Probing the Progenitors of Type Ia Supernovae using Circumstellar Material Interaction Signatures

TL;DR

This study investigates the relationship between different circumstellar material probes in Type Ia supernovae, finding no direct link between certain spectral features but confirming a statistical excess of blueshifted NaID absorption, especially in late-type galaxy hosts.

Contribution

First analysis to compare NaID and CaII spectral features as probes of circumstellar material in Type Ia supernovae using a new spectral sample.

Findings

No correlation between NaID and CaII features.

Confirmed excess of blueshifted NaID absorption in late-type galaxy hosts.

Interstellar medium origin unlikely for observed NaID features.

Abstract

This work aims to study different probes of Type Ia supernova progenitors that have been suggested to be linked to the presence of circumstellar material (CSM). In particular, we have investigated, for the first time, the link between narrow blueshifted NaID absorption profiles and the presence and strength of the broad high-velocity CaII near infrared triplet absorption features seen in Type Ia supernovae around maximum light. With the probes exploring different distances from the supernova; NaID > 10$^{17}$cm, high-velocity CaII features < 10$^{15}$cm. For this, we have used a new intermediate-resolution X-shooter spectral sample of 15 Type Ia supernovae. We do not identify a link between these two probes, implying either that, one (or both) is not physically related to the presence of CSM or that the occurrence of CSM at the distance explored by one probe is not linked to its presence at the distance probed by the other. However, the previously identified statistical excess in the presence of blueshifted (over redshifted) NaID absorption is confirmed in this sample at high significance and is found to be stronger in Type Ia supernovae hosted by late-type galaxies. This excess is difficult to explain as being from an interstellar-medium origin as has been suggested by some recent modelling, as such an origin is not expected to show a bias for blueshifted absorption. However, a circumstellar origin for these features also appears unsatisfactory based on our new results given the lack of link between the two probes of CSM investigated.