The Astrophysical Journal (Jan 2025)
An In-depth Study of Gamma Rays from the Starburst Galaxy M82 with VERITAS
- A. Acharyya,
- C. B. Adams,
- P. Bangale,
- J. T. Bartkoske,
- W. Benbow,
- J. H. Buckley,
- Y. Chen,
- J. L. Christiansen,
- A. J. Chromey,
- A. Duerr,
- M. Errando,
- M. Escobar Godoy,
- A. Falcone,
- S. Feldman,
- Q. Feng,
- J. Foote,
- L. Fortson,
- A. Furniss,
- W. Hanlon,
- D. Hanna,
- O. Hervet,
- C. E. Hinrichs,
- J. Holder,
- T. B. Humensky,
- W. Jin,
- M. N. Johnson,
- P. Kaaret,
- M. Kertzman,
- M. Kherlakian,
- D. Kieda,
- T. K. Kleiner,
- N. Korzoun,
- F. Krennrich,
- S. Kumar,
- M. J. Lang,
- M. Lundy,
- G. Maier,
- M. J. Millard,
- C. L. Mooney,
- P. Moriarty,
- R. Mukherjee,
- W. Ning,
- S. O’Brien,
- R. A. Ong,
- M. Pohl,
- E. Pueschel,
- J. Quinn,
- P. L. Rabinowitz,
- K. Ragan,
- P. T. Reynolds,
- D. Ribeiro,
- E. Roache,
- I. Sadeh,
- L. Saha,
- M. Santander,
- G. H. Sembroski,
- R. Shang,
- M. Splettstoesser,
- D. Tak,
- A. K. Talluri,
- J. V. Tucci,
- V. V. Vassiliev,
- D. A. Williams,
- S. L. Wong,
- J. Woo,
- (VERITAS Collaboration)
Affiliations
- A. Acharyya
- ORCiD
- CP3-Origins, University of Southern Denmark , Campusvej 55, 5230 Odense M, Denmark
- C. B. Adams
- ORCiD
- Physics Department, Columbia University , New York, NY 10027, USA
- P. Bangale
- ORCiD
- Department of Physics and Astronomy and the Bartol Research Institute, University of Delaware , Newark, DE 19716, USA
- J. T. Bartkoske
- ORCiD
- Department of Physics and Astronomy, University of Utah , Salt Lake City, UT 84112, USA
- W. Benbow
- ORCiD
- Center for Astrophysics ∣ Harvard & Smithsonian , Cambridge, MA 02138, USA ; [email protected], [email protected]
- J. H. Buckley
- ORCiD
- Department of Physics, Washington University , St. Louis, MO 63130, USA
- Y. Chen
- Department of Physics and Astronomy, University of California , Los Angeles, CA 90095, USA
- J. L. Christiansen
- Physics Department, California Polytechnic State University , San Luis Obispo, CA 94307, USA
- A. J. Chromey
- Center for Astrophysics ∣ Harvard & Smithsonian , Cambridge, MA 02138, USA ; [email protected], [email protected]
- A. Duerr
- ORCiD
- Department of Physics and Astronomy, University of Utah , Salt Lake City, UT 84112, USA
- M. Errando
- ORCiD
- Department of Physics, Washington University , St. Louis, MO 63130, USA
- M. Escobar Godoy
- Santa Cruz Institute for Particle Physics and Department of Physics, University of California , Santa Cruz, CA 95064, USA
- A. Falcone
- ORCiD
- Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University , University Park, PA 16802, USA
- S. Feldman
- Department of Physics and Astronomy, University of California , Los Angeles, CA 90095, USA
- Q. Feng
- ORCiD
- Department of Physics and Astronomy, University of Utah , Salt Lake City, UT 84112, USA
- J. Foote
- ORCiD
- Department of Physics and Astronomy and the Bartol Research Institute, University of Delaware , Newark, DE 19716, USA
- L. Fortson
- ORCiD
- School of Physics and Astronomy, University of Minnesota , Minneapolis, MN 55455, USA
- A. Furniss
- ORCiD
- Santa Cruz Institute for Particle Physics and Department of Physics, University of California , Santa Cruz, CA 95064, USA
- W. Hanlon
- ORCiD
- Center for Astrophysics ∣ Harvard & Smithsonian , Cambridge, MA 02138, USA ; [email protected], [email protected]
- D. Hanna
- ORCiD
- Physics Department, McGill University , Montreal, QC H3A 2T8, Canada
- O. Hervet
- ORCiD
- Santa Cruz Institute for Particle Physics and Department of Physics, University of California , Santa Cruz, CA 95064, USA
