A MULTIWAVELENGTH STUDY ON THE FATE OF IONIZING RADIATION IN LOCAL STARBURSTS

Journal Article · Mon Dec 20 04:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/725/2/2029· OSTI ID:21476660

Hanish, D J; Oey, M S ^[1]; Rigby, J R; Lee, J C ^[2]

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1. Department of Astronomy, University of Michigan, 500 Church Street, 830 Dennison, Ann Arbor, MI 48109-1042 (United States)
2. Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

The fate of ionizing radiation is vital for understanding cosmic ionization, energy budgets in the interstellar and intergalactic medium, and star formation rate indicators. The low observed escape fractions of ionizing radiation have not been adequately explained, and there is evidence that some starbursts have high escape fractions. We examine the spectral energy distributions (SEDs) of a sample of local star-forming galaxies, containing 13 local starburst galaxies and 10 of their ordinary star-forming counterparts, to determine if there exist significant differences in the fate of ionizing radiation in these galaxies. We find that the galaxy-to-galaxy variations in the SEDs are much larger than any systematic differences between starbursts and non-starbursts. For example, we find no significant differences in the total absorption of ionizing radiation by dust, traced by the 24 {mu}m, 70 {mu}m, and 160 {mu}m MIPS bands of the Spitzer Space Telescope, although the dust in starburst galaxies appears to be hotter than that of non-starburst galaxies. We also observe no excess ultraviolet flux in the Galaxy Evolution Explorer bands that could indicate a high escape fraction of ionizing photons in starburst galaxies. The small H{alpha} fractions of the diffuse, warm ionized medium (WIM) in starburst galaxies are apparently due to temporarily boosted H{alpha} luminosity within the star-forming regions themselves, with an independent, constant WIM luminosity. This independence of the WIM and starburst luminosities contrasts with WIM behavior in non-starburst galaxies and underscores our poor understanding of radiation transfer in both ordinary and starburst galaxies.

• OSTI ID: 21476660
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 725; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
BOSONS
DUSTS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
ENERGY BALANCE
ENERGY SPECTRA
EVOLUTION
GALACTIC EVOLUTION
GALAXIES
IONIZATION
IONIZING RADIATIONS
LUMINOSITY
MASSLESS PARTICLES
OPTICAL PROPERTIES
PHOTONS
PHYSICAL PROPERTIES
RADIATIONS
SORPTION
SPECTRA
STARS
TELESCOPES
ULTRAVIOLET RADIATION