Supernovae Ia ejecta velocities and host galaxy environments: the role of survey-selection effects
Abstract
The origin of the near-maximum-light Si II λ6355 velocity diversity among supernovae Ia (SNe Ia) remains uncertain. Previous studies have suggested that high-velocity (HV) and normal-velocity (NV) SNe Ia occupy systematically different host galaxy environments, implying differences in their progenitor populations. We re-examine this hypothesis using a sample of 354 nearby (z≤0.04) spectroscopically normal SNe Ia, comprising 239 NV and 115 HV events, identified in targeted and untargeted surveys. For each SN, we determine the host galaxy morphology, galactocentric distance, and physical size, and obtain homogeneous stellar mass estimates while assessing the influence of survey-selection effects. The Si II velocity distribution is well described by two Gaussian components, confirming the NV and HV populations. We find no statistically significant differences between the galactocentric distance, host galaxy size, or stellar mass distributions of the two velocity subgroups. The environmental trends reported in previous studies are recovered only with marginal statistical significance in the targeted subsample, whereas they disappear almost entirely in the untargeted subsample, consistent with survey-selection effects playing a major role in the previously inferred environmental differences between the NV and HV events. Our results weaken the interpretation that the observed Si II velocity diversity is primarily driven by systematic differences in the global host properties examined here. Instead, they favour a scenario in which intrinsic explosion asymmetries and viewing-angle effects account for a substantial fraction of the observed velocity diversity, without excluding a possible contribution from local environmental conditions or progenitor properties.
Related
- The UV-to-FIR environments of nearby Type Ia supernovae with the DustPedia Galaxy Catalogue -- I. Local versus global host properties
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- Supernovae Unite: Host-Galaxy Mass Measurements of Type Ia Supernovae and Their Impact on Cosmology
- Sound-Horizon-Agnostic Forecast for Constraints on H0 and Σmν from BAO, CMB Lensing, Supernovae and LSST-like Galaxy Lensing
BibTeX
@misc{barkhudaryan2026supernovae,
title = {{Supernovae Ia ejecta velocities and host galaxy environments: the role of survey-selection effects}},
author = {L. V. Barkhudaryan and A. A. Hakobyan and M. H. Gevorgyan and D. Kunth and G. A. Mamon and U. Burgaz and V. Adibekyan and Zh. R. Martirosyan and A. G. Karapetyan},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2608.21603},
eprint = {2608.21603},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.21603},
}
RIS
TY - UNPB
TI - Supernovae Ia ejecta velocities and host galaxy environments: the role of survey-selection effects
AU - L. V. Barkhudaryan
AU - A. A. Hakobyan
AU - M. H. Gevorgyan
AU - D. Kunth
AU - G. A. Mamon
AU - U. Burgaz
AU - V. Adibekyan
AU - Zh. R. Martirosyan
AU - A. G. Karapetyan
PY - 2026
DA - 2026/10/02
PB - arXiv
DO - 10.48550/arxiv.2608.21603
UR - https://arxiv.org/abs/2608.21603
AB - The origin of the near-maximum-light Si II λ6355 velocity diversity among supernovae Ia (SNe Ia) remains uncertain. Previous studies have suggested that high-velocity (HV) and normal-velocity (NV) SNe Ia occupy systematically different host galaxy environments, implying differences in their progenitor populations. We re-examine this hypothesis using a sample of 354 nearby (z≤0.04) spectroscopically normal SNe Ia, comprising 239 NV and 115 HV events, identified in targeted and untargeted surveys. For each SN, we determine the host galaxy morphology, galactocentric distance, and physical size, and obtain homogeneous stellar mass estimates while assessing the influence of survey-selection effects. The Si II velocity distribution is well described by two Gaussian components, confirming the NV and HV populations. We find no statistically significant differences between the galactocentric distance, host galaxy size, or stellar mass distributions of the two velocity subgroups. The environmental trends reported in previous studies are recovered only with marginal statistical significance in the targeted subsample, whereas they disappear almost entirely in the untargeted subsample, consistent with survey-selection effects playing a major role in the previously inferred environmental differences between the NV and HV events. Our results weaken the interpretation that the observed Si II velocity diversity is primarily driven by systematic differences in the global host properties examined here. Instead, they favour a scenario in which intrinsic explosion asymmetries and viewing-angle effects account for a substantial fraction of the observed velocity diversity, without excluding a possible contribution from local environmental conditions or progenitor properties.
ER -