Yu Fung Wong   (Hong Kong)

yu-fung.wong @ mpi-hd.mpg.de

The effects of cosmic-rays on the diffuse interstellar medium

Expanding on the existing radiative transfer models of the UV spectral energy distributions of starlight in spiral galaxies, I am constructing a self-consistent model to predict the spectral line emission from the diffuse cold interstellar medium (ISM), with a new software to calculate the photoelectric heating of the diffuse ISM, considering both the intensity and the spectral shape of the ambient radiation field. Lines considered will be radio tracer lines of neutral and molecular hydrogen gas, as well as the principal far-infrared cooling lines (e.g. CO lines, OI line). In particular, the effects of cosmic-rays on the efficiency of photoelectric heating in the ISM will be investigated (as they influence the electric charges of dust grains by collisional charging).
The goal is to predict the axisymmetric mass distribution of hydrogen in the diffuse ISM in spiral galaxies. In addition, considering the strength of the HeII line, I will place observational constraints on the flux of low energy cosmic-rays of galactic origin.

Supervisor:    Richard Tuffs   (MPIK)