Ultraluminous X-ray sources out to z~0.3 in the COSMOS field

Abstract

Using Chandra observations we have identified a sample of seven off-nuclear X-ray sources, in the redshift range z=0.072-0.283, located within optically bright galaxies in the COSMOS Survey. Using the multi-wavelength coverage available in the COSMOS field, we study the properties of the host galaxies of these ULXs. In detail, we derived their star formation rate from H_alpha measurements and their stellar masses using SED fitting techniques with the aim to compute the probability to have an off-nuclear source based on the host galaxy properties. We divide the host galaxies in different morphological classes using the available ACS/HST imaging. We find that our ULXs candidates are located in regions of the SFR versus M${}_{s}tar$ plane where one or more off-nuclear detectable sources are expected. From a morphological analysis of the ACS imaging and the use of rest-frame colours, we find that our ULXs are hosted both in late and early type galaxies. Finally, we find that the fraction of galaxies hosting a ULX ranges from ~0.5% to ~0.2% going from L[0.5-2 keV]=3 x 10^39 erg s^-1 to L[0.5-2 keV]= 2 x 10^40 erg s^-1.

10 pages, 9 figures, accepted for publication in Astronomy & Astrophysics

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• The Obscured Fraction of AGN in the XMM-COSMOS Survey: A Spectral Energy Distribution Perspective
• Pulsing ULXs: tip of the iceberg?
• ULXs: Neutron Stars vs Black Holes
• No magnetars in ULXs
• HLX-1 may be an SS433 system
• Variability-selected low-luminosity active galactic nuclei candidates in the 7 Ms Chandra Deep Field-South
• X-ray properties of radio-selected star forming galaxies in the Chandra-COSMOS survey
• The Brightest Cluster X-ray Sources