Sigurdson
DM kinematically decouples from standard model plasma early on; it can remain coupled to a bath of "dark radiation" until a relatively late epoch. Atomic Dark Matter model, form neutral atom-like bound states and form gravitationally-bound structures. Necessarily includes an extra dark radiation component.
1209.5753
Gaia and the dynamics of the galaxy
Famaey
Gaia mission will answer: rotation curve of the outer Galaxy, departure from axisymmetry and equilibrium of the Galaxy, hierarchical formation and secular evolution in shaping the Galaxy and its various components, properties of the Galaxy in accordance with expectations from the standard model of cosmology. Dynamics of the MW, gravitational potential and mass distribution, including DM component.
1209.5842
Escape of Lyman-alpha and continuum photons from star-formng galaxies
Yajima, Li, Zhu, Abel, Gronwall, Ciardullo
Ionizing photos from LAEs alone are not sufficient to ionize IGM at z>6, but they can maintain the ionization of IGM at 0<z<5.
1209.5930
The distribution of faint satellites around central galaxies in the CFHT legacy survey
Jiang, Jing, Li
Radial number density profile and abundance distribution of faint satellites around central galaxies in the low-z universe. 3 magnitude bins of centrals; projected radial number density of satellites obeys a power law form with the slope of -1.05, independent of central galaxy luminosity and satellite luminosity. Projected cross correlation function between central and satellite galaxies exhibits a non-monotonic trend with satellite luminosity. Decreasing trend of clustering amplitude with satellite luminosity is reversed when satellites are fainter than central galaxies by more than 2 magnitudes. Comparison with the satellite luminosity function is MW and M31: MW and M31 have 2x as many satellites as around a typical central galaxy of similar luminosity.
1209.5938
Richness-mass relation self-calibration for galaxy clusters
Anderon, Berge
(1) Derive richness-mass scaling in local universe from 53 clusters (slope and scatter). (2) Show in photo-z in 250 clusters of 0.06<z<0.9 (mostly z<0.3) with red-sequence photo-z of delta-z < 0.02. (3) Compute predicted prior of the richness-mass scaling to forecast the capabilities of future wide-field-area surveys of galaxy clusters to constrain cosmological parameters. Better knowledge of scaling parameter likely has a strong impact on the relative importance of the different probes used to constrain cosmological parameters.
1209.6021
Constraints on primordial black holes as dark matter candidates from star formation
Capela, Pshirkov, Tinyakov
Estimate amount of DM trapped in stars, considering adiabatic contraction of the DM during star formation. If DM consists partly of primordial BHs (PBHs), they will be trapped together with the rest of the DM and will be finally inherited by a star compact remnant (WD or NS), which they will destroy in a short time. Observations of WDs and NSs thus impose constraints on the abundance of PBH. Best constraints: Omega_PBH/Omega_DM < 1e-5.
Wednesday, September 26, 2012
Day 305
Tuesday. Wednesday.
1209.4900
The Effect of fluctuations on the Helium-ionizing background
Davies, Furlanetto
Don't assume uniform radiation field, but consider the discrete nature of the (rare) bright quasars that dominate the background, in He II Ly-a absorption spectra after He II reionization. Cosmological radiative transfer model includes: recent constraints on ionizing spectra and luminosity function of quasars and the distribution of IGM absorbers; effects of fluctuations on the evolving continuum opacity of IGM. Results: He II ionizing background evolves rapidly with redshift, increasing by >3.5 from z=3.5 to 2.5. Rapid evolution in mean He II Ly-a optical depth, without appealing to the reionization of He II. ...
1209.4903
Galactic outflows in absorption and emission: near-UV spectroscopy of galaxies at 1<z<2
Erb, Quider, Henry, Martin
Study large-scale outflows in 96 SF galaxies at 1<z<2 with NUV spectroscopy of FeII and MgII absorption and emission. Average blueshift of FeII interstellar absorption lines wrt systemic velocity is -85 km/s at z~1.5, a decrease of 2x from the average blueshift measured for FUV absorption lines seen in galaxies at z~2. Profiles of MgII show much more variety than the FeII profiles, which are always seen in absorption; MgII ranges from strong emission to pure absorption, with emission more common in galaxies with blue UV slopes and at lower stellar masses. Outfow velocities increase with increasing stellar mass with 2-3 sigma significance, in agreement with previous results. Find structure emission from FeII*, find several lines of evidence in support of the model in which this emission is generated by the re-emission of continuum photons absorbed in the FeII resonance transitions in outflowing gas. Photoionization models indicate that MgII emission arises from the resonant scattering of photons produced in HII regions, accounting for the differing profiles of the MgII and FeII lines. Comparison of FeII absorption and FeII* emission indicates that massive galaxies have more extended outflows and/or greater extinction, while 2d composite spectra indicate that emission from the outflow is stronger at a radius of ~10kpc in high mass galaxies than in low mass galaxies.
1209.5058
Baryon census in hydrodynamical simulations of galaxy clusters
Planelles, Borgani, Dolag, Ettori, Fabjan, Murante, Tornatore
Cosmological SPH hydro sims of galaxy clusters and groups, study the total baryon budget in clusters, and how this budget is shared between the hot diffuse component and the stellar component. TreePM+SPH GADGET-3 code: (1) non-radiative, (2) radiative cooling, SF and SN feedback included (3) (2) with feedback from AGN. Aims: implication of stellar and hot gas content on the relative role played by SN and AGN feedback, and calibration of cluster baryon fraction and its evolution as a cosmological tool. Both radiative simulation predict a trend of stellar mass fraction with cluster mass that tends to be weaker in the observed one. Predicts a trend of stellar mass fraction with cluster mass that tends to be weaker than the observed one. Include effect of AGN feedback alleviates this tension, and predicts values of the hot gas mass fraction and total baryon fraction to be in closer agreement with observation. Compute baryon content and cosmic baryon fraction Y_b as a function of cluster-centric radius and z; at R500 in massive clusters M200>2e14 Msun/h, Y_b is nearly independent of physical processes included, and characterized by a negligible redshift evolution: Y_b,500 = 0.85 with the error accounting for the intrinsic scatter in the simulations. At R2500 < R500, typical value of Y_b slightly decreases, depending on the physics included in the simulations, while its scatter increases by a factor of 2.
1209.5391
A cold milky way stellar stream in the direction of triangulum
Bonaca, Geha, Kallivayalil
Evidence for new MW stellar tidal stream in the direction of M31 and M33 from SDSS DR8, stellar density maps probing MW halo at distances between 8 and 40 kpc. A visual search of these maps recovers all of the major known stellar streams towards M31/M33 ("Triangulum stream"), consistent wit being the tidal remnant of a globular cluster.
1209.5393
Major galaxy mergers only trigger the most luminous AGN
Treister, Schawinski, Urry, Simmons
Find strong, z-independent correlation between AGN luminosity and the fraction of host galaxies undergoing a major merger. Only the most luminous AGN phases are connected to major mergers, while less luminous AGN appear to be driven by secular processes. Combining this trend with AGN luminosity functions to assess the overall cosmic growth of black holes, find that ~50% by mass is associated with major mergers, while 10% of AGN by number, the most luminous, are connected to the violent events.
1209.5394
A baryonic solution to the missing satellites problem
Brooks, Kuhlen, Zolotov, Hooper
Number of massive subhaloes dramatically reduced when considering baryonic physics (flattening of DM profile cusp in the luminous subhaloes around MW-mass galaxies). Subhaloes likely to be destroyed by stripping, and likely to have SF suppressed by photo-heating. Baryonic processes have the potential to solve the missing satellites problem.
1209.5659
The challenge of the largest structures in the universe to cosmology
Park, Choi, Kim, Gott, Kim, Kim
Sloan great wall casts doubt on the concordance cosmological model (LCDM). Show that the wall is consistent with LCDM, shown with very large simulation (Horizon run 2). A structure even 2x larger possible in future 3 mag deeper surveys than SDSS.
1209.5675
Measuring the mass distribution in galaxy clusters
Geller, Diaferio, Serra
Only 2 methods, GL and caustic technique, are independent of the assumption of dynamicla equilibrium. Extended mass profile at radii beyond the virial radius possible. For 19 clusters, compare the mass profile based on the caustic technique with WL measurements from literature (test of systematics). At virial radius, agreement to 30%, consistent with errors. At small radii, caustic technique overestimates the mass from numerical simulations. WL profiles are a good representation of the true mass profile. At radii larger than the virial radius, the lensing mass profile exceeds the caustic mass profile possibly as a result of contamination of the lensing profile by large-scale structures within the lensing kernel.
1209.4900
The Effect of fluctuations on the Helium-ionizing background
Davies, Furlanetto
Don't assume uniform radiation field, but consider the discrete nature of the (rare) bright quasars that dominate the background, in He II Ly-a absorption spectra after He II reionization. Cosmological radiative transfer model includes: recent constraints on ionizing spectra and luminosity function of quasars and the distribution of IGM absorbers; effects of fluctuations on the evolving continuum opacity of IGM. Results: He II ionizing background evolves rapidly with redshift, increasing by >3.5 from z=3.5 to 2.5. Rapid evolution in mean He II Ly-a optical depth, without appealing to the reionization of He II. ...
1209.4903
Galactic outflows in absorption and emission: near-UV spectroscopy of galaxies at 1<z<2
Erb, Quider, Henry, Martin
Study large-scale outflows in 96 SF galaxies at 1<z<2 with NUV spectroscopy of FeII and MgII absorption and emission. Average blueshift of FeII interstellar absorption lines wrt systemic velocity is -85 km/s at z~1.5, a decrease of 2x from the average blueshift measured for FUV absorption lines seen in galaxies at z~2. Profiles of MgII show much more variety than the FeII profiles, which are always seen in absorption; MgII ranges from strong emission to pure absorption, with emission more common in galaxies with blue UV slopes and at lower stellar masses. Outfow velocities increase with increasing stellar mass with 2-3 sigma significance, in agreement with previous results. Find structure emission from FeII*, find several lines of evidence in support of the model in which this emission is generated by the re-emission of continuum photons absorbed in the FeII resonance transitions in outflowing gas. Photoionization models indicate that MgII emission arises from the resonant scattering of photons produced in HII regions, accounting for the differing profiles of the MgII and FeII lines. Comparison of FeII absorption and FeII* emission indicates that massive galaxies have more extended outflows and/or greater extinction, while 2d composite spectra indicate that emission from the outflow is stronger at a radius of ~10kpc in high mass galaxies than in low mass galaxies.
