ON THE GeV AND TeV DETECTIONS OF THE STARBURST GALAXIES M82 AND NGC 253

Journal Article · Mon Jun 20 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/734/2/107· OSTI ID:21576593

Lacki, Brian C; Thompson, Todd A ^[1]; Quataert, Eliot ^[2]; Loeb, Abraham ^[3]; Waxman, Eli ^[4]

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1. Department of Astronomy, Ohio State University, Columbus, OH 43210 (United States)
2. Astronomy Department and Theoretical Astrophysics Center, 601 Campbell Hall, University of California, Berkeley, CA 94720 (United States)
3. Astronomy Department, Harvard University, 60 Garden Street, Cambridge, MA 02138 (United States)
4. Physics Faculty, Weizmann Institute, Rehovot 7600 (Israel)

The GeV and TeV emission from M82 and NGC 253 observed by Fermi, HESS, and VERITAS constrain the physics of cosmic rays (CRs) in these dense starbursts. We argue that the {gamma}-rays are predominantly hadronic in origin, as expected by previous studies. The measured fluxes imply that pionic losses are efficient for CR protons in both galaxies: we show that a fraction F{sub cal} {approx} 0.2-0.4 of the energy injected in high-energy primary CR protons is lost to inelastic proton-proton collisions (pion production) before escape, producing {gamma}-rays, neutrinos, and secondary electrons and positrons. We discuss the factor of {approx}2 uncertainties in this estimate, including supernova rate and leptonic contributions to the GeV-TeV emission. We argue that {gamma}-ray data on ULIRGs like Arp 220 can test whether M82 and NGC 253 are truly calorimetric, and we present upper limits on Arp 220 from the Fermi data. We show that the observed ratio of the GeV to GHz fluxes of the starbursts suggests that non-synchrotron cooling processes are important for cooling the CR electron/positron population. We briefly reconsider previous predictions in light of the {gamma}-ray detections, including the starburst contribution to the {gamma}-ray background and CR energy densities. Finally, as a guide for future studies, we list the brightest star-forming galaxies on the sky and present updated predictions for their {gamma}-ray and neutrino fluxes.

• OSTI ID: 21576593
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 734; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BARYON-BARYON INTERACTIONS
BARYONS
COSMIC RAY FLUX
DETECTION
ELECTROMAGNETIC RADIATION
ELECTRONS
ELEMENTARY PARTICLES
EMISSION
ENERGY DENSITY
FERMIONS
GALAXIES
GAMMA DETECTION
GAMMA RADIATION
HADRON-HADRON INTERACTIONS
HADRONS
INTERACTIONS
IONIZING RADIATIONS
LEPTONS
MASSLESS PARTICLES
MATTER
NEUTRINOS
NUCLEON-NUCLEON INTERACTIONS
NUCLEONS
PARTICLE INTERACTIONS
POSITRONS
PROTON-NUCLEON INTERACTIONS
PROTON-PROTON INTERACTIONS
PROTONS
RADIATION DETECTION
RADIATION FLUX
RADIATIONS