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