Astrophys. J., 728, 45 (2011/February-2)
Influence of the environment on polycyclic aromatic hydrocarbon emission in star-forming regions.
LEBOUTEILLER V., BERNARD-SALAS J., WHELAN D.G., BRANDL B., GALLIANO F., CHARMANDARIS V., MADDEN S. and KUNTH D.
Abstract (from CDS):
We investigate the emission properties of polycyclic aromatic hydrocarbons (PAHs) in various metallicity environments with the Infrared Spectrograph on board Spitzer. Local giant H II regions are used as references as they enable access to the distinct interstellar medium components that contribute to the mid-infrared spectrum of star-forming galaxies: photodissociation regions (PDRs), photoionized gas, stellar clusters, and embedded regions. Three objects are considered: NGC 3603 in the Milky Way, 30 Doradus in the Large Magellanic Cloud, and N 66 in the Small Magellanic Cloud. From the variations of the PAH/14 µm ratio, we find that PAHs are destroyed in the ionized gas for a radiation field such that [Ne III]/[Ne II] ≳ 3. From the variations of the PAH/Huα ratio, we find that the PAH emission sources in the giant H II regions follow the same photodestruction law regardless of metallicity. We then compare these results with observations of starburst galaxies, H II galaxies, and blue compact dwarf galaxies (BCDs). While the integrated mid-infrared spectra of BCDs are reminiscent of a warm dusty ionized gas, we observe a significant contribution to the PAH emission in starburst galaxies that is not arising from PDRs.
dust, extinction - galaxies: star clusters: general - H II regions - infrared: galaxies - infrared: ISM - ISM: molecules
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