The Density and Spectral Energy Distributions of Red Galaxies at <i>z</i> ~ 3.7

Brammer, Gabriel; Dokkum, Pieter van

doi:10.1086/511305

Cited by 34 publications

(56 citation statements)

References 30 publications

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“…Similar detections at slightly higher redshift have also been reported recently (z ∼ 3.7, Brammer & van Dokkum 2007) The photometric modelling generally suggests that these passive systems should have formed all their stars at z f > 3 in a short burst.…”

Section: Massive Galaxies At Z ∼ 4?supporting

confidence: 89%

Unveiling the oldest and most massive galaxies at very high redshift

Rodighiero¹,

Cimatti

Franceschini³

et al. 2007

A&A

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Context. The identification and characterisation of massive galaxies over a wide redshift range allow us to place stringent constraints on the cosmic history of galaxy mass assembly and on current models of galaxy formation and evolution. Aims. This work explores the existence of high-redshift massive galaxies unveiled with Spitzer+IRAC, but missed by conventional selection techniques based on optical and near-infrared observations. Methods. To this end, we used multi-wavelength imaging data available for the GOODS-South field (130 arcmin 2 ) and selected a flux-limited sample from the IRAC 3.6 µm image to S 3.6 ≥ 1.8 µJy (m(AB) < 23.26). In order to identify the most extreme objects and to complement previously published selections in this field, we confined our study to the galaxies undetected by the optical HST+ACS imaging and close to the detection limit of the K-band image (K > 23.5 AB). Our selection unveiled 20 galaxies on which we performed a detailed analysis. For each galaxy, we built a spectral energy distribution (SED) based on optical-to-8µm photometry. The SEDs were then used to estimate the photometric redshifts and to derive the main galaxies' physical properties. Further constraints were also obtained from the available X-ray and 24 µm data. Results. The majority of the sample (14 out of 20) sources show degenerate/bimodal solutions for the photometric redshifts. These can either be heavily dust-enshrouded (A V ∼ 2−4) starbursts at 2 < z < 3 with bolometric luminosities L IR > 10 12 L , or massive post-starburst galaxies in the redshift interval 4 < z < 9 with stellar masses of ∼10 11 M . The remaining six galaxies present a less ambiguous photometric redshift: with the exception of one low-z dusty source, these latter objects favour a low-extinction solution, with four of them showing best-fit photo-z solutions at z ∼ 4. One galaxy, ID-6, the only source in our sample with both an X-ray and a 24 µm detection, might be an extremely massive object at z ∼ 8 detected during a post-starburst phase with concomitant QSO activity responsible for the 24 µm and X-ray emissions (although a lower-z solution is not excluded). Conclusions. Our investigation of Spitzer-selected galaxies that have very red SEDs and completely undetected in the optical reveals a potential population of massive galaxies at z ≥ 4, which appear to include significant AGN emissions. These sources may be the oldest stellar systems at z ∼ 4, given that the estimated ages are close to the age of the Universe at that redshift. We found that these, previously unrecognised, optically obscured objects might provide an important contribution to the massive end (M > 10 11 M ) of the high-z stellar mass function, and they would almost double it. Our evidence in these mature high-z galaxies of the widespread presence of hidden AGNs may have important implications for galaxy formation, due to their feedback effects on the surrounding ISM.

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Section: Massive Galaxies At Z ∼ 4?supporting

confidence: 89%

Unveiling the oldest and most massive galaxies at very high redshift

Rodighiero¹,

Cimatti

Franceschini³

et al. 2007

A&A

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“…It may thus be possible that this effect is an artifact of differences in the color selection criteria themselves, rather than evidence of evolution. However, Brammer & van Dokkum (2007) study the evolution of optically red galaxies from z $ 3:7 to z $ 2:4, and also find evidence for substantial evolution in the rest-frame ultraviolet slopes in the same sense as described here.…”

Section: Rest-frame Optical Colorssupporting

confidence: 68%

The Multiwavelength Survey by Yale-Chile (MUSYC): Deep Near-Infrared Imaging and the Selection of Distant Galaxies

