Saturday. Two full weeks and a few days behind. Sunday.
1312.2576
Lensed Type Ia supernovae as probes of cluster mass models
Nordin, Rubin, Richard, Rykoff, Aldering, Amanulla, .. Fakhouri, … Meyers, Perlmutter, et al
First pilot study to see whether standardizable candles can be used to calibrate cluster mass maps created from SL observations (uses 3 magnified SNIa behind massive CLASH clusters). Such calibrations will be crucial when next generation HST cluster surveys (e.g. FRONTIER) provide magnification maps that will, in turn, form the basis for the exploration of the high z universe. Demonstrate that SNe can be used as "test beams" for this purpose. Use a combination of spectroscopic and photometric methods to classify the SNe and then determine the SN amplification factors using the SALT2/Union2.1 framework. Find SNe with significant amplification, up to a factor of 1.7 at ~5 sigma significance for SN-L2 behind MACSJ1720. Initially conducted theist as a blind study to avoid find tuning of parameters, and found a mean amplification difference between SNe and the cluster lensing models of 0.09 pm0.09(stat) pm0.05(sys) mag.These constraints are impressive, especially given the small sample size, and suggest no tension between cluster mass models and high-z standardized SN Ia [but the cluster mass model differs for each cluster, though…? There is no standardized cluster mass modeling, I don't think.]. However, the measured statistical dispersion of sigma_mu=0.21 mag appeared large compared to the dispersion expected based on statistical uncertainties (0.14). FUrther work with the SN and cluster lensing models, post unblinding, reduced the measured dispersion to sigma_mu=0.12 mag. This demonstrates that an explicit choice should be made and reported as to whether the SNe are used unblinded to improved the model, or blinded to test the model. As the lensed SN samples grow larger, this technique will allow improved constraints on mass sheets and assumptions regarding the structure of the DM halo.
1312.2583
Using gas kinematics to constrain 3d model of disks: IC 2531
Eigenbrot, Bershady
Deep, longslit spectra of the nearby edge-on galaxy IC 2531 to obtain gas kinematics out to 5 radial scale-lengths (40 kpc) and 4 vertical scale-heights (1.7 kpc). The large vertical range spanned by the data offers unique leverage to constrain 3d models. The shape of the observed emission-line profiles offer insights to LoS density distributions in the disk; discuss the possibility of disk-flaring in the ionized gas. Begin to quantify measurements of line shape to allow model galaxies to be compared to data across all radii and heights simultaneously.
1312.2584
Spatially resolved LMC star formation history: I. outside in evolution of the outer LMC disk
Meschin et al
Study the evolution of 3 fields in the outer LMC disk Rgc=3.5-6.2 kpc. Their SFH indicates a stellar populations gradient such that younger stellar populations are more centrally concentrated. Identify 2 main SF epochs, separated by a period of lower activity between ~7 and ~4 Gyr ago. Their relative importance varies from a similar mount of stars formed in the two epochs in the innermost field, to only 40% of the stars formed in the more recent epoch in the outermost field. The young SF epoch continues to the present time in the innermost field, but lasted only till ~0.8 and 1.3 Gyr ago at Rgc=5.5 deg and 7.1 deg, respectively. This gradient is correlated with the measured HI column density and implies an outside-in quenching of the SF, possibly related to a variation of the size of the HI disk. This could either result from gas depletion due to SF or ram-pressure stripping, or from the compression of the gas disk as ram-pressure from the MW halo acted on the LMC ISM. The latter two situations may have occurred when the LMC first approached the MW.
