To learn about AGN physics and evolution in a complete manner, both
"deep" and "wider" X-ray surveys are required; the trade-off between
the two, of course, is between sensitivity and solid-angle coverage on the
sky. None of the Chandra and XMM-Newton surveys discussed
in this paper is truly wide-field, in that the widest still only cover
1% of
the sky. (4)
Both deep and wider X-ray surveys are reviewed briefly below.
Table 1 makes it clear that deep Chandra
and XMM-Newton surveys are a
major "industry". The 21 surveys listed there have a total exposure
exceeding 70 days, and
50 scientists
have invested substantial
effort on the analysis and interpretation of these data. Comparable
effort has also been expended on multiwavelength follow-up studies
of these surveys; due to the small solid angles under investigation, superb
multiwavelength coverage can be obtained relatively economically.
| Survey Name | Exposure | Representative Reference or Note |
| Chandra | ||
| Chandra Deep Field-North | 1950 ks | D.M. Alexander et al., 2003, AJ, 126, 539 |
| Chandra Deep Field-South | 940 ks | R. Giacconi et al., 2002, ApJS, 139, 369 |
| HRC Lockman Hole | 300 ks | PI: Murray |
| Extended CDF-S | 250 ks | PI: Brandt |
| Groth-Westphal | 200 ks | PI: Nandra |
| Lynx | 185 ks | D. Stern et al., 2002, AJ, 123, 2223 |
| LALA Cetus | 177 ks | PI: Malhotra |
| LALA Boötes | 172 ks | J.X. Wang et al., 2004, AJ, 127, 213 |
| SSA13 | 101 ks | A.J. Barger et al., 2001, AJ, 121, 662 |
| 3C295 | 100 ks | V. D'Elia et al., 2004, astro-ph/0403401 |
| Abell 370 | 94 ks | A.J. Barger et al., 2001, AJ, 122, 2177 |
| SSA22 "protocluster" | 78 ks | L.L. Cowie et al., 2002, ApJ, 566, L5 |
| ELAIS | 75 ks | J.C. Manners et al., 2003, MNRAS, 343, 293 |
| WHDF | 75 ks | PI: Shanks |
| XMM-Newton | ||
| Lockman Hole | 766 ks | G. Hasinger et al., 2001, A&A, 365, L45 |
| Chandra Deep Field-South | 317 ks | A. Streblyanska et al., 2004, astro-ph/0309089 |
| 13 hr Field | 200 ks | M.J. Page et al., 2003, AN, 324, 101 |
| Chandra Deep Field-North | 180 ks | T. Miyaji et al., 2003, AN, 324, 24 |
| Subaru Deep | 100 ks | PI: Watson |
| ELAIS S1 | 100 ks | PI: Fiore |
| Groth-Westphal | 80 ks | T. Miyaji et al., 2004, astro-ph/0402617 |
The Extended Chandra Deep
Field-South is comprised of four fields (each 250 ks),
the XMM-Newton ELAIS S1 survey is comprised of four fields (each
100 ks), and the Chandra ELAIS survey is comprised of two fields
(each 75 ks). The XMM-Newton
Subaru Deep survey also has seven flanking fields (each
|
||
The two most sensitive surveys in Table 1, by a
significant factor, are the 2 Ms Chandra Deep Field-North (CDF-N;
see Figure 1) and 1 Ms Chandra Deep
Field-South (CDF-S).
Both are situated in intensively studied regions of sky with little
Galactic foreground X-ray absorption. They reach 0.5-2 keV
fluxes of 
(2.5-5)
× 10-17 erg cm-2 s-1,
corresponding to count rates of
1 count every 2-4
days. At these flux levels, even moderate-luminosity AGN (similar to
Seyfert galaxies in the local universe) can be detected to
z 10.
The CDF-N and CDF-S are clearly "pencil-beam" surveys, each covering
400
arcmin2; for reference, this is ~ 1/2 the solid
angle of the full Moon and ~ 75 times the solid angle of the original
Hubble Deep Field-North (HDF-N; see Figure 1).
Public X-ray source catalogs are available for both the CDF-N
and CDF-S (see the references in Table 1); these
contain 580 and
370 sources,
respectively.
 |
Figure 1. Adaptively smoothed image of the
2 Ms CDF-N, constructed from
data in the 0.5-2 keV (red), 2-4 keV (green), and 4-8 keV
(blue) bands. Nearly 600 sources are detected in the
|
The other deep X-ray surveys in Table 1 have generally been performed in regions of sky where (1) extensive coverage already exists at one-to-several wavelengths, and/or (2) some interesting astronomical object is present (e.g., 3C295, Abell 370, or the SSA22 "protocluster"). They are all sensitive enough to detect moderate-luminosity AGN to z ~ 3-5, and in total the surveys in Table 1 cover a solid angle of ~ 3.5 deg2 (~ 16 Moons).
4 For this reason, we denote these surveys as "wider" (relative to the deep Chandra and XMM-Newton surveys) rather than "wide-field." Back.