Constraining the Evolutionary Path of the Youngest Radio Galaxies Using Radio Morphology

Jordan Collier (University of Western Sydney)

We have observed the largest faint population of Gigahertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sources to date, using the Australia Telescope Compact Array, in order to: (1) test the hypothesis that GPS/CSS sources are the youngest radio galaxies; (2) place GPS/CSS sources into an evolutionary sequence along with a number of other young AGN candidates; and (3) search for evidence of the evolving accretion mode and its relationship to star formation (SF). GPS/CSS sources have very small radio jets, which grow in linear size as they evolve. In the radio, GPS sources are generally

To achieve our goals, we combine high-resolution radio observations with redshifts to determine the linear size of GPS/CSS sources, resolve their jets and observe their small-scale morphology. We combine this with other multi-wavelength age indicators, including the separation of nuclei, the colours and Spectral Energy Distribution of the host galaxy, the optical spectra, the electron age of the jet and luminosity functions, to see if they can be assembled into a self-consistent model. Future Very Large Baseline Interferometry (VLBI) observations will separate AGN from distributed SF, to help pinpoint the transition between SF and AGN activity caused by the merger, and perhaps even measure their timescales.

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