EDP Sciences
Free access
Issue
A&A
Volume 408, Number 1, September II 2003
Page(s) 161 - 169
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20030734


A&A 408, 161-169 (2003)
DOI: 10.1051/0004-6361:20030734

The effect of scattering on the structure and SED of protoplanetary disks

C. P. Dullemond and A. Natta

Max-Planck-Institut für Astrophysik, Postfach 1317, 85741 Garching, Germany
    e-mail: dullemon@mpa-garching.mpg.de Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
(Received 30 January 2003 / Accepted 12 May 2003)

Abstract
In this paper we investigate how the inclusion of scattering of the stellar radiation into a passive flaring disk model affects its structure and spectral energy distribution, and whether neglecting it could significantly decrease the model reliability. In order to address these questions we construct a detailed 1+1D vertical structure model in which the scattering properties of the dust can be varied. Models are presented with and without dust scattering, and for different albedos and phase functions. It is found that scattering has the effect of reducing the disk temperature at all heights, so that the disk "shrinks", i.e., the density at all intermediate heights decreases. However, this effect in most cases is more than compensated by the increase of the total extinction (absorption + scattering) cross section, so that the surface scale height increases, and images in scattered light will see a slightly thicker disk. The integrated infrared emission decreases as the albedo increases, because an increasing part of the flux captured by the disk is reflected away instead of absorbed and reprocessed. The reduction of the infrared thermal emission of the disk is stronger at short wavelengths (near infrared) and practically negligible at millimeter wavelengths. For relatively low albedo ( $\omega\lesssim 0.5$), or for strongly forward-peaked scattering ( g roughly >0.8), the infrared flux reduction is relatively small.


Key words: accretion, accretion disks -- stars: circumstellar matter -- stars: formation stars: pre-main-sequence -- infrared: stars

Offprint request: C. P. Dullemond, dullemon@mpa-garching.mpg.de




© ESO 2003