1312.2587
On the mass of the local group
Gonzalez, Kravtsov, Gnedin
Use proper motion measurements of the tangential velocity of M31, along with its radial velocity and distance, to derive the likelihood of the sum of halo masses of the MW and M31. This is done using a simple halo pairs in the Bolshoi cosmological simulation of LCDM cosmology selected to match properties and environment of the LG. The resulting likelihood gives estimate of the sum of masses of M_MW,200 + M_M31,200 = 2.40-1.05+1.95 e12 Msun (90% CL). This estimate is consistent with individual mass estimates for the MW and M31 and is (albeit somewhat on the low side) also with the mass estimated using the timing argument [?]. Show that although the timing argument is unbiased on average for all pairs, for pairs constrained to have radial and tangential velocities similar to that of the LG, the argument overestimates the sum of masses by a factor of 1.6. Using similar technique estimate the total DM mass enclosed within 1 Mpc from the LG barycenter to be M_LG(r<1 Mpc)=4.2-2.0+3.4 e12 Msun (90% CL).
1312.2593
A tale of two redshifts
Bassett, Fantaye, Hlozek, Saibu, Smith
Observed redshift z_o and model redshift z may be different, and a simple remapping z= a_1 z_o + a_2 z_o^2 allows pretty good fitting to the SNe data of a non-LCDM model redshift. But redshift remapping leaves a distinct observational signature which allow both strong constraints on remapping and reaffirmation of acceleration when current d_A, d_L and H(z) data are combined. Remapping can significantly change the inferred values of data points, blurring the line between theory and data and creating tension between different estimates of parameters such as H_0. While constraining specific models with z remapping requires careful analysis, results suggest it provides a new test of back reaction and non-standard physics.
1312.2595
Overlapping inflow events as catalysts for supermassive black hole growth
Carmona-Loaiza et al
Aim: to explore how the interaction between the rotating, infalling gas shells and the primitive large scale (~10pc) disk around a SMBH redistributes the angular momentum on scales close to the BH's sphere of influence. Angular momentum redistribution via hydrodynamical shocks leads to inflows of gas across the inner boundary, enhancing the inflow rate by more than 2-3 orders of magnitude. In all cases, the gas inflow rate across they inner parsec is higher than in the absence of the interaction, and the orientation of the angular momentum of the flow in the region changes with time due to gas mixing. Warped discs or nested misaligned rings form depending on the angular momentum content of the in falling shell relative to the disc. In the cases in which the shell falls in near counter-rotation, part of the resulting flows settle into an inner dense disc which becomes more susceptible to mass transfer.
1312.2620
Magnetic fields in cosmological simulations of disk galaxies
Pakmor, Marinacci, Springel
Observationally, B-fields reach equipartition with thermal energy and CRs in the ISM of disk galaxies such as the MW. However, thus far cosmological simulations of the formation and evolution of galaxies have usually neglected B-fields. Employ the moving-mesh code Arepo to follow for the first time the formation and evolution of a MW-like disk galaxy in its full cosmological context while taking into account B-fields. Find that a prescribed tiny B-field seed field grows exponentially by a small-scale dynamo [in a star or what?] until it saturates around z=4 with a magnetic energy of ~10% of the kinetic energy in the center of the galaxies main progenitor halo. By z=2, a well-defined gaseous disk forms in which the B-field is further amplified by a differential rotation, until it saturates at an average field strength of ~6 micro Gauss in the disk plane. In this phase, the B-field is transferred from a chaotic small-scale field to an ordered large-scale field coherent on scales comparable to the disk radius. The final B-field strength, its radial profile and the stellar structure of the disk compare well with observational data. A minor merger temporarily increases the B-field strength by about a factor of 2, before it quickly decays back into its saturation value. Results are highly insensitive to the initial seed field strength and suggest that the large-scale B-field in spiral galaxies can be explained as a result of the cosmic structure formation process.
