Issue |
A&A
Volume 420, Number 1, June II 2004
|
|
---|---|---|
Page(s) | 125 - 133 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20040101 | |
Published online | 14 May 2004 |
High-z massive galaxies in the Hubble Deep Field South
1
INAF – Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy e-mail: marcella@brera.mi.astro.it
2
INAF – Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone, Italy e-mail: [giallo, fontana]@coma.mporzio.astro.it
3
Laboratoire d'Astronomie de Marseille, Traverse du Siphon, BP 8, 13376 Marseille, France e-mail: stephane.arnouts@oamp.fr
4
INAF – Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 40131 Trieste, Italy e-mail: [cristiani, nonino]@ts.astro.it
5
European Southern Observatory, Karl-Schwarzschildstr. 2, 85748 Garching, Germany e-mail: [sdodoric, evanzell]@eso.org
6
Dipartimento di Astronomia dell'Università di Padova, Vicolo dell'Osservatorio 2, 35122 Padova, Italy
Corresponding author: P. Saracco, saracco@brera.mi.astro.it
Received:
16
May
2003
Accepted:
25
February
2004
A census of massive galaxies at redshift increasingly higher
than may provide strong constraints for the history of mass assembly
and star formation.
Here we report the analysis of three galaxies
selected in the Hubble Deep Field South at
on the basis of their unusually red
near-IR color
.
We have used population synthesis models to constrain their redshifts
and their stellar masses.
One galaxy (HDFS-1269) is at redshift
while the other two (HDFS-822 and HDFS-850) are at
.
All three galaxies have already assembled a stellar mass
of about 1011
at the observed redshift,
placing the possible merging event of their formation at
.
The inferred mass weighted age of their stellar populations implies that
the bulk of the stars formed at
.
The resulting co-moving density of
galaxies at
is
Mpc-3, about a factor two higher than the
predictions of hierarchical models.
The comparison with the local density of galaxies implies that the three galaxies
must have already formed most of their stellar mass and that they cannot follow
an evolution significantly different from a passive aging.
The comparison with the density of local
early types
(passively evolved galaxies) suggests that their co-moving density
cannot decrease by more than a factor 2.5–3 from
to
suggesting that up to 40% of the stellar mass content of bright (
)
local early type galaxies was already in place at
.
Key words: galaxies: evolution / galaxies: elliptical and lenticular, cD / galaxies: formation
© ESO, 2004
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