2007A&A...470...21R


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.16CEST10:41:51

2007A&A...470...21R - Astronomy and Astrophysics, volume 470, 21-37 (2007/7-4)

Unveiling the oldest and most massive galaxies at very high redshift.

RODIGHIERO G., CIMATTI A., FRANCESCHINI A., BRUSA M., FRITZ J. and BOLZONELLA M.

Abstract (from CDS):

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. 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. To this end, we used multi-wavelength imaging data available for the GOODS-South field (130 arcmin2) and selected a flux-limited sample from the IRAC 3.6µm image to S3.6≥1.8µJy (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>23.5AB). 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 24µm data. 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 (AV∼2-4) starbursts at 2<z<3 with bolometric luminosities LIR>1012 L, or massive post-starburst galaxies in the redshift interval 4<z<9 with stellar masses of ∼1011 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 24µm detection, might be an extremely massive object at z∼8 detected during a post-starburst phase with concomitant QSO activity responsible for the 24µm and X-ray emissions (although a lower-z solution is not excluded). 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>1011M) 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.

Abstract Copyright:

Journal keyword(s): galaxies: high-redshift - galaxies: formation - cosmology: observations - infrared: galaxies

Nomenclature: Table 1: [RCF2007] NN (Nos 1-20).

Simbad objects: 36

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Number of rows : 36

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 NAME FDF reg 01 06 03.6 -25 45 46           ~ 121 0
2 [RCF2007] 15 G 03 32 09.1992 -27 49 30.868           ~ 2 0
3 [RCF2007] 3 G 03 32 15.8331 -27 49 54.138           ~ 3 0
4 NAME Chandra Deep Field-South reg 03 32 28.0 -27 48 30           ~ 1750 1
5 NAME GOODS Southern Field reg 03 32 28.0 -27 48 30           ~ 995 1
6 [FPG2012] M70099 AGN 03 32 28.749 -27 44 35.28           ~ 9 0
7 [RCF2007] 1 G 03 32 29.8343 -27 52 57.548           ~ 3 0
8 [RCF2007] 17 G 03 32 30.4541 -27 48 16.580           ~ 3 0
9 ZFOURGE CDFS 27079 G 03 32 30.6326 -27 42 24.290           ~ 3 0
10 [RCF2007] 12 G 03 32 31.05 -27 52 18.2           ~ 1 0
11 [LBX2017] 617 AGN 03 32 33.113 -27 52 05.47   28.63 28.82   28.550 ~ 25 0
12 [RCF2007] 13 G 03 32 33.14 -27 52 04.1           ~ 1 0
13 [RCF2007] 9 AGN 03 32 33.4268 -27 53 26.456           ~ 3 0
14 [LBX2017] 657 AGN 03 32 35.1764 -27 52 15.505   30.517 28.52   31.665 ~ 19 0
15 [RCF2007] 10 G 03 32 35.8896 -27 52 36.640           ~ 3 0
16 [RCF2007] 7 G 03 32 37.32 -27 43 07.4           ~ 1 0
17 CXOCDFS J033238.1-274401 AGN 03 32 38.003 -27 44 00.69   28.60 27.92   27.023 ~ 27 0
18 NAME HUDF-J2 G 03 32 38.72681 -27 48 39.8845           ~ 26 1
19 [RCF2007] 5 G 03 32 38.75 -27 48 40.2           ~ 1 0
20 NAME Hubble Ultra Deep Field reg 03 32 39.0 -27 47 29           ~ 1215 0
21 [RCF2007] 18 G 03 32 43.31 -27 46 47.0           ~ 1 0
22 [LBX2017] 802 AGN 03 32 43.683 -27 48 50.88   29.8152 28.940     ~ 7 0
23 [RCF2007] 4 G 03 32 47.40 -27 48 49.9           ~ 1 0
24 [RCF2007] 8 AGN 03 32 47.6230 -27 55 38.745           ~ 3 0
25 [RCF2007] 14 G 03 32 48.45 -27 50 39.2           ~ 1 0
26 [RCF2007] 2 G 03 32 54.2752 -27 51 32.459           ~ 3 0
27 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14323 1
28 M 82 IG 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 5210 6
29 [OM2008] 100 QSO 10 44 09.95 +58 52 24.7 24.29     23.56   ~ 25 0
30 QSO J1148+5251 QSO 11 48 16.647 +52 51 50.31   25.73 25.04     ~ 371 0
31 NAME Hubble Deep Field reg 12 36 49.5 +62 12 58           ~ 1801 1
32 Mrk 231 Sy1 12 56 14.2340989340 +56 52 25.238555193   14.68 13.84     ~ 1733 3
33 IC 4553 SyG 15 34 57.22396 +23 30 11.6084   14.76 13.88     ~ 2617 4
34 NGC 6240 Sy2 16 52 58.861 +02 24 03.55   14.31 13.37     ~ 1440 2
35 NAME Superantennae Sy2 19 31 21.4252803168 -72 39 21.448768732   17.39 16.37 14.65   ~ 273 2
36 [MLM91] IRAS 19254-7245 S GiP 19 31 21.6 -72 39 25           ~ 16 1

    Equat.    Gal    SGal    Ecl

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2019.10.16-10:41:51

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