HII Region Metallicity Constraints Near the Site of the Strongly Lensed Supernova "SN Refsdal" at Redshift 1.49

TL;DR

This study measures the metallicity near the site of the lensed supernova SN Refsdal at redshift 1.49, providing the first local metallicity constraint at z>1, which informs supernova progenitor environments in the early universe.

Contribution

It offers the first observational measurement of local metallicity at a supernova site at redshift greater than 1, utilizing integral field spectroscopy of a strongly lensed galaxy.

Findings

Local metallicity near SN Refsdal is constrained to 12 + log(O/H) ≤ 8.67.

Average metallicity over similar HII regions is ≤ 8.11.

SN Refsdal is located in a low-metallicity environment at high redshift.

Abstract

We present the local HII region metallicity near the site of the recently discovered multiply lensed supernova (SN; "SN Refsdal") at redshift 1.49. "SN Refsdal" is located at the outer spiral arm ($\sim$7 kpc) of the lensed host galaxy, which we have previously reported to exhibit a steep negative galactocentric metallicity gradient. Based on our updated near-infrared integral field spectroscopic data, the gas-phase metallicity averaged in an intrinsic radius of $\sim$ 550 pc surrounding an HII region $\sim$ 200 pc away from the SN site is 12 + log(O/H)$_{\rm PP04N2}$ $\le$ 8.67. The metallicity averaged over nine HII regions at similar galactocentric distances ($\sim$5-7 kpc) as "SN Refsdal" is constrained to be 12 + log(O/H)$_{\rm PP04N2}$ $\le$ 8.11. Given the fortuitous discovery of "SN Refsdal" in an advantageously lensed face-on spiral, this is the first observational constraint on the local metallicity environment of an SN site at redshift $z>1$.