演講資訊

摘要：

Context. Type I superluminous supernovae (SLSNe I) are rare, powerful explosions whose mechanism and progenitors remain elusive. Several studies have shown a preference for SLSNe I to occur in low-metallicity, actively star-forming dwarf galaxies. Aims: We investigate whether the host galaxies of SLSNe I show increased evidence for interaction. Galaxy interaction can trigger star formation and provide favourable conditions for these exceptional explosions to take place. Methods: Based on SLSN host galaxy images obtained with the Hubble Space Telescope (HST), we narrowed down a sample of 42 images obtained in the rest-frame ultraviolet over the redshift range between 0 < z < 2. The number of host galaxy companions was measured by counting the number of objects detected within a given projected radius from the host. As a comparison, we used two different Monte Carlo-based methods to estimate the expected average number of companion objects in the same HST images, as well as a sample of 32 dwarf galaxies that have hosted long gamma-ray bursts (GRBs). Results: About 50% of SLSN I host galaxies 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 0.70-0.14+0.19. Our two 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 (p-value < 10-3) 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. The SLSN I hosts have more companions than GRB hosts (0.44-0.13+0.25 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 with SLSN companions being closer, on average, than those of GRBs. Conclusions: 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.

作者：

Ørum et al

期刊：

Astronomy & Astrophysics, Volume 643, id.A47, 11 pp.