ChandraMultiwavelength Project. II. First Results of X‐Ray Source Properties

We present the first results of ChaMP X-ray source properties obtained fromthe initial sample of 62 observations. The data have been uniformly reduced andanalyzed with techniques specifically developed for the ChaMP and thenvalidated by visual examination. Utilizing only near on-axis, bright X-raysources (to avoid problems caused by incompleteness and the Eddington bias), wederive the Log(N)-Log(S) relation in soft (0.5-2 keV) and hard (2-8 keV) energybands. The ChaMP data are consistent with previous results of ROSAT, ASCA andChandra deep surveys. In particular, our data nicely fill in the flux gap inthe hard band between the Chandra Deep Field data and the previous ASCA data.We check whether there is any systematic difference in the source densitybetween cluster and non-cluster fields and also search for field-to-fieldvariations, both of which have been previously reported. We found nosignificant field-to-field cosmic variation in either test within thestatistics (~1 sigma) across the flux levels included in our sample. In theX-ray color-color plot, most sources fall in the location characterized byphoton index = 1.5-2 and NH = a few x 10^20 cm^2, suggesting that they aretypical broad-line AGNs. There also exist a considerable number of sources withpeculiar X-ray colors (e.g., highly absorbed, very hard, very soft). We confirma trend that on average the X-ray color hardens as the count rate decreases.Since the hardening is confined to the softest energy band (0.3-0.9 keV), weconclude it is most likely due to absorption. We cross-correlate the X-raysources with other catalogs and describe their properties in terms of opticalcolor, X-ray-to-optical luminosity ratio and X-ray colors.