We present a study of discrete X-ray sources in and around the bulge-dominated , massive Sa galaxy , Sombrero ( M104 ) , based on new and archival Chandra observations with a total exposure of \sim 200 ks .
With a detection limit of L _ { X } \approx 10 ^ { 37 } { ~ { } ergs~ { } s ^ { -1 } } and a field of view covering a galactocentric radius of \sim 30 kpc ( 11 \farcm 5 ) , 383 sources are detected .
Cross-correlation with Spitler et al. ’ s catalogue of Sombrero globular clusters ( GCs ) identified from HST /ACS observations reveals 41 X-rays sources in GCs , presumably low-mass X-ray binaries ( LMXBs ) .
Metal-rich GCs are found to have a higher probability of hosting these LMXBs , a trend similar to that found in elliptical galaxies .
On the other hand , the four most luminous GC LMXBs , with apparently super-Eddington luminosities for an accreting neutron star , are found in metal-poor GCs .
We quantify the differential luminosity functions ( LFs ) for both the detected GC and field LMXBs , whose power-low indices ( \sim 1.1 for the GC-LF and \sim 1.6 for field-LF ) are consistent with previous studies for elliptical galaxies .
With precise sky positions of the GCs without a detected X-ray source , we further quantify , through a fluctuation analysis , the GC LF at fainter luminosities down to 10 ^ { 35 } { ~ { } ergs~ { } s ^ { -1 } } .
The derived index rules out a faint-end slope flatter than 1.1 at a 2 \sigma significance , contrary to recent findings in several elliptical galaxies and the bulge of M31 .
On the other hand , the 2-6 keV unresolved emission places a tight constraint on the field LF , implying a flattened index of \sim 1.0 below 10 ^ { 37 } { ~ { } ergs~ { } s ^ { -1 } } .
We also detect 101 sources in the halo of Sombrero .
The presence of these sources can not be interpreted as galactic LMXBs whose spatial distribution empirically follows the starlight .
Their number is also higher than the expected number of cosmic AGNs ( 52 \pm 11 [ 1 \sigma ] ) whose surface density is constrained by deep X-ray surveys .
We suggest that either the cosmic X-ray background is unusually high in the direction of Sombrero , or a distinct population of X-ray sources is present in the halo of Sombrero .