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We analyse spectroscopic measurements of 122 type Ia supernovae (SNe Ia) withz<0.09 discovered by the Palomar Transient Factory, focusing on the propertiesof the Si II 6355 and Ca II `near-infrared triplet' absorptions. We examine thevelocities of the photospheric Si II 6355, and the velocities and strengths ofthe photospheric and high-velocity Ca II, in the context of the stellar mass(Mstellar) and star-formation rate (SFR) of the SN host galaxies, as well asthe position of the SN within its host. We find that SNe Ia with faster Si II6355 tend to explode in more massive galaxies, with the highest velocity eventsonly occuring in galaxies with Mstellar > 3*10^9 solar mass. We also find someevidence that these highest velocity SNe Ia explode in the inner regions oftheir host galaxies, similar to the study of Wang et al. (2013), although thetrend is not as significant in our data. We show that these trends areconsistent with some SN Ia spectral models, if the host galaxy stellar mass isinterpreted as a proxy for host galaxy metallicity. We study the strength ofthe high-velocity component of the Ca II near-IR absorption, and show that SNeIa with stronger high-velocity components relative to photospheric componentsare hosted by galaxies with low stellar mass, blue colour, and a high sSFR.Such SNe are therefore likely to arise from the youngest progenitor systems.This argues against a pure orientation effect being responsible forhigh-velocity features in SN Ia spectra and, when combined with other studies,is consistent with a scenario where high-velocity features are related to aninteraction between the SN ejecta and circumstellar medium (CSM) local to theSN.

Type Ia Supernova Spectral Features in the Context of Their Host Galaxy Properties