We present the first quantitative detection of large-scale filamentary structure at z NOT approximately equal to 0.7 in the large cosmological volume probed by the VIMOS Public Extragalactic ...Redshift Survey (VIPERS). We use simulations to show the capability of VIPERS to recover robust topological features in the galaxy distribution, in particular the filamentary network. We then investigate how galaxies with different stellar masses and stellar activities are distributed around the filaments, and find a significant segregation, with the most massive or quiescent galaxies being closer to the filament axis than less massive or active galaxies. The signal persists even after downweighting the contribution of peak regions. Our results suggest that massive and quiescent galaxies assemble their stellar mass through successive mergers during their migration along filaments towards the nodes of the cosmic web. On the other hand, low-mass star-forming galaxies prefer the outer edge of filaments, a vorticity-rich region dominated by smooth accretion, as predicted by the recent spin alignment theory. This emphasizes the role of large-scale cosmic flows in shaping galaxy properties.
We present the first Public Data Release (PDR-1) of the VIMOS Public Extragalactic Survey (VIPERS). It comprises 57 204 spectroscopic measurements together with all additional information necessary ...for optimal scientific exploitation of the data, in particular the associated photometric measurements and quantification of the photometric and survey completeness. VIPERS is an ESO Large Programme designed to build a spectroscopic sample of similar to 100 000 galaxies with i sub(AB) < 22.5 and 0.5 < z < 1.2 with high sampling rate ( similar to 45%). The survey spectroscopic targets are selected from the CFHTLS-Wide five-band catalogues in the W1 and W4 fields. The final survey will cover a total area of nearly 24 deg super(2), for a total comoving volume between z = 0.5 and 1.2 of similar to 4 x 10 super(7) h super(-3) Mpc super(3) and a median galaxy redshift of z similar to 0.8. The release presented in this paper includes data from virtually the entire W4 field and nearly half of the W1 area, thus representing 64% of the final dataset. We provide a detailed description of sample selection, observations and data reduction procedures; we summarise the global properties of the spectroscopic catalogue and explain the associated data products and their use, and provide all the details for accessing the data through the survey database (http://vipers.inaf.it) where all information can be queried interactively.
We study the impact of the environment on the evolution of galaxies in the zCOSMOS 10 k sample in the redshift range 0.1 ≤ z ≤ 1.0 over an area of ~1.5 deg2. The considered sample of secure ...spectroscopic redshifts contains about 8500 galaxies, with their stellar masses estimated by SED fitting of the multiwavelength optical to near-infrared (NIR) photometry. The evolution of the galaxy stellar mass function (GSMF) in high and low density regions provides a tool to study the mass assembly evolution in different environments; moreover, the contributions to the GSMF from different galaxy types, as defined by their SEDs and their morphologies, can be quantified. At redshift z ~ 1, the GSMF is only slightly dependent on environment, but at lower redshifts the shapes of the GSMFs in high- and low-density environments become extremely different, with high density regions exhibiting a marked bimodality, not reproducible by a single Schechter function. As a result of this analysis, we infer that galaxy evolution depends on both the stellar mass and the environment, the latter setting the probability of a galaxy to have a given mass: all the galaxy properties related to the stellar mass show a dependence on environment, reflecting the difference observed in the mass functions. The shapes of the GSMFs of early- and late-type galaxies are almost identical for the extremes of the density contrast we consider, ranging from isolated galaxies to rich group members. The evolution toward z = 0 of the transition mass ℳcross, i.e., the mass at which the early- and late-type GSMFs match each other, is more rapid in high density environments, because of a difference in the evolution of the normalisation of GSMFs compared to the total one in the considered environment. The same result is found by studying the relative contributions of different galaxy types, implying that there is a more rapid evolution in overdense regions, in particular for intermediate stellar masses. The rate of evolution is different for sets of galaxy types divided on the basis of their SEDs or their morphologies, tentatively suggesting that the migration from the blue cloud to the red sequence occurs on a shorter timescale than the transformation from disc-like morphologies to ellipticals. Our analysis suggests that environmental mechanisms of galaxy transformation start to be more effective at z < 1. The comparison of the observed GSMFs to the same quantities derived from a set of mock catalogues based on semi-analytical models shows disagreement, in both low and high density environments: in particular, blue galaxies in sparse environments are overproduced in the semi-analytical models at intermediate and high masses, because of a deficit of star formation suppression, while at z < 0.5 an excess of red galaxies is present in dense environments at intermediate and low masses, because of the overquenching of satellites.
