The Faintest X-ray Sources from z=0-8

Understand

We use the new 4 Ms exposure of the CDF-S field obtained with the Chandra X-ray satellite to investigate the properties of the faintest X-ray sources over a wide range of redshifts.

• We use an optimized averaging procedure to investigate the weighted mean X-ray fluxes of optically selected sources in the CDF-S over the redshift range z=0-8 and down to 0.5-2 keV fluxes as low as 5e-19 erg/cm^2/s.
• None of the samples of sources at high redshifts (z>5) show any significant flux, and at z=6.5 we place an upper limit on the X-ray luminosity of 4e41 erg/s in the rest-frame 3.75-15 keV band for the sample of Bouwens et al.
• (2006).