Neutrino production in the central dark-matter spikes of active galaxies

TL;DR

The paper examines whether a high-density dark-matter spike around a supermassive black hole in active galaxies can contribute to high-energy neutrino production. It proposes a DM-annihilation–driven channel where electrons from annihilation upscatter ambient photons, enabling $p\gamma$ interactions that yield neutrinos, and develops a spike-density framework with saturation to evaluate the signal in NGC 1068 using sub-GeV DM with $m_{\text{DM}}=250$ MeV and $\braket{\sigma v}=5\times10^{-29}\ \text{cm}^3\text{s}^{-1}$. The study couples diffusion-loss modeling (including $b_{\text{ICS}}$, $b_{\text{syn}}$, $b_{\text{brem}}$, $b_{\text{ion+Col}}$) with TransportCR/Hazma-based photon-field calculations to obtain the neutrino flux, finding that the DM-induced component is far below IceCube measurements for NGC 1068 and requires an unrealistically large cross section, $\braket{\sigma v}_{\text{req}}\sim(1.7{-}1.9)\times10^{-22}\ \text{cm}^3\text{s}^{-1}$, inconsistent with CMB constraints. Nevertheless, the mechanism can contribute to the diffuse neutrino background across AGN populations, motivating future observational tests with Baikal-GVD and KM3NeT to constrain or detect such a component. The framework highlights the interplay between spike physics, DM annihilation channels, ambient photon fields, and high-energy neutrino production in the central engines of galaxies.

Abstract

Recent multi-messenger observations suggest that high-energy neutrinos may be produced close to central black holes in active galaxies. These regions may host dark-matter (DM) spikes, where the concentration of DM particles is very high. Here we explore the contribution of the DM annihilation to the target photons for the neutrino production, proton-photon interactions, estimate the associated neutrino spectrum and figure out possible future tests of this scenario.

Figures (5)

• Figure 1: Dark matter distribution around the SMBH of NGC 1068 for different values of the DM self-annihilation cross section, the shaded area correspond to the area of neutrino production.
• Figure 2: Positron annihilation spectra from the scalar model with Higgs portal couplings and vector model with kinetic mixing couplings. The grey vertical dashed line indicates the location of the monochromatic dark matter annihilation. Colorful lines correspond to $\pi^{+}\pi^{-}$ and $\mu^{+}\mu^{-}$ decay .
• Figure 3: Target photons resulting from the interaction of electrons from dark matter with the ultraviolet component of the spectral energy distribution
• Figure 4: Predictions of the observed spectra of neutrino ($\nu_{\mu}+\bar{\nu}_{\mu}$) from NGC 1068 (the disc-related component). The green line represents proton luminosity normalized by $L_{\textup{Edd}}$, the pink line represents proton luminosity normalized by $100L_{\textup{Edd}}$ and dark blue line shows the best-fit neutrino spectrum, and the corresponding blue band covers all powerlaw neutrino fluxes that are consistent with the data at 95$\%$ C.L. from IceCube data.
• Figure 5: Predictions of the observed spectra of neutrino ($\nu_{\mu}+\bar{\nu}_{\mu}$) from AGN source populations. The pink line represents proton luminosity normalized by $L_{\textup{Edd}}$,the green line represents proton luminosity normalized by $100L_{\textup{Edd}}$ and blue points correspond to measurement of the astrophysical diffuse neutrino flux by IceCube