We explore the accuracy of the clustering-based redshift estimation proposed by Ménard et al. when applied to VIMOS Public Extragalactic Redshift Survey (VIPERS) and Canada–France–Hawaii Telescope ...Legacy Survey (CFHTLS) real data. This method enables us to reconstruct redshift distributions from measurement of the angular clustering of objects using a set of secure spectroscopic redshifts. We use state-of-the-art spectroscopic measurements with i
AB < 22.5 from the VIPERS as reference population to infer the redshift distribution of galaxies from the CFHTLS T0007 release. VIPERS provides a nearly representative sample to a flux limit of i
AB < 22.5 at a redshift of >0.5 which allows us to test the accuracy of the clustering-based redshift distributions. We show that this method enables us to reproduce the true mean colour–redshift relation when both populations have the same magnitude limit. We also show that this technique allows the inference of redshift distributions for a population fainter than the reference and we give an estimate of the colour–redshift mapping in this case. This last point is of great interest for future large-redshift surveys which require a complete faint spectroscopic sample.
We present an analysis of the stellar mass growth over the last 10 Gyr ($z\le 2$) using a unique large sample of galaxies selected at $3.6~\mu$m. We have assembled accurate photometric and ...spectroscopic redshifts for ~21 200 and 1500 galaxies, respectively, with F(3.6 μm) ≥ 9.0 μJy by combining data from Spitzer-SWIRE IRAC, the VIMOS VLT Deep Survey (VVDS), UKIDSS and very deep optical CFHTLS photometry. We split our sample into quiescent (red) and active (blue) galaxies on the basis of an SED fitting procedure that we have compared with the strong rest-frame color bimodality $(NUV-r')_{\rm ABS}$. The present sample contains ~ 4400 quiescent galaxies. Our measurements of the K-rest frame luminosity function and luminosity density evolution support the idea that a large fraction of galaxies is already assembled at z ~ 1.2, with almost 80% and 50% of the active and quiescent populations already in place, respectively. Based on the analysis of the evolution of the stellar mass-to-light ratio (in K-band) for the spectroscopic sub-sample, we derive the stellar mass density for the entire sample. We find that the global evolution of the stellar mass density is well reproduced by the star formation rate derived from UV based measurements when an appropriate dust correction is applied, which supports the idea of an initial mass function that is on average universal. Over the last 8 Gyr (z ≤ 1.2) we observe that the stellar mass density of the active population shows a modest mass growth rate ($\dot{\rho}$ ~ 0.005(±0.005) $M_{\odot}$/Mpc3/yr), consistent with a constant stellar mass density, $\rho_{\star}^{\rm active}$ ~ 3.1 $\times$ 108 $M_{\odot}$/Mpc3. In contrast, an increase by a factor of ~2 for the quiescent population over the same timescale is observed. As a consequence, the growth of the stellar mass in the quiescent population must be due to the shutoff of star formation in active galaxies that migrate into the quiescent population. We estimate this stellar mass flux to be $\dot{\rho}_{A\rightarrow Q}$ ~ 0.017(±0.004) $M_{\odot}$/Mpc3/yr, which balances the major fraction of new stars born according to our best SFR estimate ($\dot{\rho}$ = 0.025(±0.003) $M_{\odot}$/Mpc3/yr). From $z = 2$ to $z = 1.2$, we observe a major build-up of the quiescent population with an increase by a factor of ~10 in stellar mass (a mass growth rate of ~ 0.063 $M_{\odot}$/Mpc3/yr). This rapid evolution suggests that we are observing the epoch when, for the first time in the history of the universe, an increasing fraction of galaxies end their star formation activity and start to build up the red sequence.
