This paper uses the First XMM-Newton Serendipitous Source Catalog compiled by the XMM-Newton Science Center to identify low- z X-ray selected normal galaxy candidates .
Our sample covers a total area of \approx 6 deg ^ { 2 } to the 0.5-2 keV limit \approx 10 ^ { -15 } erg s ^ { -1 } cm ^ { -2 } .
A total of 23 sources are selected on the basis of low X-ray–to–optical flux ratio \log f _ { X } / f _ { opt } < -2 , soft X-ray spectral properties and optical spectra , when available , consistent with stellar than AGN processes .
This sample is combined with similarly selected systems from the Needles in the Haystack Survey ( Georgantopoulos et al .
2005 ) to provide a total of 46 unique z \la 0.2 X-ray detected normal galaxies , the largest low- z sample yet available .
This is first used to constrain the normal galaxy \log N - \log S at bright fluxes ( 10 ^ { -15 } -10 ^ { -13 } erg s ^ { -1 } cm ^ { -2 } ) .
We estimate a slope of -1.46 \pm 0.13 for the cumulative number counts consistent with the euclidean prediction .
We further combine our sample with 23 local ( z \la 0.2 ) galaxies from the Chandra Deep Field North and South surveys to construct the local X-ray luminosity function of normal galaxies .
A Schechter form provides a good fit to the data with a break at \log L _ { \star } = 41.02 _ { -0.12 } ^ { +0.14 } erg s ^ { -1 } and a slope of \alpha = -1.76 \pm 0.10 .
Finally , for the sample of 46 systems we explore the association between X-ray luminosity and host galaxy properties , such as star-formation rate and stellar mass .
We find that the L _ { X } of the emission-line systems correlates with H \alpha luminosity and 1.4 GHz radio power , both providing an estimate of the current star-formation rate .
In the case of early type galaxies with absorption line optical spectra we use the K -band as proxy to stellar mass and find a correlation of the form L _ { X } \propto L _ { K } ^ { 1.5 } .
This is flatter than the L _ { X } - L _ { B } relation for local ellipticals .
This may be due to either L _ { K } providing a better proxy to galaxy mass or selection effects biasing our sample against very luminous early-type galaxies , L _ { X } > 10 ^ { 42 } erg s ^ { -1 } .