Astronomy and Astrophysics – Astronomy
Scientific paper
Feb 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010head...11.0817e&link_type=abstract
American Astronomical Society, HEAD meeting #11, #8.17; Bulletin of the American Astronomical Society, Vol. 41, p.665
Astronomy and Astrophysics
Astronomy
Scientific paper
We currently lack large, unbiased samples of low luminosity AGN (LX < 1043 erg s-1) as they are poorly represented in shallow X-ray surveys and, whilst deeper, pencil-beam surveys include much larger samples, they are predominantly X-ray and optically faint and at high redshifts, limiting the extent to which their detailed X-ray and optical properties can be constrained. This is particularly important for lower luminosity objects given the significant contribution of the host galaxy. As a result, some key features of the low luminosity AGN population, such as the distribution of nuclear absorption (eg. the type 1 / type 2 fraction), are currently rather uncertain.
We present a new study of low luminosity AGN at intermediate redshifts (z 0.01 - 0.5) based on a sample derived from the 2XMMi X-ray and the SDSS DR7 optical spectroscopic catalogues. This large sample, comprising >500 objects (possible because of the large sky area [ 100 deg2] from which this sample is drawn) is dominated by galaxies at lower X-ray luminosities, effectively because of the magnitude limit for SDSS spectroscopy. A large fraction can be readily classified as AGN on the basis of their optical line ratios and/or X-ray spectra. We use this sample to provide new constraints on the distribution of intrinsic (and extrinsic) absorption using both optical and X-ray indicators. We find that the fraction of low luminosity AGN showing significant absorption is lower than expected, although this measurement is still compromised by host galaxy contributions in the optical and the presence of additional soft components in the X-ray band. We also compare the basic properties of this sample - the distributions of galaxy masses and morphologies - with previous optical and X-ray AGN studies.
Esquej Pilar
Survey Science Centre (SSC) XMM-Newton
Watson Mike
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