Spectrophotometric properties of galaxies at intermediate redshifts
(<i>z</i> ~ 0.2–1.0)

Lamareille, F.; Contini, T.; Borgne, Jean-François Le; Brinchmann, Jarle; Charlot, S.; Richard, Johan

doi:10.1051/0004-6361:20053601

Cited by 83 publications

(111 citation statements)

References 77 publications

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“…The data were reduced with VIMOS Interactive Pipeline Graphical Interface software (VIPGI, Scodeggio et al 2005) and the redshift measured with EZ software (Garilli et al 2010) with a high success rate (≈95% in the redshift range 0.5 < z < 0.8, Lilly et al 2009). The line measurements were performed using the program Platefit (see Lamareille et al 2006, for further details). After removing the spectroscopically confirmed stars, the broad-line AGNs, and the galaxies with an insecure redshift measurement (z flag < 1.5), we end up with a parent sample of 17 211 galaxies.…”

Section: The Samplementioning

confidence: 99%

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Moresco¹,

Pozzetti

Cimatti³

et al. 2013

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Aims. We present the analysis of photometric, spectroscopic, and morphological properties for differently selected samples of passive galaxies up to z = 1 extracted from the zCOSMOS-20k spectroscopic survey. This analysis intends to explore the dependence of galaxy properties on the selection criterion adopted, study the degree of contamination due to star-forming outliers, and provide a comparison between different commonly used selection criteria. This work is a first step to fully investigating the selection effects of passive galaxies for future massive surveys such as Euclid. Methods. We extracted from the zCOSMOS-20k catalog six different samples of passive galaxies, based on morphology (3336 "morphological" early-type galaxies), optical colors (4889 "red-sequence" galaxies and 4882 "red UVJ" galaxies), specific star-formation rate (2937 "quiescent" galaxies), a best fit to the observed spectral energy distribution (2603 "red SED" galaxies), and a criterion that combines morphological, spectroscopic, and photometric information (1530 "red & passive early-type galaxies"). For all the samples, we studied optical and infrared colors, morphological properties, specific star-formation rates (SFRs), and the equivalent widths of the residual emission lines; this analysis was performed as a function of redshift and stellar mass to inspect further possible dependencies. Results. We find that each passive galaxy sample displays a certain level of contamination due to blue/star-forming/nonpassive outliers. The morphological sample is the one that presents the higher percentage of contamination, with ∼12−65% (depending on the mass range) of galaxies not located in the red sequence, ∼25−80% of galaxies with a specific SFR up to ∼25 times higher than the adopted definition of passive, and significant emission lines found in the median stacked spectra, at least for log (M/M ) < 10.25. The red & passive ETGs sample is the purest, with a percentage of contamination in color <10% for stellar masses log (M/M ) > 10.25, very limited tails in sSFR, a median value ∼20% higher than the chosen passive cut, and equivalent widths of emission lines mostly compatible with no star-formation activity. However, it is also the less economic criterion in terms of information used. Among the other criteria, we found that the best performing are the red SED and the quiescent ones, providing a percentage of contamination only slightly higher than the red & passive ETGs criterion (on average of a factor of ∼2) but with absolute values of the properties of contaminants still compatible with a red, passively evolving population. We also find a strong dependence of the contamination on the stellar mass and conclude that, almost irrespective of the adopted selection criteria, a cut at log (M/M ) > 10.75 provides a significantly purer sample in terms of star-forming contaminants. By studying the restframe color-mass and color−color diagrams, we provided two revised definitions of passive galaxies based on these criteria that better reprodu...

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Section: The Samplementioning

confidence: 99%

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Moresco¹,

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Cimatti³

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“…To easily study the spectral properties of the zCOSMOS galaxies, we used of fully automatic spectral measurement code (PlateFit, Lamareille et al 2006), which measures all the spectral features and equivalent widths of the prominent lines present in zCOSMOS spectra, given its spectral range. This code fits the stellar continuum and absorption lines making use of the STELIB library (Le Borgne et al 2003) of stellar spectra and the GALAXEV (Bruzual & Charlot 2003) stellar population synthesis models (see Lamareille et al 2006, for further details). To investigate the influence of mass and environment on the spectral features, we decided to average the values of D4000 and EW 0 (Hδ) evaluated for single spectra in bins of redshift, mass, and environment.…”

