The Vimos VLT deep survey Garilli, B.; Le Fèvre, O.; Guzzo, L. ...
Astronomy and astrophysics (Berlin),
08/2008, Letnik:
486, Številka:
3
Journal Article
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Context. The VVDS-Wide survey has been designed to trace the large-scale distribution of galaxies at z similar to 1 on comoving scales reaching similar to 100 h super(-1) Mpc, while providing a good ...control of cosmic variance over areas as large as a few square degrees. This is achieved by measuring redshifts with VIMOS at the ESO VLT to a limiting magnitude I AB = 22.5, targeting four independent fields with sizes of up to 4 deg super(2) each. Aims. We discuss the survey strategy which covers 8.6 deg super(2) and present the general properties of the current redshift sample. This includes 32 734 spectra in the four regions, covering a total area of 6.1 deg super(2) with a sampling rate of 22 to 24%. This paper accompanies the public release of the first 18 143 redshifts of the VVDS-Wide survey from the 4 deg super(2) contiguous area of the F22 field at RA = 22\rm phi . Methods. We have devised and tested an objective method to assess the quality of each spectrum, providing a compact figure-of-merit. This is particularly effective in the case of long-lasting spectroscopic surveys with varying observing conditions. Our figure of merit is a measure of the robustness of the redshift measurement and, most importantly, can be used to select galaxies with uniform high-quality spectra to carry out reliable measurements of spectral features. We also use the data available over the four independent regions to directly measure the variance in galaxy counts. We compare it with general predictions from the observed galaxy two-point correlation function at different redshifts and with that measured in mock galaxy surveys built from the Millennium simulation. Results. The purely magnitude-limited VVDS Wide sample includes 19 977 galaxies, 304 type I AGNs, and 9913 stars. The redshift success rate is above 90% independent of magnitude. A cone diagram of the galaxy spatial distribution provides us with the current largest overview of large-scale structure up to z similar to 1, showing a rich texture of over- and under-dense regions. We give the mean N (z) distribution averaged over 6.1 deg super(2) for a sample limited in magnitude to I AB = 22.5. Comparing galaxy densities from the four fields shows that in a redshift bin Delta z = 0.1 at z similar to 1 one still has factor-of-two variations over areas as large as similar to 0.25 deg super(2). This level of cosmic variance agrees with that obtained by integrating the galaxy two-point correlation function estimated from the F22 field alone. It is also in fairly good statistical agreement with that predicted by the Millennium simulations. Conclusions. The VVDS WIDE survey currently provides the largest area coverage among redshift surveys reaching z similar to 1. The variance estimated over the survey fields shows explicitly how clustering results from deep surveys of even 1 deg super(2) size should be interpreted with caution. The survey data represent a rich data base to select complete sub-samples of high-quality spectra and to study galaxy ensemble properties and galaxy clustering over unprecedented scales at these redshifts. The redshift catalog of the 4 deg super(2) F22 field is publicly available at http://cencosw.oamp.fr.
We use the unparalleled statistics of the VIPERS survey to investigate the relation between the surface mean stellar mass density Σ = ℳ/ (2 πRe2) ( 2 π R e 2 ) $ (2\,\pi{R}_{\mathrm{e}}^{2}) $ of ...massive passive galaxies (MPGs, ℳ ≥ 1011 M⊙) and their local environment in the redshift range 0.5 ≤ z ≤ 0.8. Passive galaxies were selected on the basis of their NUVrK colors (∼900 objects), and the environment was defined as the galaxy density contrast, δ, using the fifth nearest-neighbor approach. The analysis of Σ versus δ was carried out in two stellar mass bins. In galaxies with ℳ ≤ 2 × 1011 M⊙, no correlation between Σ and δ is observed. This implies that the accretion of satellite galaxies, which is more frequent in denser environments (groups or cluster outskirts) and efficient in reducing the galaxy Σ, is not relevant in the formation and evolution of these systems. Conversely, in galaxies with ℳ > 2 × 1011 M⊙, we find an excess of MPGs with low Σ and a deficit of high-Σ MPGs in the densest regions with respect to other environments. We interpret this result as due to the migration of some high-Σ MPGs (< 1% of the total population of MPGs) into low-Σ MPGs, probably through mergers or cannibalism of small satellites. In summary, our results imply that the accretion of satellite galaxies has a marginal role in the mass-assembly history of most MPGs. We have previously found that the number density of VIPERS massive star-forming galaxies (MSFGs) declines rapidily from z = 0.8 to z = 0.5, which mirrors the rapid increase in the number density of MPGs. This indicates that the MSFGs at z ≥ 0.8 migrate to the MPG population. Here, we investigate the Σ–δ relation of MSFGs at z ≥ 0.8 and find that it is consistent within 1σ with that of low-Σ MPGs at z ≤ 0.8. Thus, the results of this and our previous paper show that MSFGs at z ≥ 0.8 are consistent in terms of number and environment with being the progenitors of low-Σ MPGs at z < 0.8.
