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25th of January 2016
The AT20G visibility-spectra diagnostic plot
by Rajan Chhetri (UNSW)
The AT20G high frequency survey selects a very high fraction of active galactic nuclei (AGNs) compared to surveys at lower frequencies. The 6-km interferometer visibility using the 6 km antenna of the ATCA can be used to obtain angular resolution information on sources (Y-axis on the right). The catalogue of 6-km visibilities for AT20G sources published as the AT20G high-angular-resolution catalogue (Chhetri, Ekers, Jones and Ricci 2013). The synergistic combination of the spectral index information for the sources with the 6-km visibility gives the diagnostic plot above that can be used to clearly identify different populations of radio sources. Notable are the sources on the bottom right labelled "flat-spectrum extended sources". Combining the radio data with infrared data from WISE a number of galactic and extragalactic thermal sources (mostly planetary nebula) have been identified (details published in Chhetri, Ekers, Kimball, Miszalski, Cohen and Manick 2015). The remaining sources in this region may be either gravitational lenses or binary black hole AGNs.

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