UV spectroscopy of Core-Collapse Supernovae: A View into the Cosmic Metal Meltingpot

Supernova (SN) explosions play a pivotal role in triggering, driving, and (later on) inhibiting further star formation in galaxies. In fact, the combination of new observations and refined modelling shows that the little-understood and poorly constrained contribution of SNe to galaxy evolution processes (often hidden under the generic name of ``feedback'') is probably the weakest link in our understanding of structure formation in the Universe. Setting observational limits on the rate, environments, and energy output of high-redshift SNe is therefore one of the main science drivers of recent Hubble Space Telescope (HST) legacy programs, as well as of future missions like the James Webb Space Telescope (JWST). However, observations of high-redshift SNe in the optical (by HST), or in the near-IR (by JWST), actually sample the rest-frame UV of these objects. Thus, proper interpretation of these observations requires knowledge about the UV properties of SNe. Unfortunately, UV spectroscopy of local SNe of all types, which can only be obtained from space, is almost non-existent. Such UV data are also powerful probes of the SN environment, progenitor structure and explosion physics.

We pursued a GALEX program (cycles 1-6; PI Gal-Yam) to obtain target-of-opportunity GALEX spectroscopic observations of nearby, bright non-Ia (core-collapse) SNe. Our first paper indicated an emerging spectroscopic uniformity among Type II-P SNe. Accumulated data will help characterize the UV spectral evolution of SNe of all types.

The Hubble Space telescope (HST) provides an additional useful avenue to obtain higher quality and higher spectral resolution spectroscopy of nearby SNe. Working with Prof. Alex Filippenko from UC Berkeley (PI of several such HST programs) we have studied the UV spectrum of a nearby, peculiar SN Ic PTF12gzk, as well as the UV spectroscopic behavior of a sample of SNe IIb (these papers were part of the thesis project of Dr. Sagi Ben-Ami).