dust is but a small fraction of the mass of a galaxy yet it plays a crucial role in galactic evolution. we are well aware of how dust influences our observations of distant stars and how easily dust may mislead us with regard to the way in which stars are distributed within the galaxy, but how does it affect our view of other galaxies ? until recently most astromomers would have said that dust has very little effect on our understanding of the global properties of galaxies, but this view has changed dramatically now that better radiative transfer models and observational data are available. the major problem we intend to solve with the proposed observations is what is the fraction of stellar flux in galaxies which is reprocessed through dust ?. this is the dust opacity problem and at the moment opinions vary enormously as to the typical value of the optical depth, and how influential this issue is with regard to our understanding of galaxies. we feel that the decisive observation is to measure the contribution cold (<20k) dust makes to the fir output of galaxies and how this dust is distributed within galaxies. we plan to map at 200u a sample of 24 (22) nearby galaxies (about 20 hrs of observation) which are large enough to give some information on the spatial distribution of cold dust. our chosen sample have resolved iras 60 and 100u data. if galaxies have high opacities they must emit a large fraction of their bolometric luminosity in the fir part of the spectrum. these observations specificaly address issues such as the correlations among galaxy global properties, hidden mass, absorption of high z qso.s and primeval galaxies, tully-fisher correlations, gas-to-dust gas-to-stars ratios and the .starburst. and hidden agn phenomona.
Instrument
PHT32
Temporal Coverage
1996-10-20T16:53:41Z/1998-01-31T22:03:02Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the worlds first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
European Space Agency, DAVIES et al., 1999, 'THE DIFFUSE FIR EMISSION FROM SPIRAL GALAXIES', 1.0, European Space Agency, https://doi.org/10.5270/esa-hprnrgc
