Radiative Transfer in Cloudy Galaxies: Evolution of Far-IR Luminosity

A. N. Witt & K. D. Gordon 1996, in "Unveiling the Cosmic Infrared Background", (AIP Conference Proc. No. 348), ed. E. Dwek (NY: AIP Press), 230

The partial absorption of stellar radiation and its re-emission as thermal radiation by interstellar grains in galaxies is the principal process by which galaxies become important emitters of far-infrared and sub-millimeter radiation. The efficiency of conversion, given a fixed amount of dust with set optical properties, depends largely upon the distribution of the dust relative to the illuminating sources. Within the same basic geometry, it is the structure of the dust-carrying ISM which determines ultimately the ratio of observed far-IR to UV/optical luminosities of galaxies. We report on new multiple scattering radiative transfer calculations for galactic environments with two-phase clumpy media, which are compared with observations of samples of isolated and interacting/merging galaxies. We conclude that in addition to starbursts occurring in the latter sample, changes in the structure of the interstellar media in interacting galaxies contribute to their high far-IR luminosity with a near normal mass of interstellar matter. The changing structure of the ISM in galaxies over time is an important factor in the evolution of far-IR luminosity function of galaxies.

[Preprint]