Effects of massive star formation on the ISM of dwarf galaxies |
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| Affiliation: | 2. Centre for eResearch, The University of Auckland, Auckland, New Zealand;3. Departamento de Química Fundamental, Universidade Federal de Pernambuco, Cidade Universitária, Recife, Pernambuco, Brazil;4. Departments of Physics and of Chemistry, Quantum Theory Project, University of Florida, Gainesville, Florida, USA;1. European Commission, Joint Research Centre, Unit D3, Ispra, Italy;2. Professor Emeritus, Delft University of Technology, Delft, The Netherlands;3. United Nations University, Sustainable Cycles Programme, (UNU – ViE – SCYCLE), Bonn, Germany;4. Sofies, Weybridge, United Kingdom;1. European Commission, Joint Research Centre, Unit D3, Ispra, Italy;2. Professor Emeritus, Delft University of Technology, Delft, The Netherlands;3. United Nations University, Sustainable Cycles Programme, (UNU – ViE – SCYCLE), Bonn, Germany;4. Sofies, Weybridge, United Kingdom;1. Warwick Business School, The University of Warwick, Coventry CV4 7AL, UK;2. Industrial Engineering, Bahçeşehir University, Istanbul, Turkey |
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| Abstract: | We are studying star formation effects on the properties of the ISM in low metallicity environments using mid-infrared (MIR) and far-infrared (FIR) observations of starbursting dwarf galaxies taken with the Infrared Space Observatory (ISO) and the Kuiper Airborne Observatory (KAO). Effects of the hard pervasive radiation field on the gas and dust due to the dust-poor environments are apparent in both the dust and gas components. From a 158 μm [CII] survey we find enhanced I[CII]/FIR ratios in dwarf galaxies and I[CII]/I(CO) ratios up to 10 times higher than those for normal metallicity starburst galaxies. We consider MIR observations in understanding the star formation properties of dwarf galaxies and constraints on the stellar SED. Notably, the strong MIR [NeIII]/[NeII] ratios reveal the presence of current massive stellar populations <5 My old in NGC 1569, NGC 1140 and IIZw40. The MIR unidentified infrared bands (UIBs) are weak, if present at all, as a general characteristic in low metallicity environments, revealing the destruction of the smallest carbon particles (e.g. PAHs) over large spatial scales. This is confirmed with our dust modeling: mass fractions of PAHs are almost negligible compared to the larger silicate grains emitting in the FIR as well as the small carbon grains emitting in the MIR, which appear to be the source of the photoelectric gas heating in these galaxies, in view of the [CII] cooling. |
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