We derive the mass-metallicity relation of star-forming galaxies up to $z\sim0.9$, using data from the VIMOS VLT Deep Survey. Automatic measurement of emission-line fluxes and equivalent widths have ...been performed on the full spectroscopic sample. This sample is divided into two sub-samples depending on the apparent magnitude selection: wide ($I_{\mathrm{AB}}<22.5$) and deep $I_{\mathrm{AB}}<24$). These two samples span two different ranges of stellar masses. Emission-line galaxies have been separated into star-forming galaxies and active galactic nuclei using emission line ratios. For the star-forming galaxies the emission line ratios have also been used to estimate gas-phase oxygen abundance, using empirical calibrations renormalized in order to give consistent results at low and high redshifts. The stellar masses have been estimated by fitting the whole spectral energy distributions with a set of stellar population synthesis models. We assume at first order that the shape of the mass-metallicity relation remains constant with redshift. Then we find a stronger metallicity evolution in the wide sample as compared to the deep sample. We thus conclude that the mass-metallicity relation is flatter at higher redshift. The observed flattening of the mass-metallicity relation at high redshift is analyzed as an evidence in favor of the open-closed model.
We measure the real-space galaxy power spectrum on large scales at redshifts 0.5-1.2 using optical colour selected samples from the Canada-France-Hawaii Telescope Legacy Survey. With the redshift ...distributions measured with a preliminary ∼14 000 spectroscopic redshifts from the VIMOS Public Extragalactic Redshift Survey (VIPERS), we deproject the angular distribution and directly estimate the three-dimensional power spectrum. We use a maximum likelihood estimator that is optimal for a Gaussian random field giving well-defined window functions and error estimates. This measurement presents an initial look at the large-scale structure field probed by the VIPERS. We measure the galaxy bias of the VIPERS-like sample to be b
g= 1.38 ± 0.05 (σ8= 0.8) on scales k < 0.2 h Mpc−1 averaged over 0.5 < z < 1.2. We further investigate three photometric redshift slices, and marginalizing over the bias factors while keeping other Λ cold dark matter parameters fixed, we find the matter density Ωm= 0.30 ± 0.06.
We investigate the redshift and luminosity evolution of the galaxy colour-density relation using the data from the First Epoch VIMOS-VLT Deep Survey (VVDS). The size (6582 galaxies with good quality ...redshifts), depth ($I_{AB}\leq 24$) and redshift sampling rate (20% on the mean) of the survey enable us to reconstruct the 3D galaxy environment on relatively local scales ($R=5$$\,h^{-1}$ Mpc) up to redshift $z \sim 1.5$. Particular attention has been devoted to calibrate a density reconstruction scheme, which factors out survey selection effects and reproduces in an unbiased way the underlying “real” galaxy environment. We find that the colour-density relation shows a dramatic change as a function of cosmic time. While at lower redshift we confirm the existence of a steep colour-density relation, with the fraction of the reddest(/bluest) galaxies of the same luminosity increasing(/decreasing) as a function of density, this trend progressively disappears in the highest redshift bins investigated. Our results suggest the existence of an epoch (more remote for brighter galaxies) characterized by the absence of the colour-density relation on the $R=5$$\,h^{-1}$ Mpc scales investigated. The rest frame $u^{*}-g'$ colour–magnitude diagram shows a bimodal pattern in both low and high density environments up to redshift $z\sim 1.5$. We find that the bimodal distribution is not universal but strongly depends upon environment: at lower redshifts the colour–magnitude diagrams in low and high density regions are significantly different while the progressive weakening of the colour-density relation causes the two bimodal distributions to nearly mirror each other in the highest redshift bin investigated. Both the colour-density and the colour–magnitude-density relations, on the $R=5$$\,h^{-1}$ Mpc scales, appear to be a transient, cumulative product of genetic and environmental factors that have been operating over at least a period of 9 Gyr. These findings support an evolutionary scenario in which star formation/gas depletion processes are accelerated in more luminous objects and in high density environments: star formation activity is progressively shifting with cosmic time towards lower luminosity galaxies (downsizing), and out of high density environments.
