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W. G. Pritchard Lab Seminar: 4:30-5:30 PM, 320 Whitmore Laboratory

	            **Monday February 14, 2005**
	
Direct observation of matter flowing into black holes

Michael Eracleous

Dept of Astronomy & Astrophysics
Penn State University

Abstract:

Active galaxies and quasars are the most luminous persistent objects in 
the Universe. Their ultimate source of power is thought to be the 
accretion of matter into a super-massive black hole residing at their 
center. According to the standard dogma, gas flowing into the black hole 
forms an equatorial disk, but direct dynamical evidence of such flow in 
quasars has only become available recently. In this talk I will begin by 
reviewing the basic picture adopted by researchers in the field, 
describing the recently-discovered evidence supporting the presence of 
accretion disks in quasars, and summarizing the subtleties involved in 
interpreting the observations. One important issue is the fact that light 
emerging from the accretion disk has propagated through both the disk 
atmosphere and the black hole's strong gravitational field. In some cases 
we actually do have a direct view of the equatorial accretion disk, and I 
will describe how we might use this to study dynamical phenomena, such as 
waves. The importance of waves in the disk is that they provide a 
mechanism for the outward transport of angular momentum, allowing matter 
to flow inwards and accretion to proceed.

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