2020/04/30 by Yen-Chen Pan
Physics and Astronomy · #Astro and Planetary Science #Gamma-ray bursts and supernovae #Metallicity #Redshift #Spectral line #Stars #Stellar, planetary, and galactic studies #Supernova #White dwarf #astro-ph.GA #astro-ph.HE
paper · pdf · doi:10.3847/2041-8213/ab8e47
Accepted for publication in ApJ Letters
arxiv created 2020/04/30 · openalex publication_date 2020/05/01 · openalex created_date 2020/05/13 · arxiv updated 2020/05/27 · openalex updated_date 2026/08/05
Abstract Ejecta velocity of Type Ia supernovae (SNe Ia) is one powerful tool to differentiate between progenitor scenarios and explosion mechanisms. Here we revisit the relation between photospheric Si ii λ 6355 velocities ( v Si ii ) and host-galaxy properties with ∼280 SNe Ia. A more stringent criterion on the phase of SN spectra is adopted to classify SNe Ia in terms of their photospheric velocities. We find a significant trend that SNe Ia with faster Si ii λ 6355 (high- v Si ii SNe Ia) tend to explode in massive environments, whereas their slower counterparts can be found in both lower-mass and massive environments. This trend is further supported by the direct measurements on host gas-phase metallicities. We suggest this relation is likely caused by at least two populations of SNe Ia. Since stars of higher metallicity (at a given mass) generally form less massive white dwarfs, our results support some theoretical models that high- v Si ii SNe Ia may originate from sub-Chandrasekhar class of explosions. Previous observations also showed some evidence that high- v Si ii SNe Ia could be related to the single degenerate systems. However, we find high- v Si ii SNe Ia do not come from particularly young populations. We conclude metallicity is likely the dominant factor in forming high- v Si ii SNe Ia. This also implies their potential evolution with redshift and impact on the precision of SN Ia cosmology.