Chandra Multiwavelength Project: Normal Galaxies at Intermediate Redshift
Author
Kim, D.‐W.
Barkhouse, W. A.
Romero‐Colmenero, E.
Green, P. J.
Kim, M.
Schlegel, E.
Silverman, J. D.
Anderson, C.
Ivezic, Z.
Kashyap, V.
Note: Order does not necessarily reflect citation order of authors.
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https://doi.org/10.1086/503828Metadata
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Kim, D.‐W., W. A. Barkhouse, E. Romero‐Colmenero, P. J. Green, M. Kim, A. Mossman, E. Schlegel, et al. 2006. “ Chandra Multiwavelength Project: Normal Galaxies at Intermediate Redshift .” The Astrophysical Journal 644 (2) (June 20): 829–842. doi:10.1086/503828.Abstract
We have investigated 136 Chandra extragalactic sources, including 93 galaxies with narrow emission lines (NELGs) and 43 with only absorption lines (ALGs). Based on fX/fO, LX, X-ray spectral hardness, and optical emission-line diagnostics, we have conservatively classified 36 normal galaxies and 71 AGNs. Their redshift ranges from 0.01 to 1.2, with normal galaxies in the range z = 0.01-0.3. Our normal galaxies appear to share characteristics with local galaxies, as expected from the X-ray binary populations and the hot interstellar matter (ISM). In conjunction with normal galaxies found in other surveys, we found no statistically significant evolution in LX/LB, within the limited z range (lesssim0.1). The best-fit slope of our log(N)-log(S) relationship is -1.5 for both S (0.5-2 keV) and B (0.5-8 keV) energy bands, which is considerably steeper than that of the AGN-dominated cosmic background sources, but slightly flatter than the previous estimate, indicating that normal galaxies will not exceed the AGN population until fX(0.5-2.0 keV) ~ 2 × 10-18 ergs s-1 cm-2 (a factor of ~5 lower than the previous estimate). A group of NELGs appear to be heavily obscured in X-rays. After correcting for intrinsic absorption, their X-ray luminosities could be LX > 1044 ergs s-1, making them type 2 quasar candidates. While most X-ray-luminous ALGs do not appear to be significantly absorbed, we found two heavily obscured objects that could be as luminous as an unobscured broad-line quasar. Among 43 ALGs, we found two E+A galaxy candidates. The X-ray spectra of both galaxies are soft, and one of them has a nearby close companion galaxy, supporting the merger/interaction scenario rather than the dusty starburst hypothesis.Terms of Use
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