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Post Info TOPIC: Chandra Multiwavelength Project
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Title: Chandra Multiwavelength Project X-ray Point Source Catalogue
Authors: Minsun Kim, Dong-Woo Kim, Belinda J. Wilkes, Paul J. Green, Eunhyeuk Kim, Craig S. Anderson, Wayne A. Barkhouse, Nancy R. Evans, Zeljko Ivezic, Margarita Karovska, Vinay L. Kashyap, Myung Gyoon Lee, Peter Maksym, Amy E. Mossman, John D. Silverman, Harvey D. Tananbaum

We present the Chandra Multiwavelength Project (ChaMP) X-ray point source catalogue with ~6,800 X-ray sources detected in 149 Chandra observations covering \~10 deg². The full ChaMP catalogue sample is seven times larger than the initial published ChaMP catalogue. The exposure time of the fields in our sample ranges from 0.9 to 124 ksec, corresponding to a deepest X-ray flux limit of f_{0.5-8.0} = 9 x 10^{-16} erg/cm²/sec. The ChaMP X-ray data have been uniformly reduced and analysed with ChaMP-specific pipelines, and then carefully validated by visual inspection. The ChaMP catalogue includes X-ray photometric data in 8 different energy bands as well as X-ray spectral hardness ratios and colours. To best utilise the ChaMP catalogue, we also present the source reliability, detection probability and positional uncertainty. To quantitatively assess those parameters, we performed extensive simulations. In particular, we present a set of empirical equations: the flux limit as a function of effective exposure time, and the positional uncertainty as a function of source counts and off axis angle. The false source detection rate is ~1% of all detected ChaMP sources, while the detection probability is better than ~95% for sources with counts > 30 and off axis angle < 5 arcmin. The typical positional offset between ChaMP X-ray source and their SDSS optical counterparts is 0.7±0.4 arcsec, derived from ~900 matched sources.

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Title: Chandra Multiwavelength Project X-ray Point Source Number Counts and the Cosmic X-ray Background
Authors: Minsun Kim, Belinda J. Wilkes, Dong-Woo Kim, Paul J. Green, Wayne A. Barkhouse, Myung Gyoon Lee, John D. Silverman, Harvey D. Tananbaum

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 catalogue, ~5,500 sources are selected covering 9.6 deg² 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 2x10^{-17} to 2.4x10^{-12} (0.5-2 keV) and from 2x10^{-16} to 7.1x10^{-12} (2-8 keV) erg/cm²/sec. 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 ~1% when target sources are included.

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