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http://hdl.handle.net/20.500.12386/27460
Titolo: | Solid CO2 in quiescent dense molecular clouds. Comparison between Spitzer and laboratory spectra | Autori: | SUHASARIA, TUSHAR BARATTA, Giuseppe Ioppolo, S. Zacharias, H. PALUMBO, Maria Elisabetta |
Data pubblicazione: | 2017 | Rivista: | ASTRONOMY & ASTROPHYSICS | Numero: | 608 | Da pagina:: | A12 | Abstract: | Context. Carbon dioxide (CO<SUB>2</SUB>) is one of the most abundant species detected in icy grain mantles in star forming regions. Laboratory experiments have shown that CO<SUB>2</SUB> molecules are efficiently formed in the solid state under interstellar conditions. Specifically, solid CO<SUB>2</SUB> can be formed through energetic (e.g. UV photolysis, electron and ion bombardment) and non-energetic mechanisms (atom-addition reactions). <BR /> Aims: Here we investigate the role of low-energy cosmic-ray bombardment in the formation of solid CO<SUB>2</SUB> in quiescent dense molecular clouds. <BR /> Methods: We performed laboratory experiments to study the formation of CO<SUB>2</SUB> after ion irradiation with 200 keV H<SUP>+</SUP> of astrophysical relevant ice mixtures. Laboratory spectra are used to fit the profile of the CO<SUB>2</SUB> bending mode band observed at about 15.2 μm (660 cm<SUP>-1</SUP>) by the Spitzer Space Telescope in the line of sight to background sources. <BR /> Results: From a qualitative point of view, good fits to observations are obtained by considering either three or four laboratory components. From a quantitative point of view, a better result is obtained with four components, i.e. when a spectrum of CO<SUB>2</SUB> formed after ion irradiation of CH<SUB>3</SUB>OH ice is added to the fitting procedure. <BR /> Conclusions: Our results support the hypothesis that energetic processing of icy grain mantles is an efficient formation mechanism of CO<SUB>2</SUB> ice also in quiescent dark cloud regions, and indirectly suggest the presence of CH<SUB>3</SUB>OH in icy grain mantles in interstellar cold regions. | URI: | http://hdl.handle.net/20.500.12386/27460 | URL: | https://www.aanda.org/articles/aa/abs/2017/12/aa30504-17/aa30504-17.html | ISSN: | 0004-6361 | DOI: | 10.1051/0004-6361/201730504 | Bibcode ADS: | 2017A&A...608A..12S | Fulltext: | open |
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