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Published July 2008 | Published
Journal Article Open

Multiwavelength studies of the gas and dust disc of IRAS 04158+2805

Abstract

We present a study of the circumstellar environment of IRAS 04158+2805 based on multi-wavelength observations and models. Images in the optical and near-infrared, a polarisation map in the optical, and mid-infrared spectra were obtained with VLT-FORS1, CFHT-IR, and Spitzer-IRS. Additionally we used an X-ray spectrum observed with Chandra. We interpret the observations in terms of a central star surrounded by an axisymmetric circumstellar disc, but without an envelope, to test the validity of this simple geometry. We estimate the structural properties of the disc and its gas and dust content. We modelled the dust disc with a 3D continuum radiative transfer code, MCFOST, based on a Monte-Carlo method that provides synthetic scattered light images and polarisation maps, as well as spectral energy distributions. We find that the disc images and spectral energy distribution narrowly constrain many of the disc model parameters, such as a total dust mass of 1.0−1.75 × 10^-4 M☉ and an inclination of 62°−63°. The maximum grain size required to fit all available data is of the order of 1.6−2.8 μm although the upper end of this range is loosely constrained. The observed optical polarisation map is reproduced well by the same disc model, suggesting that the geometry we find is adequate and the optical properties are representative of the visible dust content. We compare the inferred dust column density to the gas column density derived from the X-ray spectrum and find a gas-to-dust ratio along the line of sight that is consistent with the ISM value. To our knowledge, this measurement is the first to directly compare dust and gas column densities in a protoplanetary disc.

Additional Information

© ESO 2008. Received 24 May 2006. Accepted 14 April 2008. This work is based in part on archival data obtained 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 in part by an award issued by JPL/Caltech and in part by Programme National de Physique Stellaire (PNPS) of CNRS/INSU (France). We are grateful to Sylvain Bontemps for obtaining the CFHTIR images presented here and to Jérome Bouvier for performing their basic data reduction. The CXC X-ray Observatory Center is operated by the Smithsonian Astrophysical Observatory for and on behalf of the NASA under contract NAS8-03060.

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August 22, 2023
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