Investigating the Radio Continuum - Star Formation Relation in Nearby Galaxies

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The Interstellar Medium (ISM) of star-forming galaxies is pervaded with cosmic ray electrons. They move at relativistic speeds and lose their energy in the form of synchrotron emission in the ever present magnetic field which is frozen in with the ISM. The recent, vast increase in sensitivity of radio interferometers now offers the prospect of using the radio continuum (RC) emission from normal star forming galaxies as a proxy for the spatially resolved star formation rate (SFR), virtually bypassing any of the extinction issues that plague optical/UV observations. Once properly calibrated, a non-thermal radio continuum - SFR relation will provide a robust, unbiased, extinction free tool for characterising the SFR in both the Local Universe and at high redshift. Moreover, detailed observations at multiple wavelengths across the radio part of the electromagnetic spectrum can be used to to improve our understanding of the physical origin of synchrotron emission and the various energy loss mechanisms involved. In this project, sensitive, multi wavelength, high-resolution observations using the VLA of a sample of 4 nearby spiral galaxies taken from the THINGS survey will be analysed. These VLA observations will be combined with ancillary data including H-alpha, 24um, and the FUV to separate the radio continuum emission into its thermal and non-thermal components and compare these to the SFR. These results will be used to calibrate the RC-SFR relation on a resolved basis on scales from 200 to 700 pc, explore the equipartition magnetic field properties of the galaxies, and the intrinsic scatter in the RC-SFR relation.