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Title: PROPERTIES OF NEARBY STARBURST GALAXIES BASED ON THEIR DIFFUSE GAMMA-RAY EMISSION

Abstract

The physical relationship between the far-infrared and radio fluxes of star-forming galaxies has yet to be definitively determined. The favored interpretation, the 'calorimeter model', requires that supernova generated cosmic-ray (CR) electrons cool rapidly via synchrotron radiation. However, this cooling should steepen their radio spectra beyond what is observed, and so enhanced ionization losses at low energies from high gas densities are also required. Further, evaluating the minimum energy magnetic field strength with the traditional scaling of the synchrotron flux may underestimate the true value in massive starbursts if their magnetic energy density is comparable to the hydrostatic pressure of their disks. Gamma-ray spectra of starburst galaxies, combined with radio data, provide a less ambiguous estimate of these physical properties in starburst nuclei. While the radio flux is most sensitive to the magnetic field, the GeV gamma-ray spectrum normalization depends primarily on gas density. To this end, spectra above 100 MeV were constructed for two nearby starburst galaxies, NGC 253 and M82, using Fermi data. Their nuclear radio and far-infrared spectra from the literature are compared to new models of the steady-state CR distributions expected from starburst galaxies. Models with high magnetic fields, favoring galaxy calorimetry, are overall better fits tomore » the observations. These solutions also imply relatively high densities and CR ionization rates, consistent with molecular cloud studies.« less

Authors:
;  [1]
  1. Department of Earth and Physical Sciences, York College, City University of New York, 94-20 Guy R. Brewer Blvd., Jamaica, NY 11451 (United States)
Publication Date:
OSTI Identifier:
22039086
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 755; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; CALORIMETRY; COSMIC ELECTRONS; COSMIC PHOTONS; DENSITY; ENERGY DENSITY; GALAXIES; GAMMA RADIATION; GAMMA SPECTRA; GEV RANGE; INFRARED SPECTRA; IONIZATION; MAGNETIC FIELDS; MATHEMATICAL SOLUTIONS; MEV RANGE; PHOTON EMISSION; STARS; STEADY-STATE CONDITIONS; SYNCHROTRON RADIATION

Citation Formats

Paglione, Timothy A. D., and Abrahams, Ryan D., E-mail: paglione@york.cuny.edu. PROPERTIES OF NEARBY STARBURST GALAXIES BASED ON THEIR DIFFUSE GAMMA-RAY EMISSION. United States: N. p., 2012. Web. doi:10.1088/0004-637X/755/2/106.
Paglione, Timothy A. D., & Abrahams, Ryan D., E-mail: paglione@york.cuny.edu. PROPERTIES OF NEARBY STARBURST GALAXIES BASED ON THEIR DIFFUSE GAMMA-RAY EMISSION. United States. doi:10.1088/0004-637X/755/2/106.
Paglione, Timothy A. D., and Abrahams, Ryan D., E-mail: paglione@york.cuny.edu. Mon . "PROPERTIES OF NEARBY STARBURST GALAXIES BASED ON THEIR DIFFUSE GAMMA-RAY EMISSION". United States. doi:10.1088/0004-637X/755/2/106.
@article{osti_22039086,
title = {PROPERTIES OF NEARBY STARBURST GALAXIES BASED ON THEIR DIFFUSE GAMMA-RAY EMISSION},
author = {Paglione, Timothy A. D. and Abrahams, Ryan D., E-mail: paglione@york.cuny.edu},
abstractNote = {The physical relationship between the far-infrared and radio fluxes of star-forming galaxies has yet to be definitively determined. The favored interpretation, the 'calorimeter model', requires that supernova generated cosmic-ray (CR) electrons cool rapidly via synchrotron radiation. However, this cooling should steepen their radio spectra beyond what is observed, and so enhanced ionization losses at low energies from high gas densities are also required. Further, evaluating the minimum energy magnetic field strength with the traditional scaling of the synchrotron flux may underestimate the true value in massive starbursts if their magnetic energy density is comparable to the hydrostatic pressure of their disks. Gamma-ray spectra of starburst galaxies, combined with radio data, provide a less ambiguous estimate of these physical properties in starburst nuclei. While the radio flux is most sensitive to the magnetic field, the GeV gamma-ray spectrum normalization depends primarily on gas density. To this end, spectra above 100 MeV were constructed for two nearby starburst galaxies, NGC 253 and M82, using Fermi data. Their nuclear radio and far-infrared spectra from the literature are compared to new models of the steady-state CR distributions expected from starburst galaxies. Models with high magnetic fields, favoring galaxy calorimetry, are overall better fits to the observations. These solutions also imply relatively high densities and CR ionization rates, consistent with molecular cloud studies.},
doi = {10.1088/0004-637X/755/2/106},
journal = {Astrophysical Journal},
number = 2,
volume = 755,
place = {United States},
year = {Mon Aug 20 00:00:00 EDT 2012},
month = {Mon Aug 20 00:00:00 EDT 2012}
}