arXiv subjects

Miguel Á. Sánchez-Conde

Publications and source records attributed to Miguel Á. Sánchez-Conde.

5 recordsLinked to original sources

arXiv2026

Sgr A* as a Galactic PeVatron: Multimessenger Signatures of the Magnetic Penrose Process

The magnetic Penrose process (MPP) is one of the most efficient mechanisms for extracting rotational energy from a magnetized Kerr black hole (BH), enabling charged particles to reach very-high energies. We investigate this process in Sagittarius A* (Sgr A*), the supermassive BH at the Galactic center (GC), focusing on its ultra-high-efficiency regime, in which neutrons undergo beta decay inside the BH ergosphere. As a key novelty, we compute the neutron production spectrum in the accretion flow directly from the nuclear reaction kinematics and follow neutron trajectories in the Kerr spacetime to determine the population that reaches the ergosphere and undergoes the MPP. From this population, we derive the spectrum of accelerated protons and show that Sgr A* can accelerate them up to PeV energies, strengthening its interpretation as a candidate Galactic PeVatron. We further compute the gamma-ray and neutrino emission produced through hadronic interactions of the escaping protons in the Central Molecular Zone. The predicted gamma-ray fluxes exhibit distinctive spectral features that could provide an observational signature of the MPP and may constitute a non-negligible contribution to the very-high-energy emission detected by H.E.S.S. and HAWC. The associated neutrino fluxes remain below the diffuse Galactic component inferred by IceCube, but may still contribute to the high-energy emission from the GC. Remarkably, the predicted signals lie within the projected sensitivity of SWGO for all scenarios considered here and, for some models, only a factor of a few below the nominal CTAO sensitivity, while KM3NeT/ARCA and IceCube-Gen2 will provide complementary tests. Our results establish the MPP as an observable mechanism for extracting BH rotational energy, providing a direct connection between horizon-scale physics and multimessenger observations that can be extended to other magnetized BHs.

astro-ph.HE↗

arXiv2026

Cascades from ultra-high-energy neutrinos

Neutrinos produced at the highest energies can interact with cosmic neutrino and radiation backgrounds during their propagation to Earth. The many available $νν$, $ν\barν$, and $νγ$ channels can lead to their absorption or energy redistribution, whilst the leptonic and hadronic final states may feed secondary fluxes of neutrinos, protons, and electromagnetic particles through the decay or hadronisation of the heavy leptons, bosons, and quarks produced. We present a framework to characterise these propagation effects in detail, \texttt{$ν$propa}, an extension of the CRPropa Monte Carlo code that interfaces with event generators and to dedicated computations of the relevant cross sections. It also treats flavour oscillations in vacuum. Using this code, we investigate sources at high redshifts ($z = 10$), and find a strong absorption of the prompt flux beyond~$\sim 10^{21} \; \text{eV}$, although the copious secondary neutrinos partially compensate this depletion, also contributing to the spectrum at lower energies. The framework is designed to study scenarios of cosmological neutrino production beyond~EeV energies such as superheavy dark matter, cosmic strings, and primordial black holes, and to yield reliable predictions for the forthcoming neutrino observatories.

astro-ph.HE↗

arXiv2026

Sensitivity of the Cherenkov Telescope Array Observatory to Gamma-Ray Signals in Dwarf Irregular Galaxies

