Core-collapse supernovae in low-metallicity environments and future all-sky transient surveys

¹ Astrophysics Research Centre, School of Maths and Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland, UK e-mail: dyoung06@qub.ac.uk
² Tuorla Observatory, University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland
³ Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK
⁴ Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead, CH41 1LD, UK
⁵ Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822

Received: 12 September 2007
Accepted: 17 July 2008

Abstract

Aims. Massive stars in low-metallicity environments may produce exotic explosions such as long-duration gamma-ray bursts and pair-instability supernovae when they die as core-collapse supernovae (CCSNe). Such events are predicted to be relatively common in the early Universe during the first episodes of star-formation. To understand these distant explosions it is vital to study nearby CCSNe arising in low-metallicity environments to determine if the explosions have different characteristics to those studied locally in high-metallicity galaxies. Many of the nearby supernova searches concentrate their efforts on high star-formation rate galaxies, hence biasing the discoveries to metal rich regimes. Here we determine the feasibility of searching for these CCSNe in metal-poor dwarf galaxies using various survey strategies.

Methods. We determine oxygen abundances and star-formation rates for all spectroscopically typed star-forming galaxies in the Sloan Digital Sky Survey, Data Release 5, within . We then estimate the CCSN rates for sub-samples of galaxies with differing upper-metallicity limits. Using Monte-Carlo simulations we then predict the fraction of these CCSNe that we can expect to detect using different survey strategies. We test survey capabilities using a single 2 m telescope, a network of 2 m telescopes, and the upcoming all-sky surveys of the Pan-STARRS and LSST systems.

Results. Using a single 2 m telescope (with a standard CCD camera) search we predict a detection rate of ~1.3 CCSNe yr^-1 in galaxies with metallicities below 12 + log(O/H) < 8.2 which are within a volume that will allow detailed follow-up with 4 m and 8 m telescopes (). With a network of seven 2 m telescopes we estimate ~9.3 CCSNe yr^-1 could be found, although this would require more than 1000 h of telescope time allocated to the network. Within the same radial distance, a volume-limited search in the future Pan-STARRS PS1 all-sky survey should uncover 12.5 CCSNe yr^-1 in low-metallicity galaxies. Over a period of a few years this would allow a detailed comparison of their properties. We then extend our calculations to determine the total numbers of CCSNe that can potentially be found in magnitude-limited surveys with PS1 (24 000 yr^-1, within z 0.6), PS4 (69 000 yr^-1, within z 0.8) and LSST (160 000 yr^-1, within z 0.9) surveys.