The K20 survey. V. The evolution of the near-IR Luminosity Function

Pozzetti, L.; Cimatti, A.; Zamorani, G.; Daddi, E.; Menci, Nicola; Fontana, A.; Renzini, A.; Mignoli, M.; Poli, F.; Saracco, P.; Broadhurst, T.; Cristiani, S.; D’Odorico, S.; Giallongo, E.; Gilmozzi, R.

doi:10.1051/0004-6361:20030292

Cited by 166 publications

(297 citation statements)

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“…These results had previously been inferred from the evolution of the NIR luminosity function and density (e.g., Pozzetti et al 2003;Feulner et al 2003), and are in broad agreement with the downsizing scenario proposed more than ten years ago by Cowie et al (1996), where star formation activity was stronger, earlier, and faster for massive galaxies while low mass systems continued their activity to later cosmic times. The downsizing is consistent with several results obtained at low and high redshifts, such as the mass-dependent star formation histories of early-type galaxies (Thomas et al 2005), the evolution of the fundamental plane (e.g., Treu et al 2005;van der Wel et al 2005;di Serego Alighieri et al 2005), the evolution of the optical luminosity function of early-type galaxies to z ∼ 1 (Cimatti et al 2006;Scarlata et al 2007), the evolution of the cosmic star formation density and specific star formation (Gabasch et al 2006;Feulner et al 2005;Juneau et al 2005), and the evolution of the colour-magnitude relation (Tanaka et al 2004).…”

Section: Introductionsupporting

confidence: 89%

GMASS ultradeep spectroscopy of galaxies atz ~ 2

Kurk

Cimatti

Daddi

et al. 2012

A&A

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Context. Ultra-deep imaging of small parts of the sky has revealed many populations of distant galaxies, providing insight into the early stages of galaxy evolution. Spectroscopic follow-up has mostly targeted galaxies with strong emission lines at z > 2 or concentrated on galaxies at z < 1. Aims. The populations of both quiescent and actively star-forming galaxies at 1 < z < 2 are still under-represented in our general census of galaxies throughout the history of the Universe. In the light of galaxy formation models, however, the evolution of galaxies at these redshifts is of pivotal importance and merits further investigation. In addition, photometry provides only limited clues about the nature and evolutionary status of these galaxies.We therefore designed a spectroscopic observing campaign of a sample of both massive, quiescent and star-forming galaxies at z > 1.4. Methods. To determine redshifts and physical properties, such as metallicity, dust content, dynamical masses, and star formation history, we performed ultra-deep spectroscopy with the red-sensitive optical spectrograph FORS2 at the Very Large Telescope. We first constructed a sample of objects, within the CDFS/GOODS area, detected at 4.5 μm, to be sensitive to stellar mass rather than star formation intensity. The spectroscopic targets were selected with a photometric redshift constraint (z > 1.4) and magnitude constraints (B AB < 26, I AB < 26.5), which should ensure that these are faint, distant, and fairly massive galaxies. Results. We present the sample selection, survey design, observations, data reduction, and spectroscopic redshifts. Up to 30 h of spectroscopy of 174 spectroscopic targets and 70 additional objects enabled us to determine 210 redshifts, of which 145 are at z > 1.4. The redshift distribution is clearly inhomogeneous with several pronounced redshift peaks. From the redshifts and photometry, we deduce that the BzK selection criteria are efficient (82%) and suffer low contamination (11%). Several papers based on the GMASS survey show its value for studies of galaxy formation and evolution. We publicly release the redshifts and reduced spectra. In combination with existing and on-going additional observations in CDFS/GOODS, this data set provides a legacy for future studies of distant galaxies.

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Section: Introductionsupporting

confidence: 89%

GMASS ultradeep spectroscopy of galaxies atz ~ 2

Kurk

Cimatti

Daddi

et al. 2012

A&A

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111

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“…Taking into account the redshift of the source (z = 1.985) and given its apparent magnitude (K ∼ 19.5 mag), the resulting rest-frame (k-corrected) K-band absolute magnitude is M K ∼ −25.5 mag, i.e. ∼1.6 times brighter than L * K galaxies at the same z (see Pozzetti et al 2003;Saracco et al 2006). Considering L * ∼ 2 × 10 11 L for galaxies at z ∼ 2 and assuming a stellar mass-to-light ratio of 0.5 (M/L) , we estimated a stellar mass of the order of 10 11 M for the host galaxy.…”

Section: Qso Activity and Massive Galaxiesmentioning

confidence: 99%

An X-ray bright ERO hosting a type 2 QSO

Severgnini

Caccianiga

Braito

et al. 2006

A&A

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We present the XMM-Newton and the optical-VLT spectra along with the optical and the near-infrared photometric data of one of the brightest X-ray (F 2−10 keV ∼ 10 −13 erg s −1 cm −2 ) extremely red objects (R − K ≥ 5) discovered so far. The source, XBS J0216-0435, belongs to the XMM-Newton Bright Serendipitous Survey and it has extreme X-ray-to-optical (∼220) and X-ray-to-near-infrared (∼60) flux ratios. Thanks to its brightness, the X-ray statistics are good enough for an accurate spectral analysis by which the presence of an X-ray obscured (N H > 10 22 cm −2 ) QSO (L 2−10 keV = 4 × 10 45 erg s −1 ) is determined. A statistically significant (∼99%) excess around 2 keV in the observed-frame suggests the presence of an emission line. By assuming that this feature corresponds to the iron Kα line at 6.4 keV, a first estimate of the redshift of the source is derived (z X ∼ 2). The presence of a high redshift QSO2 has been finally confirmed through dedicated VLT optical spectroscopic observations (z O = 1.985 ± 0.002). This result yields to an optical validation of a new X-ray Line Emitting Object (XLEO) for which the redshift has been firstly derived from the X-ray data. XBS J0216-0435 can be considered one of the few examples of X-ray obscured QSO2 at high redshift for which a detailed X-ray and optical spectral analysis has been possible. The spectral energy distribution from radio to X-rays is also presented. Finally from the near-infrared data the luminosity and the stellar mass of the host galaxy has been estimated finding a new example of the coexistence at high-z between massive galaxies and powerful QSOs.

