Synoptic sky surveys and the diffuse supernova neutrino background: Removing astrophysical uncertainties and revealing invisible supernovae

Abstract

The cumulative (anti)neutrino production from all core-collapse supernovae within our cosmic horizon gives rise to the diffuse supernova neutrino background (DSNB), which is on the verge of detectability. The observed flux depends on supernova physics, but also on the cosmic history of supernova explosions; currently, the cosmic supernova rate introduces a substantial (±40%) uncertainty, largely through its absolute normalization. However, a new class of wide-field, repeated-scan (synoptic) optical sky surveys is coming online, and will map the sky in the time domain with unprecedented depth, completeness, and dynamic range. We show that these surveys will obtain the cosmic supernova rate by direct counting, in an unbiased way and with high statistics, and thus will allow for precise predictions of the DSNB. Upcoming sky surveys will substantially reduce the uncertainties in the DSNB source history to an anticipated ±5% that is dominated by systematics, so that the observed high-energy flux thus will test supernova neutrino physics. The portion of the universe (z < ∼ 1) accessible to upcoming sky surveys includes the progenitors of a large fraction (≃ 87%) of the expected 10 -26 MeV DSNB event rate. We show that precision determination of the (optically detected) cosmic supernova history will also make the DSNB into a strong probe of an extra flux of neutrinos from optically invisible supernovae, which may be unseen either due to unexpected large dust obscuration in host galaxies, or because some core-collapse events proceed directly to black hole formation and fail to give an optical outburst. 97.60.Bw, 95.85.Ry, 98.70.Vc

The next-generation liquid-scintillator neutrino observatory LENA

“…Comparable neutrino fluxes are expected for ordinary SNe and those that are faint, obscured, or even failed [92,[152][153][154], so the DSNB does not depend much on the outcomes, though it may be larger than assumed here. Measured SN and predicted core collapse rates are in reasonable agreement, and the data will quickly improve [150,155,156]. The local core collapse rate is R SN (z = 0) = (1.25 ± 0.25) × 10 −4 Mpc −3 yr −1 [149].…”

“…The most interesting possibility is prompt black hole formation, as this is expected to have a nonzero rate even in standard scenarios [172,173], and present constraints allow even larger rates [112,150,151,156,174]. Even though the neutrino emission can be cut off, it is expected to be enhanced before that, such that the time-integrated total and average neutrino energies can be larger than usual [92,[152][153][154].…”

“…Other possibilities include emission from the hot, magnetized corona of a proto-neutron star or accretion disk [175] or from fallback [176]. The DSNB will thus be especially valuable for probing outcomes that may not occur for a Milky Way core collapse and the corresponding extreme physical conditions in such collapses [156,177].…”

Failed Supernovae Explain the Compact Remnant Mass Function

“…Little is observationally known about the balance between these scenarios. The diffuse SN neutrino background sets an upper limit on the failed SN rate at roughly 50%-75% of the observed SN rate (Lien et al 2010;Lunardini 2009), and there is some evidence for a mismatch between massive star formation and SN rates, which suggests a significant failed SN rate (Horiuchi et al 2011; but see Botticella et al 2012). However, theoretical studies generally favor low rates of failed SNe (∼10% of ccSN rate) at solar metallicity (e.g., Woosley et al 2002).…”

Neutrinos from failed supernovae at future water and liquid argon detectors

“…This opportunity is especially precious, considering that failed supernovae are virtually invisible to telescopes [71]. The published SuperKamiokande neutrino data already constrain the rate of failed supernovae [16]. A new, preliminary, analysis from the SuperKamiokande collaboration [17,18] considers the neutrino flux from failed supernovae, and limits it to about a factor of two from the most optimistic predictions.…”