Spectroscopic Confirmation of a Substantial Population of Luminous Red Galaxies at Redshifts
                    <i>z</i>
                    2

Dokkum, Pieter van; Schreiber, N. M. Förster; Franx, Marijn; Daddi, E.; Illingworth, G. D.; Labbé, Ivo; Moorwood, A. F. M.; Rix, Hans─Walter; Röttgering, H. J. A.; Rudnick, Gregory; Wel, Arjen van der; Werf, P. van der; Starkenburg, Lottie van

doi:10.1086/375156

Cited by 130 publications

(127 citation statements)

References 26 publications

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“…In the next model, we introduce number-density evolution of the elliptical population parameterized using φ ∝ (1 + z) −2 . The formation redshifts is set to z f = 4.0 for all galaxy types, being in more agreement with the evolved red galaxies found at z > 2 (van Dokkum et al 2003;Daddi et al 2004). The evolution in the early-type densities was not accompanied by an evolution in M , arguing that a substantial number of ellipticals formed in spiral-spiral mergers as expected for hierarchical galaxy formation.…”

Section: Comparison With Models Of Evolutionsupporting

confidence: 59%

Near-Infrared Galaxy Counts and Evolution From the Wide-Field Alhambra Survey

Cristóbal-Hornillos¹,

Aguerri²,

Moles³

et al. 2009

ApJ

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The ALHAMBRA survey aims to cover 4 deg 2 using a system of 20 contiguous, equal width, medium-band filters spanning the range 3500 Å-9700 Å plus the standard JHKs filters. Here we analyze deep near-IR number counts of one of our fields (ALH08) for which we have a relatively large area (0.5 deg 2 ) and faint photometry (J = 22.4, H = 21.3, and K = 20.0 at the 50% of recovery efficiency for point-like sources). We find that the logarithmic gradient of the galaxy counts undergoes a distinct change to a flatter slope in each band: from 0. . These observations together with faint optical counts are used to constrain models that include density and luminosity evolution of the local type-dependent luminosity functions. Our models imply a decline in the space density of evolved early-type galaxies with increasing redshift, such that only 30%-50% of the bulk of the present day red ellipticals was already in place at z ∼ 1.

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Section: Comparison With Models Of Evolutionsupporting

confidence: 59%

Near-Infrared Galaxy Counts and Evolution From the Wide-Field Alhambra Survey

Cristóbal-Hornillos¹,

Aguerri²,

Moles³

et al. 2009

ApJ

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“…The picture becomes more controversial at higher redshifts, where the evolution of the near-IR luminosity function and cosmic stellar mass density is faster, and the properties and role of the massive galaxies found at 1.5 < z < 3 (e.g. Franx et al 2003;van Dokkum et al 2003;Daddi et al 2004a;Glazebrook et al 2004;Cimatti et al 2004;Saracco et al 2004) have still to be clarified.…”

Section: Introductionmentioning

confidence: 99%

The K20 survey

Mignoli¹,

Cimatti

Zamorani³

et al. 2005

A&A

233

272

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Abstract. The K20 survey is a near infrared-selected, deep (K s < 20) redshift survey targeting galaxies in two independent regions of the sky, the Chandra Deep Field South and the field around the quasar 0055−2659, for a total area of 52 arcmin 2 . The total K s -selected sample includes 545 objects. Low-resolution (R ≈ 300−600) optical spectra for 525 of them have been obtained with the FORS1/FORS2 spectrographs at the ESO/VLT, providing 501 spectroscopic identifications (including 12 type-1 AGN and 45 stars); consequently, we were able to measure redshifts and identify stars in 96% of the observed objects, whereas the spectroscopic completeness with respect to the total photometrically selected sample is 92% (501/545). The K20 survey is therefore the most complete spectroscopic survey of a near infrared-selected sample to date. The K20 survey contains 444 spectroscopically identified galaxies, covering a redshift range of 0.05 < z < 2.73, with a mean redshift z = 0.75; excluding the 32 "low-quality" redshifts does not significantly change these values. This paper describes the final K20 spectroscopic catalogue, along with the technique used to determine redshifts, measure the spectral features and characterize the spectra. The classification of the galaxy spectra has been performed according to a simple parametric recipe that uses the equivalent widths of the two main emission lines ([OII]λ3727 and Hα+ [NII]) and two continuum indices (the 4000 Å break index, D4000, and a near-UV color index, C(28-39)). We defined three main spectroscopic classes: red early-type galaxies, blue emission-line galaxies and the intermediate galaxies, which show emission lines but a red continuum. More than 95% of the examined galaxies is included in one of these spectral types and a composite spectrum is built for each of the three galaxy classes. The full spectroscopic catalogue, the reduced individual spectra and the composite spectra are released to the community through the K20 web page (http://www.arcetri.astro.it/∼k20/). The blue emission-line and the early-type galaxies have been divided in redshift bins, and the corresponding composite spectra have been built, in order to investigate the evolution of the spectral properties of the K20 galaxies with redshift. The early-type average spectra are remarkable in their similarity, showing only subtle but systematic differences in the D4000 index, which are consistent with the ageing of the stellar population. Conversely, the star-forming galaxies present a significant "blueing" of the optical/near-UV continuum with redshift, although the [OII] equivalent width remains constant (∼33 Å) in the same redshift intervals. We reproduce the observed properties with simple, dust-free population synthesis models, suggesting that the highredshift galaxies are younger and more active than those detected at lower redshift, whilst the equivalent width of the emission lines apparently require a lower metallicity for the low-redshift objects. This may be consistent with the metallicity-luminosi...

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“…5 shows the evolution of J − K colour, suggesting that an old elliptical galaxy with R − J ≥ 5 and redshift z ∼ 1.4 would have J − K ≥ 2.25. This is consistent with the results of van Dokkum et al (2003), who found galaxies with J s − K s = 2.35 and redshifts of z > 1.2 (∼17% of the sample) and z > 2.3 respectively. Finding such an elliptical galaxy at even higher redshift requires a J − K colour around 3 (for z f = 5) and higher (for z f = 10), according to our models.…”

Section: The Relevance Of the R − J ≥ 5 Colour Criterionsupporting

confidence: 93%

Surface Density of Extremely Red Objects with R-J≥5

Hempel

Herbst

Thompson

Multiwavelength Mapping of Galaxy Formation and Evolution

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We present the results of a wide-field survey for extremely red objects (EROs), based on J and R band imaging. The survey covers 2.89 deg 2 , consisting of 50 single fields, each approximately 210 arcmin 2 in size. This survey provides a sample of 60 extended objects with a colour of R − J ≥ 5 and J band magnitudes more than 10σ above background (18 mag ≤ J ≤ 20 mag ). Thirty five of these objects have been detected in both J and R-band. We derive a surface density for such EROs of 5.7 ± 0.1 × 10 −3 arcmin −2 , which is about seven times lower than for galaxies with R − K ≥ 6. Stellar population models suggest that these EROs are massive galaxies with an old stellar population in a redshift range of 1.4 ≤ z ≤ 3.0. For this scenario, we estimate the co-moving volume density to be (9.57 ± 1.24) × 10 −6 Mpc −3 .

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Spectroscopic Confirmation of a Substantial Population of Luminous Red Galaxies at Redshifts z 2

Cited by 130 publications

References 26 publications

Near-Infrared Galaxy Counts and Evolution From the Wide-Field Alhambra Survey

Near-Infrared Galaxy Counts and Evolution From the Wide-Field Alhambra Survey

The K20 survey

Surface Density of Extremely Red Objects with R-J≥5

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