1312.2871
Micro-arcsecond radio astrometry
Reid, Honma
Astrometry: association of sources detected at different times or wavelengths, and distances are essential to estimate the size, luminosity, has, and ages of most objects. VLBI at radio, with diffraction-limited imaging at sub-milliarcsec resolution, has long held the promise of micro-arcsecond astrometry. However, only in the past decade has this been routinely achieved. Currently, parallaxes for sources across the MW are being measured with ~10 uas accuracy and proper motions of galaxies are being determined with accuracies of ~1 uas/y. The astrophysical applications of these measurements cover many fields, including SF, evolved stars, stellar and SMBHs, galactic structure, the history and fate of the Local Group, the Hubble constant, and tests of GR. This review summarizes the methods used and the astrophysical applications of micro-acrsecond radio astrometry.
1312.2927
The smallest particles in Saturn's A and C rings
Harbison, Nicholson, Hedman
Contrary to previous optical and IR work which impiled that there were few particles in the A ring <1cm, radio occultations of Saturn's main rings suggest a power law particle size-distribuiton down to sizes of order 1 cm. Lack of optical depth variations between UV and NIR wavelengths indicate a lack of micron-sized particles. A cutoff where the particle-size distribution turns over must exist, but the position and shape of it is not clear from existing studies. From forward scattered light in the A and C rings and a model of diffraction by ring particles, estimate the minimum particle size using a truncated power-law size distribution. C ring shows minimum size of ~4mm with a power law index of q=3.1 and maximum of 10m. The A ring shows a similar level of scattered flux, but modeling is complicated by the presence of self-gravity wakes and higher optical depths. If z<3, the A ring model requires a minimum particle size <1mm to be consistent with VIMS observations.
1312.2947
The MICE grad challenge light cone simulation III: Galaxy lensing mocks from all-sky lensing maps
Fosalba, Gaztanaga, Castander, Crocce
MICE-GC build halo and galaxy catalogs using HOD an halo abundance matching. Given its large volume and fine mass resolution, the MICE-GC simulation also allows an accurate modeling of the lensing observables from upcoming wide and deep galaxy surveys. In this paper, describe the construction of all-sky lensing maps, following the "onion universe" approach, and discuss their propeties in the light cone up to z=1.4 with sub-arcmin spatial resolution By comparing the convergence PS in the MICE-GC to lower mass-resolution (1e11 Msun particles) simulations, find that resolution effects are at the 5% level for multipoles l~1e3 and 20% of l~1e4. Resolution effects have a much lower impact on the simulation, as shown by comparing the MICE-GC to recent numerical fits. Use the all-sky lensing maps to model galaxy lensing properties, such as the convergence, shear, and lensed magnitudes and positions, and validate them thoroughly using galaxy shear auto and cross-correlations in harmonic and configuration space. Results show that the galaxy lensing mocks here presented can be used to accurately model lensing observables down to arc minute scales.
1312.2952
Constraining the origin of the rising cosmic ray positron fraction with the boron-to-carbon ratio
Cholis, Hooper
The rapid rise in the CR positron fraction above 10 GeV, as measured by PAMELA and AMS, suggests the existence of nearby primary sources of HE positrons, such as pulsars or annihilating/decaying DM. In contrast, the spectrum of secondary positrons produced through the collisions of CRs in the ISM is predicted to fall rapidly with energy, and thus is unable to account of the observed rise. It has been proposed, however, that secondary positrons could be produced and then accelerated in nearby SN remnants, potentially explaining the observed rise, without the need of primary positron sources. Yet, if secondary positrons are accelerated in such shocks, other secondary CR species (such as B nuclei, and antiprotons) will also be created, leading to rises in the B/C and antiproton-to-proton ratios. The measurements of the B/C ratio by PAMELA and AMS collaborations, however, show no sign of such a rise. With this new data in head, revisit the secondary acceleration scenario for the rising positron fraction. Assuming that the same SN remnants accelerate both light nuclei (protons, He) and heavier CR species, find that no more than ~25% of the observed rise in the positron fraction can result from this mechanism (at the 95% CL).
