Issue |
A&A
Volume 490, Number 3, November II 2008
|
|
---|---|---|
Page(s) | 879 - 891 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20078453 | |
Published online | 01 July 2008 |
Radio-loud AGN in the XMM-LSS field *
I. Optical identification and sample selection
1
Leiden Observatory, University of Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands e-mail: tasse@strw.leidenuniv.nl
2
CEA/DSM/DAPNIA, Service d'Astrophysique, Saclay, 91191 Gif-sur-Yvette, France
3
SUPA, Institute for Astronomy, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
4
Institut d'Astrophysique de Paris and Université Paris-Sud, Orsay, France
Received:
9
August
2007
Accepted:
11
May
2008
The XMM-Large Scale Structure survey field (XMM-LSS) is
an extragalactic window surveyed in the X-ray with the XMM-Newton
satellite. It has also been observed in the optical with the
Canada-France Hawaï Telescope (CFHTLS survey), and in the infrared
with the Spitzer Space Telescope (SWIRE survey). These surveys have
been carried out to study the structure and evolution of both baryonic
and dark matter on cosmological scales. In two previous papers, we
presented deep low frequency radio surveys of the XMM-LSS
field, with limiting flux density levels of ~4 and ~1.5 mJy/beam at 325 and 610 MHz
respectively (5σ). These radio surveys were motivated by the need to understand
the various connections between the host galaxies of radio sources and
their environments.
In this paper, we identify optical counterparts to the low frequency radio
sources, using the CFHTLS optical catalogue and images, that have an
i-band limiting magnitude of . We use a
likelihood ratio method and estimate that ~75% of the radio
sources have a detected optical counterpart. Using the CFHTLS and
SWIRE data, we derive photometric redshifts for the galaxies that are
identified with a radio source, as well as for those that are not; we
demonstrate the reliability of these photometric redshifts by deriving
the stellar mass function for galaxies at different redshifts, and
showing that it is consistent with previous determinations. We
classify the radio sources as type-1 AGN, radio galaxies, or
star-forming galaxies, and show that the radio luminosity function of
the radio galaxies agrees with previous measurements.
Key words: methods: observational / techniques: photometric / galaxies: active / galaxies: fundamental parameters / cosmology: observations / radio continuum: galaxies
© ESO, 2008
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