1209.5058
Baryon census in hydrodynamical simulations of galaxy clusters
Planelles, Borgani, Dolag, Ettori, Fabjan, Murante, Tornatore
Cosmological SPH hydro sims of galaxy clusters and groups, study the total baryon budget in clusters, and how this budget is shared between the hot diffuse component and the stellar component. TreePM+SPH GADGET-3 code: (1) non-radiative, (2) radiative cooling, SF and SN feedback included (3) (2) with feedback from AGN. Aims: implication of stellar and hot gas content on the relative role played by SN and AGN feedback, and calibration of cluster baryon fraction and its evolution as a cosmological tool. Both radiative simulation predict a trend of stellar mass fraction with cluster mass that tends to be weaker in the observed one. Predicts a trend of stellar mass fraction with cluster mass that tends to be weaker than the observed one. Include effect of AGN feedback alleviates this tension, and predicts values of the hot gas mass fraction and total baryon fraction to be in closer agreement with observation. Compute baryon content and cosmic baryon fraction Y_b as a function of cluster-centric radius and z; at R500 in massive clusters M200>2e14 Msun/h, Y_b is nearly independent of physical processes included, and characterized by a negligible redshift evolution: Y_b,500 = 0.85 with the error accounting for the intrinsic scatter in the simulations. At R2500 < R500, typical value of Y_b slightly decreases, depending on the physics included in the simulations, while its scatter increases by a factor of 2.
1209.5391
A cold milky way stellar stream in the direction of triangulum
Bonaca, Geha, Kallivayalil
Evidence for new MW stellar tidal stream in the direction of M31 and M33 from SDSS DR8, stellar density maps probing MW halo at distances between 8 and 40 kpc. A visual search of these maps recovers all of the major known stellar streams towards M31/M33 ("Triangulum stream"), consistent wit being the tidal remnant of a globular cluster.
1209.5393
Major galaxy mergers only trigger the most luminous AGN
Treister, Schawinski, Urry, Simmons
Find strong, z-independent correlation between AGN luminosity and the fraction of host galaxies undergoing a major merger. Only the most luminous AGN phases are connected to major mergers, while less luminous AGN appear to be driven by secular processes. Combining this trend with AGN luminosity functions to assess the overall cosmic growth of black holes, find that ~50% by mass is associated with major mergers, while 10% of AGN by number, the most luminous, are connected to the violent events.
1209.5394
A baryonic solution to the missing satellites problem
Brooks, Kuhlen, Zolotov, Hooper
Number of massive subhaloes dramatically reduced when considering baryonic physics (flattening of DM profile cusp in the luminous subhaloes around MW-mass galaxies). Subhaloes likely to be destroyed by stripping, and likely to have SF suppressed by photo-heating. Baryonic processes have the potential to solve the missing satellites problem.
1209.5659
The challenge of the largest structures in the universe to cosmology
Park, Choi, Kim, Gott, Kim, Kim
Sloan great wall casts doubt on the concordance cosmological model (LCDM). Show that the wall is consistent with LCDM, shown with very large simulation (Horizon run 2). A structure even 2x larger possible in future 3 mag deeper surveys than SDSS.
1209.5675
Measuring the mass distribution in galaxy clusters
Geller, Diaferio, Serra
Only 2 methods, GL and caustic technique, are independent of the assumption of dynamicla equilibrium. Extended mass profile at radii beyond the virial radius possible. For 19 clusters, compare the mass profile based on the caustic technique with WL measurements from literature (test of systematics). At virial radius, agreement to 30%, consistent with errors. At small radii, caustic technique overestimates the mass from numerical simulations. WL profiles are a good representation of the true mass profile. At radii larger than the virial radius, the lensing mass profile exceeds the caustic mass profile possibly as a result of contamination of the lensing profile by large-scale structures within the lensing kernel.
Monday, September 24, 2012
Day 304
Monday.
1209.4636
The unbiased measurement of UV spectral slopes in low luminosity galaxies at z=7
Rogers, McLure, Dunlop
UV continuum slope beta at z=7 in HST WFC3/IR bans via the J-H color, is a useful indicator of the age, metallicity, and dust content of high-z stellar populations. Redward evolution of beta with cosmic time from z=7 to 4 can be explained by a build up of dust. Use source recovery simulations to address how to best measure the UV slope of z=7 galaxies. Source detection, selection and color measurement each biased the previous measurements of beta; find robust method for measuring beta in the simulations, then remeasure the UV slopes. Sample appears consistent with an intrinsic distribution of normal star-forming galaxies with beta=-2, but need further imaging from HUDF12. Additional F140W filter would help.
1209.4639
Radio mini-halo emission from cosmic rays in galaxy clusters and heating of the cool cores
Fujita, Ohira
Proposed: cool cores of galaxy clusters are stably heated by cosmic rays (CRs); then radio mini haloes (often found in the central regions of cool core clusters) may be attributed to the synchrotron emission from the CRs. Investigate radial profiles of mini-haloes; confirm that radiative cooling of ICM is balanced with the heating by CR streaming. Streaming velocity of CRs is the sound velocity of the ICM; heating is even more stable that the case where the streaming velocity is the Alfven velocity. Assume cooling / heating equilibrium, estimate radial profiles of CR pressure in 6 clusters from x-ray observations only. Compare prediction to observed. Since CR protons interact with ICM protons, can predict the radial profiles of the resultant synchrotron radiation. Compare the predictions with the observed radial profiles of the mini-haloes in the six clusters and find that they are consistent if the momentum spectra of the CRs are steep. These results may indicate that the cores are actually being heated by the CRs. Also predict broad-band spectra of the 6 clusters, and show that non-thermal fluxes from the clusters are small in hard x-ray and gamma-ray bands.
1209.4643
Subary weak-lensing measurement of a z=0.81 cluster discovered by the Atacama cosmology telescope survey
Miyatake, .. Takada, et al
High-z SZ cluster from ACT, measured in WL. Use GL model-fitting method (PSF effects removed). Astrometric distortion effects accounted for. BG gal selection: use photo-z from BrizY (PSF matching/homogenization). S/N ~ 3.7. Fit NFW model to shear profile, find M200 (rho-bar_m) = 7.5e14 Msun/h. Consistent with SZ mass estimates, assuming hydrostatic equilibrium and virial theorem; scaling relation between SZ signal and mass derived from WL, X-ray and velocity dispersion, within measurement errors. Existence of this cluster consistent with cluster abundance prediction of LCDM model.
1209.4661
The extragalactic background light and the gamma-ray opacity of the universe
Dwek, Krennrich
Extragalactic background light (EBL) plays a crucial role in cosmological tests (resolved, unresolved, and truly diffuse background) for the formation and evolution of stellar objects and galaxies, and for setting limits on exotic energy releases in the universe. EBL also plays an important role in the propagation of very high energy gamma-rays which are attenuated en rout to z=0 by pair producing gamma-gamma interactions with the EBL and CMB. EBL affects the spectrum of the sources (predominantly blazars) in the 10GeV to 10 TeV range. Knowledge of the EBL intensity and spectrum will sllow the determination of the intrinsic blazar spectrum in a crucial energy regime that can be used to test particle acceleration mechanisms and VHE gamma-ray production models. Conversely, knowledge of the intrinsic gamma-ray spectrum and the detection of blazars at increasingly higher z will set strong limits on the EBL and its evolution. Review of EBL determination and its impact on the current understanding of the origin and production mechanisms of gamma-rays in blazers, and on energy releases in the universe. Summary and future directions in Cherenkov Telescope Array techniques.
1209.4676
A massive bubble of extremely metal poor gas around a collapsing Ly-alpha blob at z=2.54
Humphrey et al
Gaseous environment of the radio-loud quasar at z=2.54, associated with a large Ly-alpha nebula, and a spatially extended Ly-alpha-absorbing structure. Measure kinematic properties consistent with infall rate of 10/100 M./yr for the nebula, at radius >40 kpc from the quasar. Absorption in NV, CIV, SiIV with no unambiguous detection of absorption lines from any low-ionization species of metal. Absorbing gas predominantly ionized by the quasar. Scenario involving SB-driven super-bubbles, and creation of infalling filaments?
1209.4688
The first stars
Whalen
[invited review talk] PopIII stars unlikely to be detected in the very near future; properties remain unknown. Detect by (1) their SNe (2) reconciling their nucleosynthetic yields to the chemical abundances measured in ancient metal-poor stars in the galactic halo. Problem in simulation of PopIII stars, discuss the best prospects for constraining their properties observationally in the near term.
1209.4762
The effect of peculiar velocities on the epoch of reionization (EoR) 21-cm signal
Majumdar, Bharadwaj, Choudhury
Semi-numerical simulations of reionization to study the behaviour of power spectrum of EoR 21-cm signal in both real and z-space. Consider 2 models of reionization (homogeneous recombination (HR) and the other incorporating inhomogeneous recombination (IR)). Predictions of both are similar in large scales. Qualitative interpret the behaviour of both the real space and z space power spectra at large scales in terms of x_HI and the ratio P_xx/P_delta,delta.
1209.4783
Near-pristine gas at high redshifts: a window on early nucleosynthesis
Pettini, Cooke
A recently complete survey of the most metal-poor DLAs. Clarified a number of lingering issues concerning the abundances of C, N, O in the low metallicity regime, revealed the existence of DLA analogues to Carbon-enhanced metal-poor stars, and provides some of the most precise measures of the primordial abundance of Deuterium.
1209.4636
The unbiased measurement of UV spectral slopes in low luminosity galaxies at z=7
Rogers, McLure, Dunlop
UV continuum slope beta at z=7 in HST WFC3/IR bans via the J-H color, is a useful indicator of the age, metallicity, and dust content of high-z stellar populations. Redward evolution of beta with cosmic time from z=7 to 4 can be explained by a build up of dust. Use source recovery simulations to address how to best measure the UV slope of z=7 galaxies. Source detection, selection and color measurement each biased the previous measurements of beta; find robust method for measuring beta in the simulations, then remeasure the UV slopes. Sample appears consistent with an intrinsic distribution of normal star-forming galaxies with beta=-2, but need further imaging from HUDF12. Additional F140W filter would help.
1209.4639
Radio mini-halo emission from cosmic rays in galaxy clusters and heating of the cool cores
Fujita, Ohira
Proposed: cool cores of galaxy clusters are stably heated by cosmic rays (CRs); then radio mini haloes (often found in the central regions of cool core clusters) may be attributed to the synchrotron emission from the CRs. Investigate radial profiles of mini-haloes; confirm that radiative cooling of ICM is balanced with the heating by CR streaming. Streaming velocity of CRs is the sound velocity of the ICM; heating is even more stable that the case where the streaming velocity is the Alfven velocity. Assume cooling / heating equilibrium, estimate radial profiles of CR pressure in 6 clusters from x-ray observations only. Compare prediction to observed. Since CR protons interact with ICM protons, can predict the radial profiles of the resultant synchrotron radiation. Compare the predictions with the observed radial profiles of the mini-haloes in the six clusters and find that they are consistent if the momentum spectra of the CRs are steep. These results may indicate that the cores are actually being heated by the CRs. Also predict broad-band spectra of the 6 clusters, and show that non-thermal fluxes from the clusters are small in hard x-ray and gamma-ray bands.