1312.3015
Measurement of galaxy cluster integrated Comptonization and mass scaling relations with the south pole telescope
Saliwanchik et al
A new method for measuring the integrated Comptonization (YSZ) from SPT SZ multi-band data; characterize the sample of galaxy clusters detected. Test this method on simulated cluster observations and verify that it can accurately recover cluster parameters with negligible bias. In realistic simulations of an SPT-like survey, with realization of CMB anisotropy, point sources, and atmosphere and instrumental noise at typical SPT-SZ survey levels, find that YSZ is most accurately determined in a aperture comparable to the SPT beam size. Demonstrate the utility of this method to measure YZZ and to constrain mass scaling relations using X-ray mass estimates for a sample f 18 galaxy clusters from the SPT-SZ survey. Measuring YSZ within a 0.75' radius aperture, find an intrinsic log-normal scatter of 21 pm 11% in YSZ at a fixed mass. Measuring YSZ within a 0.3 Mpc projected radius (equivalent to 0.75' at the survey median z = 0.6) find a scatter of 26pm9%. Prior to this study, the SPT observable found to have the lowest scatter with mass was cluster detection significance. Demonstrate, from both simulations and SPT observed clusters, that YSZ measured within an aperture comparable to the SPT beam size is equivalent, in terms of scatter with cluster mass, to SPT cluster detection significance.
1312.3029
An atlas of galaxy spectral energy distributions from the ultraviolet to the mid-infrared
Brown, Moustakas, … et al
Present atlas of 129 SEDs for nearby galaxies, with wavelength coverage from UV to MIR. Atlas spans ellipticals, spirals, merging galaxies, blue compact dwarfs, and luminous IR galaxies (LIRGs). Combined ground-based optical drift-scan spectrophotometry with IR spectroscopy from Spitzer and Akari, with gaps in spectra coverage being filled using MAGPHYS SED models. The spectroscopy and models were normalized, constrained and verified with matched-aperture photometry measured from Swift, GALEX, SDSS, 2MASS, Spitzer and WISE images. The availability of 26 photometric bands allowed identification and mitigation of systematic errors present in the data. Comparison of SEDs with other template libraries and the observed colors of galaxies indicates that there are smaller systematic errors than existing atlases, while spanning a broader range of galaxy types. Relative to prior literature, this atlas will provide improved K-corrections, photometric redshifts and SFR calibrations.
1312.3117
The mutual interaction between population III stars and self-annihilating dark matter
Stacy, Pawlik, Bromm, Loeb
Use cosmo-sims of high-z mini halos to investigate the effect of DM annihilation (DMA) on the collapse of primordial gas. Numerically investigate the evolution of the gas as it assembles in a Pop III stellar disk. Find that when DMA effects are neglected, the disk undergoes multiple fragmentations events beginning at ~500 yr after the appearance of the first protostar. On the other hand, DMA heating and ionization of the gas speeds the initial collapse of gas to protostellar densities and also affects the stability of the developing disk against fragmentation, depending on the DM distribution. Compare the evolution when the DM density is modeled with an analytical DM profile which remains centrally peaked, and when the DM profile is simulated using N-body particles (the 'live' DM halo). When utilizing the analytical DM profile, DMA suppresses disk fragmentation for ~3500 yr after the first protostar forms, in agreement with earlier work. However, when using a 'live' DM halo, the central DM density peak is gradually flattened due to the mutual interaction between the DM and the rotating gaseous disk, reducing the effects of DMA on the gas, and enabling secondary protostars of mass ~1 Msun to be formed within ~900 yr. These simulations demonstrate that DMA is ineffective in suppressing gas collapse and subsequent fragmentation, rendering the formation of long-lived dark stars unlikely [do they mean DM-only stars? That all DM halo will have significant baryonic components?]. However, DMA effects may still be significant in the early collapse and disk formation phase of primordial gas evolution.
