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X-ray spectral analysis of optically faint sources in the Chandra Deep Fields | | Francesca Civano
; Andrea Comastri
; Marcella Brusa
; | | Date: |
19 Dec 2004 | | Journal: | Mon.Not.Roy.Astron.Soc. 358 (2005) 693-704 | | Subject: | astro-ph | | Affiliation: | 1,2), Andrea Comastri , Marcella Brusa (3,2) ( Dipartimento di Astronomia, Universita’ di Bologna; INAF - Osservatorio Astronomico di Bologna; Max Planck Institut fuer Extraterrestrische Physik, Garching, Germany | | Abstract: | We present the results of a detailed spectral analysis of optically faint hard X-ray sources in the Chandra deep fields selected on the basis of their high X-ray to optical flux ratio (X/O). The stacked spectra of high X/O sources in both Chandra deep fields, fitted with a single power-law model, are much harder than the spectrum of the X-ray background (XRB). The average slope is also insensitive to the 2-8 keV flux, being approximately constant around Gamma~1 over more than two decades, strongly indicating that high X/O sources represent the most obscured component of the XRB. For about half of the sample, a redshift estimate (in most of the cases a photometric redshift) is available from the literature. Individual fits of a few of the brightest objects and of stacked spectra in different redshift bins imply column densities in the range 10^{22-23.5} cm^{-2}. A trend of increasing absorption towards higher redshifts is suggested. | | Source: | arXiv, astro-ph/0501397 | | Services: | Forum | Review | PDF | Favorites | |
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