1209.4643
Subary weak-lensing measurement of a z=0.81 cluster discovered by the Atacama cosmology telescope survey
Miyatake, .. Takada, et al
High-z SZ cluster from ACT, measured in WL. Use GL model-fitting method (PSF effects removed). Astrometric distortion effects accounted for. BG gal selection: use photo-z from BrizY (PSF matching/homogenization). S/N ~ 3.7. Fit NFW model to shear profile, find M200 (rho-bar_m) = 7.5e14 Msun/h. Consistent with SZ mass estimates, assuming hydrostatic equilibrium and virial theorem; scaling relation between SZ signal and mass derived from WL, X-ray and velocity dispersion, within measurement errors. Existence of this cluster consistent with cluster abundance prediction of LCDM model.
1209.4661
The extragalactic background light and the gamma-ray opacity of the universe
Dwek, Krennrich
Extragalactic background light (EBL) plays a crucial role in cosmological tests (resolved, unresolved, and truly diffuse background) for the formation and evolution of stellar objects and galaxies, and for setting limits on exotic energy releases in the universe. EBL also plays an important role in the propagation of very high energy gamma-rays which are attenuated en rout to z=0 by pair producing gamma-gamma interactions with the EBL and CMB. EBL affects the spectrum of the sources (predominantly blazars) in the 10GeV to 10 TeV range. Knowledge of the EBL intensity and spectrum will sllow the determination of the intrinsic blazar spectrum in a crucial energy regime that can be used to test particle acceleration mechanisms and VHE gamma-ray production models. Conversely, knowledge of the intrinsic gamma-ray spectrum and the detection of blazars at increasingly higher z will set strong limits on the EBL and its evolution. Review of EBL determination and its impact on the current understanding of the origin and production mechanisms of gamma-rays in blazers, and on energy releases in the universe. Summary and future directions in Cherenkov Telescope Array techniques.
1209.4676
A massive bubble of extremely metal poor gas around a collapsing Ly-alpha blob at z=2.54
Humphrey et al
Gaseous environment of the radio-loud quasar at z=2.54, associated with a large Ly-alpha nebula, and a spatially extended Ly-alpha-absorbing structure. Measure kinematic properties consistent with infall rate of 10/100 M./yr for the nebula, at radius >40 kpc from the quasar. Absorption in NV, CIV, SiIV with no unambiguous detection of absorption lines from any low-ionization species of metal. Absorbing gas predominantly ionized by the quasar. Scenario involving SB-driven super-bubbles, and creation of infalling filaments?
1209.4688
The first stars
Whalen
[invited review talk] PopIII stars unlikely to be detected in the very near future; properties remain unknown. Detect by (1) their SNe (2) reconciling their nucleosynthetic yields to the chemical abundances measured in ancient metal-poor stars in the galactic halo. Problem in simulation of PopIII stars, discuss the best prospects for constraining their properties observationally in the near term.
1209.4762
The effect of peculiar velocities on the epoch of reionization (EoR) 21-cm signal
Majumdar, Bharadwaj, Choudhury
Semi-numerical simulations of reionization to study the behaviour of power spectrum of EoR 21-cm signal in both real and z-space. Consider 2 models of reionization (homogeneous recombination (HR) and the other incorporating inhomogeneous recombination (IR)). Predictions of both are similar in large scales. Qualitative interpret the behaviour of both the real space and z space power spectra at large scales in terms of x_HI and the ratio P_xx/P_delta,delta.
1209.4783
Near-pristine gas at high redshifts: a window on early nucleosynthesis
Pettini, Cooke
A recently complete survey of the most metal-poor DLAs. Clarified a number of lingering issues concerning the abundances of C, N, O in the low metallicity regime, revealed the existence of DLA analogues to Carbon-enhanced metal-poor stars, and provides some of the most precise measures of the primordial abundance of Deuterium.
Saturday, September 22, 2012
Day 303
Friday. And Saturday.
1209.4351
The SLUGGS survey: kinematics for over 2500 globular clusters in twelve early-type galaxies
Pota et al
Spectro--photometric survey of 2522 extragalactic GCs (globular clusters) around 12 early-type galaxies. Average of 160 GC radial velocities per galaxy with precision of 15 km/s per GC. Focus on the kinematics of metal-poor (blue) and metal-rich (red) GC systems (spatial and color distributions); focus on the kinematics of metal-poor and metal-rich subpopualations to ~8 effective radii from the galaxy center. Results: kinematics of red GC subpopulation strongly coupled with host galaxy stellar kinematics. Blue subpop dominated by random motions, especially in the outer regions, decoupled from the red GCs. Peculiar GC kinematic profiles seen in some galaxies; rotation-supported motion in a lenticular gal, or rotation around minor axis of blue GCs. GC kinematics are coupled with the host galaxy properties; velocity kurtosis and the slope of their velocity dispersion profiles is different between the 2 GC subpopulations in more massive galaxies.
1209.4353
A catalog of extended clusters and ultra-compact dwarf galaxies - An analysis of their parameters in early- and late-type galaxies
Bruens, Kroupa
Extended (>10pc) stellar clusters comparable to globular clusters in mass are called "extended clusters" (ECs), while objects with masses in the dwarf galaxy regime are called ultra-compact dwarf galaxies. Analyse observational parameters (luminosity, effective radius, and projected distance to the host galaxy) of all known ECs and UCDs. No clear distinction between ECs and UCDs: name them together as "extended stellar objects" (EOs). 813 EO, or which 171/642 are associated with late/early type galaxies, respectively. Most cover a luminosity range of MV=-4 to -14 mag. Vast majority of EOs < -10 mag are associated with ellipticals. The more luminous the EO, the large is its upper size limit. Luminosity functions peak at -6.4 mag (similar for early and late-related EOs), which is about one magnitude fainter than the peak of the GC luminosity function. EOs and GCs form a coherent structure in the r_eff vs. MV parameter space, while there is a clear gap between EOs and early type dwarf galaxies. Potential overlap with dwarf galaxies at high mass end. Compare EO sample with numerical models, conclude that parameters of EO sample can be well explained by star cluster origin (results of merged cluster complexes).
1209.4357
Cores and kinematics of early-types galaxies
Lauer
In early type galaxies, find that "core galaxies" rotate slowly, while "power-law galaxies" rotate rapidly (core existence based on HST classification, from ATLAS3D rotation measures); results from Faber+ confirmed. Amplitude of rotation sharply discriminates between the two types in the -19>Mv>-22 domain. Slow rotation: small set of core galaxies with Mv>-20 in concordance with more massive core galaxies... both rotation and central structure of early-type galaxies should be used together to separate systems that appear to have formed from "wet" versus "dry" mergers.
1209.4371
Implications and applications of kinematic galaxy scaling relations
Zaritsky
[Spotlight review] Galaxy scaling relations: connection between ostensibly unrelated physical characteristics of galaxies, testifies to an underlying order of galaxy formation. Review development of scaling relation that (1) unites the well-known Fundamental Plane (FP) relation of giant elliptical galaxies and Tully Fisher (TF) relation of disk galaxies, (2) Fits low mass spheroidal galaxies, including the ultra-faint satellites of our Galaxy, (3) explains the apparent shift of lenticular (S0) galaxies relative to both FP or TF, (4) describes all stellar dynamical systems, including systems with no dark matter (stellar clusters) (5) associates the numerical coefficients that account for the "tilt" of the FP away from the direct expectation drawn from virial theorem with systematic variations in the M/L ratio, (6) connects with independent results that demonstrate the robustness of mass estimators when applied at the half-light radius, and (7) results in smaller scatter for disk galaxies than the TF relation. The relation develops naturally from the virial theorem, but implies the existence of additional galaxy formation physics that must now be a focus of galaxy formation studies. Relation can be used to measure distances and galaxy masses. 2 applications: (1) cross-calibration of distance measurement methods, and (2) the determination of mass-to-light ratios of simple stellar populations as a function of age; implication for stellar initial mass function.
1209.4381
Modeling the onset of photosynthesis after the Chicxulub asteroid impact
Perez, Cardenas, Martin, Rojas
The great resilience of the unicellular biosphere against huge environmental perturbations.
1209.4434
Three-dimensional filamentation analysis of SDSS DR5 survey
Wu, Batuski, Khalil
New way to calculate the multi-scale 3d filamentation of SDSS galaxy clusters, and also to N-body sims. Compare mock to observation on 8-30 Mpc scales. SDSS has large filamentation at 10 Mpc scale, not found from either mock samples or random samples.
1209.4518
Superbubble bynamics in globular cluster infancy I. How do globular clusters first lose their cold gas?
Krause, et al
Early evolution of globular clusters: current scenarios require at least 2 generations of stars of which the first generation (1G) has been much more massive than the currently predominating 2G. Fast gas expulsion is thought to unbind the majority of the 1G stars. Gas expulsion also mandatory to remove metal-enriched supernova ejecta, which are not found in the 2G stars. Previously SN assumed to be the agent of gas expulsion; here, assume that gas expulsion happens via the formation of a super bubble [what causes the super-bubble???], and describe the kinematics by a thin-shell model. SNe driven shells are destroyed by RT instability before they reach escape speed for all but perhaps the least massive and most extended clusters. More power is required to expel the gas, which might plausibly be provided by a coherent onset of accretion onto the stellar remnants. The resulting kpc-sized bubbles might be observable in Faraday rotation maps with the planned SKA.
1209.4562
Is the 130 GeV line real? A search for systematics in the Fermi-LAT data
FInkbeinder, Su, Weniger
Galactic center feature at approximately 130 GeV: a discovery. This requires additional data, but a thorough investigation of LAT systematics. Any suspicious trends indicating spurious signal? Consider several hypothesis that might cause such artifact, find them all implausible. Search for instrumental signature in the Earth limb photons, which provide a smooth reference spectrum for null tests. Find no significant 130 GeV feature in Earth limb sample, but marginally significant 130 GeV feature with a limited range of detector incidence angles. Raises concerns about the 130 GeV galactic center feature, even though no plausible model of instrumental behavior that connects the two. Requires additional limb data; if the limb feature persists, can raise doubts about the Pass 7 processing of E>100 GeV events. At present, no instrumental systematics found that could plausible explain the excess Galactic center emission at 130 GeV.
1209.4548
Fermi-LAT gamma-ray signal from Earth limb, systematic detector effects and their implications for the 130 GeV gamma-ray excess
Hektor, Raidal, Tempel
Find no new statistically significant signal 130 GeV signal from nearby brightest galaxies, AGNs, unassociated sources, H clouds and Earth limb; known sources for Galactic center and nearby galaxy clusters. Put effort into studying Earth limb photons; in agreement with PAMELA measurement, confirming the physical origin of Limb gamma-rays. Small photon incidence angle from Earth Limb can have spurious signal (including 130 GeV), but the BG has large uncertainties in this case. Can be (likely) statistical fluctuations.
