van Breemen, J. M. and Min, M. and Chiar, J. E. and Waters, L. B. F. M. and Kemper, F. and Boogert, A. C. A. and Cami, J. and Decin, L. and Knez, C. and Sloan, G. C. and Tielens, A. G. G. M. (2011) The 9.7 and 18 μm silicate absorption profiles towards diffuse and molecular cloud lines-of-sight. Astronomy and Astrophysics, 526 . Art. No. A152. ISSN 0004-6361 http://resolver.caltech.edu/CaltechAUTHORS:20110222-150236758
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Context. Studying the composition of dust in the interstellar medium (ISM) is crucial for understanding the cycle of dust in our galaxy. Aims. The mid-infrared spectral signature of amorphous silicates, the most abundant dust species in the ISM, is studied in different lines-of-sight through the Galactic plane, thus probing different conditions in the ISM. Methods. We have analysed ten spectra from the Spitzer archive, of which six lines-of-sight probe diffuse interstellar medium material and four probe molecular cloud material. The 9.7 μm silicate absorption features in seven of these spectra were studied in terms of their shape and strength. In addition, the shape of the 18 μm silicate absorption features in four of the diffuse sightline spectra were analysed. Results. The 9.7 μm silicate absorption bands in the diffuse sightlines show a strikingly similar band shape. This is also the case for all but one of the 18 μm silicate absorption bands observed in diffuse lines-of-sight. The 9.7 μm bands in the four molecular sightlines show small variations in shape. These modest variations in the band shape are inconsistent with the interpretation of the large variations in τ_(9.7)/E(J − K) between diffuse and molecular sightlines in terms of silicate grain growth. Instead, we suggest that the large changes in τ_(9.7)/E(J − K) must be due to changes in E(J − K).
|Additional Information:||© 2011 ESO. Received 13 October 2008, Accepted 9 December 2010, Published online 13 January 2011.|
|Subject Keywords:||dust, extinction – evolution – techniques: spectroscopic – infrared: ISM – ISM: clouds|
|Official Citation:||The 9.7 and 18 μm silicate absorption profiles towards diffuse and molecular cloud lines-of-sight J. M. van Breemen, M. Min, J. E. Chiar, L. B. F. M. Waters, F. Kemper, A. C. A. Boogert, J. Cami, L. Decin, C. Knez, G. C. Sloan and A. G. G. M. Tielens A&A 526 A152 (2011) DOI: 10.1051/0004-6361/200811142|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Benjamin Perez|
|Deposited On:||23 Feb 2011 15:48|
|Last Modified:||26 Dec 2012 12:57|
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