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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
Chandra multiwavelength project: Normal galaxies at intermediate redshift
Astrophysical Journal, Volume 644, No. 2 II, Year 2006
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Description
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 (≲0.1). 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 L X > 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. © 2006. The American Astronomical Society. All rights reserved.
Authors & Co-Authors
Kim, Dong-woo
United States, Cambridge
Smithsonian Astrophysical Observatory
Barkhouse, Wayne A.
United States, Urbana
University of Illinois Urbana-champaign
Romero-Colmenero, Encarnacion
South Africa, Cape Town
South African Astronomical Observatory
Green, Paul J.
United States, Cambridge
Smithsonian Astrophysical Observatory
Kim, Minsun
United States, Cambridge
Smithsonian Astrophysical Observatory
Mossman, Amy E.
United States, Cambridge
Smithsonian Astrophysical Observatory
Schlegel, Eric M.
United States, Cambridge
Smithsonian Astrophysical Observatory
Silverman, John D.
Germany, Garching Bei Munchen
Max Planck Institute for Extraterrestrial Physics
Aldcroft, Thomas L.
United States, Cambridge
Smithsonian Astrophysical Observatory
Anderson, Craig S.
United States, Cambridge
Smithsonian Astrophysical Observatory
Ivezic, Zeljko
United States, Seattle
University of Washington
Kashyap, Vinay L.
United States, Cambridge
Smithsonian Astrophysical Observatory
Tananbaum, Harvey D.
United States, Cambridge
Smithsonian Astrophysical Observatory
Wilkes, Belinda J.
United States, Cambridge
Smithsonian Astrophysical Observatory
Statistics
Citations: 22
Authors: 14
Affiliations: 5
Identifiers
Doi:
10.1086/503828
ISSN:
0004637X
e-ISSN:
15384357
Research Areas
Environmental
Study Design
Cross Sectional Study