Astrophys. J., 763, 111 (2013/February-1)
X-ray properties of the northern galactic cap sources in the 58 month Swift/BAT catalog.
VASUDEVAN R.V., BRANDT W.N., MUSHOTZKY R.F., WINTER L.M., BAUMGARTNER W.H., SHIMIZU T.T., SCHNEIDER D.P. and NOUSEK J.
Abstract (from CDS):
We present a detailed X-ray spectral analysis of the non-beamed, hard X-ray selected active galactic nuclei (AGNs) in the northern Galactic cap of the 58 month Swift Burst Alert Telescope (Swift/BAT) catalog, consisting of 100 AGNs with b > 50°. This sky area has excellent potential for further dedicated study due to a wide range of multi-wavelength data that are already available, and we propose it as a low-redshift analog to the "deep field" observations of AGNs at higher redshifts (e.g., CDFN/S, COSMOS, Lockman Hole). We present distributions of luminosity, absorbing column density, and other key quantities for the catalog. We use a consistent approach to fit new and archival X-ray data gathered from XMM-Newton, Swift/XRT, ASCA, and Swift/BAT. We probe to deeper redshifts than the 9 month BAT catalog ( < z > = 0.043 compared to < z > = 0.03 for the 9 month catalog), and uncover a broader absorbing column density distribution. The fraction of obscured (log NH ≥ 22) objects in the sample is ∼60%, and 43%-56% of the sample exhibits "complex" 0.4-10 keV spectra. We present the properties of iron lines, soft excesses, and ionized absorbers for the subset of objects with sufficient signal-to-noise ratio. We reinforce previous determinations of the X-ray Baldwin (Iwasawa-Taniguchi) effect for iron Kα lines. We also identify two distinct populations of sources; one in which a soft excess is well-detected and another where the soft excess is undetected, suggesting that the process responsible for producing the soft excess is not at work in all AGNs. The fraction of Compton-thick sources (log NH> 24.15) in our sample is ∼9%. We find that "hidden/buried AGNs" (which may have a geometrically thick torus or emaciated scattering regions) constitute ∼14% of our sample, including seven objects previously not identified as hidden. Compton reflection is found to be important in a large fraction of our sample using joint XMM-Newton+BAT fits ( < R > = 2.7±0.75), indicating light bending or extremely complex absorption. High-energy cutoffs generally lie outside the BAT band (E > 200 keV) but are seen in some sources. We present the average 1-10 keV spectrum for the sample, which reproduces the 1-10 keV X-ray background slope as found for the brighter 9 month BAT AGN sample. The 2-10 keV log(N)-log(S) plot implies completeness down to fluxes a factor of ∼4 fainter than seen in the 9 month catalog. We emphasize the utility of this northern Galactic cap sample for a wide variety of future studies on AGNs.
galaxies: active - surveys - X-rays: galaxies
VizieR on-line data:
<Available at CDS (J/ApJ/763/111): table1.dat table3.dat>
SWIFT J1138.9+2529, SWIFT J1158.9+4234 and SWIFT J1445.6+2702 are not in SIMBAD.
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