Journal Club: Extreme magnification of a star at redshift 1.5 by a galaxy-cluster lens

Dr. Claudio Dalla Vecchia
See the live streaming of this talk on Wednesday April 18, 15:30 GMT (GMT+1 Summer time).

Abstract

Galaxy-cluster gravitational lenses can magnify background galaxies by a total factor of up to ~50. Here we report an image of an individual star at redshift z = 1.49 (dubbed “MACS J1149 Lensed Star 1 (LS1)”) magnified by > 2000. A separate image, detected briefly 0.26'' from LS1, is likely a counterimage of the first star demagnified for multiple years by an object greater or equal to 3 solar mass in the cluster. For reasonable assumptions about the lensing system, microlensing fluctuations in the stars’ light curves can yield evidence about the mass function of intracluster stars and compact objects, including binary fractions and specific stellar evolution and supernova models. Dark-matter subhalos or massive compact objects may help to account for the two images’ long-term brightness ratio.

 

Cafe afterwards in the Library.

About the talk

Journal Club: Extreme magnification of a star at redshift 1.5 by a galaxy-cluster lens
Dr. Claudio Dalla Vecchia
Wednesday April 18, 2018
en     en