Cambrésy, L. and Rho, J. and Marshall, D. J. and Reach, W. T. (2011) Variation of the extinction law in the Trifid nebula. Astronomy and Astrophysics, 527 . Art. No. 141. ISSN 0004-6361 http://resolver.caltech.edu/CaltechAUTHORS:20110322-091237395
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Context. In the past few years, the extinction law has been measured in the infrared wavelengths for various molecular clouds and different laws have been obtained. Aims. In this paper we seek variations of the extinction law within the Trifid nebula region. Such variations would demonstrate local dust evolution linked to variation of the environment parameters such as the density or the interstellar radiation field. Methods. The extinction values, A_λ/A_v, are obtained using the 2MASS, UKIDSS and Spitzer/GLIMPSE surveys. The technique is to inter-calibrate color-excess maps from different wavelengths to derive the extinction law and to map the extinction in the Trifid region. Results. We measured the extinction law at 3.6, 4.5, and 5.8 μm and we found a transition at A_v ≈ 20 mag. Below this threshold the extinction law is as expected from models for R_v = 5.5 whereas above 20 mag of visual extinction, it is flatter. Using these results the color-excess maps are converted into a composite extinction map of the Trifid nebula at a spatial resolution of 1 arcmin. A tridimensional analysis along the line-of-sight allowed us to estimate a distance of 2.7 ± 0.5 kpc for the Trifid. The comparison of the extinction with the 1.25 mm emission suggests the millimeter emissivity is enhanced in the dense condensations of the cloud. Conclusions. Our results suggest a dust transition at large extinction which has not been reported so far as well as dust emissivity variations.
|Additional Information:||© 2011 ESO. Received 4 October 2010. Accepted 21 December 2010. Published online 11 February 2011. We thank the anonymous referee for his comments that help to clarify and improve this paper. We thank T. Dame for providing us with the CO datacube and for his assistance in using it. We are also grateful to A. Boogert for his help understanding the possible ice contributions to our analysis. 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. This work is based in part on data obtained as part of the UKIRT Infrared Deep Sky Survey. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.|
|Subject Keywords:||dust, extinction; ISM: individual object: Trifid nebula; infrared: ISM; radio continuum: ISM|
|Official Citation:||Variation of the extinction law in the Trifid nebula A141 L. Cambrésy, J. Rho, D. J. Marshall and W. T. Reach Published online: 11 February 2011 DOI: 10.1051/0004-6361/201015863|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||22 Mar 2011 20:32|
|Last Modified:||26 Dec 2012 13:06|
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