1209.4596
The large-scale cross-correlation of damped Lyman alpha systems with the Lyman alpha forest: first measurements from BOSS
Font-Ribera (Andreu), Miralda-Escude, Lee (Khee-Gan), Ross, Schneider, White, York
First measurement of large-scale cross-correlation of Lyman slpha forest absorption and Damped Lyman alpha systems (DLA), using SDSS DR9 (BOSS). X-corr detected up to scales of 40 Mpc/h, and is well fitter by linear theory prediction of standard CDM of structure formation with the expected redshiftdistortions, confirming its origin in the gravitational evolution of structure. Amplitude of DLA-Lyman alpha cross-correlation depends on only one free parameter, the bias factor of the DLA systems, once the Lyman alpha forest bias factors are known from independent Lyman alpha forest correlation measurements. Measure the DLA bias factor to be b_D=2.17 beta_F^0.22, where the Lyman alpha forest redshift distortion parameter beta_F is expected to be above unity. This bias factor implies a typical host halo mass for DLAs that is much larger than expected in present DLA models, and is reproduced if the DLA cross section scales with halo mass as M_h^alpha, which alpha=1.1 for beta_F=1. Matching the observed DLA bias factor and rate of incidence requires that atomic gas remains extended in massive haloes over larger areas than predicted in present simulations of galaxy formation, with typical DLA proper sizes larger than 20 kpc in host haloes of masses ~ 1e12 solar masses. Infer that typical galaxies at z~2 to 3 are surrounded by systems of atomic clouds that are much more extended than the luminous parts of galaxies and contain ~10% of the baryons in the host halo.
1209.4351
The SLUGGS survey: kinematics for over 2500 globular clusters in twelve early-type galaxies
Pota et al
Spectro--photometric survey of 2522 extragalactic GCs (globular clusters) around 12 early-type galaxies. Average of 160 GC radial velocities per galaxy with precision of 15 km/s per GC. Focus on the kinematics of metal-poor (blue) and metal-rich (red) GC systems (spatial and color distributions); focus on the kinematics of metal-poor and metal-rich subpopualations to ~8 effective radii from the galaxy center. Results: kinematics of red GC subpopulation strongly coupled with host galaxy stellar kinematics. Blue subpop dominated by random motions, especially in the outer regions, decoupled from the red GCs. Peculiar GC kinematic profiles seen in some galaxies; rotation-supported motion in a lenticular gal, or rotation around minor axis of blue GCs. GC kinematics are coupled with the host galaxy properties; velocity kurtosis and the slope of their velocity dispersion profiles is different between the 2 GC subpopulations in more massive galaxies.
1209.4353
A catalog of extended clusters and ultra-compact dwarf galaxies - An analysis of their parameters in early- and late-type galaxies
Bruens, Kroupa
Extended (>10pc) stellar clusters comparable to globular clusters in mass are called "extended clusters" (ECs), while objects with masses in the dwarf galaxy regime are called ultra-compact dwarf galaxies. Analyse observational parameters (luminosity, effective radius, and projected distance to the host galaxy) of all known ECs and UCDs. No clear distinction between ECs and UCDs: name them together as "extended stellar objects" (EOs). 813 EO, or which 171/642 are associated with late/early type galaxies, respectively. Most cover a luminosity range of MV=-4 to -14 mag. Vast majority of EOs < -10 mag are associated with ellipticals. The more luminous the EO, the large is its upper size limit. Luminosity functions peak at -6.4 mag (similar for early and late-related EOs), which is about one magnitude fainter than the peak of the GC luminosity function. EOs and GCs form a coherent structure in the r_eff vs. MV parameter space, while there is a clear gap between EOs and early type dwarf galaxies. Potential overlap with dwarf galaxies at high mass end. Compare EO sample with numerical models, conclude that parameters of EO sample can be well explained by star cluster origin (results of merged cluster complexes).
1209.4357
Cores and kinematics of early-types galaxies
Lauer
In early type galaxies, find that "core galaxies" rotate slowly, while "power-law galaxies" rotate rapidly (core existence based on HST classification, from ATLAS3D rotation measures); results from Faber+ confirmed. Amplitude of rotation sharply discriminates between the two types in the -19>Mv>-22 domain. Slow rotation: small set of core galaxies with Mv>-20 in concordance with more massive core galaxies... both rotation and central structure of early-type galaxies should be used together to separate systems that appear to have formed from "wet" versus "dry" mergers.
1209.4371
Implications and applications of kinematic galaxy scaling relations
Zaritsky
[Spotlight review] Galaxy scaling relations: connection between ostensibly unrelated physical characteristics of galaxies, testifies to an underlying order of galaxy formation. Review development of scaling relation that (1) unites the well-known Fundamental Plane (FP) relation of giant elliptical galaxies and Tully Fisher (TF) relation of disk galaxies, (2) Fits low mass spheroidal galaxies, including the ultra-faint satellites of our Galaxy, (3) explains the apparent shift of lenticular (S0) galaxies relative to both FP or TF, (4) describes all stellar dynamical systems, including systems with no dark matter (stellar clusters) (5) associates the numerical coefficients that account for the "tilt" of the FP away from the direct expectation drawn from virial theorem with systematic variations in the M/L ratio, (6) connects with independent results that demonstrate the robustness of mass estimators when applied at the half-light radius, and (7) results in smaller scatter for disk galaxies than the TF relation. The relation develops naturally from the virial theorem, but implies the existence of additional galaxy formation physics that must now be a focus of galaxy formation studies. Relation can be used to measure distances and galaxy masses. 2 applications: (1) cross-calibration of distance measurement methods, and (2) the determination of mass-to-light ratios of simple stellar populations as a function of age; implication for stellar initial mass function.
1209.4381
Modeling the onset of photosynthesis after the Chicxulub asteroid impact
Perez, Cardenas, Martin, Rojas
The great resilience of the unicellular biosphere against huge environmental perturbations.
1209.4434
Three-dimensional filamentation analysis of SDSS DR5 survey
Wu, Batuski, Khalil
New way to calculate the multi-scale 3d filamentation of SDSS galaxy clusters, and also to N-body sims. Compare mock to observation on 8-30 Mpc scales. SDSS has large filamentation at 10 Mpc scale, not found from either mock samples or random samples.
1209.4518
Superbubble bynamics in globular cluster infancy I. How do globular clusters first lose their cold gas?
Krause, et al
Early evolution of globular clusters: current scenarios require at least 2 generations of stars of which the first generation (1G) has been much more massive than the currently predominating 2G. Fast gas expulsion is thought to unbind the majority of the 1G stars. Gas expulsion also mandatory to remove metal-enriched supernova ejecta, which are not found in the 2G stars. Previously SN assumed to be the agent of gas expulsion; here, assume that gas expulsion happens via the formation of a super bubble [what causes the super-bubble???], and describe the kinematics by a thin-shell model. SNe driven shells are destroyed by RT instability before they reach escape speed for all but perhaps the least massive and most extended clusters. More power is required to expel the gas, which might plausibly be provided by a coherent onset of accretion onto the stellar remnants. The resulting kpc-sized bubbles might be observable in Faraday rotation maps with the planned SKA.
1209.4562
Is the 130 GeV line real? A search for systematics in the Fermi-LAT data
FInkbeinder, Su, Weniger
Galactic center feature at approximately 130 GeV: a discovery. This requires additional data, but a thorough investigation of LAT systematics. Any suspicious trends indicating spurious signal? Consider several hypothesis that might cause such artifact, find them all implausible. Search for instrumental signature in the Earth limb photons, which provide a smooth reference spectrum for null tests. Find no significant 130 GeV feature in Earth limb sample, but marginally significant 130 GeV feature with a limited range of detector incidence angles. Raises concerns about the 130 GeV galactic center feature, even though no plausible model of instrumental behavior that connects the two. Requires additional limb data; if the limb feature persists, can raise doubts about the Pass 7 processing of E>100 GeV events. At present, no instrumental systematics found that could plausible explain the excess Galactic center emission at 130 GeV.
1209.4548
Fermi-LAT gamma-ray signal from Earth limb, systematic detector effects and their implications for the 130 GeV gamma-ray excess
Hektor, Raidal, Tempel
Find no new statistically significant signal 130 GeV signal from nearby brightest galaxies, AGNs, unassociated sources, H clouds and Earth limb; known sources for Galactic center and nearby galaxy clusters. Put effort into studying Earth limb photons; in agreement with PAMELA measurement, confirming the physical origin of Limb gamma-rays. Small photon incidence angle from Earth Limb can have spurious signal (including 130 GeV), but the BG has large uncertainties in this case. Can be (likely) statistical fluctuations.
1209.4596
The large-scale cross-correlation of damped Lyman alpha systems with the Lyman alpha forest: first measurements from BOSS
Font-Ribera (Andreu), Miralda-Escude, Lee (Khee-Gan), Ross, Schneider, White, York
First measurement of large-scale cross-correlation of Lyman slpha forest absorption and Damped Lyman alpha systems (DLA), using SDSS DR9 (BOSS). X-corr detected up to scales of 40 Mpc/h, and is well fitter by linear theory prediction of standard CDM of structure formation with the expected redshiftdistortions, confirming its origin in the gravitational evolution of structure. Amplitude of DLA-Lyman alpha cross-correlation depends on only one free parameter, the bias factor of the DLA systems, once the Lyman alpha forest bias factors are known from independent Lyman alpha forest correlation measurements. Measure the DLA bias factor to be b_D=2.17 beta_F^0.22, where the Lyman alpha forest redshift distortion parameter beta_F is expected to be above unity. This bias factor implies a typical host halo mass for DLAs that is much larger than expected in present DLA models, and is reproduced if the DLA cross section scales with halo mass as M_h^alpha, which alpha=1.1 for beta_F=1. Matching the observed DLA bias factor and rate of incidence requires that atomic gas remains extended in massive haloes over larger areas than predicted in present simulations of galaxy formation, with typical DLA proper sizes larger than 20 kpc in host haloes of masses ~ 1e12 solar masses. Infer that typical galaxies at z~2 to 3 are surrounded by systems of atomic clouds that are much more extended than the luminous parts of galaxies and contain ~10% of the baryons in the host halo.
Friday, September 21, 2012
Day 302
Thursday.
1209.4078
Testing the Copernican principle by constraining spatial homogeneity
Valkenburg, Marra, Clarkson
Include DE in the Copernical principle, current observations place reasonably tight constraints on possible late-time violations of the Copernican principle. Possible radial inhomogeneity marginalized over to obtain constraints of cosmological constant.