Quadri¹,

Marchesini²,

Dokkum³

et al. 2007

Astron J

104

112

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We present deep near-infrared JHK imaging of four 10 0 ; 10 0 fields. The observations were carried out as part of the Multiwavelength Survey by Yale-Chile ( MUSYC) with ISPI on the CTIO 4 m telescope. The typical pointsource limiting depths are J $ 22:5, H $ 21:5, and K $ 21 (5 ; Vega). The effective seeing in the final images is $1.0 00 . We combine these data with MUSYC UBVRIz imaging to create K-selected catalogs that are unique for their uniform size, depth, filter coverage, and image quality. We investigate the rest-frame optical colors and photometric redshifts of galaxies that are selected using common color selection techniques, including distant red galaxies (DRGs), star-forming and passive BzKs, and the rest-frame UV-selected BM, BX, and Lyman break galaxies (LBGs). These techniques are effective at isolating large samples of high-redshift galaxies, but none provide complete or uniform samples across the targeted redshift ranges. The DRG and BM/BX/LBG criteria identify populations of red and blue galaxies, respectively, as they were designed to do. The star-forming BzKs have a very wide redshift distribution, extending down to z $ 1, a wide range of colors, and may include galaxies with very low specific star formation rates. In comparison, the passive BzKs are fewer in number, have a different distribution of K magnitudes, and have a somewhat different redshift distribution. By combining either the DRG and BM/BX/LBG criteria, or the star-forming and passive BzK criteria, it appears possible to define a reasonably complete sample of galaxies to our flux limit over specific redshift ranges. However, the redshift dependence of both the completeness and sampled range of rest-frame colors poses an ultimate limit to the usefulness of these techniques.

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“…There also exist at z ≲ 3 galaxies with suppressed or absent star formation (e.g. Kriek et al 2006; van Dokkum, Kriek & Franx 2009; Papovich et al 2010), although such systems are much rarer or absent at z ≳ 3.5 (Brammer & van Dokkum 2007; Stutz, Papovich & Eisenstein 2008). The UV luminosity functions at z ≲ 3 may be incomplete for these types of galaxies.…”

Section: The Properties Of Galaxies At Constant Number Densitymentioning

confidence: 99%

The rising star formation histories of distant galaxies and implications for gas accretion with time

Papovich

Finkelstein

Ferguson

et al. 2010

Monthly Notices of the Royal Astronomical Society

235

318

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Distant galaxies show correlations between their current star formation rates (SFRs) and stellar masses, implying that their star formation histories (SFHs) are highly similar. Moreover, observations show that the ultraviolet luminosities and stellar masses grow from z= 8 to 3, implying that the SFRs increase with time. We compare the cosmologically averaged evolution in galaxies at 3 < z < 8 at constant comoving number density, n= 2 × 10−4 Mpc−3. This allows us to study the evolution of stellar mass and star formation in the galaxy predecessors and descendants in ways not possible using galaxies selected at constant stellar mass or SFR, quantities that themselves evolve strongly in time. We show that the cosmologically averaged SFRs of these galaxies increase smoothly from z= 8 to 3 as Ψ(t) ∼tα with α= 1.7 ± 0.2. This conflicts with assumptions that the SFR is either constant or declines exponentially in time. Furthermore, we show that the stellar mass growth in these galaxies is consistent with this derived SFH. This provides evidence that the slope of the high‐mass end of the initial mass function is approximately Salpeter unless the duty cycle of star formation is much less than unity. We argue that these relations follow from gas accretion (either through accretion or delivered by mergers) coupled with galaxy disc growth under the assumption that the SFR depends on the local gas surface density. This predicts that gas fractions decrease from z= 8 to 3 on average as fgas∼ (1 +z)0.9 for galaxies with this number density. The implied galaxy gas accretion rates at z > 4 are as fast and may even exceed the SFR: this is the ‘gas accretion epoch’. At z < 4 the SFR overtakes the implied gas accretion rate, indicating a period where galaxies consume gas faster than it is acquired. At z≲ 3, galaxies with this number density depart from these relations implying that star formation and gas accretion are slowed at later times.

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The Density and Spectral Energy Distributions of Red Galaxies at z ~ 3.7

Cited by 34 publications

References 30 publications

Unveiling the oldest and most massive galaxies at very high redshift

Unveiling the oldest and most massive galaxies at very high redshift

The Multiwavelength Survey by Yale-Chile (MUSYC): Deep Near-Infrared Imaging and the Selection of Distant Galaxies

The rising star formation histories of distant galaxies and implications for gas accretion with time

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