- C. E. Hinrichs
- ORCiD
- Center for Astrophysics ∣ Harvard & Smithsonian , Cambridge, MA 02138, USA ; [email protected], [email protected]; Department of Physics and Astronomy, Dartmouth College , 6127 Wilder Laboratory, Hanover, NH 03755, USA
- J. Holder
- ORCiD
- Department of Physics and Astronomy and the Bartol Research Institute, University of Delaware , Newark, DE 19716, USA
- T. B. Humensky
- ORCiD
- Department of Physics, University of Maryland , College Park, MD, USA; NASA GSFC , Greenbelt, MD 20771, USA
- W. Jin
- ORCiD
- Department of Physics and Astronomy, University of California , Los Angeles, CA 90095, USA
- M. N. Johnson
- ORCiD
- Santa Cruz Institute for Particle Physics and Department of Physics, University of California , Santa Cruz, CA 95064, USA
- P. Kaaret
- ORCiD
- Department of Physics and Astronomy, University of Iowa , Van Allen Hall, Iowa City, IA 52242, USA
- M. Kertzman
- Department of Physics and Astronomy, DePauw University , Greencastle, IN 46135-0037, USA
- M. Kherlakian
- DESY , Platanenallee 6, 15738 Zeuthen, Germany ; [email protected]
- D. Kieda
- ORCiD
- Department of Physics and Astronomy, University of Utah , Salt Lake City, UT 84112, USA
- T. K. Kleiner
- ORCiD
- DESY , Platanenallee 6, 15738 Zeuthen, Germany ; [email protected]
- N. Korzoun
- ORCiD
- Department of Physics and Astronomy and the Bartol Research Institute, University of Delaware , Newark, DE 19716, USA
- F. Krennrich
- Department of Physics and Astronomy, Iowa State University , Ames, IA 50011, USA
- S. Kumar
- ORCiD
- Department of Physics, University of Maryland , College Park, MD, USA
- M. J. Lang
- ORCiD
- School of Natural Sciences, University of Galway , University Road, Galway, H91 TK33, Ireland
- M. Lundy
- ORCiD
- Physics Department, McGill University , Montreal, QC H3A 2T8, Canada
- G. Maier
- ORCiD
- DESY , Platanenallee 6, 15738 Zeuthen, Germany ; [email protected]
- M. J. Millard
- ORCiD
- Department of Physics and Astronomy, University of Iowa , Van Allen Hall, Iowa City, IA 52242, USA
- C. L. Mooney
- ORCiD
- Department of Physics and Astronomy and the Bartol Research Institute, University of Delaware , Newark, DE 19716, USA
- P. Moriarty
- ORCiD
- School of Natural Sciences, University of Galway , University Road, Galway, H91 TK33, Ireland
- R. Mukherjee
- ORCiD
- Department of Physics and Astronomy, Barnard College, Columbia University , NY 10027, USA
- W. Ning
- ORCiD
- Department of Physics and Astronomy, University of California , Los Angeles, CA 90095, USA
- S. O’Brien
- ORCiD
- Physics Department, McGill University , Montreal, QC H3A 2T8, Canada; Arthur B. McDonald Canadian Astroparticle Physics Research Institute, 64 Bader Lane, Queen’s University , Kingston, ON K7L 3N6, Canada
- R. A. Ong
- ORCiD
- Department of Physics and Astronomy, University of California , Los Angeles, CA 90095, USA
- M. Pohl
- ORCiD
- DESY , Platanenallee 6, 15738 Zeuthen, Germany ; [email protected]; Institute of Physics and Astronomy, University of Potsdam , 14476 Potsdam-Golm, Germany
- E. Pueschel
- ORCiD
- Fakultät für Physik & Astronomie, Ruhr-Universität Bochum , D-44780 Bochum, Germany
- J. Quinn
- ORCiD
- School of Physics, University College Dublin , Belfield, Dublin 4, Ireland
- P. L. Rabinowitz
- Department of Physics, Washington University , St. Louis, MO 63130, USA
- K. Ragan
- ORCiD
- Physics Department, McGill University , Montreal, QC H3A 2T8, Canada
- P. T. Reynolds
- Department of Physical Sciences, Munster Technological University , Bishopstown, Cork, T12 P928, Ireland
