Radiative transfer through inhomogeneous molecular clouds and its implications
Abstract
This thesis seeks to calculate and describe how starlight penetrates clumpy interstellar molecular clouds. The ubiquity of stellar radiation, turbulent gas clouds and strongly extincting dust in our Galaxy and beyond guarantees that a basic understanding of the effects of clumpiness on interstellar radiative transfer will be useful, especially in a more detailed treatment of the interstellar physics which depends on radiation. Developing a somewhat novel Reverse Monte Carlo radiative transfer method we find that realistic clumpiness (supersonic magnetohydrodynamical turbulence) leads to a radically different intracloud radiation field compared to those found in simpler geometries. After describing its basic statistical properties we apply the radiative transfer results to grain heating, modelling dust emission from objects similar to the Perseus and Ophiucus molecular clouds. Comparing these synthetic data with real observational data we clarify the need for more thorough reduction methods if accurate cloud masses and the detection of subtle physical effects are desired. Staying with dust, we calculate the alignment of grains via radiative torques, and the subsequent polarized sub-mm signal from magnetized molecular clouds and prestellar cores. We find that detectable polarization degrees are theoretically possible, stressing the need for multi-wavelength sub-mm polarimetry. Turning to astrochemistry we find much enhanced photoionization rates in clumpy clouds, which we then incorporate into large time-dependent parametric chemical models. We begin to describe a rather different (photo- driven) chemistry than is expected from homogeneous cloud modelling, illustrating its effects by considering the ionization fraction which is so important for the formation of stars.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 2006
- Bibcode:
- 2006PhDT........22B
- Keywords:
-
- Radiative transfer;
- Molecular clouds;
- Star formation;
- Astronomy, Astrophysics, Radiation