[Previous] | [Session 138] | [Next]
C.R. Mullis (ESO), J.P. Henry (IfA), I.M. Gioia (IRA-CNR), H. Boehringer, U.G. Briel, W. Voges (MPE), J.P. Huchra (CfA)
In the {\em ROSAT\/} All-Sky Survey, an 80.7 deg2 region around the north ecliptic pole (NEP) constitutes the deepest observation of the X-ray sky ever achieved with such a large, contiguous solid angle. Here 445 unique sources are detected with fluxes measured at greater than 4\sigma significance. We have identified the physical nature of 443 (99.6%) of the {\em ROSAT\/} NEP X-ray sources through a comprehensive program of imaging and spectroscopy. Active galactic nuclei (AGN) are the dominant constituents comprising nearly half (49.0%) of the sample.
The {\em ROSAT\/} NEP sample of 217 AGN is particularly well suited for a clustering analysis. The AGN are drawn from a contiguous, wide-angle region in the sky sampled to a relatively deep X-ray flux limit (~3 \times 10-14 erg s-1 cm-2, 0.5 -- 2.0 keV). The AGN sample is essentially complete and we have spectroscopically measured redshifts for the entire sample. Furthermore, the survey selection function is well determined and only a function of X-ray flux. Finally, our low-redshift determination of the AGN correlation function complements the high-redshift results obtained for optically selected AGN.
We have measured the degree of clustering in the {\em ROSAT\/} NEP AGN data by calculating the two-point spatial correlation function. The significance of the clustering signal (>3.5\sigma) suggests these results are likely the best constraints reported so far for X-ray selected AGN. Our results indicate that X-ray luminous AGN are spatially clustered in a manner similar to that of normal galaxies and optically selected AGN (i.e., r0 ~6\,h-1 Mpc). Furthermore, the NEP determination is a measure of the local behavior (z~.4) of AGN clustering and thus argues that the correlation strength has not evolved strongly since z ~1.4, the redshift typically probed by optical AGN correlation studies.
If you would like more information about this abstract, please follow the link to http://www.eso.org/~cmullis/nep.html. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.
The author(s) of this abstract have provided an email address for comments about the abstract: cmullis@eso.org