Cosmology Lunchtime Seminar

Week of Monday, December 11th 2017

Monday, December 11th 2017
12:15 pm:
Speaker: Patrick Kelly, UMN
Subject:  Using A Highly Magnified Star and the Multiply Imaged Supernova Refsdal to Constrain the Outcomes of Star Formation, Stellar Evolution, and the Abundance of Primordial Black Holes

We recently detected an individual blue supergiant star in a multiply imaged spiral galaxy at redshift z=1.49 behind the MACS J1149 galaxy cluster (z=0.54). In the spring of 2016, the star (dubbed LS1) appeared to brighten by a factor of three in Hubble Space Telescope imaging due to microlensing by a star in the intracluster medium of the foreground cluster. Lens models of the cluster show that the star, which is adjacent to the galaxy cluster’s critical curve, likely became magnified briefly by more than a factor of 2000. Additional monitoring subsequently revealed a second transient object which may be LS1’s counterimage in October 2016. I will describe ongoing work to model LS1’s light curve and to draw conclusions about the stellar population in the intracluster medium, the outcomes of massive stellar evolution, and the abundance of primordial black holes. The multiply imaged supernova, SN Refsdal, has appeared as five separate images, and a new measurement of its time delay provides useful and complementary constraints on the cluster lens model.

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