1209.4079
On the true shape of the upper end of the stellar initial mass function: the case of R136
Banerjee, Kroupa
IMF of star cluster near upper mass limit: determines the high mass stellar content, and hence the dynamics of the cluster. ... If ejection of massive stars is efficient, then the true IMF is more top-heavy than the observed one.
1209.4080
Warm-hot gas in groups and galaxies toward H2356-309
Williams, Mulchaey, Kollmeier
Three X-ray absorption line systems in the quasar spectra. Trace 1e5-7 K gas, Could be WHIM (the low-z "missing baryons") or linked to galaxies, groups, in filaments. Observations with spectroscopy show they all nominally lie within the virial radii of nearby galaxies and/or groups, and could arise in these virialized structures rather than (or in addition to) the WHIM. A fourth system doesn't seem to have a galaxy associated with it. Conclude that most X-ray absorbers are coincident with galaxy and/or group environments, though some could still trace the large-scale filamentary WHIM gas predicted by simulations.
Recent Suzaku X-ray measurements show gas mass fraction f_gas appear to be considerably larger than the cosmic mean at the virial radius R200, questioning the accuracy of the cosmological parameter estimations. Use a large suite of cosmological hydrodynamical simulations to study biases of f_gas. Compute mass profiles, find anisotropic gas and total mass distributions that imply an angular variance of f_gas at the level of 30%. This anisotropic distribution originates from the recent formation epoch of clusters, and from the strong internal baryon-to-dark-matter density bias.
1209.4084
Quenching star formation at intermediate redshifts: downsizing of the mass flux density in the green valley
Goncalves, Martin, Menendez-Delmestre, Wyder, Koekemoer
Clear bimodality indicates transition from blue to red must be a rapid process. Study >100 green valley galaxies at z~0.8, with DEIMOS spectroscopy. Infer SFH and measure stellar mass flux density transiting from blue to red when the universe was half its current age. Results indicate that the process happened more rapidly and for more massive galaxies in the past, suggesting a top-down scenario in which the massive end of the red sequence is forming first. Another aspect of downsizing: mass flux density moving towards smaller galaxies in recent times.
1209.4086
Evolutionary paths among different red galaxy types at 0.3<z<1.5 and the late buildup of massive E-S0's through major mergers
Report observational evidence of the existence of dominant evolutionary path among massive red galaxies at 0.6<z<1.5, consisting in the conversion of ire. disks into irr. spheroids, and of these ones into regular spheroids. This result implies that (1) massive red regular galaxies at low z derive from the irregular ones populating the red sequence at z~1.5, (2) progenitors of the bulk of present-day massive red regular galaxies have been blue disks that have migrated to the red sequence mostly through major mergers at 0.6<z<1.2, and (3) the formation of E-S0's that end up with M*>1e11Msun at z=0 through gas-rich major mergers has frozen since z~0.6. All these support that major mergers have played the dominant role in the definitive buildup of present-day E-S0's with M*>1e11 Msun at 0.6<z<1.2, in good agreement with hierarchical scenarios of galaxy formation.
1209.4097
Pulsations in short GRBs from black hole-neutron star mergers
Stone, Loeb, Berger
SGRBs: its origins? Observations suggest merger of binary compact object system, but unclear how to distinguish between binary neutron star progenitor and a black hole-neutron star progenitor. Quasi-periodic signal of jet precession as an observational signature of SGRBs originating in mixed binary systems, and quantify fraction of mixed binaries capable of producing SGRBs.
1209.4098
Colors of extreme exoEarth environments
Hegde, Kaltenegger
Explore potentially detectable surface features on rocky exoplanets and their connection to and importance as a habitat for extremophiles. Look for clear atmospheres on rocky planets.
1209.4141
The history of star formation in galaxies
Brown, Postman, Calzetti
NASA white paper. How and when galaxies assemble their stellar populations? How does this assembly vary with environment? It's hierarchical, but insight of assembly comes from trying to reconstruct the galaxy's SFH, chemical evolution, and kinematics. Need multi-band photometry that reach Lsun MS stars. HST can obtain such data for local group galaxies.
1209.4143
THe impacts of ultraviolet radiation feedback on galaxies during the epoch of reoinisation
Hasegawa, Semelin
During EoR, in simulations find that SF is significantly suppressed due to internal UV and SN feedback. In low mass galaxies with M<1e9 Msun, a large amount of gas is evacuated by photo-evaporation, results in the suppression of SF. SF in massive haloes also strongly suppressed despite the fact that these haloes hardly lose any gas---mainly caused by (i) small scale clumpy structures are smoothed by internal feedback, and (ii) dense gas in the galaxies mostly neutral, but H2 formation and cooling disturbed by mild photo-heating. Consistent with observations at z=6-7.
1209.4305
Star-formation laws in extreme starbursts
Garcia-Burillo, Usero, Alonso-Herrero
SFE of dense molecular gas (from FIR/HCN ratio) is factor 3-4 higher in extreme starbursts compared to normal galaxies. Duality on the Kennicutt-Schmidt laws. ...
1209.4078
Testing the Copernican principle by constraining spatial homogeneity
Valkenburg, Marra, Clarkson
Include DE in the Copernical principle, current observations place reasonably tight constraints on possible late-time violations of the Copernican principle. Possible radial inhomogeneity marginalized over to obtain constraints of cosmological constant.
1209.4079
On the true shape of the upper end of the stellar initial mass function: the case of R136
Banerjee, Kroupa
IMF of star cluster near upper mass limit: determines the high mass stellar content, and hence the dynamics of the cluster. ... If ejection of massive stars is efficient, then the true IMF is more top-heavy than the observed one.
1209.4080
Warm-hot gas in groups and galaxies toward H2356-309
Williams, Mulchaey, Kollmeier
Three X-ray absorption line systems in the quasar spectra. Trace 1e5-7 K gas, Could be WHIM (the low-z "missing baryons") or linked to galaxies, groups, in filaments. Observations with spectroscopy show they all nominally lie within the virial radii of nearby galaxies and/or groups, and could arise in these virialized structures rather than (or in addition to) the WHIM. A fourth system doesn't seem to have a galaxy associated with it. Conclude that most X-ray absorbers are coincident with galaxy and/or group environments, though some could still trace the large-scale filamentary WHIM gas predicted by simulations.
Recent Suzaku X-ray measurements show gas mass fraction f_gas appear to be considerably larger than the cosmic mean at the virial radius R200, questioning the accuracy of the cosmological parameter estimations. Use a large suite of cosmological hydrodynamical simulations to study biases of f_gas. Compute mass profiles, find anisotropic gas and total mass distributions that imply an angular variance of f_gas at the level of 30%. This anisotropic distribution originates from the recent formation epoch of clusters, and from the strong internal baryon-to-dark-matter density bias.
1209.4084
Quenching star formation at intermediate redshifts: downsizing of the mass flux density in the green valley
Goncalves, Martin, Menendez-Delmestre, Wyder, Koekemoer
Clear bimodality indicates transition from blue to red must be a rapid process. Study >100 green valley galaxies at z~0.8, with DEIMOS spectroscopy. Infer SFH and measure stellar mass flux density transiting from blue to red when the universe was half its current age. Results indicate that the process happened more rapidly and for more massive galaxies in the past, suggesting a top-down scenario in which the massive end of the red sequence is forming first. Another aspect of downsizing: mass flux density moving towards smaller galaxies in recent times.
1209.4086
Evolutionary paths among different red galaxy types at 0.3<z<1.5 and the late buildup of massive E-S0's through major mergers
Report observational evidence of the existence of dominant evolutionary path among massive red galaxies at 0.6<z<1.5, consisting in the conversion of ire. disks into irr. spheroids, and of these ones into regular spheroids. This result implies that (1) massive red regular galaxies at low z derive from the irregular ones populating the red sequence at z~1.5, (2) progenitors of the bulk of present-day massive red regular galaxies have been blue disks that have migrated to the red sequence mostly through major mergers at 0.6<z<1.2, and (3) the formation of E-S0's that end up with M*>1e11Msun at z=0 through gas-rich major mergers has frozen since z~0.6. All these support that major mergers have played the dominant role in the definitive buildup of present-day E-S0's with M*>1e11 Msun at 0.6<z<1.2, in good agreement with hierarchical scenarios of galaxy formation.
1209.4097
Pulsations in short GRBs from black hole-neutron star mergers
Stone, Loeb, Berger
SGRBs: its origins? Observations suggest merger of binary compact object system, but unclear how to distinguish between binary neutron star progenitor and a black hole-neutron star progenitor. Quasi-periodic signal of jet precession as an observational signature of SGRBs originating in mixed binary systems, and quantify fraction of mixed binaries capable of producing SGRBs.
1209.4098
Colors of extreme exoEarth environments
Hegde, Kaltenegger
Explore potentially detectable surface features on rocky exoplanets and their connection to and importance as a habitat for extremophiles. Look for clear atmospheres on rocky planets.
1209.4141
The history of star formation in galaxies
Brown, Postman, Calzetti
NASA white paper. How and when galaxies assemble their stellar populations? How does this assembly vary with environment? It's hierarchical, but insight of assembly comes from trying to reconstruct the galaxy's SFH, chemical evolution, and kinematics. Need multi-band photometry that reach Lsun MS stars. HST can obtain such data for local group galaxies.
1209.4143
THe impacts of ultraviolet radiation feedback on galaxies during the epoch of reoinisation
Hasegawa, Semelin
During EoR, in simulations find that SF is significantly suppressed due to internal UV and SN feedback. In low mass galaxies with M<1e9 Msun, a large amount of gas is evacuated by photo-evaporation, results in the suppression of SF. SF in massive haloes also strongly suppressed despite the fact that these haloes hardly lose any gas---mainly caused by (i) small scale clumpy structures are smoothed by internal feedback, and (ii) dense gas in the galaxies mostly neutral, but H2 formation and cooling disturbed by mild photo-heating. Consistent with observations at z=6-7.
1209.4305
Star-formation laws in extreme starbursts
Garcia-Burillo, Usero, Alonso-Herrero
SFE of dense molecular gas (from FIR/HCN ratio) is factor 3-4 higher in extreme starbursts compared to normal galaxies. Duality on the Kennicutt-Schmidt laws. ...
Wednesday, September 19, 2012
Day 301
Wednesday.
1209.3770
Characterizing the otpical variability of bright blazers: variability-based selection of Fermi AGN
Ruan, ..., Ivezic, Kochanek, et al
Use of optical photometric variability to select and identify blazars in large-scale time-domain surveys, for identification of blazar counterparts to ~30% of the gamma-ray sources in Fermi. Use data from LINEAR astroid survey (optical). Impose cuts on minimum tau (characteristic timescales of variability) and sigma (driving amplitudes on short timescales) allows for blazar selection with high efficiency and completeness. Estimate tau for blazars is ~3 years in rest frame of jet, in contrast to ~320 day disk flux for quasars.
