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摘要
The 9-month Swift Burst Alert Telescope ( BAT) catalog provides the first unbiased (N(H) < 10(24) cm(-2)) look at local (< z > = 0.03) active galactic nuclei (AGNs). In this paper, we present the collected X-ray properties (0.3-12 keV) for the 153 AGNs detected. In addition, we examine the X-ray properties for a complete sample of nonbeamed sources, above the Galactic plane (b >= 15 degrees.). Of these, 45% are best fit by simple power law models, while 55% require the more complex partial covering model. One of our goals was to determine the fraction of "hidden" AGNs, which we define as sources with scattering fractions less than or equal to 0.03 and ratios of soft to hard X-ray flux less than or equal to 0.04. We found that "hidden" AGNs constitute a high percentage of the sample (24%), proving that they are a very significant portion of local AGNs. Further, we find that the fraction of absorbed sources does increase at lower unabsorbed 2-10 keV luminosities, as well as accretion rates. This suggests that the unified model requires modification to include luminosity dependence, as suggested by models such as the "receding torus" model. Some of the most interesting results for the BAT AGN sample involve the host galaxy properties. We found that 33% are hosted in peculiar/irregular galaxies and only 5/74 are hosted in ellipticals. Further, 54% are hosted in interacting/merger galaxies. Finally, we present both the average X-ray spectrum (0.1-10 keV) and log N-log S in the 2-10 keV band. With our average spectrum, we have the remarkable result of reproducing the measured CXB X-ray power law slope of Gamma approximate to 1.4. From the log N-log S relationship, we show that we are complete to log S >= -11 in the 2-10 keV band. Below this value, we are missing as many as 3000 sources at log S = -12. Both the collected X-ray properties of our uniform sample and the log N-log S relationship will now provide valuable input to X-ray background models for z approximate to 0.
- 出版日期2009-1-10
