Abstract
Supernova (SN) Refsdal is the first multiply-imaged, highly-magnified, and
spatially-resolved SN ever observed. The SN exploded in a highly-magnified
spiral galaxy at z=1.49 behind the Frontier Fields Cluster MACS1149, and
provides a unique opportunity to study the environment of SNe at high z. We
exploit the time delay between multiple images to determine the properties of
the SN and its environment, before, during, and after the SN exploded. We use
the integral-field spectrograph MUSE on the VLT to simultaneously target all
observed and model-predicted positions of SN Refsdal. We find MgII emission at
all positions of SN Refsdal, accompanied by weak FeII* emission at two
positions. The measured ratios of OII to MgII emission of 10-20 indicate a
high degree of ionization with low metallicity. Because the same high degree of
ionization is found in all images, it cannot be caused by SN Refsdal, but
rather by previous SNe or a young and hot stellar population. We find no
variability of the OII line over a period of 57 days. This suggests that
there is no variation in the OII luminosity of the SN over this period, or
that the SN contribution to the OII emission is too small to distinguish with
our observations.
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