A SPITZER INFRARED SPECTROGRAPH DETECTION OF CRYSTALLINE SILICATES IN A PROTOSTELLAR ENVELOPE
- Department of Physics and Astronomy, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 (United States)
- Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States)
- Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 264723, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)
- National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)
- NHSC/IPAC, California Institute of Technology, 770 South Wilson Avenue, Pasadena, CA 91125 (United States)
We present the Spitzer Space Telescope Infrared Spectrograph spectrum of the Orion A protostar HOPS-68. The mid-infrared spectrum reveals crystalline substructure at 11.1, 16.1, 18.8, 23.6, 27.9, and 33.6 {mu}m superimposed on the broad 9.7 and 18 {mu}m amorphous silicate features; the substructure is well matched by the presence of the olivine end-member forsterite (Mg{sub 2}SiO{sub 4}). Crystalline silicates are often observed as infrared emission features around the circumstellar disks of Herbig Ae/Be stars and T Tauri stars. However, this is the first unambiguous detection of crystalline silicate absorption in a cold, infalling, protostellar envelope. We estimate the crystalline mass fraction along the line of sight by first assuming that the crystalline silicates are located in a cold absorbing screen and secondly by utilizing radiative transfer models. The resulting crystalline mass fractions of 0.14 and 0.17, respectively, are significantly greater than the upper limit found in the interstellar medium ({approx}<0.02-0.05). We propose that the amorphous silicates were annealed within the hot inner disk and/or envelope regions and subsequently transported outward into the envelope by entrainment in a protostellar outflow.
- OSTI ID:
- 21562642
- Journal Information:
- Astrophysical Journal Letters, Vol. 733, Issue 2; Other Information: DOI: 10.1088/2041-8205/733/2/L32; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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