Constraints on core-collapse supernova progenitors from correlations with Hα emission

We present observational constraints on the nature of the different core-collapse supernova (SN) types through an investigation of the association of their explosion sites with recent star formation (SF), as traced by Hα + [NII] line emission. We discuss results on the analysed data of the positions of 168 core-collapse SNe with respect to the Hα emission within their host galaxies.

From our analysis we find that overall the type II progenitor population does not trace the underlying SF. Our results are consistent with a significant fraction of SNII arising from progenitor stars of less than 10M_solar. We find that the SNe of type Ib show a higher degree of association with HII regions than those of type II (without accurately tracing the emission), while the type Ic population accurately traces the Hα emission. This implies that the main core-collapse SN types form a sequence of increasing progenitor mass, from the type II, to Ib and finally Ic. We find that the type IIn subclass display a similar degree of association with the line emission to the overall SNII population, implying that at least the majority of these SNe do not arise from the most massive stars. We also find that the small number of SN `impostors' within our sample do not trace the SF of their host galaxies, a result that would not be expected if these events arise from massive luminous blue variable star progenitors.

Based on observations made with the Isaac Newton Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Institute de Astrofisica de Canarias, and on observations made with the Liverpool Telescope operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council.

E-mail: jxa@astro.livjm.ac.uk