NOAO/KPNO--NSO,

DEPARTMENT OF ASTRONOMY

AND STEWARD OBSERVATORY

AND NRAO

The University of Arizona

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JOINT COLLOQUIUM

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• Dr. Liliya L.R. Williams

• University of Minnesota, Department of Astronomy

• "Weak Lensing of Point Sources: Quasars, Gamma-Ray Bursts, and Supernovae"

ABSTRACT:

In the last decade gravitational lensing has become an indispensable tool of cosmologists. Strong and weak lensing are routinely used to map out mass distribution on sub-galactic to supercluster scales. Weak lensing distorts, or shears the shapes of background extended sources, like galaxies. In this talk I will describe the theory and observations of weak lensing of unresolved, or point sources. The signature produced by this type of lensing is angular correlations on the sky between high redshift sources, QSOs and GRB, and intervening mass distribution, traced by visible galaxies. In addition to correlations, weak lensing of high-redshift supernova provide a different probe: they allow us to directly measure the magnification due to lensing. Just like weak shear lensing, weak lensing of point sources can be used to measure mass distribution in the Universe. I will talk about the current status and challenges presented by this technique.

• Thursday, December 4, 2003

• at 4:00 p.m.

• in Steward Observatory Lecture Hall-Room N210

Refreshments at 3:30 p.m. in the Lobby