2007/06/12 by A. Ptak, Ptak, A., B. Mobasher +7
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.0706.1791
36 pages, 36 figures, formatted with emulateapj. Accepted for publication in ApJ. Higher resolution version available at http://xassist.pha.jhu.edu/ptak/goods_xlf_emulateapj.pdf
arxiv created 2007/06/12 · arxiv updated 2009/12/01
We present soft (0.5-2 keV) X-ray luminosity functions (XLFs) in the Great Observatories Origins Deep Survey (GOODS) fields, derived for galaxies at z~0.25 and 0.75. SED fitting was used to estimate photometric redshifts and separate galaxy types, resulting in a sample of 40 early-type galaxies and 46 late-type galaxies. We estimate k-corrections for both the X-ray/optical and X-ray/NIR flux ratios, which facilitates the separation of AGN from the normal/starburst galaxies. We fit the XLFs with a power-law model using both traditional and Markov-Chain Monte Carlo (MCMC) procedures. The XLFs differ between z<0.5 and z>0.5, at >99% significance levels for early-type, late-type and all (early and late-type) galaxies.We also fit Schechter and log-normal models to the XLFs, fitting the low and high redshift XLFs for a given sample simultaneously assuming only pure luminosity evolution. In the case of log-normal fits, the results of MCMC fitting of the local FIR luminosity function were used as priors for the faint and bright-end slopes (similar to ``fixing'' these parameters at the FIR values except here the FIR uncertainty is included). The best-fit values of the change in log L* with redshift were dlogL* = 0.23 +/- 0.16 dex (for early-type galaxies) and 0.34 +/- 0.12 dex (for late-type galaxies), corresponding to (1+z)1.6 and (1+z)2.3. These results were insensitive to whether the Schechter or log-normal function was adopted.