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T. Nakazato, T. Nakamoto, M. Umemura (Center for Computational Physics, University of Tsukuba)
Deeply embedded young stellar objects (Class I objects) are thought to be in the first phase of planetary system formation. To study the structure of the Class I objects is helpful to understand the initial stage of the planetary system formation. However, the inclination of the system, which is an essential factor to reveal their structure, cannot be obtained easily. That is one of reasons why the structure of Class I objects is not understood well yet. Here we propose a new method to determine the inclination of the Class I objects.
We numerically modeled the Class I objects. Our model, which employed the two-dimensional axisymmetric approximation, consisted of four components; a central star, a protoplanetary disk, an envelope surrounding the former two components, and a cavity in the envelope excavated by an outflow. We numerically solved the radiative equilibrium state in the system and obtained model SEDs. We found that the apparent luminosity of the Class I objects, L\rm app, which is evaluated from the frequency integral of an SED, depends strongly on the inclination, while the peak flux, (\nu L\nu)\rm max, depends on it weakly. Thus, the ratio of the apparent luminosity to the peak flux, fL \equiv L\rm app / (\nu L\nu) \rm max, which is almost independent of the intrinsic luminosity, is a good indicator of the inclination, although it also depends on the angle of the outflow cavity, \theta\rm bp. We provide here a relation between the inclination and the outlow cavity angle as a function of the ratio fL. If the outflow cavity angle is known, it is possible to infer the inclination of the object using the relation. And \theta\rm bp is an observable. Thus, our method is applicable to determining the inclination.
The author(s) of this abstract have provided an email address for comments about the abstract: nakazato@rccp.tsukuba.ac.jp