Neutrino Probes of Galactic and Extragalactic Supernovae

Neutrinos are a messenger of extreme condition inside a supernova core and a new-born neutron star. Since current ground-based detectors have potential to detect ~10,000 neutrinos from supernova at the galactic center, they could tell us lots of important physics. It includes: explosion mechanism, shock wave propagation, core temperature, and gravitational binding energy, as well as neutrino properties as elementary particle. In addition to the galactic supernova neutrino burst, one can still learn about them with diffuse supernova neutrino background, which is also soon to be detected. We review current situation from both points of view, and discuss prospects for future neutrino astrophysics

Power spectrum tomography of dark matter annihilation with local galaxy distribution

Cross-correlating the gamma-ray background with local galaxy catalogs potentially gives stringent constraints on dark matter annihilation. We provide updated theoretical estimates of sensitivities to the annihilation cross section from gamma-ray data with Fermi telescope and 2MASS galaxy catalogs, by elaborating the galaxy power spectrum and astrophysical backgrounds, and adopting the Markov-Chain Monte Carlo simulations. In particular, we show that taking tomographic approach by dividing the galaxy catalogs into more than one redshift slice will improve the sensitivity by a factor of a few to several. If dark matter halos contain lots of bright substructures, yielding a large annihilation boost (e.g., a factor of $\sim$100 for galaxy-size halos), then one may be able to probe the canonical annihilation cross section for thermal production mechanism up to masses of $\sim$700 GeV. Even with modest substructure boost (e.g., a factor of $\sim$10 for galaxy-size halos), on the other hand, the sensitivities could still reach a factor of three larger than the canonical cross section for dark matter masses of tens to a few hundreds of GeV.Comment: 28 pages, 14 figures. Accepted by JCA

Constraints on the annihilation cross section of dark matter particles from anisotropies in the diffuse gamma-ray background measured with Fermi-LAT

Annihilation of dark matter particles in cosmological halos (including a halo of the Milky Way) contributes to the diffuse gamma-ray background (DGRB). As this contribution will appear anisotropic in the sky, one can use the angular power spectrum of anisotropies in DGRB to constrain properties of dark matter particles. By comparing the updated analytic model of the angular power spectrum of DGRB from dark matter annihilation with the power spectrum recently measured from the 22-month data of Fermi Large Area Telescope (LAT), we place upper limits on the annihilation cross section of dark matter particles as a function of dark matter masses. We find that the current data exclude <\sigma v> >~ 10^{-25} cm^3 s^{-1} for annihilation into b\bar{b} at the dark matter mass of 10 GeV, which is a factor of three times larger than the canonical cross section. The limits are weaker for larger dark matter masses. The limits can be improved further with more Fermi-LAT data as well as by using the power spectrum at lower multipoles (l <~ 150), which are currently not used due to a potential Galactic foreground contamination.Comment: 13 pages, 18 figures, comments welcom

Constraints on decaying dark matter from the extragalactic gamma-ray background

If dark matter is unstable and the mass is within GeV-TeV regime, its decays produce high-energy photons that give contribution to the extragalactic gamma-ray background (EGRB). We constrain dark matter decay by analyzing the 50-month EGRB data measured with Fermi satellite, for different decay channels motivated with several supersymmetric scenarios featuring R-parity violation. We adopt the latest astrophysical models for various source classes such as active galactic nuclei and star-forming galaxies, and take associated uncertainties properly into account. The lower limits for the lifetime are very stringent for a wide range of dark matter mass, excluding the lifetime shorter than 10^28 s for mass between a few hundred GeV and ~1TeV, e.g., for b\bar{b} decay channel. Furthermore, most dark matter models that explain the anomalous positron excess are also excluded. These constraints are robust, being little dependent on astrophysical uncertainties, unlike other probes such as Galactic positrons or anti-protons.Comment: 20 pages, 6 figures, published versio

Diffuse emission of high-energy neutrinos from gamma-ray burst fireballs

Gamma-ray bursts (GRBs) have been suggested as possible sources of the high-energy neutrino flux recently detected by the IceCube telescope. We revisit the fireball emission model and elaborate an analytical prescription to estimate the high-energy neutrino prompt emission from pion and kaon decays, assuming that the leading mechanism for the neutrino production is lepto-hadronic. To this purpose, we include hadronic, radiative and adiabatic cooling effects and discuss their relevance for long- (including high- and low-luminosity) and short-duration GRBs. The expected diffuse neutrino background is derived, by requiring that the GRB high-energy neutrino counterparts follow up-to-date gamma-ray luminosity functions and redshift evolutions of the long and short GRBs. Although dedicated stacking searches have been unsuccessful up to now, we find that GRBs could contribute up to a few % to the observed IceCube high-energy neutrino flux for sub-PeV energies, assuming that the latter has a diffuse origin. Gamma-ray bursts, especially low-luminosity ones, could however be the main sources of the IceCube high-energy neutrino flux in the PeV range. While high-luminosity and low-luminosity GRBs have comparable intensities, the contribution from the short-duration component is significantly smaller. Our findings confirm the most-recent IceCube results on the GRB searches and suggest that larger exposure is mandatory to detect high-energy neutrinos from high-luminosity GRBs in the near future.Comment: 28 pages, including 8 figures. Matches version published in JCA

