O.M. Stewart Colloquium Series

Monday, February 13, 2017 4:00pm

Room 120 Physics Building


Patrick Kelly, University of CA - Berkeley, presents, "Using Galaxy Cluster Lenses as Extreme Probes," Monday, Feb. 13 at 4:00 p.m. in Room 120, Physics Building. Refreshments will be served at 3:30 p.m., Rm 223A.


Distant galaxies can be highly magnified by foreground galaxy clusters, making cluster lenses powerful tools for studying the high-redshift universe. The James Webb Space Telescope, when pointed toward foreground clusters of galaxies, will be sensitive to even low-luminosity galaxies at redshifts z >6 (~35th magnitude) thought to drive reionization.  In regions of high amplification, however, cluster magnification maps, derived from models of cluster dark matter distributions, show strong disagreements. I will describe the first strongly lensed, multiply imaged supernova (SN), which appeared in the MACS1149 cluster field in late 2014 and then again, offset by ~8 arcseconds, in late 2015.  The time delay between the appearances of the SN disagrees with most but not all predictions, and illustrates a promising method for identifying the best assumptions about the distribution of dark matter in clusters.  I will next discuss a new and direct way to study individual massive stars near cosmic “high noon” (z~2), as well as the composition of dark matter in the form of compact objects.  Detections of hundreds of thousands of SNe and thousands of lensed transients by the Large Synoptic Survey Telescope and the Wide-Field Infrared Survey Telescope, with follow up from X-ray to radio wavelengths, will allow new insights into star formation and stellar evolution beginning at z~15-20, as well as the nature of dark matter and dark energy.