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) ge...

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高速Ia型超新星具有独特的宿主环境

Ia型超新星（SNe Ia）的射出速度是一种区分祖先情景和爆炸机制的强大工具。在这里，我们重新研究光球Si iiλ6355速度（v Si ii）与主星系性质之间的关系，该速度约为280 SNe Ia。根据SN光谱的光球速度，采用更严格的SN光谱相位标准对SNe Ia进行分类。我们发现一个明显的趋势是，在较大的环境中，具有更快的Si iiλ6355（高v Si ii的SNe Ia）的SNe Ia倾向于爆炸，而在较低质量的环境和大规模的环境中都可以找到速度较慢的对应物。直接测量主体气相金属度进一步支持了这种趋势。我们建议这种关系可能是由至少两个SNe Ia人群引起的。由于较高金属度的恒星（在给定质量下）会...