Radio Supernovae as Distance Indicators

Abstract

Long-term monitoring of the radio emission from supernovae with the Very Large Array (VLA) shows that the radio "light curves" evolve in a systematic fashion with a distinct peak flux density (and thus, in combination with a distance, a peak spectral luminosity) at each frequency and with a well-defined time from explosion to that peak. Studying these two quantities at 6 cm wavelength, peak spectral luminosity (L6 cm peak), and time after explosion date (t0) to reach that peak (t6 cm peak - t0), we find that they appear related. In particular, based on two objects, Type Ib supernovae may be approximate radio "standard candles" with a 6 cm peak luminosity of L6 cm peak ≈ 19.9 × 1026 ergs s-1 Hz-1; also, based on two objects, Type Ic supernovae may be approximate radio standard candles with a 6 cm peak luminosity of L6 cm peak ≈ 6.5 × 1026 ergs s-1 Hz-1; and, based on 12 objects, Type II supernovae appear to obey a relation L6 cm peak ≃ 5.5 × 1023(t6 cm peak - t0)1.4 ergs s-1 Hz-1, with time measured in days. If these relations are supported by further observations, they provide a means for determining distances to supernovae, and thus to their parent galaxies, from purely radio continuum observations. With currently available sensitivity of the VLA, it is possible to employ these relations for objects further than the Virgo Cluster out to ~100 Mpc. With planned improvements to the VLA and the possible construction of more sensitive radio telescopes, these techniques could be extended to z ~ 1 for some classes of bright radio supernovae.