Probing dust grain evolution in IM Lupi's circumstellar disc

Multi-wavelength observations and modelling of the dust disc

¹ School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK e-mail: pinte@astro.ex.ac.uk
² Laboratoire d'Astrophysique de Grenoble, CNRS/UJF UMR 5571, 414 rue de la Piscine, BP 53, 38041 Grenoble Cedex 9, France
³ Spitzer Science Center, Caltech, Pasadena, CA 91125, USA
⁴ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
⁵ Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
⁶ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
⁷ Astronomy Dept, UC Berkeley, Berkeley CA 94720-3411, USA
⁸ Division of Geological and Planetary Sciences 150-21, California Institute of Technology, Pasadena, CA 91125, USA
⁹ Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1562, USA
¹⁰ Eureka Scientific and Goddard Space Flight Center, Code 667, Greenbelt, MD 20771, USA
¹¹ The University of Texas at Austin, Department of Astronomy, 1 University Station C1400, Austin, Texas 78712–0259, USA
¹² Max Planck Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
¹³ Eureka Scientific, Inc., NC Branch, 113 Castlefern Dr., Cary, NC 27513, USA
¹⁴ Space Science Institute, Corrales NM, 87048, USA
¹⁵ University of Kiel, Institute of Theoretical Physics and Astrophysics, Leibnizstrasse 15, 24098 Kiel, Germany
¹⁶ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
¹⁷ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany

Received: 4 May 2008
Accepted: 28 July 2008

Abstract

Aims. We present a panchromatic study, involving a multiple technique approach, of the circumstellar disc surrounding the T Tauri star IM Lupi (Sz 82).

Methods. We have undertaken a comprehensive observational study of IM Lupi using photometry, spectroscopy, millimetre interferometry and multi-wavelength imaging. For the first time, the disc is resolved from optical and near-infrared wavelengths in scattered light, to the millimetre regime in thermal emission. Our data-set, in conjunction with existing photometric data, provides an extensive coverage of the spectral energy distribution, including a detailed spectrum of the silicate emission bands. We have performed a simultaneous modelling of the various observations, using the radiative transfer code MCFOST, and analysed a grid of models over a large fraction of the parameter space via Bayesian inference.

Results. We have constructed a model that can reproduce all of the observations of the disc. Our analysis illustrates the importance of combining a wide range of observations in order to fully constrain the disc model, with each observation providing a strong constraint only on some aspects of the disc structure and dust content. Quantitative evidence of dust evolution in the disc is obtained: grain growth up to millimetre-sized particles, vertical stratification of dust grains with micrometric grains close to the disc surface and larger grains which have settled towards the disc midplane, and possibly the formation of fluffy aggregates and/or ice mantles around grains.