1312.3133
The environmental dependence of neutral hydrogen in the GIMIC simulations
Cunnama et al
Use Galaxies-Intergalactic Medium Interaction Calculation (GIMIC) cosmo hydrosim at z=0 to study the distribution and environmental dependence of neutral Hydrogen (HI) gas in the outskirts of simulated galaxies. This gas can currently be probed directly in, e.g., Lya absorption via the observation of BG quasars. Radio facilities, such as SKA, will provide a complementary probe of the diffuse HI in emission and will constrain the physics underpinning the complex interplay between accretion and feedback mechanisms which affect the IGM. Extract a sample of 488 galaxies from a re-simulation of the average cosmic density GIMIC region. Estimate the HI content of these galaxies and the surrounding IGM within which they reside. Investigate the average HI radial profiles by stacking the individual profiles according to both mass and environment. Find high HI column densities at large impact parameters in group environments and markedly lower HI densities for non-group galaxies. Suggest that these results likely arise from the combined effects of ram pressure stripping and tidal interactions present in group environments.
1312.3181
Trigonometric parallaxes to star-forming regions within 4 kpc of the galactic center
Sanna et al
Report 4 trigonometric parallaxes for high-mass SF regions within 4 kpc of the Galactic center; associated with large-scale features in CO and HI longitude-velocity diagrams. Outline some major features of the inner MW: the Connecting arm, the nearing and far 3kpc arms, and the Norma arm. The connecting erin in the first Galactic quadrant lies closer to the Glactic center than the far 3 kpc arm and is offset by the long-bar's major axis near its leading edge, supporting the presence of an inner Lindbald resonance. Assuming the 3 kpc arms are a continuous physical structure, the relative Galactocentric distance of its near and far sides suggests highly elliptical streamlines of gas around the bar(s) and a bar coronation radius, r_CR > 3.6 kpc. At a Galactic longitude near 10 deg and a hello centric distance of about 5 kpc, the near 3 kpc arm and the Norma arm intersect on a face-on view of the Galaxy, while passing at different Galactic latitudes. Provide an accurate distance measurement to the W31 SF complex of 4.95pm0.5 kpc from the Sun, which associates it with at bright CO feature belonging to the near 3 kpc arm.
1312.3223
Formation of molecular clouds and global conditions for star formation
Dobbs, et al
Giant molecular clouds (GMCs) are the primary reservoirs of cold, SF molecular gas in the MW and similar galaxies, and thus any understanding of SF must encompass a model for GMC formation, evolution, and destruction. These models are necessarily constrained by measurements of interstellar molecular and atomic gas, and the emergent, newborn stars. Both observations and theory have undergone great advances in recent years, the latter driven largely by improved numerical simulations, and the former by the advent of large-scale surveys with new telescopes and instruments. Offer a thorough review of the current state of the field.
1312.3233
A comparison between semi-analytic model predictions for the CANDELS survey
Lu, Wechsler, … et al
Compare the predictions of three independently developed SAM models that are being used to aid in the interpretation of results from the CANDELS survey. These models are each applied to the same set of halo merger trees extracted from the "Bolshoi" simulation and are carefully tuned to match the local galaxy stellar mass function using Bayesian Inference coupled with MCMC or by hand. The comparisons reveal that in spite of the significantly different parameterizations for SF and feedback processes, the three models yield qualitatively similar predictions for the assembly histories of galaxy stellar mass and SF over cosmic time. Show that the SAMs generally require strong outflows to suppress SF in low-mass halos to match the present day stellar mass function. However, all of the models considered produce predictions for the SFRs and metallicities of low-mass galaxies that are inconsistent with existing data and diverge between the models. Suggest that large differences in the metallicity relations and small differences in the stellar mass assembly histories of model galaxies stem from different assumptions for the outflow mass-loading factor. Importantly, while more accurate observational measurements for stellar mass, SFR and metallicity of galaxies at 1<z<5 will discriminate between models, the discrepancies between the models and existing data of these observables have already revealed challenging problems in understanding SF and its feedback in galaxy formation. The three sets of models are being used to construct catalogs of mock galaxies on light cones that have the same geometry as the CANDELS survey, which should be particularly useful for quantifying the biases and uncertainties on measurements and inferences from the real observations.
