The interacting nature of dwarf galaxies hosting superluminous supernovae

• Published in: arXiv.org 2020-09
• Main Authors: Ørum, Simon Vanggaard, Ivens, David Lykke, Strandberg, Patrick, Leloudas, Giorgos, Man, Allison W S, Schulze, Steve
• Format: Article
• Language: English
• Subjects: Dwarf galaxies; Explosions; Gamma ray bursts; Gamma rays; Metallicity; Monte Carlo simulation; Object recognition; Red shift; Star & galaxy formation; Star formation; Statistical significance; Supernovae
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2009.03925

(Abridged) Type I superluminous supernovae (SLSNe I) are rare, powerful explosions whose mechanism and progenitors remain elusive. SLSNe I show a preference for low-metallicity, actively star-forming dwarf galaxies. We investigate whether the hosts of SLSNe I show increased evidence for interaction. We use a sample of 42 SLSN I images obtained with \(\textit{HST}\) and measure the number of companion galaxies by counting the objects detected within a given radius from the host. As a comparison, we used two Monte Carlo-based methods to estimate the expected average number of companion objects in the same images, as well as a sample of 32 galaxies that have hosted long gamma-ray bursts (GRBs). About 50% of SLSN I hosts have at least one major companion (within a flux ratio of 1:4) within 5 kpc. The average number of major companions per SLSN I host galaxy is \(0.70^{+0.19}_{-0.14}\). Our Monte Carlo comparison methods yield a lower number of companions for random objects of similar brightness in the same image or for the SLSN host after randomly redistributing the sources in the same image. The Anderson-Darling test shows that this difference is statistically significant independent of the redshift range. The same is true for the projected distance distribution of the companions. The SLSN I hosts are, thus, found in areas of their images, where the object number density is greater than average. SLSN I hosts have more companions than GRB hosts (\(0.44^{+0.25}_{-0.13}\) companions per host distributed over 25% of the hosts) but the difference is not statistically significant. The difference between their separations is, however, marginally significant. The dwarf galaxies hosting SLSNe I are often part of interacting systems. This suggests that SLSNe I progenitors are formed after a recent burst of star formation. Low metallicity alone cannot explain this tendency.