Daniel Rosa Gonzalez

Neutrino emission from astrophysical sources has long been considered a signature of cosmic-ray acceleration. The IceCube Neutrino Observatory has observed a diffuse flux of TeV–PeV neutrinos, but very few confirmed sources have emerged. With the recent publication of the IceCube Event Catalog (IceCat-1), IceCube has released a list of probable astrophysical neutrinos from 2011 May to 2020 December, with follow-up alerts released via the Astrophysical Multi-messenger Observatory Network (AMON). Using the archival data from the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory, we search for gamma-ray outbursts spatially coincident with these neutrino alerts using a Bayesian block algorithm. In this work, we consider 380 alerts, up to 2026 May 19, that are within HAWC’s field of view. We observe approximately a 5% coincident detection rate, which is consistent with expectations from background. Two of these detections contain the active galactic nuclei (AGNs) Mrk 421 and Mrk 501. We discuss the possibility of these AGNs producing the observed neutrino events when considering the HAWC results.

Multi-TeV gamma-ray emission around eHWC J1850+001 (a source from the first HAWC catalog of gamma-ray sources emitting above 56 TeV) is spatially coincident with the pulsar wind nebula (PWN) G32.64+0.53, powered by PSR J1849-0001. The absence of counterparts in radio, optical, and GeV energy ranges, contrasted with clear detections in X-rays and very-high-energy (VHE) gamma rays, is indicative of a nonthermal leptonic origin for the nebula. We apply a systematic analysis pipeline, including a sophisticated model for the Galactic diffuse emission, to 2860 days of data from the HAWC Observatory. Our detailed analysis confirms that the ultra-high-energy (UHE) emission originates from G32.64+0.53, and we measure its spectrum up to 270 TeV with significant emission well beyond 100 TeV. We fit the multiwavelength observations with a time-dependent leptonic model powered by the pulsar’s rotational energy, and the results establish the nebula as a leptonic PeV accelerator, capable of accelerating electrons to a maximum energy of E _cut ≥ 2.9 PeV (95% one-sided lower bound). The model also constrains the nebular magnetic field to 4.28 μ G, supporting a leptonic PWN origin for the observed UHE emission.

We present a new study on the MeV–TeV γ -ray origin of HESS J1857+026 using data collected from the Fermi–LAT, VERITAS, and HAWC observatories. A spatial and spectral study of HESS J1857+026 including radiative modeling of the MeV–TeV spectrum determines the likely dominant γ -ray origin as a pulsar wind nebula (PWN) powered by the energetic pulsar PSR J1856+0245. The MeV–TeV spectrum is further characterized through basic evolutionary radiative modeling assuming a PWN origin to constrain the physical properties of the system such as the magnetic field strength and PWN age. The results of the PWN evolutionary model are consistent with the observational constraints of the system, finding an age of the system between τ = [16, 21] kyr and a magnetic field strength between B = [0.4, 1.6] μ G. These estimates support an evolved PWN scenario where the observed γ -ray emission is generated by the relativistic electrons' inverse Compton (IC) scattering off local photon fields; however, the low-energy ( E < 10 GeV) spectral component could be dominated by hadronic emission originating from a supernova remnant (SNR). For a PWN component above 10 GeV, we measure the conditions for particle diffusion, finding that the local diffusion ( D (50 TeV) ∼ 10 ²⁸ cm ⁻² s ⁻¹ ) is suppressed compared to the interstellar medium (ISM) value, in agreement with similar TeV PWNe. By measuring the radial surface brightness profiles of the γ -ray source across multiple instruments, we demonstrate that the combined MeV–TeV spatial information is a powerful tool to constrain particle diffusion properties.