1209.3771
Perturbation theory approach for the power spectrum: from dark matter in real space to haloes in redshift space
Gil-Marin, Wagner, Verde, Porciani, Jiminez
Investigate the accuracy of Eularian perturbation theory for describing the matter and galaxy power spectra in real and redshift space. Compare analytical results with N-body sims (160 boxes of 13.8 (Gpc/h)^3): resumming terms in standard perturbative approach is accurate to <2% for k<0.2 h/Mpc at z<1.5. Higher order terms in the resummed propagator increases accuracy. If halo bias known, f can be recovered with in <5%.
1209.3775
Using machine learning for discovery in synoptic survey imaging
Brink, Richards, Poznanski, Bloom, Rice, ... et al
Using Palomar Transient Factory, 30k objects, demonstrate a missed detection rate of <7.7% and false-positive rate of 1% for an optimized ML classifier of 23 features, selected ot avlid feature correlation and over-fitting from an initial library of 42 attributes. ML enables maximum science gain for future synoptic survey, and enable fast follow-up decisions.
1209.3785
Hair of astrophysical black holes
Lyutikov
The "no hair" theorem is not applicable to black holes formed from collapse of a rotating neutron star; it can trap B-field lines before and during collapse. ...
1209.3786
Measuring the ultimate mass of galaxy clusters: redshifts and mass profiles from the Hectospec cluster survey (HeCS)
Rines, Geller, Diaferio, Kurtz
Measuring cluster mass profiles into the infall regions provide an estimate of the ultimate mass of cluster haloes. Use Caustic technique to meausre cluster mass profiles from galaxy redshifts from HeCS. 58 clusters at 0.1<z<0.3 surveyed based on X-ray flux; 21k redshifts measured, 10k are cluster members. Cluster members trace out infall patterns around clusters. Velocity dispersions decline with radius. Determination of the velocity dispersion is insensitive to the inclusion of blue members.
1209.3788
Evidence for two distinct stellar initial mass functions
Zaritsky, Colucci, Pessev, Bernstein, Chandar
Measurement of 20 local group stellar clusters. The young (age < 1e9.5 yr) clusters are well-described by a bottom-heavy IMF (Salpeter) while older clusters are better described by top-heavy IMF (light Kroupa), although neither of these specific forms is a unique solution. Sample is currently small, finding depends on 4 key clusters. Need more samples.
1209.3790
A new HSTHerschel deep field at the North ecliptic pole: prepareing the way for JWST, SPICA and Euclid
Serjeant et al
Propose a co-ordinated multi-observatory survey at NEP, an extragalactic deep field, covered by Planck, WISE, eROSITA, Herschel, HST, JWST, SPICA, Euclid, AKARI, LOVAR, SCUBA-2. Scans wavelengths of redshifted PAH and slilcate features. Need 10 sq arcmin in UV/optical, and a wide field survey of >100 sq arcmin coordinated with submm SPIRE. White paper submitted to HST.
1209.3805
The A2667 giant arc at z=1.03: evidence for large-scale shocks at high redshift
Yuan, Kewley, Swinbank, Richard
Intrinsic spatial resolution of 110-405 pc of the arc. Central 350 pc dominated with SF. Elevated [NII]/Halpha is contaminated by a significant fraction of shock excitation due to galactic outflows. Shocked regions may mimic flat or inverted metallicity gradients at high z.
1209.3825
The central density of R136 in 30 Doradus
Selman, Melnick
It's about 1.5e4 Msun/pc^3.
1209.3968
New approach to measure the quasar luminosity function in 0.7<z<4.0 from dedicated SDSS-III and MMT data
Palanque-Delabrouille et al
1877 quasar spectra at 0.68<z<4 from MMT, derive quasar LF. 30 qso/deg^2.
1209.4033
PeV neutrinos from the propagation of ultra-high energy cosmic rays
Roulet, Sigl, Vliet, Mollerach
As the title says. Found a PeV neutrino, assess if it's from HECR.
1209.3770
Characterizing the otpical variability of bright blazers: variability-based selection of Fermi AGN
Ruan, ..., Ivezic, Kochanek, et al
Use of optical photometric variability to select and identify blazars in large-scale time-domain surveys, for identification of blazar counterparts to ~30% of the gamma-ray sources in Fermi. Use data from LINEAR astroid survey (optical). Impose cuts on minimum tau (characteristic timescales of variability) and sigma (driving amplitudes on short timescales) allows for blazar selection with high efficiency and completeness. Estimate tau for blazars is ~3 years in rest frame of jet, in contrast to ~320 day disk flux for quasars.
1209.3771
Perturbation theory approach for the power spectrum: from dark matter in real space to haloes in redshift space
Gil-Marin, Wagner, Verde, Porciani, Jiminez
Investigate the accuracy of Eularian perturbation theory for describing the matter and galaxy power spectra in real and redshift space. Compare analytical results with N-body sims (160 boxes of 13.8 (Gpc/h)^3): resumming terms in standard perturbative approach is accurate to <2% for k<0.2 h/Mpc at z<1.5. Higher order terms in the resummed propagator increases accuracy. If halo bias known, f can be recovered with in <5%.
1209.3775
Using machine learning for discovery in synoptic survey imaging
Brink, Richards, Poznanski, Bloom, Rice, ... et al
Using Palomar Transient Factory, 30k objects, demonstrate a missed detection rate of <7.7% and false-positive rate of 1% for an optimized ML classifier of 23 features, selected ot avlid feature correlation and over-fitting from an initial library of 42 attributes. ML enables maximum science gain for future synoptic survey, and enable fast follow-up decisions.
1209.3785
Hair of astrophysical black holes
Lyutikov
The "no hair" theorem is not applicable to black holes formed from collapse of a rotating neutron star; it can trap B-field lines before and during collapse. ...
1209.3786
Measuring the ultimate mass of galaxy clusters: redshifts and mass profiles from the Hectospec cluster survey (HeCS)
Rines, Geller, Diaferio, Kurtz
Measuring cluster mass profiles into the infall regions provide an estimate of the ultimate mass of cluster haloes. Use Caustic technique to meausre cluster mass profiles from galaxy redshifts from HeCS. 58 clusters at 0.1<z<0.3 surveyed based on X-ray flux; 21k redshifts measured, 10k are cluster members. Cluster members trace out infall patterns around clusters. Velocity dispersions decline with radius. Determination of the velocity dispersion is insensitive to the inclusion of blue members.
1209.3788
Evidence for two distinct stellar initial mass functions
Zaritsky, Colucci, Pessev, Bernstein, Chandar
Measurement of 20 local group stellar clusters. The young (age < 1e9.5 yr) clusters are well-described by a bottom-heavy IMF (Salpeter) while older clusters are better described by top-heavy IMF (light Kroupa), although neither of these specific forms is a unique solution. Sample is currently small, finding depends on 4 key clusters. Need more samples.
1209.3790
A new HSTHerschel deep field at the North ecliptic pole: prepareing the way for JWST, SPICA and Euclid
Serjeant et al
Propose a co-ordinated multi-observatory survey at NEP, an extragalactic deep field, covered by Planck, WISE, eROSITA, Herschel, HST, JWST, SPICA, Euclid, AKARI, LOVAR, SCUBA-2. Scans wavelengths of redshifted PAH and slilcate features. Need 10 sq arcmin in UV/optical, and a wide field survey of >100 sq arcmin coordinated with submm SPIRE. White paper submitted to HST.
1209.3805
The A2667 giant arc at z=1.03: evidence for large-scale shocks at high redshift
Yuan, Kewley, Swinbank, Richard
Intrinsic spatial resolution of 110-405 pc of the arc. Central 350 pc dominated with SF. Elevated [NII]/Halpha is contaminated by a significant fraction of shock excitation due to galactic outflows. Shocked regions may mimic flat or inverted metallicity gradients at high z.
1209.3825
The central density of R136 in 30 Doradus
Selman, Melnick
It's about 1.5e4 Msun/pc^3.
1209.3968
New approach to measure the quasar luminosity function in 0.7<z<4.0 from dedicated SDSS-III and MMT data
Palanque-Delabrouille et al
1877 quasar spectra at 0.68<z<4 from MMT, derive quasar LF. 30 qso/deg^2.
1209.4033
PeV neutrinos from the propagation of ultra-high energy cosmic rays
Roulet, Sigl, Vliet, Mollerach
As the title says. Found a PeV neutrino, assess if it's from HECR.
Tuesday, September 18, 2012
Day 300
Tuesday.
1209.3305
Solving the cooling flow problem through mechanical AGN feedback
Gaspari, Brighenti, Ruszkowski
X-ray observation indicate AGN heating as the balancing counterpart of cooling. Argue: mechanical feedback (massive subrelativistic outflows) is key to solving the cooling flow problem (dramatically quenching the cooling rates for several Gyr without destroying the cool-core structure). Used 3d hydrocode FLASH: show AGN outflow can further reproduced buoyant bubbles, weak shocks, metal dredge-up and turbulence (fundamental observed features). Turbulence essential to drive NL thermal instabilities, causing the formation of extended cold gas, a residual of the quenched cooling flow and, later, fuel for the feedback engine. Compared to clusters, groups and galaxies require a gentler mechanical feedback, in order to avoid catastrophic overheating. Highlight the essential characteristics for a realistic AGN feedback, with emphasis on observational consistency.
1209.3306
A re-examination of galactic conformity and a comparison with semi-analytic models of galaxy formation
Kauffmann, Li, Zhang, Weinmann
Observed correlation between SF in central galaxies and in their neighbors ("galactic conformity") needs physical explanation. From SDSS DR7, local galaxies (z<0.03): conformity extends over a central galaxy stellar mass range spanning 2 orders of magnitude. In central galaxies with masses less than 1e10 Msun, conformity extends out to scales >4Mpc, well beyond the virial radii of their DM haloes. For low mass central galaxies, large-scale conformity with neighbours is only seen when the centrals have low SFR or gas content. At high stellar masses, conformity with neighbours applies in the gas-rich regime, clearly confined to scales comparable to virial radius of DM halo of the central galaxy. Mock catalogue from Guo+(2011) does not show conformity. Conformity between low-mass, gas-poor central galaxies and their distant neighbours cannot be explained within the framework of HOD models. Likely a signature of pre-heating of IGM gas at an earlier epoch [really?]. Smaller scale conformity between high-mass, gas-rich central galaxies and close neighbours may be a signature of ongoing gas accretion onto central galaxies in a minority of massive DM haloes.
