Using images of the Digitized Sky Survey we measured coodinates for 17298 galaxies having poorly defined coordinates. As a control, we measured with the same method 1522 galaxies having accurate coordinates. The comparison with our own measurements shows that the accuracy of the method is about 6 arcsec on each axis (RA and DEC).
We demonstrate how the Fundamental Manifold (FM) can be used to cross-calibrate distance estimators even when those "standard candles" are not found in the same galaxy. Such an approach greatly increases the number of distance measurements that can be utilized to check for systematic distance errors and the types of estimators that can be compared. Here we compare distances obtained using Type Ia supernova (SN Ia), Cepheids, surface brightness fluctuations, the luminosity of the tip of the red giant branch, circumnuclear masers, eclipsing binaries, RR Lyrae stars, and the planetary nebulae luminosity functions. We find no significant discrepancies (differences are <2{sigma}) between distance methods, although differences at the ~10% level cannot yet be ruled out. The potential exists for significant refinement because the data used here are heterogeneous B-band magnitudes that will soon be supplanted by homogeneous, near-infrared magnitudes. We illustrate the use of FM distances to (1) revisit the question of the metallicity sensitivity of various estimators, confirming the dependence of SN Ia distances on host galaxy metallicity, and (2) provide an alternative calibration of H_0_ that replaces the classical ladder approach in the use of extragalactic distance estimators with one that utilizes data over a wide range of distances simultaneously.
We make publicly available a catalog of calibrated environmental measures for galaxies in the five 3D-Hubble Space Telescope (HST)/CANDELS deep fields. Leveraging the spectroscopic and grism redshifts from the 3D-HST survey, multiwavelength photometry from CANDELS, and wider field public data for edge corrections, we derive densities in fixed apertures to characterize the environment of galaxies brighter than JH_140_<24mag in the redshift range 0.5<z<3.0. By linking observed galaxies to a mock sample, selected to reproduce the 3D-HST sample selection and redshift accuracy, each 3D-HST galaxy is assigned a probability density function of the host halo mass, and a probability that it is a central or a satellite galaxy. The same procedure is applied to a z=0 sample selected from Sloan Digital Sky Survey. We compute the fraction of passive central and satellite galaxies as a function of stellar and halo mass, and redshift, and then derive the fraction of galaxies that were quenched by environment specific processes. Using the mock sample, we estimate that the timescale for satellite quenching is t_quench_~2-5Gyr; it is longer at lower stellar mass or lower redshift, but remarkably independent of halo mass. This indicates that, in the range of environments commonly found within the 3D-HST sample (M_h_<~10^14^M_{sun}_), satellites are quenched by exhaustion of their gas reservoir in the absence of cosmological accretion. We find that the quenching times can be separated into a delay phase, during which satellite galaxies behave similarly to centrals at fixed stellar mass, and a phase where the star formation rate drops rapidly ({tau}_f_~0.4-0.6Gyr), as shown previously at z=0. We conclude that this scenario requires satellite galaxies to retain a large reservoir of multi-phase gas upon accretion, even at high redshift, and that this gas sustains star formation for the long quenching times observed.
We present an all-sky catalogue of 395 nearby galaxy groups revealed in the Local Supercluster and its surroundings. The groups and their associations are identified among 10914 galaxies at |b|>15{deg} with radial velocities V_LG_<3500km/s. Our group-finding algorithm requires the group members to be located inside their zero-velocity surface. Hereby, we assume that individual galaxy masses are proportional to their total K-band luminosities, M/L_K_=6M_{sun}_/L_{sun}_. The sample of our groups, where each group has n>=4 members, is characterized by the following medians: mean projected radius <R>=268kpc, radial velocity dispersion {sigma}_V_=74km/s, K-band luminosity L_K_=1.2x10^11^L_{sun}_, virial and projected masses M_vir_=2.4x10^12^ and M_p_=3.3x10^12^M_{sun}_, respectively. Accounting for measurement error reduces the median masses by 30 per cent. For 97 per cent of identified groups the crossing time does not exceed the cosmic time, 13.7Gyr, with the median at 3.8Gyr. We examine different properties of the groups, in particular of the known nearby groups and clusters in Virgo and Fornax. About a quarter of our groups can be classified as fossil groups where the dominant galaxy is at least 10 times brighter than the other group members.
A study of the group properties of galaxies in our immediate neighborhood provides a singular opportunity to observationally constrain the halo mass function, a fundamental characterization of galaxy formation. Detailed studies of individual groups have provided the coefficients of scaling relations between a proxy for the virial radius, velocity dispersion, and mass that usefully allow groups to be defined over the range 10^10^-10^15^M_{sun}_. At a second hierarchical level, associations are defined as regions around collapsed halos extending to the zero-velocity surface at the decoupling from cosmic expansion. The most remarkable result of the study emerges from the construction of the halo mass function from the sample. At ~10^12^M_{sun}_, there is a jog from the expectation Sheth-Tormen function, such that halo counts drop by a factor ~3 in all lower mass bins.
