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Dust properties inside molecular clouds from coreshine modeling and observations

Lefèvre, C. and Pagani, L. and Juvela, M. and Paladini, R. and Lallement, R. and Marshall, D. J. and Andersen, M. and Bacmann, A. and McGehee, P. M. and Montier, L. and Noriega-Crespo, A. and Pelkonen, V.-M. and Ristorcelli, I. and Steinacker, J. (2014) Dust properties inside molecular clouds from coreshine modeling and observations. Astronomy and Astrophysics, 572 . Art. No. A20. ISSN 0004-6361.

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Context. Using observations to deduce dust properties, grain-size distribution, and physical conditions in molecular clouds is a highly degenerate problem. Aims. The coreshine phenomenon, a scattering process at 3.6 and 4.5 µm that dominates absorption, has revealed its ability to explore the densest parts of clouds. We use this effect to constrain the dust parameters. The goal is to investigate to what extent grain growth (at constant dust mass) inside molecular clouds is able to explain the coreshine observations. We aim to find dust models that can explain a sample of Spitzer coreshine data. We also examine the consistency with near-infrared data we obtained for a few clouds. Methods. We selected four regions with a very high occurrence of coreshine cases: Taurus- Perseus, Cepheus, Chameleon, and L183/L134. We built a grid of dust models and investigated the key parameters to reproduce the general trend of surface brightnesses and intensity ratios of both coreshine and near-infrared observations with the help of a 3D Monte Carlo radiative transfer code. The grid parameters allowed us to investigate the effect of coagulation upon spherical grains up to 5 µm in size derived from the DustEm diffuse interstellar medium grains. Fluffiness (porosity or fractal degree), ices, and a handful of classical grain- size distributions were also tested. We used the near- and mostly mid-infrared intensity ratios as strong discriminants between dust models. Results. The determination of the background-field intensity at each wavelength is a key issue. In particular, an especially strong background field explains why we do not see coreshine in the Galactic plane at 3.6 and 4.5 µm. For starless cores, where detected, the observed 4.5 µm/3.6 µm coreshine intensity ratio is always lower than ~0.5, which is also what we find in the models for the Taurus- Perseus and L183 directions. Embedded sources can lead to higher fluxes (up to four times higher than the strongest starless core fluxes) and higher coreshine ratios (from 0.5 to 1.1 in our selected sample). Normal interstellar radiation-field conditions are sufficient to find suitable grain models at all wavelengths for starless cores. The standard interstellar grains are not able to reproduce observations and, because of the multiwavelength approach, only a few grain types meet the criteria set by the data. Porosity does not affect the flux ratios, while the fractal dimension helps to explain coreshine ratios, but does not seem able to reproduce near-infrared observations without a mix of other grain types. Conclusions. Combined near- and mid-infrared wavelengths confirm the potential of revealing the nature and size distribution of dust grains. Careful assessment of the environmental parameters (interstellar and background fields, embedded or nearby reddened sources) is required to validate this new diagnostic.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Paladini, R.0000-0002-5158-243X
McGehee, P. M.0000-0003-0948-6716
Noriega-Crespo, A.0000-0002-6296-8960
Pelkonen, V.-M.0000-0002-8898-1047
Additional Information:© 2014 ESO. Received 28 April 2014. Accepted 16 July 2014. Published online 20 November 2014. This research has made use of observations from Spitzer Space Telescope and data from the NASA/IPAC Infrared Science Archive, which are operated by the Jet Propulsion Laboratory (JPL) and the California Institute of Technology under contract with NASA. Based on observations obtained with WIRCam, a joint project of CFHT, Taiwan, Korea, Canada, France, and the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institute National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. 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. This research makes a large use of the CDS (Strasbourg, France) services, especially Aladin (Bonnarel et al. 2000), Simbad and Vizier (Ochsenbein et al. 2000) and of the NASA Lambda data base at GSFC. We thank J.-Ph. Bernard, Nathalie Ysard and Vincent Guillet for fruitful discussions, Michiel Min for providing us his agglomerates of monomers in advance of publication and the DIM ACAV and “Région Ile de France” for financial support. M.J. and V.-M.P. acknowledge the support of Academy of Finland grant 250741. M.A., J.S. acknowledge support from the ANR (SEED ANR-11-CHEX-0007-01). We thank the referee for the careful reading of our paper and the valuable comments.
Funding AgencyGrant Number
DIM ACAV “Région Ile de France”UNSPECIFIED
Academy of Finland250741
Agence Nationale pour la Recherche (ANR)SEED ANR-11-CHEX-0007-01
Subject Keywords:ISM: clouds; dust, extinction; infrared: ISM; radiative transfer
Record Number:CaltechAUTHORS:20150116-123218674
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Official Citation:Dust properties inside molecular clouds from coreshine modeling and observations C. Lefèvre, L. Pagani, M. Juvela, R. Paladini, R. Lallement, D. J. Marshall, M. Andersen, A. Bacmann, P. M. McGehee, L. Montier, A. Noriega-Crespo, V.-M. Pelkonen, I. Ristorcelli and J. Steinacker A&A 572 A20 (2014) DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:53832
Deposited By: Ruth Sustaita
Deposited On:17 Jan 2015 03:27
Last Modified:09 Mar 2020 13:19

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