2006A&A...454..447T

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 (L_X>10⁴²erg/s) 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 log(f<sub>X</sub>/f<sub>O</sub>)←2 for separating AGN from NGs. We also performed a similar search in two nearby-galaxy samples from the literature. With XMM-Newton (Chandra) we covered an area of ∼8.2 (∼5.8) deg<sup>2</sup> down to a flux limit of ∼10<sup>–15</sup> (∼1.6x10<sup>–15</sup>) erg/cm2/s. We classified 2dFGRS spectra using emission-line intensity ratios. 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, HII nuclei, and 2 spectra as possible HII 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 HII and 3 absorption-line galaxies have log(f<sub>X</sub>/f<sub>O</sub>)>-2. Furthermore, all 44 galaxies in the first literature sample have log(f<sub>X</sub>/f<sub>O</sub>)←2 and L<sub>X</sub><10<sup>42</sup>erg/s. In the second literature sample, out of a total of 170 ``normal'' galaxies, we found 16 galaxies with log(f_X/f_O)>-2, the majority of which are massive ellipticals. Three of these have L_X>10⁴²erg/s. 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 log(f_X/f_O)←2 criterion seems to select primarily against the brightest, massive ellipticals.