Broadband Radio Spectra of Star-forming Galaxies
Abstract
Simple models of radio spectra for star forming galaxies are unsatisfactory. Calorimeter models of the radio-infrared correlation predict a spectral aging break below 1 GHz. Simple free-free absorption models predict steep low-frequency turndowns in the spectra of strongly star-forming galaxies (such as ULIRGs). To investigate this, we have combined previous data with 74 MHz data from the VLSS to derive broad-band spectra (30 MHz to 10 GHz) of a large set of both normal spirals and strongly starbursting galaxies. We find significant disagreement between these simple models and the observed spectra. The spectra of many galaxies are consistent a single power-law spectrum over the entire frequency range; a few spectra do show low-frequency flattening, but not nearly enough to agree with the simple models. We will discuss how these spectra correlate with the size and power of the galaxy. We will discuss possible new models of the observed spectra, which incorporate inhomogeneities in the galaxy's magnetic field and absorbing column.
- Publication:
-
American Astronomical Society Meeting Abstracts #213
- Pub Date:
- January 2009
- Bibcode:
- 2009AAS...21341802M