TeV Gamma-Ray Diffuse Emissions in the Galactic Center Region with CTAO LST-1

Imaging Atmospheric Cherenkov Telescopes (IACTs), including H.E.S.S., MAGIC, and VERITAS, have detected very-high-energy gamma rays from the central region of the Milky Way. The PeVatron hypothesis posits that the supermassive black hole Sagittarius A* (Sgr A*) accelerates cosmic rays to PeV energies, producing a diffuse gamma-ray emission extending up to tens of TeV across the central molecular zone. However, previous IACT studies have yielded inconsistent results due to methodological differences, complicating direct comparison and interpretation. H.E.S.S. initially suggested a power-law spectrum within the sector-annulus region (20-60 pc), whereas the MAGIC telescopes recently presented a 2-sigma hint of a spectral cutoff at ∼ 20 TeV for the total ridge emission (∼ 200 pc), although H.E.S.S. and VERITAS have not obtained a sign of cut-off for that emission. The first Large-Sized Telescope (LST-1) at the Northern site of the Cherenkov Telescope Array Observatory (CTAO) offers enhanced TeV sensitivity, despite its higher energy threshold, at large zenith angles. Its wide field of view (∼ 4.5 deg) enables more uniform Galactic ridge coverage than other Northern IACTs. In this study, LST-1 observations reconfirm a spectral cutoff around 20 TeV with a significance of about 3 sigma over a pure power law, demonstrating its capability of TeV observations of extended sources and refining our understanding of cosmic-ray acceleration in the Galactic Center.

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Publication Details

Published
2025-09-23
DOI
https://doi.org/10.22323/1.501.0542
Primary Topic
Astrophysics and Cosmic Phenomena
Type
article
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article

TeV Gamma-Ray Diffuse Emissions in the Galactic Center Region with CTAO LST-1

Ievgen Vovk, M. Strzys, Shotaro Abe, Hidetoshi Kubo et al.
Astrophysics and Cosmic Phenomena
article

TeV Gamma-Ray Diffuse Emissions in the Galactic Center Region with CTAO LST-1

Ievgen Vovk, M. Strzys, Shotaro Abe, Hidetoshi Kubo, M. Teshima
article en

Abstract

Imaging Atmospheric Cherenkov Telescopes (IACTs), including H.E.S.S., MAGIC, and VERITAS, have detected very-high-energy gamma rays from the central region of the Milky Way. The PeVatron hypothesis posits that the supermassive black hole Sagittarius A* (Sgr A*) accelerates cosmic rays to PeV energies, producing a diffuse gamma-ray emission extending up to tens of TeV across the central molecular zone. However, previous IACT studies have yielded inconsistent results due to methodological differences, complicating direct comparison and interpretation. H.E.S.S. initially suggested a power-law spectrum within the sector-annulus region (20-60 pc), whereas the MAGIC telescopes recently presented a 2-sigma hint of a spectral cutoff at ∼ 20 TeV for the total ridge emission (∼ 200 pc), although H.E.S.S. and VERITAS have not obtained a sign of cut-off for that emission. The first Large-Sized Telescope (LST-1) at the Northern site of the Cherenkov Telescope Array Observatory (CTAO) offers enhanced TeV sensitivity, despite its higher energy threshold, at large zenith angles. Its wide field of view (∼ 4.5 deg) enables more uniform Galactic ridge coverage than other Northern IACTs. In this study, LST-1 observations reconfirm a spectral cutoff around 20 TeV with a significance of about 3 sigma over a pure power law, demonstrating its capability of TeV observations of extended sources and refining our understanding of cosmic-ray acceleration in the Galactic Center.

National Science Foundation, Sveučilište u Zagrebu, Comunidad de Madrid, Ministerio de Ciencia, Innovación y Universidades, Centres de Recerca de Catalunya, European Commission, Deutsche Forschungsgemeinschaft, Ministry of Education, Culture, Sports, Science and Technology, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Fundação de Amparo à Pesquisa do Estado de São Paulo, Ministerstvo Školství, Mládeže a Tělovýchovy, Bundesministerium für Bildung und Forschung, Generalitat de Catalunya, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Max-Planck-Gesellschaft, Narodowe Centrum Nauki, Hrvatska Zaklada za Znanost, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Fundação Araucária, Centre National de la Recherche Scientifique, Ministerio de Ciencia e Innovación, Istituto Nazionale di Astrofisica, Sveučilište Josipa Jurja Strossmayera u Osijeku, Junta de Andalucía, Ministério da Ciência, Tecnologia, Inovações e Comunicações, Istituto Nazionale di Fisica Nucleare, Japan Society for the Promotion of Science, Consejo Superior de Investigaciones Científicas, Staatssekretariat für Bildung, Forschung und Innovation, European Regional Development Fund, Agencia Estatal de Investigación, Institut National de Physique Nucléaire et de Physique des Particules, Institute for Cosmic Ray Research, University of Tokyo
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