A Multiwavelength Study on the Fate of Ionizing Radiation in Local Starbursts

Abstract

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 of a sample of local star-forming galaxies, containing thirteen local starburst galaxies and ten 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 is 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 24um, 70um, and 160um 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 GALEX 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 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.

10 pages, 8 figures, accepted to ApJ 10/11/10

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Cited by in corpus (11)

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• The Effect of Galactic Properties on the Escape Fraction of Ionizing Photons
• New Constraints on the Escape of Ionizing Photons From Starburst Galaxies Using Ionization-Parameter Mapping
• On how leakage can affect the Star Formation Rate estimation using Halpha luminosity
• Inferring the HII region escape fraction of ionizing photons from infrared emission lines in metal-poor star-forming dwarf galaxies
• Hubble Space Telescope Wide Field Camera 3 Observations of Escaping Lyman Continuum Radiation from Galaxies and Weak AGN at Redshifts $z$$\simeq$2.3-4.1
• From HI to Stars: HI Depletion in Starbursts and Star-Forming Galaxies in the ALFALFA H-alpha Survey
• SSGSS: The Spitzer-SDSS-GALEX Spectroscopic Survey
• An HI study of the collisional ring galaxy NGC 922
• Dust Emission from Evolved and Unevolved HII Regions in the Large Magellanic Cloud
• Stellar associations powering HII regions $\unicode{x2013}$ II. Escape fraction of ionizing photons