Guilt by association: The 13 µm dust emission feature and its correlation to other gas and dust features

G.C. Sloan (Cornell), K.E. Kraemer (Air Force Research Lab., Boston Univ.), J.H. Goebel (NASA Ames), S.D. Price (Air Force Research Lab.)

2003, ApJ, 594, 483

A study of all full-scan spectra of optically thin oxygen-rich circumstellar dust shells in the database produced by the Short Wavelength Spectrometer on ISO reveals that the strength of several infrared spectral features correlates with the strength of the 13 µm dust feature. These correlated features include dust features at 19.8 and 28.1 µm and the bands produced by warm carbon dioxide molecules (the strongest of which are at 13.9, 15.0, and 16.2 µm). The database does not provide any evidence for a correlation of the 13 µm feature with a dust feature at 32 µm, and it is more likely that the weak emission feature at 16.8 µm arises from carbon dioxide gas rather than dust. The correlated dust features at 13, 20, and 28 µm tend to be stronger with respect to the total dust emission in semi-regular and irregular variables associated with the asymptotic giant branch than in Mira variables or supergiants. This family of dust features also tend to be stronger in systems with lower infrared excesses and thus lower mass-loss rates. We hypothesize that the dust features arise from crystalline forms of alumina (13 µm) and silicates (20 and 28 µm).

Sample SE1-8 and SE1-6t spectra (with and without 13 µm features) (gzipped tar file)

The above tar file provides sample dust spectra from the SWS on ISO at each SE index. They were produced by averaging, for each SE index, 2-3 of the spectra with the strongest and weakest 13 µm features. The files se1-6t.dat have strong 13 µm features, and the files se1-8.dat have weak 13 µm features. Note that there are no se7t.dat and se8t.dat files, due to the lack of 13 µm features at these SE indices. Each file contains wavelength (in µm) and flux density (in Jy) in two columns.

Feel free to use these data in any way you see fit in your research. If they prove useful, we would be grateful if you cite our paper.

Home Library

Last modified 8 August, 2008. © Gregory C. Sloan and others.