Issue |
A&A
Volume 454, Number 2, August I 2006
APEX Special Booklet
|
|
---|---|---|
Page(s) | 447 - 452 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20054630 | |
Published online | 11 July 2006 |
Searching for X-ray luminous “normal” galaxies in 2dFGRS
1
Institute of Astronomy & Astrophysics, National Observatory of Athens, I. Metaxa & V. Pavlou, Penteli 15236, Greece e-mail: pana@astro.noa.gr
2
Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Rd., London, SW7 2AW, UK
Received:
2
December
2005
Accepted:
26
February
2006
Aims.We cross-correlated the Chandra XASSIST and
XMM-Newton Serendipitous Source Catalogues with the 2 degree Field Galaxy
Redshift Survey (2dFGRS) database. Our aim was to identify the most
X-ray luminous ( erg s-1) examples of galaxies in the
local Universe whose X-ray emission is dominated by stellar processes
rather than AGN activity (“normal” galaxies), as well as to test
the empirical criterion
for separating AGN from NGs. We also
performed a similar search in two nearby-galaxy
samples from the literature.
Methods.With
XMM-Newton (Chandra) we covered an area of ∼8.2 (5.8) deg2 down to a flux limit of
(
) erg cm-2 s-1. We classified
2dFGRS spectra using
emission-line intensity ratios.
Results.We found 18 (20) 2dFGRS galaxies with XMM-Newton (Chandra), which
constitute our XMM-Newton-2dFGRS (Chandra-2dFGRS) correlation sample. We classified 6 2dFGRS
spectra as
star-forming, nuclei, and 2 spectra as possible
nuclei. The rest of the objects are absorption-line galaxies and AGN,
including 3 possible LINERs. No luminous “normal” galaxies
have been found, but out of 19 “normal” galaxies in this sample,
5
and 3 absorption-line galaxies have
. Furthermore, all 44 galaxies in the first literature sample
have
and
erg s-1. In the second literature sample,
out of a total of 170 “normal” galaxies,
we found 16
galaxies with
, the majority of which are massive
ellipticals. Three of these have
erg s-1.
Conclusions.We found no luminous “normal” galaxies in our XMM-Newton-2dFGRS and Chandra-2dFGRS
correlation samples. We found three such galaxies in the second literature sample.
Considering all samples, we find that the criterion
seems to select primarily against the brightest, massive
ellipticals.
Key words: X-rays: galaxies / galaxies: starburst / galaxies: active
© ESO, 2006
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