1999MNRAS.307..481C

We present the results of radio continuum observations of the interacting galaxies NGC 4490 and 4485. Observations have been made in the B-, C- and D-array configurations of the VLA at 1.49, 4.86 and 8.44GHz, and with the Ryle Telescope at 15.2GHz. The radio continuum maps have been fitted with a model spectrum consisting of an aged synchrotron and a thermal component, and have been decomposed into maps of each component. We find that the data are consistent with a high, ongoing star formation rate over the entire disc of NGC 4490, and that the electron age across NGC 4490 is consistent with a scenario in which NGC 4490 has been undergoing star formation at a constant rate for at least 10⁸yr. Combined with other evidence, we suggest that NGC 4490 is a young galaxy with an age of approximately 2x10⁹yr, and that it has had an approximately constant star formation rate during this period equal to the current rate of ∼4.7M_☉.yr^–1. Furthermore, the effects of the interaction have not had sufficient time to affect the star formation rate in NGC 4490 significantly, although NGC 4485 has been severely affected by the interaction.