1312.3241
Trigonometric parallaxes for 1,507 nearby mid-to-late M-dwarfs
Dittmann et al
MEarth survey: search for small rocky planets around the smallest, nearest stars to the sun as identified by high proper motion with red colors. Average precision of 5 milliarcseconds; combined with 2MASS photometry, allow absolute K_s magnitude for each star, allowing better estimates of the stellar parameters than those obtained with photometric estimates alone and to better prioritize the targets chosen to monitor at high cadence for planetary transits. The MEarth sample is mostly complete out to a distance of 25 parsecs for stars of type M5.5V and earlier, and mostly complete for later type stars out to 20 parsecs. Find 8 stars that are within 10 parsecs of the Sun for which there did not exist a published trigonometric parallax distance estimate. Release a catalog of the trigonometric parallax measurements for 1,507 mid-to-late M-dwarfs, as well as new estimates of their masses and radii.
1312.3313
Planck data reconsidered
Spergel, Flauger, Hlozek
The tension between the best fit parameters derived by the Planck team and a number of other astronomical measurements suggests either systematics in the astronomical measurements, systematics in the Planck data, the need for new physics, or a combination thereof. Reanalyze the Planck data and find that the 217 GHz x 217 GHz detector set spectrum used in the Planck analysis is responsible for some of this tension. use a map-based FG cleaning procedure, relying on a combination of 353 GHz and 545 GHz maps to reduce residual FGs in the intermediate frequency maps used for cosmological inference. For the baseline data analysis, which uses 47% of the sky and makes use of both 353 and 545 GHz data for FG cleaning, find the LCDM cosmo parameters Omega_c h^2 = 0.1169 pm 0.0025, n_s=0.9671 pm 0.0069, H0=68.0 pm 1.1 km/s/Mpc, Omega_b h^2 = 0.02197 pm 0.00027, ln 10^10 A_s = 3.080 pm 0.025, and tau = 0.089pm0.013. While in broad agreement with the results reported by the Planck team, these revised parameters imply a universe with a lower matter density of Omega_M=0.302 pm 0.015, and parameter values generally more consistent with pre-Planck CMB analyses and astronomical observations. Compare cleaning procedure with the FG modeling used by the Planck team and find good agreement. The difference in parameters between analysis and that of the Planck team is mostly due to the use of cross-spectra from the publicly available survey maps instead of their use of the detector set cross-spectra which include pixels only observed in one of the surveys. Show evidence suggesting residual systematics in the detector set spectra used in the Planck likelihood code, which is substantially reduced for this spectra.
1312.3320
A Herschel [C II] Galactic plane survey II: CO-dark H2 in clouds
Langer et al
Find that a significant fraction of the warm molecular ISM gas is invisible in HI and CO, but is detected in [CII]. The fraction of CO-dark H2 is greatest in the diffuse clouds and decreases with increasing total column density, and is lowest in the massive clouds.
1312.3323
The structure of Exoplanets
Spiegel, Fortney, Sotin
Review the diverse range of interior structures that are known to, and speculated to, exist in exoplanetary systems --- from mostly degenerate objects that are more than 10 times as massive a Jupiter, to intermediate-mass Neptune-lie objects with large cores and moderate hydrogen/helium envelopes, to rocky objects with roughly the mass of the Earth.