Aims. We analyse the properties of the host galaxies of a NeV-selected sample to investigate whether and how they are affected by the AGN. Methods. We have selected a sample of galaxies at 0.62 < z ...< 1.2 from the VIMOS Public Extragalactic Redshift Survey (VIPERS) and divided it in blue cloud galaxies, red passive galaxies and green valley galaxies using the NUVrK diagram. Within each category, galaxies with AGN activity were identified based on the detection of the high-ionisation NeVλ3426 emission line. For each galaxy we derived several properties (stellar age and mass, the (r−K) colour, the OII luminosity) and compared them between active and inactive galaxies matched in stellar mass and redshift. Results. We find statistically significant differences in the properties between active and inactive galaxies. These differences imply that the AGN is more often found in galaxies with younger stellar populations and more recent star-forming activity than their parent samples. Interestingly, the AGN identified through the NeVλ3426 emission line is not commonly found by traditional AGN-selection techniques based on shallow X-ray data, mid-IR colours, and classical line diagnostic diagrams, and might thus reveal a specific evolutionary phase. The spectral analysis reveals a sub-set of AGN within the blue cloud that has spectral signatures implying a sudden suppression of star formation activity similar to post-starburst galaxies. Conclusion. Using the rich dataset of the large VIPERS sample we identify a novel class of active post-starburst galaxies that would be missed by traditional selection techniques. These galaxies belong to the blue cloud, but their star-formation activity has been recently suppressed, possibly by the AGN identified through the presence of the NeVλ3426 emission line in their spectra. Our results support the idea that AGN feedback may be responsible for halting star-formation in active blue galaxies and for their transition into the red sequence, at least in the 0.6–1.2 redshift range and for stellar masses greater than 5 × 1010 ℳ⊙. Our results are based on a complete spectroscopic sample and limited by the NeV observability, and the AGN can be variable and with a relatively short duty cycle. Considering this, AGN feedback that makes blue galaxies quickly transition to the red sequence may be even more common than previously believed.
The VIPERS galaxy survey has measured the clustering of 0.5 < z < 1.2 galaxies, enabling a number of measurements of galaxy properties and cosmological redshift-space distortions (RSD). Because the ...measurements were made using one-pass of the VIMOS instrument on the Very Large Telescope (VLT), the galaxies observed only represent approximately 47% of the parent target sample, with a distribution imprinted with the pattern of the VIMOS slitmask. Correcting for the effect on clustering has previously been achieved using an approximate approach developed using mock catalogues. Pairwise inverse probability (PIP) weighting has recently been proposed to correct for missing galaxies, and we apply it to mock VIPERS catalogues to show that it accurately corrects the clustering for the VIMOS effects, matching the clustering measured from the observed sample to that of the parent. We then apply PIP-weighting to the VIPERS data, and fit the resulting monopole and quadrupole moments of the galaxy two-point correlation function with respect to the line-of-sight, making measurements of RSD. The results are close to previous measurements, showing that the previous approximate methods used by the VIPERS team are sufficient given the errors obtained on the RSD parameter.