1209.3039
Rhapsody: I. structural properties and formation history from a statistical sample of re-simulated cluster-size haloes
Wu, Hahn, Wechsler, Mao, Behroozi
Using 96 "zoom-in" simulations of DM haloes of 1e14.8 Msun/h selected from 1Gpc^3 volume, study properties of main haloes and how they are affected by formation history (back to z=12) over 5 decades in mass. Deviation from NFW/Einasto depend on formation time. Late-forming haloes tend to have considerable deviations from both models, partly due to massive sub haloes, while early-forming haloes deviate less, but still significantly, from NFW model, and are better described by Einasto. Find: halo shapes depend only moderately on formation time. Departure from spherical symmetry impacts the density profiles through the anisotropic distribution of massive subhaloes [the other way around?]. Further evidence of impact of subhaloes provided by analyzing the phase-space structure. A detailed analysis of the properties of the subhalo population in Rhapsody presented in another paper.
1209.3320
Project Lyman: quantifying 11 Gyrs of metagalactic ionizing background evolution
McCandliss et al
Timing and duration of reioinization epoch: the photon escape count from SF galaxies is used to "fine-tune" the timing and duration between 13.4 and 12.7 Gyrs ago (12<z<6). Direct observation of Lyman continuum (LyC) increasingly improbable at z>3 due to steady increase of intervening Lyman limit systems towards high z. Thus UV and U-band optical bandpasses provide the only hope for direct observations of the types of environment that favor LyC escape. Observation will provide crucial LyC escape fraction info. [white paper for NASA]
1209.3325
A fast flare and direct redshift constraint in far-UV spectra of the blazar S50716+714
Danforth et al
Constrain z from the flare (a first), consistent with host galaxy redshift.
1209.3339
Annual modulation of dark matter: a review
Freese, Lisanti, Savage
For standard assumptions, the count rate has a cosine dependence over time (maximum in June). Presence of substructure in galactic halo, interactions between dark and baryonic matter, can also be probed.
1209.3457
Seeing the first supernovae at the edge of the universe with JWST
Whalen, Fryer, Holz, ... et al
Masses of PopIII stars can be estimated from their SNe explosions. JWST and WFIRST will detect these explosions out to z~30 and 20, respectively.
1209.3473
The accuracy of the UV continuum as an indicator of the star formation rate in galaxies
Wilkins et al
The rest-frame UV luminosity often used as indicator of instantaneous SFR in a galaxy, but the precise value of calibration relating the UV luminosity to SFR is sensitive to various physical properties (e.g., recent SF and metal enrichment histories, choice of IMF). So a single calibration is not appropriate, based on the distribution of these properties. And that's what they find.
1209.3498
H{\alpha} and UV luminosities and star formation rates in a large sample of luminous compact galaxies
Parnovsky, Izotova, Izotov
Results of SFR study from GALEX observations in 800 LCGs. Global galaxy characteristics (Z, L, M*) are intermediate between nearby blue compact dwarf and high-z (z>2-3) Lyman break galaxies. SFRs corrected for interstellar extinction derived from SDSS spectra. SFR derived from FUV and NUV vary a wide range (0.18 to 113 Msun/yr), with median of 3.8 and 5.2 Msun/yr, respectively. Consider evolution of L with SB age, and introduce new characteristics (the luminosity of Ha, FUV and NUV) at zero SB age.
1209.3635
On the origin of elemental abundances in the terrestrial planets
Elser, Meyer, Moore
Combine circumstellar disk models, chemical equilibrium calculations, dynamical simulations of planet formation to study bulk composition of rocky planets. Condensation sequence modeled to estimate the initial abundance of solids in the disk; planetesimal growth also modeled. Calculate elemental abundances in the resulting planets. No model could reproduce the abundance properties of all planets. Choice of initial planetsimal disk mass and disk model has significant effect on composition gradients. Higher pressure and temperature in disk result in larger variations in the bulk chemical compositions. Massive planets and planets with small semi-major axis are more sensitive to these variations than smaller planets at larger radial distance. Only these large variations in the simulated abundances can potentially explain the diverse bulk composition of the SS planets. Mercury's bulk composition can not be reproduced in these models.
1209.3665
Gas fraction and star formation efficiency at z<1.0
Combes et al
Observation of 39 galaxies at 0.6<z<1.0 added to the full CO line survey in 0.2<z<1. Study the decline of SFR in this epoch. Find gas fraction in sample increases strongly with redshift, and is the most determining factor in the cosmic SF evolution. The SFE evolution is shallower; conlucde that it plays a less significant role in setting the cosmic SFE.
1209.3305
Solving the cooling flow problem through mechanical AGN feedback
Gaspari, Brighenti, Ruszkowski
X-ray observation indicate AGN heating as the balancing counterpart of cooling. Argue: mechanical feedback (massive subrelativistic outflows) is key to solving the cooling flow problem (dramatically quenching the cooling rates for several Gyr without destroying the cool-core structure). Used 3d hydrocode FLASH: show AGN outflow can further reproduced buoyant bubbles, weak shocks, metal dredge-up and turbulence (fundamental observed features). Turbulence essential to drive NL thermal instabilities, causing the formation of extended cold gas, a residual of the quenched cooling flow and, later, fuel for the feedback engine. Compared to clusters, groups and galaxies require a gentler mechanical feedback, in order to avoid catastrophic overheating. Highlight the essential characteristics for a realistic AGN feedback, with emphasis on observational consistency.
1209.3306
A re-examination of galactic conformity and a comparison with semi-analytic models of galaxy formation
Kauffmann, Li, Zhang, Weinmann
Observed correlation between SF in central galaxies and in their neighbors ("galactic conformity") needs physical explanation. From SDSS DR7, local galaxies (z<0.03): conformity extends over a central galaxy stellar mass range spanning 2 orders of magnitude. In central galaxies with masses less than 1e10 Msun, conformity extends out to scales >4Mpc, well beyond the virial radii of their DM haloes. For low mass central galaxies, large-scale conformity with neighbours is only seen when the centrals have low SFR or gas content. At high stellar masses, conformity with neighbours applies in the gas-rich regime, clearly confined to scales comparable to virial radius of DM halo of the central galaxy. Mock catalogue from Guo+(2011) does not show conformity. Conformity between low-mass, gas-poor central galaxies and their distant neighbours cannot be explained within the framework of HOD models. Likely a signature of pre-heating of IGM gas at an earlier epoch [really?]. Smaller scale conformity between high-mass, gas-rich central galaxies and close neighbours may be a signature of ongoing gas accretion onto central galaxies in a minority of massive DM haloes.
1209.3039
Rhapsody: I. structural properties and formation history from a statistical sample of re-simulated cluster-size haloes
Wu, Hahn, Wechsler, Mao, Behroozi
Using 96 "zoom-in" simulations of DM haloes of 1e14.8 Msun/h selected from 1Gpc^3 volume, study properties of main haloes and how they are affected by formation history (back to z=12) over 5 decades in mass. Deviation from NFW/Einasto depend on formation time. Late-forming haloes tend to have considerable deviations from both models, partly due to massive sub haloes, while early-forming haloes deviate less, but still significantly, from NFW model, and are better described by Einasto. Find: halo shapes depend only moderately on formation time. Departure from spherical symmetry impacts the density profiles through the anisotropic distribution of massive subhaloes [the other way around?]. Further evidence of impact of subhaloes provided by analyzing the phase-space structure. A detailed analysis of the properties of the subhalo population in Rhapsody presented in another paper.
1209.3320
Project Lyman: quantifying 11 Gyrs of metagalactic ionizing background evolution
McCandliss et al
Timing and duration of reioinization epoch: the photon escape count from SF galaxies is used to "fine-tune" the timing and duration between 13.4 and 12.7 Gyrs ago (12<z<6). Direct observation of Lyman continuum (LyC) increasingly improbable at z>3 due to steady increase of intervening Lyman limit systems towards high z. Thus UV and U-band optical bandpasses provide the only hope for direct observations of the types of environment that favor LyC escape. Observation will provide crucial LyC escape fraction info. [white paper for NASA]
1209.3325
A fast flare and direct redshift constraint in far-UV spectra of the blazar S50716+714
Danforth et al
Constrain z from the flare (a first), consistent with host galaxy redshift.
1209.3339
Annual modulation of dark matter: a review
Freese, Lisanti, Savage
For standard assumptions, the count rate has a cosine dependence over time (maximum in June). Presence of substructure in galactic halo, interactions between dark and baryonic matter, can also be probed.
1209.3457
Seeing the first supernovae at the edge of the universe with JWST
Whalen, Fryer, Holz, ... et al
Masses of PopIII stars can be estimated from their SNe explosions. JWST and WFIRST will detect these explosions out to z~30 and 20, respectively.
1209.3473
The accuracy of the UV continuum as an indicator of the star formation rate in galaxies
Wilkins et al
The rest-frame UV luminosity often used as indicator of instantaneous SFR in a galaxy, but the precise value of calibration relating the UV luminosity to SFR is sensitive to various physical properties (e.g., recent SF and metal enrichment histories, choice of IMF). So a single calibration is not appropriate, based on the distribution of these properties. And that's what they find.
1209.3498
H{\alpha} and UV luminosities and star formation rates in a large sample of luminous compact galaxies
Parnovsky, Izotova, Izotov
Results of SFR study from GALEX observations in 800 LCGs. Global galaxy characteristics (Z, L, M*) are intermediate between nearby blue compact dwarf and high-z (z>2-3) Lyman break galaxies. SFRs corrected for interstellar extinction derived from SDSS spectra. SFR derived from FUV and NUV vary a wide range (0.18 to 113 Msun/yr), with median of 3.8 and 5.2 Msun/yr, respectively. Consider evolution of L with SB age, and introduce new characteristics (the luminosity of Ha, FUV and NUV) at zero SB age.
1209.3635
On the origin of elemental abundances in the terrestrial planets
Elser, Meyer, Moore
Combine circumstellar disk models, chemical equilibrium calculations, dynamical simulations of planet formation to study bulk composition of rocky planets. Condensation sequence modeled to estimate the initial abundance of solids in the disk; planetesimal growth also modeled. Calculate elemental abundances in the resulting planets. No model could reproduce the abundance properties of all planets. Choice of initial planetsimal disk mass and disk model has significant effect on composition gradients. Higher pressure and temperature in disk result in larger variations in the bulk chemical compositions. Massive planets and planets with small semi-major axis are more sensitive to these variations than smaller planets at larger radial distance. Only these large variations in the simulated abundances can potentially explain the diverse bulk composition of the SS planets. Mercury's bulk composition can not be reproduced in these models.
1209.3665
Gas fraction and star formation efficiency at z<1.0
Combes et al
Observation of 39 galaxies at 0.6<z<1.0 added to the full CO line survey in 0.2<z<1. Study the decline of SFR in this epoch. Find gas fraction in sample increases strongly with redshift, and is the most determining factor in the cosmic SF evolution. The SFE evolution is shallower; conlucde that it plays a less significant role in setting the cosmic SFE.
Monday, September 17, 2012
Day 299
Monday.