Dwarf irregular galaxies (dIrrs) are rotationally supported galaxies with a low star formation rate. Thus, their gamma-ray astrophysical emission is expected to be low, making them interesting targets for WIMP dark matter (DM) indirect searches. In this work, we build upon previous work on these objects in this DM context, and identify the best four dIrrs to be observed by the forthcoming Cherenkov Telescope Array Observatory (CTAO). Since dIrrs have not been detected in gamma rays yet, we first explore the prospects for detecting their astrophysical emission with the CTAO. Secondly, we compute the CTAO sensitivity prospects to a DM annihilating signal from these objects, accounting for the presence of DM substructures in them. We do so for both cuspy and cored DM density profiles, as the cusp-core debate remains particularly open for dIrrs. Our best combined limits show the potential to exclude DM annihilation cross-section values around $2\times 10^{-24} \ \mathrm{cm^{3}}\mathrm{s^{-1}}$ for 100 GeV WIMP masses annihilating in the $τ^+τ^-$ channel. These prospective results are competitive with and complementary to benchmark targets such as galaxy clusters. We also analyze the case of the velocity-dependent annihilation cross-section (Sommerfeld enhancement), obtaining projected DM constraints that exceed those expected for dwarf spheroidal galaxies, thanks to the contribution of subhalos to the signal. We conclude that dIrrs are compelling targets for the CTAO, not only for DM indirect searches but also as possible astrophysical sources.

astro-ph.HE↗

arXiv2026

Impact of baryons on the population of Galactic subhalos and implications for dark matter searches

We have used Auriga --a set of state-of-the-art cosmological hydrodynamical simulations of Milky Way-size systems-- to study the impact of baryons on the Galactic subhalo population. A DM-only run counterpart of Auriga allows us to compare results with and without baryons. We repopulate the original suites with low-mass subhalos orders of magnitude lighter than the mass resolution limit, starting from a detailed characterization of Auriga data in the well-resolved subhalo mass range. The survival of low-mass subhalos to tidal forces is unclear and under debate nowadays, thus in our study we stay agnostic and consider two different levels of subhalo resilience to tidal stripping ('fragile' and 'resilient' subhalos). We find baryons to alter the Galactic substructure significantly, by decreasing its overall abundance by a factor $\sim2.4$ (fragile) and $\sim1.9$ (resilient) and subhalo concentration --here defined in terms of maximum circular velocity-- by $\sim1.5$ with respect to the DM-only scenario. This has important consequences for indirect searches of DM. As an example, we investigated the case of using unidentified gamma-ray sources to set constraints on the DM particle properties, assuming some of them may be dark satellites. Our results show the importance of including baryons to properly characterize the Galactic subhalo population, as well as to propose the most optimal subhalo search strategies, not only via its potential DM annihilation products but also through their gravitational signatures (e.g.~stellar streams, strong lensing).

astro-ph.GA↗

arXiv2025

Search for cosmic-ray induced gamma-ray emission from local galaxy clusters using Fermi-LAT data

Galaxy clusters are the most massive gravitationally bound structures in the Universe. Even if clusters are nearly virialized structures, they undergo merging processes, creating merging shocks, and suffer from feedback from galaxies and Active Galactic Nuclei; causing complex turbulent motions and amplifying their magnetic fields. These processes act as acceleration mechanisms for the plasma of the intracluster medium (ICM), originating a population of cosmic rays (CRs). Leptonic CRs have long been detected, but we should also expect a CR hadronic population that, through interactions with the ICM, should produce neutral pions that decay into gamma-rays. The detection of diffuse gamma-ray emission from galaxy clusters is one of the long-awaited milestones for the high-energy astroparticle physics community. Still, no unambiguous detection has yet been obtained. In this talk, we will present the results of a combined cluster analysis searching for CR-induced gamma-ray signals, using 16 years of Fermi-LAT data. In our previous work (di Mauro et al. 2023) we obtained from the combined analysis of 49 local galaxy clusters (12 years of data) a hint of signal between 2.5-3 sigma. These results are consistent with other works as well, which consistently find a non-vanishing hint of signal, around the detection threshold. In this new work, we use a sample of near, well-known galaxy clusters and develop CR-induced emission templates using well-established X-ray measurements for calibration, assuming self similarity for the members of our sample. To strengthen the robustness of our analysis, we define benchmark models to encapsulate the uncertainties in the spectral and spatial profiles for the CR-induced emission and perform the standard template-fitting analysis using the likelihood ratio test.

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