1312.3328
Identifying clustering at high redshift through actively star-forming galaxies
Davies et al
Identifying galaxy clustering at high z (i.e., z>1) is essential to our understanding of the current cosmological model. However, at increasing z, clusters evolve considerably in SF activity and so are less likely to be identified using the widely-used red sequence method. Assess the viability of instead identifying high z clustering [or clusters?] using actively SF galaxies (SMGs associated with over-densityes of BzKs/LBGs). Perform both a 2- and 3-D clustering analysis to determine whether or not true (3D) clustering can be identified where only 2d data are available. As expected, find that 2d clustering signals are weak at best and inferred results are method dependent. In the 3d analysis, identify 12 SMGs associated with an over-density of galaxies coincident both spatially and in redshift - just 8% of SMGs with known redshifts in the sample. Where an SMG in the target fields lacks a known redshift, their sightline is no more likely to display clustering than blank sky fields; prior redshift information for the SMG is required to identify a true cluster signal. Find that the strength of clustering in the volume around typical SMGs, while identifiable, is not exceptional. However, a small number of highly clustered regions are identified, all associated with an SMG. The most notable of these potentially contains an SMG, a QSO and 36 SF galaxies (a >20 sigma over-density) all at z~1.8. This region is highly likely to represent an actively SF cluster and illustrates the success of using SF galaxies to select sites of early clustering Given the increasing number of deep fields with large volumes of spectroscopy, or high quality and reliable photometric redshifts, this opens a new avenue for cluster identification in the young Universe.
1312.3329
The SCUBA-2 cosmology legacy survey: Ultraluminous star-forming galaxies in a a z=1.6 cluster
Smail et al
Analyze new SCUBA-2 sub millimeter and archival SPIRE FIR imaging of a z=1.62 cluster, which lies in the UKIDSS/UDS field of the SCUBA-2 cosmology legacy survey. Combining these tracers of obscured SF activity with the extensive photometric and spectroscopic information available for this field, identify 31 FIR/submillimeter-detected probably cluster members with bolometric luminosities >1e12 L_sun and show that by virtue of their dust content and activity, these represent some of the reddest and brightest galaxies in this structure. Exploit Cycle-1 ALMA sub millimeter continuum imaging which covers one of these sources to confirm the identification of a SCUBA-2-detected ultra luminous star-forming galaxy in this structure. Integrating the total SF activity in the central region of the structure, estimate that it is an order of magnitude higher (in a mass-normalised sense) than clusters at z~0.5-1. However, also find that the most active cluster members do not reside in the densest regions of the structure, which instead host a population of passive and massive, red galaxies. Suggest that while the passive and active populations have comparable NIR luminosities at z=1.6, M(H)~-23, the subsequent stronger fading of the more active galaxies me ands that they will evolve into passive systems at the preset-day which are less luminous than the descendants of those galaxies which were already passive at z~1.6 (M(H)~-20.5 and M(H)~-21.5 respectively at z~0). Conclude that the massive galaxy population in the dense cores of present-day clusters were already in place at z=1.6 and that in this cluster, continuing infall of less extreme, but still ultra luminous, SF galaxies onto a pre-existing structure is seen.
1312.3336
The dependency of AGN infrared color-selection on source luminosity and obscuration: an observational perspective in CDFS and COSMOS
Messias et al
Confirm that AGN IR-selection is genuinely biased toward unobscured AGN, but only at intermediate luminosities. At the highest luminosities, where AGN IR-selection is more efficient, there is no obscuration bias. Showa that type-1 AGNs are intrinsically more luminous than type-2 AGN only at z<~1.6 [does that make sense, if the difference between types 1 and 2 are the dust obscuration angles?] thus resulting in more type-1 AGN being selected the shallower the IR survey is.
