HAWK-I infrared supernova search in starburst galaxies

Context. The use of SN rates to probe explosion scenarios and to trace the cosmic star formation history received a boost from a number of synoptic surveys. There has been a recent claim of a mismatch by a factor of two between star formation and core collapse SN rates, and different explanations have been proposed for this discrepancy. Aims. We attempted an independent test of the relation between star formation and supernova rates in the extreme environment of starburst galaxies, where both star formation and extincti on are extremely high. Methods. To this aim we conducted an infrared supernova search in a sample of local starburts galaxies. The rational to search in the infrared is to reduce the bias due to extinction, which is one of the putative reasons for the observed discrepancy between star formation and supernova rates. To evaluate the outcome of the search we developed a MonteCarlo simulation tool that is used to predict the number and properties of the expected supernovae based on the search characteristics and the current understanding of starburst galaxies and supernovae. Results. During the search we discovered 6 supernovae (4 with spectroscopic classification) which is in excellent agreement with the prediction of the MonteCarlo simulation tool that is, on average, 5.3± 2.3 events. Conclusions. The number of supernovae detected in starburst galaxies is consistent with that predicted from their high star formatio n rate when we recognize that a major fraction (∼ 60%) of the events remains hidden in the unaccessible, high density nuclear regions because of a combination of reduced search effi ciency and high extinction.