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تسجيل مستخدم جديدPolycyclic aromatic hydrocarbons in spatially resolved extragalactic star forming complexes
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The abundance of polycyclic aromatic hydrocarbons (PAHs) in low- and high-metallicity galaxies has been widely discussed since the time when detailed infrared data for extragalactic objects were first obtained. On the scales of entire galaxies, a smaller PAH abundance in lower-metallicity galaxies is often observed. We study this relationship for star-forming regions in nearby galaxies, for a sample containing more than 200 HII complexes, using spatially-resolved observations from the Herschel Space Observatory and Spitzer Space Telescope. We use a model for the dust emission to estimate the physical parameters (PAH abundance, metallicity, ultraviolet radiation field, etc.) of these complexes. The same correlation of PAH abundance with metallicity, as seen for entire galaxies, is apparently preserved at smaller scales, at least when the Kobulnicky & Kewley metallicity calibration is used. We discuss possible reasons for this correlation, noting that traces of less-effective PAH formation in low-metallicity AGB stars should be smeared out by radial mixing in galactic disks. Effective destruction by the harder and more intensive ultraviolet field in low-metallicity environments is qualitatively consistent with our data, as the ultraviolet field intensity, derived from the infrared photometry, is indeed smaller in HII complexes with lower metallicity.
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As images and spectra from ISO and Spitzer have provided increasingly higher-fidelity representations of the mid-infrared (MIR) and Polycyclic Aromatic Hydrocarbon (PAH) emission from galaxies and galactic and extra-galactic regions, more systematic
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The amount of deuterium locked up in polycyclic aromatic hydrocarbons (PAHs) has to date been an uncertain value. We present a near-infrared (NIR) spectroscopic survey of HII regions in the Milky Way, Large Magellanic Cloud (LMC), and Small Magellani
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