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arXiv · astro-ph/0410669

Chandra-SDSS Normal and Star-Forming Galaxies I: X-ray Source Properties of Galaxies Detected by Chandra in SDSS DR2

A. E. Hornschemeier·T. M. Heckman·A. F. Ptak·C. A. Tremonti·E. J. M. Colbert
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Abstract

We have cross-correlated X-ray catalogs derived from archival Chandra ACIS observations with a Sloan Digital Sky Survey (SDSS) Data Release 2 (DR2) galaxy catalog to form a sample of 42 serendipitously X-ray detected galaxies over the redshift interval 0.03 < z < 0.25. This pilot study will help fill in the "redshift gap" between local X-ray-studied samples of normal galaxies and those in the deepest X-ray surveys. Our chief purpose is to compare optical spectroscopic diagnostics of activity (both star-formation and accretion) with X-ray properties of galaxies. Our work supports a normalization value of the X-ray-star-formation-rate (X-ray-SFR) correlation consistent with the lower values published in the literature. The difference is in the allocation of X-ray emission to high-mass X-ray binaries relative to other components such as hot gas, low-mass X-ray binaries, and/or AGN. We are able to quantify a few pitfalls in the use of lower-resolution, lower signal-to-noise optical spectroscopy to identify X-ray sources (as has necessarily been employed for many X-ray surveys). Notably, we find a few AGN that likely would have been misidentified as non-AGN sources in higher-redshift studies. However, we do not find any X-ray hard, highly X-ray-luminous galaxies lacking optical spectroscopic diagnostics of AGN activity. Such sources are members of the "X-ray Bright, Optically Normal Galaxy" (XBONG) class of AGN.

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A. E. Hornschemeier, T. M. Heckman, A. F. Ptak, C. A. Tremonti, E. J. M. Colbert. 2004-10-28. Chandra-SDSS Normal and Star-Forming Galaxies I: X-ray Source Properties of Galaxies Detected by Chandra in SDSS DR2. https://doi.org/10.1086/426371

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