arXiv subjects

D. F. G. Fiorillo

Publications and source records attributed to D. F. G. Fiorillo.

3 recordsLinked to original sources

arXiv2026

Diffuse neutrino flux from relativistic reconnection in AGN coronae

IceCube observations point to Active Galactic Nuclei (AGN) as promising contributors to the observed astrophysical neutrino flux. Close to the central black hole, protons can be accelerated through magnetic reconnection to very high energies and subsequently interact with abundant X-ray photons in the source, leading to neutrino production. We investigate whether the diffuse neutrino flux observed by IceCube can originate, via proton acceleration, in reconnection-powered coronae of non-jetted AGN. We create a library of neutrino spectral templates, over a large grid of values for the three key model parameters: the proton plasma magnetization of the corona $σ_{\rm p}$, the X-ray coronal luminosity, and the black hole mass. Synchrotron cooling of pions and muons plays a significant role due to the large coronal magnetic fields. We couple the single-source model with a mock AGN catalog, consistent with the observed X-ray and mid-infrared AGN samples at redshifts $z=0-4$, to infer the diffuse neutrino flux. Coronal emission satisfactorily explains the most recent IceCube measurements of the diffuse neutrino flux up to energies of $\sim 1$~PeV, provided that $\sim$10\% of the AGN coronae have $σ_{\rm p} \sim 10^5$, while the rest are distributed over a range of lower magnetizations. Coronal emission is suppressed at higher energies by pion and muon cooling, so that another population is required, with jetted AGN being strong candidates.

astro-ph.HE↗

arXiv2026

Neutrino and pair creation in reconnection-powered coronae of accreting black holes

A ubiquitous feature of accreting black hole systems is their hard X-ray emission which is thought to be produced through Comptonization of soft photons by electrons and positrons in the vicinity of the black hole, in a region with optical depth of order unity. The origin and composition of this Comptonizing region, known as the corona, is a matter open for debate. In this paper we investigate the role of relativistic protons accelerated in black-hole magnetospheric current sheets for the pair enrichment and neutrino emission of AGN coronae. Our model has two free parameters, namely the proton plasma magnetization $σ_{\rm p}$, which controls the peak energy of the neutrino spectrum, and the Eddington ratio $λ_{\rm X, Edd}$ (defined as the ratio between X-ray luminosity $L_{\rm X}$ and Eddington luminosity $L_{\rm Edd}$), which controls the amount of energy transferred to secondary particles. For sources with $λ_{\rm X, Edd} \gtrsim λ_{\rm Edd, crit}$ (where $λ_{\rm Edd, crit} \sim 10^{-1}$ for $σ_{\rm p}=10^5$ or $\sim 10^{-2}$ for $σ_{\rm p}=10^7$), proton-photon interactions and $ γγ$ annihilation produce enough secondary pairs to achieve Thomson optical depths $τ_{\rm T} \sim 0.1-10$. In the opposite case of $λ_{\rm X, Edd} \lesssim λ_{\rm Edd, crit}$, the coronal pairs cannot originate only from hadronic interactions. Additionally, we find that the neutrino luminosity scales as $L^2_{\rm X}/L_{\rm Edd}$ for $λ_{\rm X, Edd} \lesssim λ_{\rm Edd, crit}$, while it is proportional to $L_{\rm X}$ for higher $λ_{\rm X, Edd}$ values. We apply our model to four Seyfert galaxies, including NGC 1068, and discuss our results in light of recent IceCube observations.

astro-ph.HE↗

arXiv2022

Observable Signatures of Cosmic Rays Transport in Starburst Galaxies on Gamma-ray and Neutrino Observations

The gamma-ray emission from Starburst and Starforming Galaxies (SBGs and SFGs) strongly suggest a correlation between star-forming activity and gamma-ray luminosity. However, the very nature of cosmic-ray (CR) transport and the degree of their confinement within SBG cores are still open questions. We aim at probing the imprints left by CR transport on gamma-ray and neutrino observations of point-like SFGs and SBGs, looking into quantitative ways to discriminate among different transport models. Moreover, following the reported scenarios, we quantitatively assess the SBGs and SFGs contribution to the Extra-galactic Gamma-Ray Background (EGB data) and the IceCube diffuse observations (HESE data). We analyse the 10-year Fermi-LAT spectral energy distributions of 13 nearby galaxies with two different CR transport models, taking into account the corresponding IR and UV observations. We generate mock gamma-ray data to simulate the CTA performance in detecting these sources. In the way, we propose a test to discriminate between the two CR models, quantifying the statistical confidence at which one model can be preferred over the other. We point out that current data already give a slight preference to CR models which are dominated by advection in their nucleus. Moreover, we show that CTA will allow us to firmly disfavour models dominated by diffusion over self-induced turbulence, compared to advection-dominated models, with Bayes factors which can be as large as $10^7$ for some of the SBGs. Finally, we estimate the diffuse gamma-ray and neutrino fluxes of SFGs and SBGs, showing that they can explain $25\%$ of the diffuse HESE data, while remaining consistent with gamma-ray limits on non-blazar sources.

astro-ph.HE↗