Aims. We seek is to identify old and massive galaxies at 0.5 < z < 2.1 on the basis of the magnesium index MgUV and then study their physical properties. Methods. We computed the MgUV index based on ...the best spectral fitting template of ∼3700 galaxies using data from the VLT VIMOS Deep Survey (VVDS) and VIMOS Ultra Deep Survey (VUDS) galaxy redshift surveys. Based on galaxies with the largest signal to noise and the best fit spectra we selected 103 objects with the highest spectral MgUV signature. We performed an independent fit of the photometric data of these galaxies and computed their stellar masses, star formation rates, extinction by dust and age, and we related these quantities to the MgUV index. Results. We find that the MgUV index is a suitable tracer of early-type galaxies at an advanced stage of evolution. Selecting galaxies with the highest MgUV index allows us to choose the most massive, passive, and oldest galaxies at any epoch. The formation epoch tf computed from the fitted age as a function of the total mass in stars supports the downsizing formation paradigm in which galaxies with the highest mass formed most of their stars at an earlier epoch.
Aims. We present a study of a large filamentary structure at z ~ 0.73 in the field of the COSMOS survey, the so-called COSMOS Wall. This structure encompasses a comprehensive range of environments ...from a dense cluster and a number of galaxy groups to filaments, less dense regions, and adjacent voids. It thus provides a valuable laboratory for the accurate mapping of environmental effects on galaxy evolution at a look-back time of ~6.5 Gyr, when the Universe was roughly half its present age. Methods. We performed deep spectroscopic observations with VIMOS at VLT of a K-band selected sample of galaxies in this complex structure, building a sample of galaxies complete in galaxy stellar mass down to a lower limit of log(ℳ∗/ℳ⊙) ~ 9.8, which is significantly deeper than previously available data. Thanks to its location within the COSMOS survey, each galaxy benefits from a wealth of ancillary information: HST-ACS data with I-band exposures down to IAB ~ 28 complemented by extensive multiwavelength ground- and space-based observations spanning the entire electromagnetic spectrum. Results. In this paper we detail the survey strategy and weighting scheme adopted to account for the biases introduced by the photometric preselection of our targets. We present our galaxy stellar mass and rest-frame magnitudes estimates together with a group catalog obtained with our new data and their member galaxies color/mass distribution. Conclusions. Owing to our new sample we can perform a detailed, high definition mapping of the complex COSMOS Wall structure. The sharp environmental information, coupled with high quality spectroscopic information and rich ancillary data available in the COSMOS field, enables a detailed study of galaxy properties as a function of local environment in a redshift slice where environmental effects are important, and in a stellar mass range where mass and environment driven effects are both at work.
Context. Studies of the infrared (IR) emission of cosmic sources have proven essential to constraining the evolutionary history of cosmic star formation and the gravitational accretion of nuclear ...black holes, because many of these events occur inside heavily dust-extinguished environments. Aims. The Spitzer Space Telescope has provided a large amount of data to constrain the nature and cosmological evolution of infrared source populations. In the present paper we exploit a large homogeneous dataset to derive a self-consistent picture of IR emission based on the time-dependent $\lambda_{\rm eff}$ = 24, 15, 12, and 8 μm monochromatic and bolometric IR luminosity functions (LF) over the full 0 < z < 2.5 redshift range. Methods. Our present analysis is based on a combination of data from deep Spitzer surveys of the VIMOS VLT Deep Survey (VVDS-SWIRE) and GOODS fields. To our limiting flux of S24 = 400 μJy, our sample derived from VVDS-SWIRE includes 1494 sources, and 666 and 904 sources brighter than S24 = 80 μJy are catalogued in GOODS-S and GOODS-N, respectively, for a total area of ~0.9 square degrees. Apart from a few galaxies, we obtain reliable optical identifications and redshifts for all these sources, providing a rich and robust dataset for our luminosity function determination. The final combined reliable sample includes 3029 sources, the fraction with photometric redshifts being 72% over all redshifts and almost all galaxies at z > 1.5. Based on the multiwavelength information available in these areas, we constrain the LFs at 8, 12, 15, and 24 μm. We also infer the total IR luminosities from our best-fit model of the observed SEDs of each source, and use this to derive the bolometric (8–1000 μm) LF and comoving volume emissivity to z ~ 2.5. Results. In the redshift interval 0 < z < 1, the bolometric IR luminosity density evolves as (1 + z)$^{3.8\pm0.4}$. Although it is more uncertain at higher-z, our results show a flattening in the IR luminosity density at z > 1. The mean redshift of the peak in the source number density shifts with luminosity: the brightest IR galaxies appear to form stars at earlier cosmic times (z > 1.5), while star formation in the less luminous galaxies continues until more recent epochs (z ~ 1 for LIR < 1011 $L_{\odot}$), in overall agreement with similar analyses in the literature. Conclusions. Our results are indicative of a rapid increase in the galaxy IR comoving volume emissivity up to z ~ 1 and a constant average emissivity at z > 1. We also appear to measure a difference in the evolutionary rate of the source number densities as a function of luminosity, which is consistent with the downsizing evolutionary patterns reported for other samples of cosmic sources.