Section: D4000 and Ew 0 (Hδ) Definitionsmentioning

confidence: 99%

zCOSMOS 10k-bright spectroscopic sample

Moresco

Pozzetti

Cimatti

et al. 2010

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Aims. We present the analysis of the U − V rest-frame color distribution and some spectral features as a function of mass and environment for a sample of early-type galaxies up to z = 1 extracted from the zCOSMOS spectroscopic survey. This analysis is used to place constraints on the relative importance of these two properties in controlling galaxy evolution. Methods. We used the zCOSMOS 10k-bright sample, limited to the AB magnitude range 15 < I < 22.5, from which we extracted two different subsamples of early-type galaxies. The first sample ("red galaxies") was selected using a photometric classification (2098 galaxies), while in the second case ("ETGs") we combined morphological, photometric, and spectroscopic properties to obtain a more reliable sample of elliptical, red, passive, early-type galaxies (981 galaxies). The analysis is performed at fixed mass to search for any dependence of the color distribution on environment, and at fixed environment to search for any mass dependence. Results. In agreement with the low redshift results of the SDSS, we find that the color distribution of red galaxies is not strongly dependent on environment for all mass bins, exhibiting only a weak trend such that galaxies in overdense regions (log 10 (1 + δ) ∼ 1.2) are redder than galaxies in underdense regions (log 10 (1 + δ) ∼ 0.1), with a difference of Δ(U − V) rest = 0.027 ± 0.008 mag. On the other hand, the dependence on mass is far more significant, and we find that the average colors of massive galaxies (log 10 (M/M ) ∼ 10.8) are redder by Δ(U − V) rest = 0.093 ± 0.007 mag than low-mass galaxies (log 10 (M/M ) ∼ 10) throughout the entire redshift range. We study the color-mass (U − V) rest ∝ S M · log 10 (M/M ) relation, finding a mean slope S M = 0.12 ± 0.005, while the color-environment (U − V) rest ∝ S δ · log 10 (1 + δ) relation is flatter, with a slope always smaller than S δ ≈ 0.04. The spectral analysis that we perform on our ETGs sample is in good agreement with our photometric results: we study the 4000 Å break and the equivalent width of the Hδ Balmer line, finding for D4000 a dependence on mass ( ΔD4000 = 0.11 ± 0.02 between log 10 (M/M ) ∼ 10.2 and log 10 (M/M ) ∼ 10.8), and a much weaker dependence on environment ( ΔD4000 = 0.05 ± 0.02 between high and low environment quartiles). The same is true for the equivalent width of Hδ, for which we measure a difference of ΔEW 0 (Hδ) = 0.28 ± 0.08 Å across the same mass range and no significant dependence on environment. By analyzing the lookback time of early-type galaxies, we support the possibility of a downsizing scenario, in which massive galaxies with a stronger D4000 and an almost constant equivalent width of Hδ formed their mass at higher redshift than lower mass ones. We also conclude that the main driver of galaxy evolution is the galaxy mass, the environment playing a subdominant role.

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“…Here we provide a brief outline of the fitting procedure. We refer to Lamareille et al (2006) for full details, and both Tremonti et al (2004) and Brinchmann et al (2004) for further details of the original pipeline developed for the higher resolution SDSS spectra. The best-fit stellar continuum derived from a grid of stellar population synthesis models (Bruzual & Charlot 2003, hereafter BC03) was subtracted from the observed spectrum.…”

Section: The Spectral Measurements and Sample Selectionmentioning

confidence: 99%

K+a galaxies in the zCOSMOS survey

Vergani

Zamorani

Lilly³

et al. 2009

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Aims. The identities of the main processes triggering and quenching star-formation in galaxies remain unclear. A key stage in evolution, however, appears to be represented by post-starburst galaxies. To investigate the prevalence of these galaxies and their impact on galaxy evolution in general, we initiated a multiwavelength study of galaxies with k + a spectral features in the well-studied COSMOS field. Methods. We examine a mass-selected sample of k + a galaxies in the COSMOS field at z = 0.48−1.2 using the spectroscopic zCOSMOS sample. To classify galaxies in their k + a phase, we use a spectroscopic criterion, based on the amplitude of the Hδ absorption line and the absence of the [OII] emission line. We develop our analysis for a well-defined sample by imposing stringent confidence levels on the spectroscopic redshifts and spectral measurements. We compare our results for two mass-selected samples of star-forming and quiescent galaxies selected using a purely spectral classification scheme from the 10 000 zCOSMOS catalogue (i.e. , based on measurements of 4000 Å break and EW[OII]). Results. In our mass-limited sample, k+a galaxies occupy the brightest tail of the luminosity distribution. They are as massive as quiescent galaxies and populate the green valley in the colour versus luminosity (or stellar mass) distribution. A small percentage (<8%) of these galaxies have radio and/or X-ray counterparts (implying an upper limit to the SFR of ∼8 M yr −1 ). Over the entire redshift range explored, the class of post-starburst galaxies is morphologically a heterogeneous population with a similar incidence of bulge-dominated and disky galaxies. This distribution does not vary with the strength of the Hδ absorption line but instead with stellar mass in a way reminiscent of the well-known mass-morphology relation. The results about the incidence of asymmetries and the concentration of the light distribution derived from HST/ACS images imply that this galaxy population possibly represents an intermediate stage of galaxy evolution. Although k + a galaxies are also found in underdense regions, they appear to reside typically in a similarly rich environment as quiescent galaxies on a physical scale of ∼2-8 Mpc, and in groups they show a morphological early-to-late type ratio similar to the quiescent galaxy class. With the current data set, we do not find evidence of statistical significant evolution in either the number/mass density of k + a galaxies at intermediate redshift with respect to the local values, or the spectral properties, although more solid results on this and other aspects will be obtained following the completion of the survey. Conclusions. Several mechanisms related and unrelated to the environment are at work in quenching star-formation activity in galaxies on short timescales (<1 Gyr). Those galaxies, which are affected by a sudden quenching of their star-formation activity, may increase the stellar mass of the red-sequence by up to a non-negligible level of ∼10%.

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Spectrophotometric properties of galaxies at intermediate redshifts (z ~ 0.2–1.0)

Cited by 83 publications

References 77 publications

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zCOSMOS 10k-bright spectroscopic sample

K+a galaxies in the zCOSMOS survey

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