Tracing the Mass-Dependent Star Formation History of Late-Type Galaxies Using X-Ray Emission: Results from the Chandra Deep Fields

• Published in: The Astrophysical journal 2008-07, Vol.681 (2), p.1163-1182
• Main Authors: Lehmer, B. D, Brandt, W. N, Alexander, D. M, Bell, E. F, Hornschemeier, A. E, McIntosh, D. H, Bauer, F. E, Gilli, R, Mainieri, V, Schneider, D. P, Silverman, J. D, Steffen, A. T, Tozzi, P, Wolf, C
• Format: Article
• Language: English
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/588459

We report on the X-ray evolution over the last [sim]9 Gyr of cosmic history (i.e., since [image]) of late-type galaxy populations in the Chandra Deep Field-North and Extended Chandra Deep Field-South (CDF-N and E-CDF-S, respectively; jointly CDFs) survey fields. Our late-type galaxy sample consists of 2568 galaxies, which were identified using rest-frame optical colors and HST morphologies. We utilized X-ray stacking analyses to investigate the X-ray emission from these galaxies, emphasizing the contributions from normal galaxies that are not dominated by active galactic nuclei (AGNs). Over this redshift range, we find significant increases (factors of [sim]5-10) in the X-ray-to-optical mean luminosity ratio ([image] /[image]) and the X-ray-to-stellar mass mean ratio ([image] /[image]) for galaxy populations selected by [image] and [image], respectively. When analyzing galaxy samples selected via SFR, we find that the mean X-ray-to-SFR ratio ([image] /SFR) is consistent with being constant over the entire redshift range for galaxies with SFR = 1-100 [image] yr[image], thus demonstrating that X-ray emission can be used as a robust indicator of star formation activity out to [image]. We find that the star formation activity (as traced by X-ray luminosity) per unit stellar mass in a given redshift bin increases with decreasing stellar mass over the redshift range z = 0.2-1, which is consistent with previous studies of how star formation activity depends on stellar mass. Finally, we extend our X-ray analyses to Lyman break galaxies at [image] and estimate that [image] /[image] at [image] is similar to its value at [image].