Monte Carlo Radiative Transfer in Prestellar Cores & Protostellar Disks

Details Monte Carlo Radiative Transfer in Prestellar Cores & Protostellar Disks Monte Carlo Radiative Transfer in Prestellar Cores & Protostellar Disks

Nov 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003phdt........17s&link_type=abstract

Ph.D. Thesis, University of Wales, Cardiff, 2003

Statistics

Computation

2

Radiative Transfer, Monte Carlo, Star Formation, Prestellar Cores, Protostellar Disks, Computational Methods

Scientific paper

We implement a Monte Carlo radiative transfer method with frequency distribution adjustment (PHAETHON), and use it to study prestellar cores and protostellar disks.The code calculates temperature profiles, SEDs and isophotal maps, that can be directly compared to observations.
We find that the temperature profiles in embedded prestellar cores are less steep than those in non-embedded cores. Deeply embedded cores (in ambient clouds with visual extinctions larger than 15-25) are almost isothermal at around 7-8 K. The temperatures inside cores in ambient molecular clouds of even moderate thickness (Av~5) are less than 12 K, which is lower than what previous studies have assumed. Thus, previous mass calculations of embedded cores (e.g. in ρ Oph) based on millimetre continuum observations, may underestimate core masses by up to a factor of 2.
We also find that the SEDs of slightly asymmetric cores are essentially independent of the viewing angle. However, the isophotal maps depend strongly on the viewing angle. At submm and mm wavelengths cores appear elongated when viewed close to edge-on. At wavelengths near the peak of the core emission (150-250 micron) the isophotal maps are strongly affected by the core temperature; there are characteristic features on these maps which depend on the observer's viewing angle, and on the detailed density and temperature structure of the core.
We extend PHAETHON to treat the radiative transfer in systems with arbitrary geometries resulting from Smoothed Particle Hydrodynamics (SPH) simulations. We use the SPH tree to construct radiative transfer cells that interact with the radiation, with a procedure that creates cells with linear size on the order of the SPH resolution. We apply this method to study GM Aurigae, a T Tauri star with a circumstellar disk. We examine the case of an axisymmetric disk and the case of a non-axisymmetric, perturbed disk and find that both models are consistent with the observed SED of the system.

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