Detection of Neutrinos from Supernovae in Nearby Galaxies

While existing detectors would see a burst of many neutrinos from a Milky Way supernova, the supernova rate is only a few per century. As an alternative, we propose the detection of $\sim 1$ neutrino per supernova from galaxies within 10 Mpc, in which there were at least 9 core-collapse supernovae since 2002. With a future 1 Mton scale detector, this could be a faster method for measuring the supernova neutrino spectrum, which is essential for calibrating numerical models and predicting the redshifted diffuse spectrum from distant supernovae. It would also allow a $\gtrsim {10}^4$ times more precise trigger time than optical data alone for high-energy neutrinos and gravitational waves.

Figure 1

Cumulative calculated core-collapse supernova rate versus distance. The dashed line is the continuum limit using the GALEX $z=0$ star formation rate [6]. For our particular local volume, and its fortuitous enhancement, we use a galaxy catalog [11]; the stepped line is based on star formation rates for individual galaxies, and the band is the uncertainty. Some major galaxies are indicated, and those in boxes have especially high optical supernova rates (see Table ).

Figure 2

Probability of detecting at least one (dotted and dashed curves) or at least two (solid curves) supernova neutrinos versus distance. Background considerations restrict the useful energy intervals, labeled here, and explained in the text. The upper set of curves is for a 1 Mton detector, and the lower set for the 22.5 kton Super-Kamiokande detector; for another detector size, scale the distance to compensate. The shaded band indicates the calculated cumulative supernova rate. The probabilities for single background events are $\simeq 0.4$ (1 Mton) and $\simeq 0.02$ (Super-Kamiokande detector), independent of distance.

Figure 3

Spectrum of detected supernova neutrinos ($D=4\mathrm{Mpc}$) in a 1 Mton detector. The backgrounds shown are relevant for a neutrino-optical coincidence, and are reduced for a neutrino-neutrino coincidence. The shaded bands indicate the energy intervals for signal selection (see Fig. 2); at low energies, other backgrounds (not shown) are very large.