We investigate of the properties of ~2000 Herschel/SPIRE far-infrared-selected galaxies from 0 <z< 4 in the CFHTLS-D1 field. Using a combination of extensive spectroscopy from the VVDS and ORELSE ...surveys, deep multiwavelength imaging from CFHT, VLA, Spitzer, XMM-Newton, and Herschel, and well-calibrated spectral energy distribution fitting, Herschel-bright galaxies are compared to optically-selected galaxies at a variety of redshifts. Herschel-selected galaxies are observed to span a range of stellar masses, colors, and absolute magnitudes equivalent to galaxies undetected in SPIRE. Though many Herschel galaxies appear to be in transition, such galaxies are largely consistent with normal star-forming galaxies when rest-frame colors are utilized. The nature of the star-forming “main sequence” is studied and we warn against adopting this framework unless the main sequence is determined precisely. Herschel galaxies at different total infrared luminosities (LTIR) are compared. Bluer optical colors, larger nebular extinctions, and larger contributions from younger stellar populations are observed for galaxies with larger LTIR, suggesting that low-LTIR galaxies are undergoing rejuvenated starbursts while galaxies with higher LTIR are forming a larger percentage of their stellar mass. A variety of methods are used to select powerful active galactic nuclei (AGN). Galaxies hosting all types of AGN are observed to be undergoing starbursts more commonly and vigorously than a matched sample of galaxies without powerful AGN and, additionally, the fraction of galaxies with an AGN increases with increasing star formation rate at all redshifts. At all redshifts (0 <z< 4) the most prodigious star-forming galaxies are found to contain the highest fraction of powerful AGN. For redshift bins that allow a comparison (z> 0.5), the highest LTIR galaxies in a given redshift bin are unobserved by SPIRE at subsequently lower redshifts, a trend linked to downsizing. In conjunction with other results, this evidence is used to argue for prevalent AGN-driven quenching in starburst galaxies across cosmic time.
The VIMOS Ultra Deep Survey Durkalec, A.; Le Fèvre, O.; Pollo, A. ...
Astronomy and astrophysics (Berlin),
04/2018, Letnik:
612
Journal Article
Recenzirano
Odprti dostop
We present a study of the dependence of galaxy clustering on luminosity and stellar mass in the redshift range 2 < z < 3.5 using 3236 galaxies with robust spectroscopic redshifts from the VIMOS Ultra ...Deep Survey (VUDS), covering a total area of 0.92 deg2. We measured the two-point real-space correlation function wp(rp) for four volume-limited subsamples selected by stellar mass and four volume-limited subsamples selected by MUV absolute magnitude. We find that the scale-dependent clustering amplitude r0 significantly increases with increasing luminosity and stellar mass. For the least luminous galaxies (MUV < −19.0), we measured a correlation length r0 = 2.87 ± 0.22 h−1 Mpc and slope γ = 1.59 ± 0.07, while for the most luminous (MUV < −20.2) r0 = 5.35 ± 0.50 h−1 Mpc and γ = 1.92 ± 0.25. These measurements correspond to a strong relative bias between these two subsamples of Δb∕b* = 0.43. Fitting a five-parameter halo occupation distribution (HOD) model, we find that the most luminous (MUV < −20.2) and massive (M⋆ > 1010 h−1 M⊙) galaxies occupy the most massive dark matter haloes with ⟨Mh⟩ = 1012.30 h−1 M⊙. Similar to the trends observed at lower redshift, the minimum halo mass Mmin depends on the luminosity and stellar mass of galaxies and grows from Mmin = 109.73 h−1 M⊙ to Mmin = 1011.58 h−1 M⊙ from the faintest to the brightest among our galaxy sample, respectively. We find the difference between these halo masses to be much more pronounced than is observed for local galaxies of similar properties. Moreover, at z ~ 3, we observe that the masses at which a halo hosts, on average, one satellite and one central galaxy is M1 ≈ 4Mmin over all luminosity ranges, which is significantly lower than observed at z ~ 0; this indicates that the halo satellite occupation increases with redshift. The luminosity and stellar mass dependence is also reflected in the measurements of the large-scale galaxy bias, which we model as bg,HOD (>L) = 1.92 + 25.36(L/L*)7.01. We conclude our study with measurements of the stellar-to-halo mass ratio (SHMR). We observe a significant model-observation discrepancy for low-mass galaxies, suggesting a higher than expected star formation efficiency of these galaxies.
