Browsing by Author "Marcotulli, Lea"
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Item A Cross-correlation Study between IceCube Neutrino Events and the Fermi Unresolved Gamma-ray Sky(2023-04-21) Negro, Michela; Crnogorčević, Milena; Burns, Eric; Charles, Eric; Marcotulli, Lea; Caputo, ReginaWith the coincident detections of electromagnetic radiation together with gravitational waves (GW170817) or neutrinos (TXS 0506+056), the new era of multimessenger astrophysics has begun. Of particular interest are the searches for correlation between the high-energy astrophysical neutrinos detected by the IceCube Observatory and gamma-ray photons detected by the Fermi Large Area Telescope (LAT). So far, only sources detected by the LAT have been considered in correlation with IceCube neutrinos, neglecting any emission from sources too faint to be resolved individually. Here, we present the first cross-correlation analysis considering the unresolved gamma-ray background (UGRB) and IceCube events. We perform a thorough sensitivity study and, given the lack of identified correlation, we place upper limits on the fraction of the observed neutrinos that would be produced in proton-proton (p-p) or proton-gamma (p-gamma) interactions from the population of sources contributing to the UGRB emission and dominating its spatial anisotropy (aka blazars). Our analysis suggests that, under the assumption that there is no intrinsic cutoff and/or hardening of the spectrum above Fermi-LAT energies, and that all gamma-rays from the unresolved blazars dominating the UGRB fluctuation field are produced by neutral pions from p-p (p-gamma) interactions, up to 60% (30%) of such population may contribute to the total neutrino events observed by IceCube. This translates into a O(1%) maximum contribution to the astrophysical high-energy neutrino flux observed by IceCube at 100 TeV.Item Supermassive black holes at high redshifts(arXiv, 2019-03-14) Paliya, Vaidehi S.; Ajello, Marco; Marcotulli, Lea; Tomsick, John; Perkins, Jeremy S.; Prandini, Elisa; D'Ammando, Filippo; De Angelis, Alessandro; Thompson, David; Li, Hui; Dominguez, Alberto; Beckmann, Volker; Guiriec, Sylvain; Wadiasingh, Zorawar; Coppi, Paolo; Harding, J. Patrick; Petropoulou, Maria; Hewitt, John W.; Ojha, Roopesh; Marcowith, Alexandre; Doro, Michele; Castro, Daniel; Baring, Matthew; Hays, Elizabeth; Orlando, Elena; Guiriec, Sylvain; Bozhilov, Vladimir; Agudo, Ivan; Venters, Tonia; McEnery, Julie; The, Lih-Sin; Hartmann, Dieter; Buson, Sara; Longo, Francesco; Gasparrini, DarioMeV blazars are the most luminous persistent sources in the Universe and emit most of their energy in the MeV band. These objects display very large jet powers and accretion luminosities and are known to host black holes with a mass often exceeding 10⁹M⊙. An MeV survey, performed by a new generation MeV telescope which will bridge the entire energy and sensitivity gap between the current generation of hard X-ray and gamma-ray instruments, will detect >1000 MeV blazars up to a redshift of z=5−6. Here we show that this would allow us: 1) to probe the formation and growth mechanisms of supermassive black holes at high redshifts, 2) to pinpoint the location of the emission region in powerful blazars, 3) to determine how accretion and black hole spin interplay to power the jet.Item The High Energy X-ray Probe (HEX-P): the most powerful jets through the lens of a superb X-ray eye(2023-11-08) Marcotulli, Lea; Ajello, Marco; Böttcher, Markus; Coppi, Paolo; Rani, Bindu; HEX-P Collaboration; et al.A fraction of the active supermassive black holes at the centers of galaxies in our Universe are capable of launching extreme kiloparsec-long relativistic jets. These jets are known multiband (radio to γ-ray) and multimessenger (neutrino) emitters, and some of them have been monitored over several decades at all accessible wavelengths. However, many open questions remain unanswered about the processes powering these highly energetic phenomena. These jets intrinsically produce soft-to-hard X-ray emission that extends from E ∼ 0.1keV up to E > 100keV. Simultaneous broadband X-ray coverage, combined with excellent timing and imaging capabilities, is required to uncover the physics of jets. Indeed, truly simultaneous soft-to-hard X-ray coverage, in synergy with current and upcoming high-energy facilities (such as IXPE, COSI, CTAO, etc.) and neutrino detectors (e.g., IceCube), would enable us to disentangle the particle population responsible for the high-energy radiation from these jets. A sensitive hard X-ray survey (F₈₋₂₄ₖₑᵥ < 10−¹⁵ erg cm−² s−¹) could unveil the bulk of their population in the early Universe. Acceleration and radiative processes responsible for the majority of their X-ray emission would be pinned down by microsecond timing capabilities at both soft and hard X-rays. Furthermore, imaging jet structures for the first time in the hard X-ray regime could unravel the origin of their high-energy emission. The proposed Probe-class mission concept High Energy X-ray Probe (HEX-P) combines all these required capabilities, making it the crucial next-generation X-ray telescope in the multi-messenger, time-domain era. HEX-P will be the ideal mission to unravel the science behind the most powerful accelerators in the universe.