Context. For more than two decades we have known that galaxy morphological segregation is present in the Local Universe. It is important to see how this relation evolves with cosmic time. Aims. To ...investigate how galaxy assembly took place with cosmic time, we explore the evolution of the morphology-density relation up to redshift z ~ 1 using about 10 000 galaxies drawn from the zCOSMOS Galaxy Redshift Survey. Taking advantage of accurate HST/ACS morphologies from the COSMOS survey, of the well-characterised zCOSMOS 3D environment, and of a large sample of galaxies with spectroscopic redshift, we want to study here the evolution of the morphology-density relation up to z ~ 1 and its dependence on galaxy luminosity and stellar mass. The multi-wavelength coverage of the field also allows a first study of the galaxy morphological segregation dependence on colour. We further attempt to disentangle between processes that occurred early in the history of the Universe or late in the life of galaxies. Methods. The zCOSMOS field benefits of high-resolution imaging in the F814W filter from the Advanced Camera for Survey (ACS). We use standard morphology classifiers, optimised for being robust against band-shifting and surface brightness dimming, and a new, objective, and automated method to convert morphological parameters into early, spiral, and irregular types. We use about 10 000 galaxies down to IAB = 22.5 with a spectroscopic sampling rate of 33% to characterise the environment of galaxies up to z ~ 1 from the 100 kpc scales of galaxy groups up to the 100 Mpc scales of the cosmic web. The evolution of the morphology-density relation in different environments is then studied for luminosity and stellar-mass selected, volume-limited samples of galaxies. The trends are described and related to the various physical processes that could play a relevant role in the build-up of the morphology-density relation. Results. We confirm that the morphological segregation is present up to z ~ 1 for luminosity-selected, volume-limited samples. The behaviour of the morphology-density relation gets flatter at fixed masses expecially above 1010.6 $M_{\odot}$. We suggest the existence of a critical mass above which the physical processes governing galaxy stellar mass also determine the shaping of the galaxy more than its environment. We finally show that at a fixed morphology there is still a residual variation in galaxy colours with density. Conclusions. The observed evolution with redshift of the morphology-density relation offers an opportunity to trace the effect of nature and nurture as a function of environment. Even though it is based mainly on a biased view, the environmental dependence of the morphological evolution for luminosity-selected, volume-limited samples seems to indicate that nurture is in play. On the other hand, the lack of evolution observed for early-type and spiral galaxies that are more massive than 1010.8 $M_{\odot}$ independents of the environment indicates that nature has imprinted these properties early in the life of these galaxies. We conclude that the relative contribution of nature and nurture in different environments strongly depends on the mass of galaxies, consistent with a downsizing scenario.
We present a detailed analysis of the Galaxy Stellar Mass Function (GSMF) of galaxies up to z =2.5 as obtained from the VIMOS VLT Deep Survey (VVDS). Our survey offers the possibility to investigate ...the GSMF using two different samples: (1) an optical ( I-selected 17.5 <I_{\rm AB}<24) main spectroscopic sample of about 6500 galaxies over 1750 arcmin super(2) and (2) a near-IR ( K-selected K_{\rm AB}<22.34 similar to {\rm and} similar to K_{\rm AB}<22.84) sample of about 10 200 galaxies, with photometric redshifts accurately calibrated on the VVDS spectroscopic sample, over 610 arcmin super(2). We apply and compare two different methods to estimate the stellar mass {\cal M}_{\rm stars} from broad-band photometry based on different assumptions about the galaxy star-formation history. We find that the accuracy of the photometric stellar mass is satisfactory overall, and show that the addition of secondary bursts to a continuous star formation history produces systematically higher (up to 40%) stellar masses. We derive the cosmic evolution of the GSMF, the galaxy number density and the stellar mass density in different mass ranges. At low redshift ( z\simeq0.2) we find a substantial population of low-mass galaxies (<10 { similar to M_\odot) composed of faint blue galaxies ( M_I-M_K \simeq 0.3). In general the stellar mass function evolves