We present the Chandra Multiwavelength Project ( ChaMP ) X-ray point source number counts and the cosmic X-ray background ( CXRB ) flux densities in multiple energy bands .
From the ChaMP X-ray point source catalog , \sim 5 , 500 sources are selected covering 9.6 ~ { } deg ^ { 2 } in sky area .
To quantitatively characterize the sensitivity and completeness of the ChaMP sample , we perform extensive simulations .
We also include the ChaMP+CDFs ( Chandra Deep Fields ) number counts to cover large flux ranges from 2 \times 10 ^ { -17 } to 2.4 \times 10 ^ { -12 } ( 0.5-2 keV ) and from 2 \times 10 ^ { -16 } to 7.1 \times 10 ^ { -12 } ( 2-8 keV ) erg~ { } cm ^ { -2 } ~ { } sec ^ { -1 } .
The ChaMP and the ChaMP+CDFs differential number counts are well fitted with a broken power law .
The best fit faint and bright power indices are 1.49 ^ { +0.02 } _ { -0.02 } and 2.36 ^ { +0.05 } _ { -0.05 } ( 0.5-2 keV ) , and 1.58 ^ { +0.01 } _ { -0.01 } and 2.59 ^ { +0.06 } _ { -0.05 } ( 2-8 keV ) , respectively .
We detect breaks in the differential number counts and they appear at different fluxes in different energy bands .
Assuming a single power law model for a source spectrum , we find that the same population ( s ) of soft X-ray sources causes the break in the differential number counts for all energy bands .
We measure the resolved CXRB flux densities from the ChaMP and the ChaMP+CDFs number counts with and without bright target sources .
Adding the known unresolved CXRB to the ChaMP+CDF resolved CXRB , we also estimate total CXRB flux densities .
The fractions of the resolved CXRB without target sources are 78 ^ { +1 } _ { -1 } \% and 81 ^ { +2 } _ { -2 } \% in the 0.5-2 keV and 2-8 keV bands , respectively , somewhat lower , though generally consistent with earlier numbers since their large errors .
These fractions increase by \sim 1 \% when target sources are included .