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“…Age downsizing occurs separately for each of the two populations causing galaxy bimodality, i.e., a red peak (Thomas et al 2005;Fontana et al 2004; Thomas et al 2009) and a blue one (Noeske et al 2007a,b). However, it remains unclear whether the age downsizing is coupled with a mass-assembly downsizing scenario for galaxy evolution and formation (Fontana et al 2004Pozzetti et al 2003Pozzetti et al , 2007Cimatti et al 2006;Bundy et al 2006), i.e., if the more massive galaxies assembled their mass earlier than lower mass ones. Furthermore, do low-mass galaxies contain younger stars and assemble later even within the same spectral type?…”

Section: Introductionmentioning

confidence: 99%

“…Very deep surveys have been exploited to describe the shape of the stellar mass function at high redshift Drory et al 2005;Gwyn & Hartwick 2005;Bundy et al 2006;Pozzetti et al 2007), but a clear picture about stellar mass assembly and how it depends on mass (mass-assembly downsizing) and galaxy type has not yet emerged. Previous studies have explored the evolution of different galaxy types in deep near-IR surveys, such as K20, by means of the K-band luminosity function (Pozzetti et al 2003) and the galaxy stellar mass function (Fontana et al 2004), using spectral classification (i.e., absorption-line galaxies versus emissionline galaxies), and in larger optical and near-IR surveys such as VVDS, COMBO17, and DEEP2, using colours or spectra to define galaxy types (Bell et al 2004;Cimatti et al 2006;Faber et al 2007;Zucca et al 2006;Arnouts et al 2007;Vergani et al 2008). Even if the results of these surveys remain disputed (compare for example Bell et al 2004;, for the same dataset), most of these studies agree that luminous and rather massive old galaxies were already quite common at z ∼ 1 and that their number density declines rapidly at yet higher redshift.…”

Section: Introductionmentioning

confidence: 99%

zCOSMOS – 10k-bright spectroscopic sample

Pozzetti

Bolzonella

Zucca

et al. 2010

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We present the galaxy stellar mass function (GSMF) to redshift z 1, based on the analysis of about 8500 galaxies with I < 22.5 (AB mag) over 1.4 deg 2 , which are part of the zCOSMOS-bright 10k spectroscopic sample. We investigate the total GSMF, as well as the contributions of early-and late-type galaxies (ETGs and LTGs, respectively), defined by different criteria (broad-band spectral energy distribution, morphology, spectral properties, or star formation activities). We unveil a galaxy bimodality in the global GSMF, whose shape is more accurately represented by 2 Schechter functions, one linked to the ETG and the other to the LTG populations. For the global population, we confirm a mass-dependent evolution ("mass-assembly downsizing"), i.e., galaxy number density increases with cosmic time by a factor of two between z = 1 and z = 0 for intermediate-to-low mass (log(M/M ) ∼ 10.5) galaxies but less than 15% for log(M/M ) > 11. We find that the GSMF evolution at intermediateto-low values of M (log(M/M ) < 10.6) is mostly explained by the growth in stellar mass driven by smoothly decreasing star formation activities, despite the redder colours predicted in particular at low redshift. The low residual evolution is consistent, on average, with ∼0.16 merger per galaxy per Gyr (of which fewer than 0.1 are major), with a hint of a decrease with cosmic time but not a clear dependence on the mass. From the analysis of different galaxy types, we find that ETGs, regardless of the classification method, increase in number density with cosmic time more rapidly with decreasing M, i.e., follow a top-down building history, with a median "building redshift" increasing with mass (z > 1 for log(M/M ) > 11), in contrast to hierarchical model predictions. For LTGs, we find that the number density of blue or spiral galaxies with log(M/M ) > 10 remains almost constant with cosmic time from z ∼ 1. Instead, the most extreme population of star-forming galaxies (with high specific star formation), at intermediate/high-mass, rapidly decreases in number density with cosmic time. Our data can be interpreted as a combination of different effects. Firstly, we suggest a transformation, driven mainly by SFH, from blue, active, spiral galaxies of intermediate mass to blue quiescent and subsequently (1−2 Gyr after) red, passive types of low specific star formation. We find an indication that the complete morphological transformation, probably driven by dynamical processes, into red spheroidal galaxies, occurred on longer timescales or followed after 1−2 Gyr. A continuous replacement of blue galaxies is expected to be accomplished by low-mass active spirals increasing their stellar mass. We estimate the growth rate in number and mass density of the red galaxies at different redshifts and masses. The corresponding fraction of blue galaxies that, at any given time, is transforming into red galaxies per Gyr, due to the quenching of their SFR, is on average ∼25% for log(M/M ) < 11. We conclude that the build-up of galaxies and in particular of...

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The K20 survey. V. The evolution of the near-IR Luminosity Function

Cited by 166 publications

References 50 publications

GMASS ultradeep spectroscopy of galaxies atz ~ 2

GMASS ultradeep spectroscopy of galaxies atz ~ 2

An X-ray bright ERO hosting a type 2 QSO

zCOSMOS – 10k-bright spectroscopic sample

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