X-ray Emission Of AGNs And X-ray Cluster Survey

In the past half centery, X-ray astronomy has experienced a fast develop-ment, and became one of the most important and promising fields of modern astrophysics. Two X-ray astronomy topics are involved in this dissertation:X-ray emission of active galactic nucleus (AGN) and X-ray survey of galaxy clus-ters. AGN reveals the violent accretion process of super-massive black hole, while galaxy clusters trace the large scale structure of the universe. In the introduc-tion, we introduce the development of X-ray astronomy, the instruments involved in our work, and background knowledge of AGN and galaxy cluster. There are three aspects of our work:study of narrow Fe Kα line in AGN (Chapter2), study of AGN’s intrinsic X-ray emission (Chapter3), Swift X-ray cluster survey and related work (Chapter4-6).To study the narrow Fe Ka line of AGN. we compile a sample of89Seyfert galaxies with both [O IV]25.89/mi line luminosities observed by Spitzer IRS and X-ray spectra observed by XMM-Newton EPIC. Using [O Ⅳ] emission as a proxy for AGN intrinsic luminosity, we find that although type2AGN have higher line equivalent widths, the narrow Fe K lines in Compton-thin and Compton-thick Seyfert2galaxies are2.9+0.8-0.6and5.6+1.9-1.4times weaker in terms of luminosity than Seyfert1galaxies, respectively. This indicates that different correction factors need to be applied for various types of AGN before the narrow Fe K line luminosity could serve as an intrinsic AGN luminosity indicator. This is the first observational evidence showing that the narrow Fe K line emission in AGN is anisotropic. The observed difference is consistent with theoretical calculations assuming a smoothly distributed obscuring torus and could provide independent constraints on the dumpiness of the torus.It’s believed that hard X-ray emission in radio quite AGN is produced in an optically thin thermal corona around the supermassive black hole. However little is known on the physical nature of the corona itself. We present an ob-servational investigation on whether the intrinsic hard X-ray emission from the corona is isotropic as many studies have assumed. We compile a sample of178Seyfert galaxies with both [O IV]25.89μm line luminosities measured with Spitzer IRS and X-ray spectra observed by XMM-Newton EPIC or Chandra. Compton-thick sources were carefully excluded. We model the X-ray spectra to obtain the absorption-corrected2-10keV continuum luminosities. Using the [O Ⅳ] emis-sion as a proxy of AGN intrinsic luminosity, we find that the intrinsic2-10keV luminosity of Seyfert1is≥3times higher than that of Compton-thin Seyfert2galaxies. This striking anisotropy suggests the X-ray emission is produced in bipo-lar outflowing plasma, and therefore provides a natural link between the so-called corona and the jet base in these systems. Another consequence of this discovery is that one has to make corrections to the anisotropy before utilizing hard X-ray emission as intrinsic luminosity proxy of AGN, such as measuring the fraction of obscured AGN.The Swift X-ray Cluster Survey (SXCS) is an ongoing project aimed at find-ing serendipitously galaxy clusters in the Swift X-ray Telescope (XRT) archive. Despite of its low collecting area, XRT has characteristics which arc optimal for X-ray cluster surveys:a low background and an almost constant PSF across the field-of-view (FOV). Tundo et al.[208] used a first chunk of the XRT archive including336GRB follow-up fields, resulting in a catalog of72extended Xray sources. We are extending it to larger sky coverage (the whole XRT archive) and higher sensitivity. A new software "EXSdetect" is developed for this extended survey. Combining Voronoi tessellation and Friend-of-friend techniques, it de-tects extended sources from X-ray images efficiently. Performing it in extended SXCS gives rise to a large catalog of-300extended sources. Besides SXCS,"EXSdetect" can also be used in the X-ray data archive of other instruments and that of future X-ray missions.