- D. Ribeiro
- ORCiD
- School of Physics and Astronomy, University of Minnesota , Minneapolis, MN 55455, USA
- E. Roache
- Center for Astrophysics ∣ Harvard & Smithsonian , Cambridge, MA 02138, USA ; [email protected], [email protected]
- I. Sadeh
- ORCiD
- DESY , Platanenallee 6, 15738 Zeuthen, Germany ; [email protected]
- L. Saha
- ORCiD
- Center for Astrophysics ∣ Harvard & Smithsonian , Cambridge, MA 02138, USA ; [email protected], [email protected]
- M. Santander
- ORCiD
- Department of Physics and Astronomy, University of Alabama , Tuscaloosa, AL 35487, USA
- G. H. Sembroski
- Department of Physics and Astronomy, Purdue University , West Lafayette, IN 47907, USA
- R. Shang
- ORCiD
- Department of Physics and Astronomy, Barnard College, Columbia University , NY 10027, USA
- M. Splettstoesser
- ORCiD
- Santa Cruz Institute for Particle Physics and Department of Physics, University of California , Santa Cruz, CA 95064, USA
- D. Tak
- ORCiD
- SNU Astronomy Research Center, Seoul National University , Seoul 08826, Republic of Korea
- A. K. Talluri
- School of Physics and Astronomy, University of Minnesota , Minneapolis, MN 55455, USA
- J. V. Tucci
- Department of Physics, Indiana University Indianapolis , Indianapolis, IN 46202, USA
- V. V. Vassiliev
- Department of Physics and Astronomy, University of California , Los Angeles, CA 90095, USA
- D. A. Williams
- ORCiD
- Santa Cruz Institute for Particle Physics and Department of Physics, University of California , Santa Cruz, CA 95064, USA
- S. L. Wong
- ORCiD
- Physics Department, McGill University , Montreal, QC H3A 2T8, Canada
- J. Woo
- ORCiD
- Columbia Astrophysics Laboratory, Columbia University , New York, NY 10027, USA
- (VERITAS Collaboration)
- DOI
- https://doi.org/10.3847/1538-4357/adab71
- Journal volume & issue
-
Vol. 981,
no. 2
p. 189
Abstract
Assuming Galactic cosmic rays originate in supernovae and the winds of massive stars, starburst galaxies should produce very-high-energy (VHE; E > 100 GeV) gamma-ray emission via the interaction of their copious quantities of cosmic rays with the large reservoirs of dense gas within the galaxies. Such VHE emission was detected by VERITAS from the starburst galaxy M82 in 2008–09. An extensive, multiyear campaign followed these initial observations, yielding a total of 254 hr of good-quality VERITAS data on M82. Leveraging modern analysis techniques and the larger exposure, these VERITAS data show a more statistically significant VHE signal (∼6.5 standard deviations, σ ). The corresponding photon spectrum is well fit by a power law (Γ = 2.3 ± 0.3 _stat ± 0.2 _sys ), and the observed integral flux is F (>450 GeV) = (3.2 ± 0.6 _stat ± 0.6 _sys ) × 10 ^−13 cm ^−2 s ^−1 , or ∼0.4% of the Crab Nebula flux above the same energy threshold. The improved VERITAS measurements, when combined with various multiwavelength data, enable modeling of the underlying emission and transport processes. A purely leptonic scenario is found to be a poor representation of the gamma-ray spectral energy distribution (SED). A lepto-hadronic scenario with cosmic rays following a power-law spectrum in momentum (index s ≃ 2.25) and with significant bremsstrahlung below 1 GeV provides a good match to the observed SED. The synchrotron emission from the secondary electrons indicates that efficient nonradiative losses of cosmic-ray electrons may be related to advective escape from the starburst core.
Keywords
- Gamma-ray astronomy
- Star forming regions
- Galactic cosmic rays
- Star clusters
- Gamma-rays
- Gamma-ray sources
