Starburst Evolution on the IRAS–Color Diagram

Summary

ABSTRACT

In order to study effects of the starburst activity on far-infrared (FIR) colors, we have constructed starburst models which are able to trace FIR color evolution of starburst activity.

INTRODUCTION

The IRAS mission discovered that FIR emission properties of galaxies are significantly altered by starburst activity. Therefore, the FIR properties of galaxies are used to study the nature of starburst activity, in principle. Since, however, it is difficult to know properties of dust grains unambiguously, little effort has been made to construct starburst models which are able to reproduce FIR properties of galaxies (cf. Rowan-Robinson 1992). We here present a simple starburst model capable for calculating FIR emission of starburst galaxies.

MODEL AND RESULTS

The infrared continuum emission comes from dust grains embedded in ionized gas and from those in molecular clouds. The large grains are in thermal equilibrium with the radiation field and radiate as a blackbody with an emissivity Q_λ ∝ λ^-1. On the other hand, small grains are heated transiently by single UV photons. In our model, emission at 12 and 25 μm mainly comes from small grains in the molecular clouds and large grains in the ionized gas, while emission at 60 and 100 μm comes from large grains in the molecular clouds. The basic concept of our model was given in Mouri and Taniguchi (1992). Our new model is now able to calculate FIR emission from 12 to 100 μm directly and to trace the full phase of starburst evolution. Detailed description will be given elsewhere.