ICES IN THE QUIESCENT IC 5146 DENSE CLOUD

Journal Article · Sun Apr 10 00:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/731/1/9· OSTI ID:21574797

Chiar, J E ^[1]; Pendleton, Y J; Allamandola, L J; Ennico, K; Greene, T P; Roellig, T L; Sandford, S A ^[2]; Boogert, A C. A. ^[3]; Geballe, T R; Mason, R E ^[4]; Keane, J V ^[5]; Lada, C J ^[6]; Werner, M W ^[7]; Whittet, D C. B. ^[8]; Decin, L ^[9]; Eriksson, K ^[10]

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1. SETI Institute, Carl Sagan Center, 189 Bernardo Avenue, Mountain View, CA 94035 (United States)
2. NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035 (United States)
3. IPAC, NASA Herschel Science Center, Mail Code 100-22, California Institute of Technology, Pasadena, CA 91125 (United States)
4. Gemini Observatory, Northern Operations Center, 670 North A'ohoku Place, Hilo, HI 96720 (United States)
5. Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
6. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
7. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)
8. New York Center for Astrobiology, Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States)
9. Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven (Belgium)
10. Department of Physics and Astronomy, Uppsala University, Box 515, 751 20 Uppsala (Sweden)

This paper presents spectra in the 2 to 20 {mu}m range of quiescent cloud material located in the IC 5146 cloud complex. The spectra were obtained with NASA's Infrared Telescope Facility SpeX instrument and the Spitzer Space Telescope's Infrared Spectrometer. We use these spectra to investigate dust and ice absorption features in pristine regions of the cloud that are unaltered by embedded stars. We find that the H{sub 2}O-ice threshold extinction is 4.03 {+-} 0.05 mag. Once foreground extinction is taken into account, however, the threshold drops to 3.2 mag, equivalent to that found for the Taurus dark cloud, generally assumed to be the touchstone quiescent cloud against which all other dense cloud and embedded young stellar object observations are compared. Substructure in the trough of the silicate band for two sources is attributed to CH{sub 3}OH and NH{sub 3} in the ices, present at the {approx}2% and {approx}5% levels, respectively, relative to H{sub 2}O-ice. The correlation of the silicate feature with the E(J - K) color excess is found to follow a much shallower slope relative to lines of sight that probe diffuse clouds, supporting the previous results by Chiar et al.

• OSTI ID: 21574797
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 731; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
CLOUDS
DUSTS
ICE
INFRARED SPECTRA
SORPTION
SPECTRA