Core-Collapse Supernovae from the Palomar Transient Factory: Indications for a Different Population in Dwarf Galaxies
Abstract
We use the first compilation of 72 core-collapse supernovae (SNe) from the Palomar Transient Factory (PTF) to study their observed subtype distribution in dwarf galaxies compared to giant galaxies. Our sample is the largest single-survey, untargeted, spectroscopically classified, homogeneous collection of core-collapse events ever assembled, spanning a wide host-galaxy luminosity range (down to M_r ~ -14 mag) and including a substantial fraction (>20%) of dwarf (M_r >= -18 mag) hosts. We find more core-collapse SNe in dwarf galaxies than expected and several interesting trends emerge. We use detailed subclassifications of stripped-envelope core-collapse SNe and find that all Type I core-collapse events occurring in dwarf galaxies are either SNe Ib or broad-lined SNe Ic (SNe Ic-BL), while "normal" SNe Ic dominate in giant galaxies. We also see a significant excess of SNe IIb in dwarf hosts. We hypothesize that in lower metallicity hosts, metallicity-driven mass loss is reduced, allowing massive stars that would have appeared as "normal" SNe Ic in metal-rich galaxies to retain some He and H, exploding as Ib/IIb events. At the same time, another mechanism allows some stars to undergo extensive stripping and explode as SNe Ic-BL (and presumably also as long-duration gamma-ray bursts). Our results are still limited by small-number statistics, and our measurements of the observed N(Ib/c)/N(II) number ratio in dwarf and giant hosts (0.25_{-0.15}^{+0.3} and 0.23_{-0.08}^{+0.11}, respectively; 1 sigma uncertainties) are consistent with previous studies and theoretical predictions. As additional PTF data accumulate, more robust statistical analyses will be possible, allowing the evolution of massive stars to be probed via the dwarf-galaxy SN population.
Keywords
Cite
@article{arxiv.1004.0615,
title = {Core-Collapse Supernovae from the Palomar Transient Factory: Indications for a Different Population in Dwarf Galaxies},
author = {Iair Arcavi and Avishay Gal-Yam and Mansi M. Kasliwal and Robert M. Quimby and Eran O. Ofek and Shrinivas R. Kulkarni and Peter E. Nugent and S. Bradley Cenko and Joshua S. Bloom and Mark Sullivan and D. Andrew Howell and Dovi Poznanski and Alexei V. Filippenko and Nicholas Law and Isobel Hook and Jakob Jonsson and Sarah Blake and Jeff Cooke and Richard Dekany and Gustavo Rahmer and David Hale and Roger Smith and Jeff Zolkower and Viswa Velur and Richard Walters and John Henning and Kahnh Bui and Dan McKenna and Janet Jacobsen},
journal= {arXiv preprint arXiv:1004.0615},
year = {2015}
}
Comments
22 pages, 4 figures, ApJ accepted