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Twenty-two early type galaxies that were detected by IRAS have been searched for continuum emission at millimeter and submillimeter wavelengths using the JCMT. IRAS was relatively insensitive to cold dust that emits primarily at these longer wavelengths. In this first survey we were able to detect or achieve useful limits on the emission from 14 of the 22 galaxies observed.
The observed flux densities were combined with the IRAS measurements from Knapp et al (1989) to obtain estimates of the dust temperatures. The JCMT beamsize is 15 to 18 arcsec depending on wavelength, while the IRAS beamsizes are much bigger (approximately 2 and 4 arcminutes for the 60 and 100 micron points). Since the emission curves are normalized to the JCMT flux densities that come from a much smaller area on the sky the temperatures determined are upper limits to the true dust temperatures. The dust temperatures can be combined with our submillimeter flux densities to estimate dust masses. Since the temperatures are upper limits the dust masses inferred are lower limits to the actual dust masses within each entire galaxy.
These results are compared to HI and CO data and to the blue luminosities of the galaxies. The results are consistent with a model where the dust to gas ratio is similar to the Galactic one and the amount of cold dust is an order of magnitude greater than the amount of warm dust (as is also seen in our Galaxy). However the total dust mass, normalized to the the luminosity of the entire galaxy, is much lower than is found in spiral galaxies, as expected.
