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2.2. Wider X-ray Surveys

Wider Chandra and XMM-Newton surveys (see Table 2) are a comparably large and important "industry" to the deep surveys. These typically involve investigation of X-ray sources in ~ 4-150 X-ray observations of moderate exposure (usually 20-60 ks, but sometimes as short as approx 5 ks); the observations are sometimes obtained from the public data archives. The wider surveys serve to bridge the observational "gap" between the deepest Chandra observations and the deepest observations made by previous X-ray missions (e.g., ROSAT; see Figure 2), and they effectively target the intermediate 0.5-8 keV flux levels (10-15 - 10-13 erg cm-2 s-1) which contribute most significantly to the XRB.

Table 2. Some Wider X-ray Surveys with Chandra and XMM-Newton

Survey Name Omega (deg2) Representative Reference or Note


ChaMP 14 D.W. Kim et al., 2004, ApJS, 150, 19
Clusters Serendipitous 1.1 P. Gandhi et al., 2004, MNRAS, 348, 529
CYDER ... F.J. Castander et al., 2003, AN, 324, 40
Lockman Hole NW 0.4 A.T. Steffen et al., 2003, ApJ, 596, L23
MUSYC 1 PI: van Dokkum
NOAO DWFS 9.3 PI: Jones
SEXSI 2.2 F.A. Harrison et al., 2003, ApJ, 596, 944
SWIRE Lockman 0.6 PI: Wilkes
1 hr Field 0.2 PI: McHardy
13 hr Field 0.2 I.M. McHardy et al., 2003, MNRAS, 342, 802


AXIS ... X. Barcons et al., 2002, A&A, 382, 522
CFRS 0.6 T.J. Waskett et al., 2003, MNRAS, 341, 1217
HELLAS2XMM 2.9 A. Baldi et al., 2002, ApJ, 564, 190
LSS 64 M. Pierre et al., 2004, astro-ph/0305191
Survey Science Center ... M.G. Watson et al., 2001, A&A, 365, L51
VIMOS 2.3 PI: Hasinger
2dF 1.5 A. Georgakakis et al., 2003, MNRAS, 344, 161


The second column above lists estimated survey solid angles; survey sensitivities are not uniform but rather vary significantly across these solid angles. In some cases, survey solid angles are not well defined and thus are not listed. In these cases, the reader should consult the listed reference or note for further details.

The wider X-ray surveys provide a broad census of the X-ray source population, often generating enormous numbers of sources (1000-6000 or more; e.g., see Figure 2). They thereby allow discovery of both intrinsically rare source types as well as low-redshift examples of sources found in the deep X-ray surveys. However, complete multiwavelength follow-up often must be compromised for reasons of observational economy; thus many of the wider surveys target specific source types of interest. Often targeted are sources with unusually hard X-ray spectra, sources with unusually large X-ray-to-optical flux ratios, or sources that appear likely to be at high redshift based upon optical imaging data.

Figure 2

Figure 2. Number of sources predicted from the ChaMP survey (for 137 ChaMP fields from Chandra Cycle 1 and Cycle 2) compared to numbers of sources from the Chandra Deep Fields and the ROSAT surveys analyzed by T. Miyaji, G. Hasinger, & M. Schmidt, 2000, A&A, 353, 25. An impressive approx 6000 ChaMP sources are expected in total, and these largely lie at intermediate 0.5-2 keV flux levels of (4-60) × 10-16 erg cm-2 s-1. From D.W. Kim, R.A. Cameron, J.J. Drake, et al., 2004, ApJS, 150, 19.

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