Effects of a neutrino-dark energy coupling on oscillations of high-energy neutrinos

If dark energy (DE) is a dynamical field rather than a cosmological constant, an interaction between DE and the neutrino sector could exist, modifying the neutrino oscillation phenomenology and causing CP and apparent Lorentz violating effects. The terms in the Hamiltonian for flavor propagation induced by the DE-neutrino coupling do not depend on the neutrino energy, while the ordinary components decrease as $\Delta m^2/E_{\nu}$. Therefore, the DE-induced effects are absent at lower neutrino energies, but become significant at higher energies, allowing to be searched for by neutrino observatories. We explore the impact of the DE-neutrino coupling on the oscillation probability and the flavor transition in the three-flavor framework, and investigate the CP-violating and apparent Lorentz violating effects. We find that DE-induced effects become observable for $E_{\nu}m_{\text{eff}} \sim 10^{-20}~ \text{GeV}^2$, where $m_{\rm eff}$ is the effective mass parameter in the DE-induced oscillation probability, and CP is violated over a wide energy range. We also show that current and future experiments have the sensitivity to detect anomalous effects induced by a DE-neutrino coupling and probe the new mixing parameters. The DE-induced effects on neutrino oscillation can be distinguished from other new physics possibilities with similar effects, through the detection of the directional dependence of the interaction, which is specific to this interaction with DE. However, current experiments will not yet be able to measure the small changes of $\sim 0.03\%$ in the flavor composition due to this directional effect.Comment: 11 pages, 15 figure

High-energy neutrinos from reverse shocks in choked and successful relativistic jets

Highly relativistic jets are a key element of current gamma-ray burst models, where the jet kinetic energy is converted to radiation energy at optically thin shocks. High-energy neutrinos are also expected, from interactions of protons accelerated in the same shocks. Here we revisit the early evolution of a relativistic jet, while the jet is still inside the star, and investigate its neutrino emission. In particular we study propagation of mildly relativistic and ultrarelativistic jets through a type Ib progenitor, and follow reverse shocks as the jets cross the star. We show that protons can be accelerated to 10^4-10^5 GeV at reverse shocks, and efficiently produce mesons. The mesons experience significant cooling, suppressing subsequent neutrino emission. We show, however, that the neutrino yield from the reverse shock is still reasonably large, especially for low-luminosity and long-duration jets, where meson cooling is less severe. We discuss implications of our results in the context of neutrinos from choked jets, which are completely shock heated and do not break out of the star. From a choked jet with isotropic equivalent energy of 10^{53} erg at 10 Mpc, we expect ~20 neutrino events at IceCube.Comment: 11 pages, 7 figures, 2 tables; accepted for publication in Physical Review

Constraints on diffuse gamma-ray emission from structure formation processes in the Coma cluster

We analyze 5-year (63 months) data of the Large Area Telescope on board Fermi satellite from the Coma galaxy cluster in the energy range between 100 MeV and 100 GeV. The likelihood analyses are performed with several templates motivated by models predicting gamma-ray emission due to structure formation processes. We find no excess emission and derive the most stringent constraints to date on the Coma cluster above 100 MeV, and on the tested scenarios in general. The upper limits on the integral flux range from 10^-10 to 10^-9 cm^-2s^-1, and are stringent enough to challenge different scenarios. We find that the acceleration efficiency of cosmic ray protons and electrons at shocks must be below approximately 15% and 1%, respectively. Additionally, we argue that the proton acceleration efficiency should be lower than 5% in order to be consistent with radio data. This, however, relays on magnetic field estimates in the cluster. In particular, this implies that the contribution to the diffuse extragalactic gamma-ray background due to gamma-rays from structure formation processes in clusters of galaxies is negligible, below 1%. Finally, we discuss future detectability prospects for Astro-H, Fermi after 10-yr of operation, and the Cherenkov Telescope Array.Comment: 10 pages, 4 figures. Changed to match published versio

Angular power spectrum analysis on current and future high-energy neutrino data

Astrophysical neutrino events have been measured in the last couple of years, which show an isotropic distribution, and the current discussion is their astrophysical origin. We use both isotropic and anisotropic components of the diffuse neutrino data to constrain the contribution of a broad number of extra-galactic source populations to the observed neutrino sky. We simulate up-going muon neutrino events by applying statistical distributions for the flux of extragalactic sources, and by Monte Carlo method we exploit the simulation for current and future IceCube, IceCube-Gen2 and KM3NeT exposures. We aim at constraining source populations by studying their angular patterns, for which we assess the angular power spectrum. We leave the characteristic number of sources ($N_{\star}$) as a free parameter, which is roughly the number of neutrino sources over which the measured intensity is divided. With existing two-year IceCube data, we can already constrain very rare, bright sources with $N_{\star}\lesssim$100. This can be improved to $N_{\star}\lesssim 10^4$-$10^5$ with IceCube-Gen2 and KM3NeT with ten-year exposure, constraining the contribution of BL Lacs ($N_{\star}=6\times10^{2}$). On the other hand, we can constrain weak sources with large number densities, like starburst galaxies ($N_{\star} = 10^{7}$), if we measure an anisotropic neutrino sky with future observations.Comment: 19 pages, 19 figures. Accepted by JCA