Context. The narrow-line Seyfert 1 galaxy IRAS 17020+4544 is one of the few known sources to exhibit a multiphase outflow in the highly ionized and molecular phases consistent with active galactic nucleus (AGN) feedback operating in the “energy-conserving” regime. Aims. We aim to characterize the properties of the ionized warm ionized gas in IRAS 17020+4544 using new optical integral-field spectroscopic (IFS) data, and to assess the presence of outflowing ionized gas and its connection with the other gas phases and its role in the AGN feedback. Methods. We analyzed new optical seeing-limited IFS observations obtained with MEGARA at the Gran Telescopio Canarias in both low- ( R ∼ 6000; LR) and medium-resolution ( R ∼ 12 000; MR) modes. We modeled the H α and [OIII] λ 5007 emission lines using multi-Gaussian fitting to characterize in detail the ionized gas kinematics, particularly that of the ionized outflow, in order to derive its energetics and compare it with those of the X-ray and molecular phases. Diagnostic diagrams (WHAN, WHaD, and BPT) were used to investigate the dominant ionization mechanism. Results. We identify a fast ionized outflow traced by both H α and [OIII] emission lines, with similar extensions ( R _out ∼ 1 kpc and ∼0.5 kpc, respectively) and velocities ( v _out ∼ 1460 and 1240 km s ⁻¹ , respectively). A slower ionized outflow ( v _out ∼ 450 km s ⁻¹ ) is also detected in the secondary component of the [OIII] line. The fast outflow follows an energy-conserving regime in both H α and the [OIII] lines (from the LR setup), while the slower outflow follows a “momentum-driven” regime. The ionized outflows are enclosed within the molecular outflow detected with NOEMA ( R _CO = 2.8 ± 0.3 kpc), and the large momentum boosts derived in both phases suggest efficient AGN feedback, likely dominated by radiatively driven winds (quasar-mode) rather than kinetic (jet-driven) processes. Ionization diagnostics indicate that the outflow is primarily AGN-driven, although a contribution from star-formation-driven excitation cannot be ruled out, and some contribution from shocks cannot be excluded on smaller scales. Conclusions. Our results support a scenario in which the multiphase outflow in IRAS17020+4544 is AGN-driven and energy-conserving in the different (i.e., highly ionized, warm ionized, and molecular) phases, efficiently coupling the AGN energy to the host galaxy’s interstellar medium. The molecular outflow appears to be the dominant phase, while the ionized phase contributes less to the mass budget and feedback efficiency.

Aims. The existence of massive disc galaxies with little or no bulge challenges conventional Λ cold dark matter model, which typically favours dynamically hot central structures due to early collapse and mergers. The study of these bulgeless disc galaxies is the aim of the Bulgeless Evolution And the Rise of Discs (BEARD) survey, as they offer a unique opportunity to investigate the link between galaxy morphology and the properties of their satellite systems. Methods. Using the high-resolution cosmological hydrodynamical simulation TNG50-1, we studied the satellite populations of 135 bulgeless galaxies. We compared their satellite properties to those of a bulge-dominated control sample with matched stellar masses. Our analysis focuses on satellite abundance, luminosity functions, spatial distribution, orbital alignment, and infall histories. Results. We find that satellite abundance is largely independent of host galaxy morphology. However, satellites around bulgeless galaxies exhibit luminosity functions with a steeper faint-end slope, are more centrally concentrated, and show stronger orbital alignment with the host disc plane. The orbital alignment originates from coherent post-infall dynamical evolution that depends on host galaxy morphology. The infall of more massive satellites can additionally perturb this process, contributing to a weakening or temporary stalling of the secular alignment. Conclusions. Due to the co-evolution of the host galaxy and the satellite system, the morphology of the central galaxy leaves a clear imprint on its satellite system. Bulgeless galaxies tend to have dynamically colder, more aligned, and more centrally concentrated satellite populations. These trends reflect a more quiet merger history and support the use of satellite properties as tracers of host galaxy formation pathways.

Axion-like particles (ALPs) are hypothetical particles and compelling candidates for cold dark matter. Their existence could be probed through their conversions into photons in the presence of magnetic fields. In this work, we explore the effect of these photon-ALP conversions by searching for an attenuation in the observed gamma ray spectra of galactic sources that emit at energies of hundreds of TeV. We analyze data from the High-Altitude Water Cherenkov (HAWC) Observatory for the source 3HWC J1908+063. No evidence of photon-ALP conversions was found, and we set constraints on the ALP parameter space. Specifically, we derive exclusion limits for ALPs with masses in the range 10 ^-8 eV ≤ m _a ≤ 10 ^-6 eV and photon-ALP couplings in the range 10 ^-12 GeV ^-1 ≤ g _aγ ≤ 10 ^-10 GeV ^-1 , based on HAWC observations.