1312.3337
Increased insolation threshold for runaway greenhouse processes on Earth like planets
Leconte et al
Because the solar luminosity increases over geological timescales, Earth climate is expected to warm, increasing water evaporation which, in turn, enhances the atmospheric greenhouse effect. Above a certain critical insolation, this destabilizing greenhouse feedback can "runaway" until all the oceans are evaporated. Through increases in stratospheric humidity, warming may also cause oceans to escape to space before the runaway greenhouse occurs. The critical insolation [amount of solar radiation reaching a given area] thresholds for these processes, however, remain uncertain because they have so far been evaluated with unidimensional models that canon account for the dynamical and cloud feedback effects that are key stabilizing features of Earth's climate. Use a 3d global climate model to show that the threshold for the runaway greenhouse is about 375 W/m^2, significantly higher than previously thought. Model is specifically developed to quantify the climate response of Earth-like planets to increase insolation in hot and extremely moist atmospheres. In contrast with previous studies, find that clouds have a destabilizing feedback on the long term warming. However, subsident [gradual sinking of an area of land], unsaturated regions created by the Hadley circulation have a stabilizing effect that is strong enough to defer the runaway greenhouse limit to higher insolation than inferred from 1d models. Furthermore, because of wavelength-dependent radiative effects, the stratosphere remains cold and dry enough to hamper atmospheric water escape, even at large fluxes. This has strong implications for Venus early water history and extends the size of the habitable zone around other stars.
1312.3415
Testing local anisotropy using the method of smoothed residuals I - Methodology
Appleby, Shafieloo
Discuss method of smoothed residuals, which has recently been used to search for anisotropic signals in low-z distance measurements (SNe). In this short note, focus on some details regarding the implementation of the method, particularly the issue of effectively detecting signals in data that are inhomogeneously distributed on the sky. Using simulated data, argue that the original method proposed in Colin+ will not detect spurious signals due to incomplete sky coverage, and that introducing additional Gaussian weighting to the statistic can hinder its ability to detect a signal. Issues related to the width of the Gaussian smoothing are also discussed.
1312.3442
Gas-to-dust mass ratios in local galaxies over a 2 dex metallicity range
Rémi-Ruyer et al
Analyze the behavior of the gas-to-dust ratio (G/D) of local universe galaxies over a large metallicity range. Combine Dwarf Galaxy Survey, KINGFISH survey and a subsample from Galametz+, totaling 126 galaxies, covering a 2 dex metallicity range, with 30% of the sample with 12+log(O/H) < 8.0. The dust masses are homogeneously determined with a semi-empirical dust model, including submm constraints. The atomic and molecular gas masses are compiled from the literature. Two XCO are used to estimate molecular gas masses: the Galactic XCO, and a XCO depending on the metallicity (as Z^-2). Correlations with morphological types, stellar masses, SFRs and sSFRs are discussed. The trend between G/D and metallicity is empirically modeled using power-laws (slope of -1 and free) and a broken power-law. Compare the evolution of the G/D with predictions from chemical evolution models. Find that out of the five tested galactic parameters, metallicity is the galactic property deriving the observed G/D. The G/D versus metallicity relation cannot be represented by a power-law with a slope of -1 over the whole metallicity range. The observed trend is steeper for metallicities lower than ~8.0. A large scatter is observed in the G/D for a given metallicity, with a dispersion of 0.37 dex in metallicity bins of ~0.1 dex. The broken power-law reproduces best the observed G/D and provides estimates of the G/D that are accurate to a factor of 1.6. The good agreement of the G/D and its scatter with the three tested chemical evolution models shows that the scatter is intrinsic to galactic properties, reflecting the different SFHs, dust destruction efficiencies, dust grain size distributions and chemical compositions across the sample.
1312.3468
Exoplanetary searches with gravitational microlensing: polarization issues
Zakharov et al
There are different methods for finding exoplanets such as radial spectral shifts, astrometrical measurements, transits, timing etc. Gravitational microlensing (including pixel-lensing) is among the most promising techniques with the potential of detecting Earth-like planets at distances about a few astronomical units from their host star or near the so-called snow line with a temperature in the range 0-100 C on a solid surface of an exoplanet. Emphasize the importance of polarization measurements which can help to resolve degeneracies in theoretical models. In particular, the polarization angle could give additional information about the relative position of the lens with respect to the source.
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