Chiar, J. E. and Ennico, K. and Pendleton, Y. J. and Boogert, A. C. A. and Greene, T. and Knez, C. and Lada, C. and Roellig, T. and Tielens, A. G. G. M. and Werner, M. and Whittet, D. C. B. (2007) The Relationship between the Optical Depth of the 9.7 μm Silicate Absorption Feature and Infrared Differential Extinction in Dense Clouds. Astrophysical Journal Letters, 666 (2). L73-L76. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20091028-110429977
- Published Version
Restricted to Repository administrators only
See Usage Policy.
Use this Persistent URL to link to this item: http://resolver.caltech.edu/CaltechAUTHORS:20091028-110429977
We have examined the relationship between the optical depth of the 9.7 μm silicate absorption feature (τ_(9.7)) and the near-infrared color excess, E(J - K_s), in the Serpens, Taurus, IC 5146, Chameleon I, Barnard 59, and Barnard 68 dense clouds/cores. Our data set, based largely on Spitzer IRS spectra, spans E(J - K_s) = 0.3-10 mag (corresponding to visual extinction between about 2 and 60 mag). All lines of sight show the 9.7 μm silicate feature. Unlike in the diffuse ISM where a tight linear correlation between the 9.7 μm silicate feature optical depth and the extinction (A_V) is observed, we find that the silicate feature in dense clouds does not show a monotonic increase with extinction. Thus, in dense clouds, τ_(9.7) is not a good measure of total dust column density. With few exceptions, the measured τ_(9.7) values fall well below the diffuse ISM correlation line for E(J - K_s) > 2 mag (A_V > 12 mag). Grain growth via coagulation is a likely cause of this effect.
|Additional Information:||© 2007 The American Astronomical Society. Received 2007 May 23; accepted 2007 July 23; published 2007 August 20. This work is based (in part) on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Support for this work was provided by NASA. The authors thank the referee, Viktor Zubko, for his helpful suggestions. Facilities: Spitzer(IRS).|
|Subject Keywords:||dust, extinction; infrared : ISM; ISM : clouds; ISM : molecules|
|Official Citation:||The Relationship between the Optical Depth of the 9.7 μm Silicate Absorption Feature and Infrared Differential Extinction in Dense Clouds J. E. Chiar, K. Ennico, Y. J. Pendleton, A. C. A. Boogert, T. Greene, C. Knez, C. Lada, T. Roellig, A. G. G. M. Tielens, M. Werner, and D. C. B. Whittet 2007 ApJ 666 L73-L76 doi: 10.1086/521789|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||02 Nov 2009 18:28|
|Last Modified:||26 Dec 2012 11:30|
Repository Staff Only: item control page