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The Chandra Large Area Synoptic X-ray Survey (CLASXS) of the Lockman Hole-Northwest: The X-ray CatalogWe present the X-ray catalog and basic results from our Chandra Large Area Synoptic X-ray Survey (CLASXS) of the Lockman Hole-Northwest field. Our 9 ACIS-I fields cover a contiguous solid angle of approx. 0.4 sq deg and reach fluxes of 5 x 10(exp -16) ergs/sq cm/s (0.4-2 keV) and 3 x 10(exp -15) ergs/sq cm/s (2-8 keV). Our survey bridges the gap between ultradeep pencil-beam surveys, such as the Chandra Deep Fields (CDFs), and shallower, large area surveys, allowing a better probe of the X-ray sources that contribute most of the 2-10 keV cosmic X-ray background (CXB). We find a total of 525 X-ray point sources and 4 extended sources. At approx. 10(exp -14)ergs/sq cm/s (2-8 keV), our number counts are significantly higher than those of several non-contiguous, large area surveys. Such a large difference is an indication of clustering in the X-ray sources. On the other hand, the integrated flux from the CLASXS field, combined with ASCA and Chandra ultradeep surveys, is consistent with results from other large area surveys, within the variance of the CXB. We see spectral evolution in the hardening of the sources at fluxes below 10(exp -14) ergs/sq cm/s, which agrees with previous observations from Chandra and XMM-Newton. About 1/3 of the sources in the CLASXS field have multiple observations, allowing variability tests. Above 4 x 10(exp -14) ergs/sq cm/s (0.4-8 keV), approx. 61% of the sources are variable. We also investigated the spectral variability of the variable sources. While most show spectral softening with increasing flux, or no significant spectral change, there are a few sources that show a different trend. Four extended sources in CLASXS is consistent with the previously measured LogN-LogS of galaxy clusters. Using X-ray spectra and optical colors, we argue that 3 of the 4 extended sources are galaxy clusters or galaxy groups. We report the discovery of a gravitational lensing arc associated with one of these sources. Using red sequence and brightest cluster galaxy methods, we find that the redshifts of the extended sources are in the range z approx. 0.5 - 1. The inferred masses within the Einstein radii are consistent with the mass profiles of local groups scaled to the same virial radii.
Document ID
20040182344
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Yang, Y.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Mushotzky, R. F.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Steffen, A. T.
(Wisconsin Univ. Madison, WI, United States)
Barger, A. J.
(Wisconsin Univ. Madison, WI, United States)
Cowie, L. L.
(Hawaii Univ. Honolulu, HI, United States)
Date Acquired
August 22, 2013
Publication Date
January 1, 2004
Subject Category
Astronomy
Funding Number(s)
CONTRACT_GRANT: NSF AST-00-84816
CONTRACT_GRANT: CXC-GO2-3191A
CONTRACT_GRANT: NSF AST-02-39425
CONTRACT_GRANT: NSF AST-00-84847
Distribution Limits
Public
Copyright
Other

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