The environments of Type Ia supernovae with different relative equivalent width of Si II feature in their spectra

TL;DR

This study investigates how the spectral feature of Si II in Type Ia supernovae relates to their environments and brightness, revealing differences in brightness but similar environments, which informs explosion mechanism theories.

Contribution

It introduces a classification of SNe Ia based on Si II REW and analyzes environmental differences, providing new insights into their explosion mechanisms.

Findings

BL SNe Ia are dimmer than NL SNe Ia.

No significant environmental differences between BL and NL SNe Ia.

Spectral REW correlates with brightness but not environment.

Abstract

Although type Ia supernovae are so important in many astrophysical field, e.g. in cosmology, their explosion mechanism and progenitor system are still unclear. In physics, the relative equivalent width (REW) of the Si II 635.5 nm absorption feature reflects the velocity interval of silicon in the supernova ejecta and then may provide constraints on the explosion mechanism of SNe Ia. In this paper, we divide the SNe Ia into broad line (BL) and normal line (NL) subsamples based on their REW of Si II 635.5 nm absorption lines around maximum light, and find that the BL SNe Ia have a dimmer mean brightness than NL ones, which possibly results from their different metallicities. However, based on the pixel statistics study on the environments of two subsamples, we do not find any significant potential difference on the environments between BL and NL SNe Ia, which implies that the explosion mechanism of SNe Ia could be independent of their progenitor populations.