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学术报告:Probing AGN Accretion Disk Structure with Microlensing and the Swift AGN and Cluster Survey

2019年01月17日 03:16 姜云国 点击:[]


报告时间: 7月9日上午 9:00报告地点: 闻天楼南楼211报告人: The University of Oklahoma, Depart. of Physics and Astronomy 戴新宇 Abstract:Gravitational microlensing provides a unique tool to study the emission regions of quasars from the smallest X-ray emission region to the larger BLR region. I will review the recent progress of the field focusing on the constraints on the non-thermal X-ray emission, based on our Chandra long-term monitoring results (over 3 Msec) of a sample of lenses. We discover for the first time chromatic microlensing differences between the soft and hard X-ray bands in the X-ray continuum emission. Our results indicate that the coronae above the accretion disk thought to generate X-rays have a non-uniform electron distribution, and the hard X-ray emission region is smaller than the soft region in two cases tracking the event horizon of black holes. We detect metal emission lines for almost all X-ray images in all lenses. We measure larger equivalent line widths in lensed quasars compared to a large sample of normal non-lensed AGNs of similar luminosities. We conclude that the iron line emission region is smaller than that of the X-ray continuum, possibly resulting from strong gravitational lensing near the black hole. Both the X-ray and optical emission region sizes scale with the black hole mass with similar slopes, but with a much smaller normalization for the X-ray emission. With the order of magnitude increase of effective area by Athena, I will discuss the perspective of quasar microlensing in the Athena era. The Swift AGN and Cluster Survey (SACS) uses 125 square degrees of Swift XRT serendipitous fields with variable depths surrounding gamma-ray bursts to provide a medium depth (4e-15erg/cm^2/s) and area survey filling the gap between deep, narrow Chandra/XMM-Newton surveys and wide, shallow ROSAT surveys. Here we present a catalog of 22,563 point sources and 442 extended sources and examine the number counts of the AGN and galaxy cluster populations. SACS provides excellent constraints on the AGN and cluster number counts, and the cluster number counts span a much larger continuous flux range than previous surveys. Using the public SDSS data, we have measured photometric redshifts for the majority of z<0.5 Swift clusters that fall in the SDSS regions. Deep optical or IR follow-up observations of this cluster sample will significantly increase the number of higher redshift (z > 0.5) X-ray-selected clusters.

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