We present the results of a new search for bright star-forming galaxies at redshift z=~7 within the UltraVISTA second data release (DR2) and UKIDSS (UKIRT Infrared Deep Sky Survey) UDS (Ultra Deep Survey) DR10 data, which together provide 1.65deg^2^ of near-infrared imaging with overlapping optical and Spitzer data. Using a full photometric redshift analysis, to identify high-redshift galaxies and reject contaminants, we have selected a sample of 34 luminous (-22.7<M_UV_<-21.2) galaxies with 6.5<z<7.5. Crucially, the deeper imaging provided by UltraVISTA DR2 confirms all of the robust objects previously uncovered by Bowler et al., validating our selection technique. Our new expanded galaxy sample includes the most massive galaxies known at z=~7, with M*=~10^10^M_{sun}_, and the majority are resolved, consistent with larger sizes (r_1/2_=~1-1.5kpc) than displayed by less massive galaxies. From our final robust sample, we determine the form of the bright end of the rest-frame UV galaxy luminosity function (LF) at z=~7, providing strong evidence that it does not decline as steeply as predicted by the Schechter-function fit to fainter data. We exclude the possibility that this is due to either gravitational lensing, or significant contamination of our galaxy sample by active galactic nuclei (AGN). Rather, our results favour a double power-law form for the galaxy LF at high redshift, or, more interestingly, an LF which simply follows the form of the dark matter halo mass function at bright magnitudes. This suggests that the physical mechanism which inhibits star formation activity in massive galaxies (i.e. AGN feedback or some other form of 'mass quenching') has yet to impact on the observable galaxy LF at z=~7, a conclusion supported by the estimated masses of our brightest galaxies which have only just reached a mass comparable to the critical 'quenching mass' of M*=~10^10.2^M_{sun}_ derived from studies of the mass function of star-forming galaxies at lower redshift.
We present a new determination of the ultraviolet (UV) galaxy luminosity function (LF) at redshift z=~7 and 8, and a first estimate at z=~9. An accurate determination of the form and evolution of the galaxy LF during this era is of key importance for improving our knowledge of the earliest phases of galaxy evolution and the process of cosmic reionization. Our analysis exploits to the full the new, deepest Wide Field Camera 3/infrared imaging from our Hubble Space Telescope (HST) Ultra-Deep Field 2012 (UDF12) campaign, with dynamic range provided by including a new and consistent analysis of all appropriate, shallower/wider area HST survey data. Our new measurement of the evolving LF at z=~7 to 8 is based on a final catalogue of =~600 galaxies, and involves a step-wise maximum-likelihood determination based on the photometric redshift probability distribution for each object; this approach makes full use of the 11-band imaging now available in the Hubble Ultra-Deep Field (HUDF), including the new UDF12 F140W data, and the latest Spitzer IRAC imaging. The final result is a determination of the z=~7 LF extending down to UV absolute magnitudes M_1500_=-16.75 (AB mag) and the z=~8 LF down to M_1500_=-17.00. Fitting a Schechter function, we find M_1500_^*^=-19.90^+0.23^_-0.28^, log{phi}^*^=-2.96^+0.18^_-0.23_ and a faint-end slope {alpha}=-1.90^+0.14^_-0.15_ at z=~7, and M_1500_^*^=-20.12^+0.37^_-0.48_, log{phi}^*^=-3.35^+0.28^_-0.47_ and {alpha}=-2.02^+0.22^_-0.23_ at z=~8. These results strengthen previous suggestions that the evolution at z>7 appears more akin to 'density evolution' than the apparent 'luminosity evolution' seen at z=~5-7. We also provide the first meaningful information on the LF at z=~9, explore alternative extrapolations to higher redshifts, and consider the implications for the early evolution of UV luminosity density. Finally, we provide catalogues (including derived z_phot_, M_1500_ and photometry) for the most robust z~6.5-11.9 galaxies used in this analysis. We briefly discuss our results in the context of earlier work and the results derived from an independent analysis of the UDF12 data based on colour-colour selection.
We present two new nonparametric methods for quantifying galaxy morphology: the relative distribution of the galaxy pixel flux values (the Gini coefficient or G) and the second-order moment of the brightest 20% of the galaxy's flux (M_20_). We test the robustness of G and M_20_ to decreasing signal-to-noise ratio (S/N) and spatial resolution and find that both measures are reliable to within 10% for images with average S/N per pixel greater than 2 and resolutions better than 1000 and 500pc, respectively. We have measured G and M_20_, as well as concentration (C), asymmetry (A), and clumpiness (S) in the rest-frame near-ultraviolet/optical wavelengths for 148 bright local "normal" Hubble-type galaxies (E-Sd) galaxies, 22 dwarf irregulars, and 73 0.05<z<0.25 ultraluminous infrared galaxies (ULIRGs).
Galaxies in the Hubble Ultra Deep Field (UDF) larger than 10 pixels (0.3") have been classified according to morphology, and their photometric properties are presented. There are 269 spiral, 100 elliptical, 114 chain, 126 double-clump, 97 tadpole, and 178 clump-cluster galaxies.
We study how optical galaxy morphology depends on mass and star formation rate (SFR) in the Illustris Simulation. To do so, we measure automated galaxy structures in 10808 simulated galaxies at z=0 with stellar masses 109.7<M*/M_{sun}_< 1012.3. We add observational realism to idealized synthetic images and measure non-parametric statistics in rest-frame optical and near-IR images from four directions. We find that Illustris creates a morphologically diverse galaxy population, occupying the observed bulge strength locus and reproducing median morphology trends versus stellar mass, SFR, and compactness. Morphology correlates realistically with rotation, following classification schemes put forth by kinematic surveys. Type fractions as a function of environment agree roughly with data. These results imply that connections among mass, star formation, and galaxy structure arise naturally from models matching global star formation and halo occupation functions when simulated with accurate methods. This raises a question of how to construct experiments on galaxy surveys to better distinguish between models. We predict that at fixed halo mass near 10^12^M_{sun}_, disc-dominated galaxies have higher stellar mass than bulge-dominated ones, a possible consequence of the Illustris feedback model. While Illustris galaxies at M*~10^11^M_{sun}_ have a reasonable size distribution, those at M*~10^10^M_{sun}_ have half-light radii larger than observed by a factor of 2. Furthermore, at M*~10^10.5^-10^11^M_{sun}_, a relevant fraction of Illustris galaxies have distinct 'ring-like' features, such that the bright pixels have an unusually wide spatial extent.