Dwarf spheroidal galaxies (dSphs) are excellent targets for indirect dark matter (DM) searches using gamma-ray telescopes because they are thought to have high DM content and a low astrophysical background. The sensitivity of these searches is improved by combining the observations of dSphs made by different gamma-ray telescopes. We present the results of a combined search by the most sensitive currently operating gamma-ray telescopes, namely: the satellite-borne Fermi -LAT telescope; the ground-based imaging atmospheric Cherenkov telescope arrays H.E.S.S., MAGIC, and VERITAS; and the HAWC water Cherenkov detector. Individual datasets were analyzed using a common statistical approach. Results were subsequently combined via a global joint likelihood analysis. We obtain constraints on the velocity-weighted cross section 〈 σv 〉 for DM self-annihilation as a function of the DM particle mass. This five-instrument combination allows the derivation of up to 2-3 times more constraining upper limits on 〈 σv 〉 than the individual results over a wide mass range spanning from 5 GeV to 100 TeV. Depending on the DM content modeling, the 95% confidence level observed limits reach 1.5×10 ^-24 cm ³ s ^-1 and 3.2×10 ^-25 cm ³ s ^-1 , respectively, in the τ ⁺ τ ^- annihilation channel for a DM mass of 2 TeV.

Neutrino emission from astrophysical sources has long been considered a signature of cosmic-ray acceleration. The IceCube neutrino observatory has observed a diffuse flux of TeV-PeV neutrinos, but very few confirmed sources have emerged. With the recent publication of IceCube Event Catalog (IceCat-1), IceCube has released a list of the most promising astrophysical neutrino events since May 2011. Using the archival data from the High Altitude Water Cherenkov (HAWC) $γ$-ray observatory, we perform a coincidence search for gamma rays and neutrinos using a Bayesian Block algorithm with the public IceCube alerts from IceCat-1, along with additional alerts issued later. In this work, we consider 368 alerts, up to July 8, 2025, that are within HAWC's field of view. We observe approximately a 5\% coincident detection rate, which is consistent with expectations from background. Two of these detections contain the Active Galactic Nuclei (AGN) Markarian 421 and Markarian 501. We discuss the likelihood that the neutrino/$γ$-ray coincidences are false positives and a brief overview of the results.

We study the formation and evolution of bulgeless galaxies within the Milky Way-Andromeda analogue sample of the TNG50 simulation. Through kinematic decomposition with M ORDOR , we identified bulgeless galaxies with a bulge-to-disc mass ratio of B / D ≤ 0.08, in line with the Bulgeless Evolution And the Rise of Discs (BEARD) survey and Milky Way constraints. We compared the identified bulgeless galaxies to those that are bulge-dominated, which have a bulge-to-disc mass ratio of B / D > 1. We find that 74% of bulgeless galaxies experience at least one major merger (stellar mass ratio 1:4) throughout their lifespan. Bulgeless galaxies form later ( z ₅₀ ∼ 0.7) compared to bulge-dominated counterparts ( z ₅₀ ∼ 1.2). Bulgeless galaxies have lower-mass haloes and higher specific stellar angular momentum, which is compatible with Milky Way observations. However, specific star formation rates and hydrogen gas fractions are slightly higher than Milky Way observations. Our analysis of the redshift evolution of stellar components reveals that bulgeless galaxies have gradual disc growth with high thin disc-to-total mass ratios ( D / T > 0.5) since z ∼ 1 and minimal bulge growth ( B / T < 0.1) since z ∼ 1.5. In contrast, bulge-dominated galaxies have earlier disc formation, which is disrupted, resulting in higher morphology evolution. Bulgeless galaxies are more likely to undergo gas-rich, coplanar, and corotating mergers, promoting disc survival, compared to bulge-dominated galaxies that encounter a broader spectrum of mergers. We also observed differences in galaxy structure between bulgeless and bulge-dominated galaxies without major mergers, suggesting the relevance of early gas accretion and alignment. Bulgeless galaxies have younger stellar populations and more extended star formation histories than bulge-dominated galaxies, which rapidly quench and have older stellar populations. These findings elucidate the distinct merger-driven and secular pathways that give rise to Milky Way galaxies.