Type-Ia Supernova Remnant Shell At $Z=3.5$ Seen In The Three Sightlines Toward The Gravitationally Lensed Qso B1422+231

TL;DR

This study used high-resolution near-infrared spectroscopy of a gravitationally lensed quasar to detect a supernova remnant shell at high redshift, revealing detailed structure and composition of early universe supernova remnants.

Contribution

First detection of a supernova remnant shell at z=3.5 with spatially resolved absorption lines, constraining its size, expansion velocity, and chemical composition.

Findings

Detected a supernova remnant shell at z=3.5 with radius 50-100 pc

Observed significant variance in absorption lines between sightlines

Identified FeII-rich gas indicating a Type Ia supernova origin

Abstract

Using the Subaru 8.2m Telescope with an IRCS Echelle spectrograph, we obtained high-resolution (R=10,000) near-infrared (1.01-1.38 \mu m) spectra of images A and B of the gravitationally lensed QSO B1422+231 (z=3.628) consisting of four known lensed images. We detected MgII absorption lines at z=3.54, which show a large variance of column densities (~ 0.3 dex) and velocities (~ 10 km/s) between the sightlines A and B with a projected separation of only 8.4h_{70}^{-1} pc at the redshift. This is the smallest spatial structure of the high-z gas clouds ever detected after Rauch et al. found a 20-pc scale structure for the same z=3.54 absorption system using optical spectra of images A and C. The observed systematic variances imply that the system is an expanding shell as originally suggested by Rauch et al. By combining the data for three sightlines, we managed to constrain the radius and expansion velocity of the shell (~ 50-100 pc, 130 km/s), concluding that the shell is truly a supernova remnant (SNR) rather than other types of shell objects, such as a giant HII region. We also detected strong FeII absorption lines for this system, but with much broader Doppler width than that of \alpha-element lines. We suggest that this FeII absorption line originates in a localized FeII-rich gas cloud that is not completely mixed with plowed ambient interstellar gas clouds showing other \alpha-element low-ion absorption lines. Along with the Fe richness, we conclude that the SNR is produced by an SNIa explosion.