A parameter study of self-consistent disk models around Herbig AeBe stars

TL;DR

This study explores how various parameters affect the structure and spectral energy distribution of protoplanetary disks around Herbig AeBe stars, emphasizing the dominant role of small dust mass in disk classification.

Contribution

It provides a comprehensive parameter study of self-consistent disk models, highlighting the continuous nature of the transition between flaring and self-shadowed disks based on small dust mass.

Findings

Small dust mass is the key parameter influencing SED classification.

No natural dichotomy exists between Group I and II disks; transition is continuous.

Moderate grain growth weakens the 1um spectral feature, affecting observational interpretation.

Abstract

We present a parameter study of self-consistent models of protoplanetary disks around Herbig AeBe stars. We use the code developed by Dullemond and Dominik, which solves the 2D radiative transfer problem including an iteration for the vertical hydrostatic structure of the disk. This grid of models will be used for several studies on disk emission and mineralogy in followup papers. In this paper we take a first look on the new models, compare them with previous modeling attempts and focus on the effects of various parameters on the overall structure of the SED that leads to the classification of Herbig AeBe stars into two groups, with a flaring (group I) or self-shadowed (group II) SED. We find that the parameter of overriding importance to the SED is the total mass in grains smaller than 25um, confirming the earlier results by Dullemond and Dominik. All other parameters studied have only minor influences, and will alter the SED type only in borderline cases. We find that there is no natural dichotomy between group I and II. From a modeling point of view, the transition is a continuous function of the small dust mass. We also show that moderate grain growth produces spectra with weak or no 1um feature, both for flaring (Group I) and non-flaring (Group II) sources. The fact that sources with weak features have been found mostly in Group I sources is therefore surprising and must be due to observational biases or evolutionary effects.