Issue |
A&A
Volume 428, Number 3, December IV 2004
|
|
---|---|---|
Page(s) | 817 - 821 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20041819 | |
Published online | 07 December 2004 |
A search for clusters at high redshift
IV. Spectroscopy of Hα emitters in a proto-cluster at z = 2.16
1
Sterrewacht Leiden, PO Box 9513, 2300 RA, Leiden, The Netherlands e-mail: kurk@arcetri.astro.it
2
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany
Received:
10
August
2004
Accepted:
7
October
2004
Radio galaxy PKS 1138-262 is a massive galaxy at , located in a dense environment. We have found an overdensity of Lyα emitting galaxies in this field, consistent with a proto-cluster
structure associated with the radio galaxy. Recently, we have
discovered forty candidate Hα emitters by their excess near infrared
narrow band flux. Here, we present infrared spectroscopy of
nine of the brightest candidate Hα emitters. All these candidates
show an emission line at the expected wavelength. The identification
of three of these lines with Hα is confirmed by accompanying
[
] emission. The spectra of the other candidates are
consistent with Hα emission at
, one being a QSO as
indicated by the broadness of its emission line. The velocity
dispersion of the emitters (360 km s-1) is significantly smaller
than that of the narrow band filter used for their selection (1600 km s-1). We therefore conclude that the emitters are associated
with the radio galaxy. The star formation rates (SFRs) deduced from
the Hα flux are in the range 6-44
yr-1 and the SFR
density observed is 5-10 times higher than in the HDF-N at
. The properties of the narrow emission lines indicate that the
emitters are powered by star formation and contain very young (<100 Myr) stellar populations with moderately high metallicities.
Key words: galaxies: active / galaxies: clusters: general / galaxies: evolution / cosmology: observations / cosmology: early Universe
© ESO, 2004
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