Chandra multiwavelength project (ChaMP): Normal galaxies at intermediate redshift

Abstract

We have investigated 136 Chandra extragalactic sources without broad emission lines, including 93 NELG and 43 ALG. Based on fx/fo, LX, X-ray spectral hardness and optical emission line diagnostics, we have conservatively classified 36 normal galaxies (20 spirals and 16 ellipticals) and 71 AGNs. Their redshift ranges from 0.01 to 1.2, while normal galaxies are at z=0.01-0.3. Our sample galaxies appear to share similar characteristics with local galaxies in terms of X-ray luminosities and spectral properties, as expected from the X-ray binary populations and the hot ISM. In conjunction with normal galaxies found in other surveys, we found no statistically significant evolution in LX/LB, within the limited z range (<0.1). We have built our log(N)-log(S) relationship of normal galaxies in the flux range, fX (0.5-8.0) = 10-15-10-13 erg sec -1 cm-2, after correcting completeness by a series of simulations. The best-fit slope is -1.5 for both soft (0.5-2.0 KeV) and broad (0.5-8.0 KeV) energy bands, which is considerably steeper than that of AGN-dominated cosmic background sources at faint fluxes, but slightly flatter than the previous estimate, indicating normal galaxies will exceed in number over the AGN population at fX < 10-18 erg sec -1 cm-2. © 2006 International Astronomical Union.