Metallicity effects on cosmic Type Ib/c supernovae and gamma-ray burst rates

Abstract

Type Ib/c supernovae (SNeIb/c) are likely to be associated with long gamma-ray bursts (GRBs), and therefore it is important to compare the SN rate in galaxies with the GRB rate. To do this we computed SNIb/c rates in galaxies of different morphological types (ellipticals, spirals and irregulars) by assuming different histories of star formation and different SNIb/c progenitors. We included some recent suggestions about the dependence of the minimum mass of single Wolf-Rayet (WR) stars on the stellar metallicity and therefore on galactic chemical evolution. We adopted several cosmic star formation rates (i.e. relative to a comoving unitary volume of the Universe) as a function of cosmic time, either observationally or theoretically derived, including the one computed with our galaxy models. We then computed the cosmic SNIb/c rates. Our results show that the predicted SNIb/c rates in spirals and irregulars can reproduce well the present observed rates if both single WR stars and massive binary systems are taken into account as SNIb/c progenitors. The metallicity effects on the minimum mass for single WR stars are evident mainly in the early phases of galaxy evolution and do not influence substantially the predicted local Type Ib/c rates. We reached the following conclusions. (i) The ratio cosmic GRB rate /cosmic Type Ib/c rate varies in the range 10-2-10-4 in the whole redshift range, thus suggesting that only a small fraction of all SNeIb/c gives rise to GRBs. (ii) The metallicity dependence of SNIb/c progenitors produces lower cosmic SNIb/c rates at early times, for any chosen cosmic star formation rate. (iii) Different theoretical cosmic star formation rates, computed under different scenarios of galaxy formation, produce SNIb/c cosmic rates that differ mainly at very high redshifts. However, it is difficult to draw firm conclusions on the high-redshift trend because of the large uncertainties in the data. (iv) GRBs can be important tracers of star formation at high redshifts if their luminosity function does not vary with redshift, and they can help in discriminating among galaxy formation models. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.