Forbidden Fe+ emission from supernova remnants in M33

Supernovae remnants are known to be luminous sources of infrared [FeII]emission. By studying how the luminosity scales with age, environment and otherrelevant factors, we can construct an [FeII] luminosity function for supernovaeremnants. This will enable us to predict supernovae rates in starburst galaxiesthat are too distant for individual remnants to be resolved. First, however, werequire accurate luminosities for a sample of remnants of varying ages, and invarying physical environments. As part of this project we have carried out aninitial study of a small sample of evolved (ages greater than a few thousandyears) remnants in M33. From these data we tentatively conclude that there isevidence for the peak luminosity in the [FeII] lines of these sources to arisein a narrow range of ages. In other respects, the M33 remnants are similar totheir galactic and Magellanic Cloud counterparts in the observed peakluminosity. From this, and internal evidence as to the environment present inthese regions, we conclude that the luminosity of evolved remnants is onlymarginally dependent on density and metallicity.Comment: 12 pages, uuencoded compressed postscript. Also available as postscript file from ftp://aaoepp.aao.gov.au/local/sll/snr.ps Accepted for publication in Monthly Notices of the Royal Astronomical Societ