Aims.
Our aim is to analyze the variance of the intergalactic medium (IGM) transmission by studying this parameter in the rest-frame UV spectra of a large sample of high-redshift galaxies.
Methods.
...We made use of the VIMOS Ultra Deep Survey and the VANDELS public survey to gain insight into the far UV spectrum of 2.7 <
z
< 6 galaxies. Using the SPARTAN fitting software, we estimated the IGM toward individual galaxies and then divided them into two sub-samples characterized by a transmission above or below the theoretical prescription. We created average spectra of combined VUDS and VANDELS data for each set of galaxies in seven redshift bins.
Results.
The resulting spectra clearly exhibit the variance of the IGM transmission that can be seen directly from high-redshift galaxy observations. Computing the optical depth based on the IGM transmission, we find an excellent agreement with results for quasi-stellar objects. In addition, our measurements appear to suggest that there is a large dispersion of redshift where a complete Gunn-Peterson Trough occurs, depending on the line of sight.
Context. The mechanisms giving rise to diffuse radio emission in galaxy clusters and, in particular, their connection with cluster mergers are still being debated. Aims. We explore the internal ...dynamics of Abell 2254, which has been shown to host a very clumpy and irregular radio halo. Methods. Our analysis is mainly based on redshift data for 128 galaxies acquired at the Telescopio Nazionale Galileo. We combined galaxy velocities and positions to select 110 cluster galaxies and analyze its internal dynamics. We also used new (g′, r′, i′) photometric data acquired at the Isaac Newton Telescope, and (V, i′) photometric data available in the Subaru Archive. X-ray data from the XMM-Newton Science Archive were analyzed to study the hot gas component. Results. We estimate the cluster redshift ⟨z⟩ = 0.177, a high line-of-sight (LOS) velocity dispersion, σV ~ 1350 km s-1, and the X-ray temperature kT ~ 6.4 keV. Both our optical and X-ray analyses reveal complex dynamical activity. The analysis of the 2D galaxy distribution reveals the presence of two density peaks, one to the east and the other to the west (E and W peaks). Using the full 3D information we detect a high-velocity (ΔVrf,LOS ~ 3000 km s-1), low-mass (σV ~ 200–500 km s-1) group at the position of the 2D E peak. For the main system we compute a velocity dispersion σV ~ 1000–1200 km s-1. In the assumption of a bimodal system we estimate a mass Msys = 1.5–2.9 \hbox{$\times 10^{15}\;h_{70}^{-1}\;M_{\odot}$}×1015h70-1M⊙. The X-ray morphological analysis, which is based on power ratios, centroid shifts, and concentration parameter, confirms that Abell 2254 is a dynamically disturbed cluster. The X-ray isophotes are elongated in the east direction, in agreement with a merger in the post core-crossing phase. A simple bimodal model finds that data are consistent with a bound, outgoing subcluster observed a few fractions of Gyr after the core crossing. However, both optical and X-ray analyses suggest that the main system is, in turn, a nonrelaxed structure, indicating north-south as a possible direction for a past accretion. Conclusions. We conclude that Abell 2254, for its mass and merging structure, fits well among the typical clusters with radio halos. We briefly discuss how the particular irregularity of the radio halo might be linked to the complexity of the Abell 2254 structure.
Aims. We present a detailed study of the giant radio halo in the galaxy cluster Abell 697 to constrain its origin and connection with the cluster dynamics. Methods. We performed high sensitivity GMRT ...observations at 325 MHz, which showed that the radio halo is much brighter and larger at this frequency than in previous 610 MHz observations. To derive the integrated spectrum in the frequency range 325 MHz-1.4 GHz, we reanalysed archival VLA data at 1.4 GHz and used proprietary GMRT data at 610 MHz. Results. Our multifrequency analysis shows that the total radio spectrum of the giant radio halo in A 697 is very steep, with $\alpha_{\rm~325\, MHz}^{\rm~1.4\, GHz}$ ≈ 1.7–1.8. Owing to energy arguments, a hadronic origin of the halo is disfavoured by this steep spectrum. Very steep spectrum halos in merging clusters are predicted in the case that the emitting electrons are accelerated by turbulence. Observations with upcoming low frequency arrays will be able to test these expectations.
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