Far-infrared astronomy at TIFR

Abstract

The balloon-borne far-infrared (FIR) telescopes built at TIFR have led to new scientific results in fields as diverse as (a) planetary atmosphere, (b) Galactic star forming regions, and (c) extragalactic studies. These include precise measurement of FIR brightness temperature of Saturn, leading to new information about its atmosphere. High angular resolution FIR mappings of Galactic sources associated with H II region-molecular cloud complexes have given new information about structure and energetics of young (e.g. W31 complex) as well as evolved (e.g. Carina complex) star forming regions. Whereas the young regions are dominated by embedded energy sources, the evolved ones have more of externally heated dust clouds. The wavelength dependence of the dust emissivity in southern H II regions RCW 57 and RCW 122, is substantially flatter than that found for normal H II regions. A study of the two Seyfert galaxies NGC 4945 and Circinus, which have several properties in common, shows opposite behaviours in the FIR. While the Circinus galaxy exhibits only central emission, NGC 4945 shows considerable extended emission originating from cooler dust.