8th HEAD Meeting, 8-11 September, 2004
Session 35 Surveys and the Cosmic X-ray Background
Oral, Saturday, September 11, 2004, 4:00-5:38pm

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[35.05] The X-Ray-derived Cosmological Star Formation History and the Galaxy X-Ray Luminosity Functions in the Chandra Deep Fields

A. Ptak, A. Hornschemeier, C. Norman (JHU), B. Mobasher (STSci)

The cosmological star formation rate in the combined Chandra Deep Fields North and South is derived from our X-ray luminosity function for galaxies in these deep fields. Mild evolution is seen up to redshift order unity with star formation rate (1 + z)3. This is the first directly observed normal star-forming galaxy X-ray luminosity function (XLF) at cosmologically interesting redshifts. This provides the most direct measure yet of the X-ray-derived cosmic star formation history of the universe. We make use of Bayesian statistical methods to classify the galaxies and the two types of active galactic nuclei (AGNs), finding the most useful discriminators to be the X-ray luminosity, X-ray hardness ratio, and X-ray to optical flux ratio. There is some residual AGN contamination in the sample at the bright end of the luminosity function. Incompleteness slightly flattens the XLF at the faint end of the luminosity function. We will discuss the preliminary results of improving our analysis using available GOODS data. The GOODS data will greatly improve our Bayesian analysis by providing improved redshifts and many more flux measurements for each source. This will also allow for the additional segregation of the galaxies by both morphological and activity types.

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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.