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The properties and redshift evolution of intermediate-luminosity off-nuclear x-ray sources in the Chandra Deep Fields.

Lehmer, B. D. and Brandt, W. N. and Hornschemeier, A. E. and Alexander, D. M. and Bauer, F. E. and Koekemoer, A. M. and Schneider, D. P. and Steffen, A. T. (2007) 'The properties and redshift evolution of intermediate-luminosity off-nuclear x-ray sources in the Chandra Deep Fields.', Astronomical journal., 131 (5). pp. 2394-2405.


We analyze a population of intermediate-redshift (z~0.05-0.3) off-nuclear X-ray sources located within optically bright galaxies in the Great Observatories Origins Deep Survey and Galaxy Evolution from Morphology and SEDs fields. A total of 24 off-nuclear source candidates are classified using deep Chandra X-Ray Observatory exposures from the Chandra Deep Field-North, Chandra Deep Field-South, and Extended Chandra Deep Field-South 15 of these are newly identified. These sources have average X-ray spectral shapes and optical environments similar to those observed for off-nuclear intermediate-luminosity (LX>=1039 ergs s-1 in the 0.5-2.0 keV band) X-ray objects (IXOs; sometimes referred to as ultraluminous X-ray sources) in the local universe. This sample improves the available source statistics for intermediate-redshift off-nuclear sources with LX>~1039.5 ergs s-1, and it places significant new constraints on the redshift evolution of the off-nuclear source frequency in field galaxies. The fraction of intermediate-redshift field galaxies containing an off-nuclear source with LX>~1039 ergs s-1 is suggestively elevated (~80% confidence level) with respect to that observed for IXOs in the local universe; we calculate this elevation to be a factor of ~1.9+1.4-1.3. A rise in this fraction is plausibly expected as a consequence of the observed increase in global star formation density with redshift, and our results are consistent with the expected magnitude of the rise in this fraction.

Item Type:Article
Keywords:Cosmology, Observations, Diffuse Radiation, Surveys, X-rays.
Full text:Full text not available from this repository.
Publisher Web site:
Date accepted:30 January 2006
Date deposited:No date available
Date of first online publication:30 October 2007
Date first made open access:No date available

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