The Supernova Progenitor Mass Distributions of M31 and M33: Further Evidence for an Upper Mass Limit

TL;DR

This study analyzes supernova remnant progenitor masses in M31 and M33, revealing a potential upper mass limit for supernova progenitors around 35-45 solar masses, suggesting a cutoff in massive star explosions.

Contribution

It provides the largest combined sample of supernova progenitor masses in M31 and M33 and identifies a possible upper mass limit for supernova progenitors.

Findings

Progenitor mass distributions are steeper than Salpeter IMF.

Estimated maximum progenitor mass is around 35-45 solar masses.

There is a deficit of very massive stars among observed supernova remnants.

Abstract

Using Hubble Space Telescope (HST) photometry to measure star formation histories, we age-date the stellar populations surrounding supernova remnants (SNRs) in M31 and M33. We then apply stellar evolution models to the ages to infer the corresponding masses for their supernova progenitor stars. We analyze 33 M33 SNR progenitors and 29 M31 SNR progenitors in this work. We then combine these measurements with 53 previously published M31 SNR progenitor measurements to bring our total number of progenitor mass estimates to 115. To quantify the mass distributions, we fit power laws of the form $dN/dM \propto M^{-\alpha}$. Our new, larger sample of M31 progenitors follows a distribution with $\alpha = 4.4\pm 0.4$, and the M33 sample follows a distribution with $\alpha = 3.8^{+0.4}_{-0.5}$. Thus both samples are consistent within the uncertainties, and the full sample across both galaxies gives $\alpha = 4.2\pm 0.3$. Both the individual and full distributions display a paucity of massive stars when compared to a Salpeter initial mass function (IMF), which we would expect to observe if all massive stars exploded as SN that leave behind observable SNR. If we instead fix $\alpha = 2.35$ and treat the maximum mass as a free parameter, we find $M_{max} \sim 35-45M_{sun}$, indicative of a potential maximum cutoff mass for SN production. Our results suggest that either SNR surveys are biased against finding objects in the youngest (<10 Myr old) regions, or the highest mass stars do not produce SNe.