1209.3013
On the lack of evolution in galaxy star formation efficiency
Behroozi, Wechsler, Conroy
Calculate instantaneous efficiency of galaxy SF (SFR divided by baryon accretion rate) using reconstructed SFH, from z=8 to 0. Efficiency probes a peak near a characteristic halo mass of 1e11.7 Msun, which coincides with predictions for the mass scale relevant to virial shock heating of accreted gas. Above the characteristic halo mass, efficiency falls off as the mass to the -4/3 power; blow this, the efficiency falls off at an average scaling of mass to the 2/3 power. By comparison, the shape and normalization of the efficiency change vary little since z=4. Time independent SF efficiency explains the shape of cosmic SFR since z=4 in terms of DM accretion rates. Rise in cosmic SF from early times until z=2 is sensitive to galaxy formation efficiency. Mass dependence of efficiency strongly limits where most SF occurs, with the result that 2/3 or all SF has occurred inside halos within a factor of 3 of the characteristic mass, a range that includes the mass of the MW.
1209.3015
Stringent and robust constraints on the dark matter annihilation cross section from the region of the galactic center
Hooper, Kelso, Queiroz
GC constraint just as strong as dwarf spheroidals. Robustly rule out DM particles with M<285 GeV.
1209.3016
No clear submillimetre signature of suppressed star formation amongst X-ray luminous AGNs
Harrison et al
Herschel-SPIRE submillimeter observations that support AGN suppresses SF? Extend these results to achieve an order of magnitude improvement in the number of sources, analysis finds no strong evidence for suppressed SF for Lx>1e44 erg/s at z=1-3. The mean SFRs were constant over the broad X-ray luminosity range. The previous CDF-N results were likely due to low number statistics. Discuss results in the context of current theoretical models, suggest that it will be challenging to see the signature of suppressed SF simply on the basis of an X-ray luminosity threshold.
1209.3018
Dark matter halo merger histories beyond cold dark matter: I - methods and application to warm dark matter
Bension ... Cole, Moustakas, ... Frenk, et al
Methodology to accurately compute halo mass functions, progenitor mass functions, merger rates and merger trees in non-cold dark matter universes using a self-consistent treatment of the generalized extended Press-Schechter formalism. Permits rapid exploration of the subhalo population of galactic haloes in dark matter models with a variety of different particle properties or universes with rolling, truncated, or more complicated power spectra. Compare with analytically derived mass function/merger histories with WDM N-body sims and find excellent agreement. Coarse-grained statistics such as the mass accretion history of haloes can be almost indistinguishable between cold and warm dark matter cases; but the halo mass function and progenitor MFs differ significantly (WDM suppressed below the free-streaming scale of the DM.
1209.3033
Radio astronomy with the lunar lander: opening up the last unexplored frequency regime
Wolt et al
Broadband (1kHz-100MHz) tripole antenna envisaged to be place on the European Lunar Lander located at the Lunar South Pole allows for sensitive measurements of the exosphere and ionosphere, and their interaction with the Earths magnetosphere, solar particles, wind and CMEs and studies of radio communication on the moon (for future lunar human and science exploration).
1209.3041
The low-temerature nuclear spin equilibrium of H3+ in collisions with H2
Grussie et al
Difference in nuclear spin excitation temperatures of the 2 species (in space). Measure the steady-state ortho/para ratio of H3_ in collisions with H2 molecules in a temperature-variable RF ion trap between 45-100K, results close to the expected thermal outcome, agree very well with a previous micro-canonical model.
1209.3072
Estimation of halo ellipticity using spin-3 flexion
Er, Bartelmann
The spin-3 gravitational flexion can add useful information on the ellipticity of lensing haloes. General formalism to decompose general fields in to radial and tangential components, the ratio of the tangential and radial flexion components directly estimates the lens ellipticity. Any centroid offset will significantly bias the estimate, which can be used to determine the center of the lens halo.
1209.3114
eROSITA science book: mapping the structure of the energetic universe
Merloni ... Böhringer, ... Reiprich,... et al
eROSITAis the primary instrument on the Russian SRG mission, launch ~2014. Deep survey of the entire X-ray sky. 20x more sensitive than the ROSAT all-sky survey in soft X-ray (0.5-2 keV); in hard (2-10keV) it will provide the first ever true imaging survey of the sky at those energies. Science: detection of very large samples (1e5 objects) of galaxy clusters out to z>1, for cosmological model testing and LSS studies. Also expected to yield 3e6 AGN samples (both obscured and un-obscured) in the cosmic structure; accreting binaries, active stars, and diffuse emission within the Galaxy, as well as SS bodies that emit X-rays via the charge exchange process. Deep imaging survey at high spectral resolution, with its scanning strategy sensitive to a range of variability timescales from tens of seconds to years, will open up a vast discovery space for study of rare, unpredicted, or unpredictable high-ernergy astrophysical phenomena. Present main scientific goals of the mission, with strong emphasis on the early survey phases.
1209.3142
Anti-lensing: the bright side of voids
Bolejko, Clarkson, Maartens, Bacon, Meures, Beynon
The standard "demagnification effect" by voids is swamped by a relativistic Doppler term that is typically neglected. Objects on the far size of a void are brighter than they would be otherwise. Thus the local dynamics of matter in and near the void is crucial and is only captured by the full relativistic lensing convergence.
1209.3213
Herschel-ATLAS/GAMA: spatial clustering of low-redshift sub-mm galaxies
van Kampen et al
Measured spatial clustering length r_0 is comparable to that of optically-selected, moderately star-formaing (blue) galaxies.
1209.3013
On the lack of evolution in galaxy star formation efficiency
Behroozi, Wechsler, Conroy
Calculate instantaneous efficiency of galaxy SF (SFR divided by baryon accretion rate) using reconstructed SFH, from z=8 to 0. Efficiency probes a peak near a characteristic halo mass of 1e11.7 Msun, which coincides with predictions for the mass scale relevant to virial shock heating of accreted gas. Above the characteristic halo mass, efficiency falls off as the mass to the -4/3 power; blow this, the efficiency falls off at an average scaling of mass to the 2/3 power. By comparison, the shape and normalization of the efficiency change vary little since z=4. Time independent SF efficiency explains the shape of cosmic SFR since z=4 in terms of DM accretion rates. Rise in cosmic SF from early times until z=2 is sensitive to galaxy formation efficiency. Mass dependence of efficiency strongly limits where most SF occurs, with the result that 2/3 or all SF has occurred inside halos within a factor of 3 of the characteristic mass, a range that includes the mass of the MW.
1209.3015
Stringent and robust constraints on the dark matter annihilation cross section from the region of the galactic center
Hooper, Kelso, Queiroz
GC constraint just as strong as dwarf spheroidals. Robustly rule out DM particles with M<285 GeV.
1209.3016
No clear submillimetre signature of suppressed star formation amongst X-ray luminous AGNs
Harrison et al
Herschel-SPIRE submillimeter observations that support AGN suppresses SF? Extend these results to achieve an order of magnitude improvement in the number of sources, analysis finds no strong evidence for suppressed SF for Lx>1e44 erg/s at z=1-3. The mean SFRs were constant over the broad X-ray luminosity range. The previous CDF-N results were likely due to low number statistics. Discuss results in the context of current theoretical models, suggest that it will be challenging to see the signature of suppressed SF simply on the basis of an X-ray luminosity threshold.
1209.3018
Dark matter halo merger histories beyond cold dark matter: I - methods and application to warm dark matter
Bension ... Cole, Moustakas, ... Frenk, et al
Methodology to accurately compute halo mass functions, progenitor mass functions, merger rates and merger trees in non-cold dark matter universes using a self-consistent treatment of the generalized extended Press-Schechter formalism. Permits rapid exploration of the subhalo population of galactic haloes in dark matter models with a variety of different particle properties or universes with rolling, truncated, or more complicated power spectra. Compare with analytically derived mass function/merger histories with WDM N-body sims and find excellent agreement. Coarse-grained statistics such as the mass accretion history of haloes can be almost indistinguishable between cold and warm dark matter cases; but the halo mass function and progenitor MFs differ significantly (WDM suppressed below the free-streaming scale of the DM.
1209.3033
Radio astronomy with the lunar lander: opening up the last unexplored frequency regime
Wolt et al
Broadband (1kHz-100MHz) tripole antenna envisaged to be place on the European Lunar Lander located at the Lunar South Pole allows for sensitive measurements of the exosphere and ionosphere, and their interaction with the Earths magnetosphere, solar particles, wind and CMEs and studies of radio communication on the moon (for future lunar human and science exploration).
1209.3041
The low-temerature nuclear spin equilibrium of H3+ in collisions with H2
Grussie et al
Difference in nuclear spin excitation temperatures of the 2 species (in space). Measure the steady-state ortho/para ratio of H3_ in collisions with H2 molecules in a temperature-variable RF ion trap between 45-100K, results close to the expected thermal outcome, agree very well with a previous micro-canonical model.
1209.3072
Estimation of halo ellipticity using spin-3 flexion
Er, Bartelmann
The spin-3 gravitational flexion can add useful information on the ellipticity of lensing haloes. General formalism to decompose general fields in to radial and tangential components, the ratio of the tangential and radial flexion components directly estimates the lens ellipticity. Any centroid offset will significantly bias the estimate, which can be used to determine the center of the lens halo.
1209.3114
eROSITA science book: mapping the structure of the energetic universe
Merloni ... Böhringer, ... Reiprich,... et al
eROSITAis the primary instrument on the Russian SRG mission, launch ~2014. Deep survey of the entire X-ray sky. 20x more sensitive than the ROSAT all-sky survey in soft X-ray (0.5-2 keV); in hard (2-10keV) it will provide the first ever true imaging survey of the sky at those energies. Science: detection of very large samples (1e5 objects) of galaxy clusters out to z>1, for cosmological model testing and LSS studies. Also expected to yield 3e6 AGN samples (both obscured and un-obscured) in the cosmic structure; accreting binaries, active stars, and diffuse emission within the Galaxy, as well as SS bodies that emit X-rays via the charge exchange process. Deep imaging survey at high spectral resolution, with its scanning strategy sensitive to a range of variability timescales from tens of seconds to years, will open up a vast discovery space for study of rare, unpredicted, or unpredictable high-ernergy astrophysical phenomena. Present main scientific goals of the mission, with strong emphasis on the early survey phases.
1209.3142
Anti-lensing: the bright side of voids
Bolejko, Clarkson, Maartens, Bacon, Meures, Beynon
The standard "demagnification effect" by voids is swamped by a relativistic Doppler term that is typically neglected. Objects on the far size of a void are brighter than they would be otherwise. Thus the local dynamics of matter in and near the void is crucial and is only captured by the full relativistic lensing convergence.
1209.3213
Herschel-ATLAS/GAMA: spatial clustering of low-redshift sub-mm galaxies
van Kampen et al
Measured spatial clustering length r_0 is comparable to that of optically-selected, moderately star-formaing (blue) galaxies.
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