Radio Supernovae as Distance Indicators

Long-term monitoring of the radio emission from supernovae with the VeryLarge Array (VLA) shows that the radio ``light curves'' evolve in a systematicfashion with a distinct peak flux density (and thus, in combination with adistance, a peak spectral luminosity) at each frequency and a well-defined timefrom explosion to that peak. Studying these two quantities at 6 cm wavelength,peak spectral luminosity (L_{6 cm peak}) and time after explosion date (t_0) toreach that peak (t_{6 cm peak} - t_0), we find that they appear related. Inparticular, based on two objects, Type Ib supernovae may be approximate radio``standard candles'' with a 6 cm peak luminosity L_{6 cm peak} \approx 19.9 X10^{26} erg s^{-1} Hz^{-1}; also based on two objects, Type Ic supernovae maybe approximate radio ``standard candles'' with a 6 cm peak luminosity L_{6 cmpeak} \approx 6.5 X 10^{26} erg s^{-1} Hz^{-1}; and, based on twelve objects,Type II supernovae appear to obey a relation L_{6 cm peak} \simeq 5.5 X 10^{23}(t_{6 cm peak} - t_0)^{1.4} erg s^{-1} Hz^{-1}, with time measured in days. Ifthese relations are supported by further observations, they provide a means fordetermining distances to supernovae, and thus to their parent galaxies, frompurely radio continuum observations.Comment: 31 pages, including 3 PostScript figures. To appear in the Astrophysical Journal (1998 June 10 issue