slowly up to z\sim0.9 and more rapidly above this redshift, in particular for low mass systems. Conversely, a massive population is present up to z =2.5 and has extremely red colours ( M_I-M_K\simeq 0.7-0.8). We find a decline with redshift of the overall number density of galaxies for all masses (59\pm5% for 10 proportional to similar to M_\odot$--> {\cal M}_{\rm stars} > 10 proportional to similar to M_\odot at z =1), and a mild mass-dependent average evolution ("mass-downsizing"). In particular our data are consistent with mild/negligible (<30%) evolution up to z\sim0.7 for massive galaxies ( }6\times10 6M_\odot$--> {>}6\times10 6M_\odot). For less massive systems the no-evolution scenario is excluded. Specifically, a large fraction ({\ge}50\%) of massive galaxies have been assembled and converted most of their gas into stars at z\sim1, ruling out "dry mergers" as the major mechanism of their assembly history below z\simeq1. This fraction decreases to {\sim}33\% at z\sim2. Low-mass systems have decreased continuously in number density (by a factor of up to 4.1\pm0.9) from the present age to z =2, consistent with a prolonged mass assembly also at z <1. The evolution of the stellar mass density is relatively slow with redshift, with a decrease of a factor of 2.3\pm0.1 at z =1 and about 4.5\pm0.3 at z =2.5.
Aims. Using the VIMOS Public Extragalactic Redshift Survey (VIPERS) we aim to jointly estimate the keyparameters that describe the galaxy density field and its spatial correlations in redshift space. ...Methods. We use the Bayesian formalism to jointly reconstruct the redshift-space galaxy density field, power spectrum, galaxy bias and galaxy luminosity function given the observations and survey selection function. The high-dimensional posterior distribution is explored using the Wiener filter within a Gibbs sampler. We validate the analysis using simulated catalogues and apply it to VIPERS data taking into consideration the inhomogeneous selection function. Results. We present joint constraints on the anisotropic power spectrum, and the bias and number density of red and blue galaxy classes in luminosity and redshift bins as well as the measurement covariances of these quantities. We find that the inferred galaxy bias and number density parameters are strongly correlated although they are only weakly correlated with the galaxy power spectrum. The power spectrum and redshift-space distortion parameters are in agreement with previous VIPERS results with the value of the growth rate fsigma sub(8) = 0.38 with 18% uncertainty at redshift 0.7.
We used the VIMOS Public Extragalactic Redshift Survey (VIPERS) final data release (PDR-2) to investigate the performance of colour-selected populations of galaxies as tracers of linear large-scale ...motions. We empirically selected volume-limited samples of blue and red galaxies as to minimise the systematic error on the estimate of the growth rate of structure fσ8 from the anisotropy of the two-point correlation function. To this end, rather than rigidly splitting the sample into two colour classes we defined the red or blue fractional contribution of each object through a weight based on the (U − V) colour distribution. Using mock surveys that are designed to reproduce the observed properties of VIPERS galaxies, we find the systematic error in recovering the fiducial value of fσ8 to be minimised when using a volume-limited sample of luminous blue galaxies. We modelled non-linear corrections via the Scoccimarro extension of the Kaiser model (with updated fitting formulae for the velocity power spectra), finding systematic errors on fσ8 of below 1–2%, using scales as small as 5 h−1 Mpc. We interpret this result as indicating that selection of luminous blue galaxies maximises the fraction that are central objects in their dark matter haloes; this in turn minimises the contribution to the measured ξ(rp,π) from the 1-halo term, which is dominated by non-linear motions. The gain is inferior if one uses the full magnitude-limited sample of blue objects, consistent with the presence of a significant fraction of blue, fainter satellites dominated by non-streaming, orbital velocities. We measured a value of f σ8 = 0.45 ± 0.11 over the single redshift range 0.6 ≤ z ≤ 1.0, corresponding to an effective redshift for the blue galaxies 〈z〉=0.85. Including in the likelihood the potential extra information contained in the blue-red galaxy cross-correlation function does not lead to an appreciable improvement in the error bars, while it increases the systematic error.
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