Aims. Various galaxy classification schemes have been developed so far to constrain the main physical processes regulating evolution of different galaxy types. In the era of a deluge of astrophysical ...information and recent progress in machine learning, a new approach to galaxy classification has become imperative. Methods. In this paper, we employ a Fisher Expectation-Maximization (FEM) unsupervised algorithm working in a parameter space of 12 rest-frame magnitudes and spectroscopic redshift. The model (DBk) and the number of classes (12) were established based on the joint analysis of standard statistical criteria and confirmed by the analysis of the galaxy distribution with respect to a number of classes and their properties. This new approach allows us to classify galaxies based on only their redshifts and ultraviolet to near-infrared (UV–NIR) spectral energy distributions. Results. The FEM unsupervised algorithm has automatically distinguished 12 classes: 11 classes of VIPERS galaxies and an additional class of broad-line active galactic nuclei (AGNs). After a first broad division into blue, green, and red categories, we obtained a further sub-division into: three red, three green, and five blue galaxy classes. The FEM classes follow the galaxy sequence from the earliest to the latest types, which is reflected in their colours (which are constructed from rest-frame magnitudes used in the classification procedure) but also their morphological, physical, and spectroscopic properties (not included in the classification scheme). We demonstrate that the members of each class share similar physical and spectral properties. In particular, we are able to find three different classes of red passive galaxy populations. Thus, we demonstrate the potential of an unsupervised approach to galaxy classification and we retrieve the complexity of galaxy populations at z ∼ 0.7, a task that usual, simpler, colour-based approaches cannot fulfil.
Aims. The three-point correlation function (3PCF) is a powerful probe to investigate the clustering of matter in the Universe in a complementary way with respect to lower-order statistics, providing ...additional information with respect to the two-point correlation function and allowing us to shed light on biasing, non-linear processes, and deviations from Gaussian statistics. In this paper, we analyse the first data release of the VIMOS Public Extragalactic Redshift Survey (VIPERS), determining the dependence of the three-point correlation function on luminosity and stellar mass at z = 0.5,1.1 . Methods. We exploit the VIPERS Public Data Release 1, consisting of more than 50 000 galaxies with B-band magnitudes in the range − 21.6 ≲ MB − 5log (h) ≲ − 19.9 and stellar masses in the range 9.8 ≲ log (M⋆ h-2M⊙ ) ≲ 10.7. We measure both the connected 3PCF and the reduced 3PCF in redshift space, probing different configurations and scales, in the range 2.5 <rh-1 Mpc < 20. Results. We find a significant dependence of the reduced 3PCF on scales and triangle shapes, with stronger anisotropy at larger scales (r ~ 10h-1 Mpc ) and an almost flat trend at smaller scales, r ~ 2.5h-1 Mpc . Massive and luminous galaxies present a larger connected 3PCF, while the reduced 3PCF is remarkably insensitive to magnitude and stellar masses in the range we explored. These trends, already observed at low redshifts, are confirmed for the first time to be still valid up to z = 1.1, providing support to the hierarchical scenario for which massive and bright systems are expected to be more clustered. The possibility of using the measured 3PCF to provide independent constraints on the linear galaxy bias b has also been explored, showing promising results in agreement with other probes.
From first epoch observations of the VIMOS VLT Deep Survey (VVDS) we have derived luminosity functions for galaxy samples selected by spectral type out to z =1.5. With the VVDS we are able to ...investigate within the same sample the evolution of the type dependent luminosity function selected in several rest-frame bands over 70% of the age of the Universe. The simple lesssim0.5 mag for early type galaxies to similar to 1 mag for the latest type galaxies, while the slope of the luminosity function of each spectral type is consistent with being redshift-independent. The luminosity function of early type galaxies is consistent with passive evolution up to alpha, and continuum images of the Sculptor Group spiral galaxy NGC 55 obtained with the WFI instrument at the 2.2-m telescope of ESO. We identified 21 new planetary nebula candidates. We constructed the O IIIlambda5007 Planetary Nebula Luminosity Function (PNLF) and determined a most likely distance of 2.30 pm 0.35 Mpc. The distance to NGC 55 is a bit larger than previously determined distances, which means that the Sculptor Group is further away from the Local Group than previously thought. The PNLF distance to NGC 55 is comparable to the PNLF distance of NGC 300 (Soffner et al. 1996, A&A, 306, 9), adding support to the suggestion that these galaxies form a bound pair. There doesn't seem to be a shortage of planetary nebula candidates in this metal poor galaxy.
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