Issue |
A&A
Volume 500, Number 2, June III 2009
|
|
---|---|---|
Page(s) | 705 - 723 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/200810630 | |
Published online | 19 March 2009 |
Searching for massive galaxies at z ≥ 3.5 in GOODS-North*
1
Dipartimento di Astronomia e Scienza dello Spazio, Università degli Studi di Firenze, Largo E. Fermi 3 50125 Firenze, Italy e-mail: mancini@arcetri.astro.it
2
Osservatorio Astrofisico di Arcetri (OAF), INAF-Firenze, Largo E. Fermi 5, 50125 Firenze, Italy
3
CEA-Saclay,DSM/DAPNIA/Service d'Astrophysique, 91191 Gif-Sur Yvette Cedex, France
4
Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy
5
NOAO, 950 N. Cherry Ave. PO 26732, Tucson, AZ 85726-6732, USA
6
Dipartimento di Astronomia, Università di Padova, Vicolo Osservatorio 2, 35122 Padova, Italy
7
INAF-Bologna, via Ranzani, 40127 Bologna, Italy
Received:
17
July
2008
Accepted:
21
January
2009
Aims. We constrain the space density and properties of massive galaxy candidates at redshifts of in the Great Observatories Origin Deep Survey North (GOODS-N) field. By selecting sources in the Spitzer + IRAC bands, a sample highly complete in stellar-mass is assembled, including massive galaxies that are very faint in the optical/near-IR bands and would be missed by samples selected at shorter wavelengths.
Methods. The sample was selected to
mag at
m using photometric redshifts obtained by fitting the galaxies spectral energy distribution at optical, near-IR bands, and IRAC bands. We also require that the brightest band (in AB scale) in which candidates are detected is the IRAC
m band to ensure that the near-IR
m (rest-frame) peak is falling in or beyond this band.
Results. We found 53 candidates, of masses in the range
. At least ~81% of these galaxies are missed by traditional Lyman Break selection methods based on ultraviolet light. Spitzer + MIPS emission is detected for 60% of the sample of
galaxy candidates. Although in some cases
this might suggest a residual contamination from lower redshift star-forming galaxies or Active Galactic Nuclei, 37% of these objects are also detected in the sub-mm/mm bands in SCUBA, AzTEC, and MAMBO surveys, and have properties fully consistent with vigorous starburst galaxies at
.
The comoving number density of galaxies with stellar masses of above 5
(a reasonable stellar-mass completeness limit for our sample) is 2.6
10-5 Mpc-3 (using the volume within
), and the corresponding stellar mass density is
Mpc-3, or about 3% of the local density above the same stellar mass limit. For the subsample of MIPS-undetected galaxies, we measure a number density of
10-5 Mpc-3 and a stellar mass density of
Mpc-3. Even in the unlikely case that
these are all truly quiescent galaxies, this would imply an increase in the space density
of passive galaxies by a factor of
between
and
, and by
to
.
Key words: cosmology: observations / galaxies: formation / Galaxy: evolution / infrared: galaxies / galaxies: high-redshift / galaxies: photometry
© ESO, 2009
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