PACO spectrally selected sample

The Planck Australia Telescope Compact Array (Planck-ATCA) Co-eval Observations (PACO) have provided multi-frequency (5-40GHz) flux density measurements of complete samples of Australia Telescope 20GHz (AT20G) radio sources at frequencies below and overlapping with Planck frequency bands, almost simultaneously with Planck observations. In this work we analyse the data in total intensity for the spectrally selected PACO sample, a complete sample of 69 sources brighter than S20GHz=200mJy selected from the AT20G survey catalogue to be inverted or upturning between 5 and 20GHz.

We study the spectral behaviour and variability of the sample. We use the variability between AT20G (2004-2007) and PACO (2009-2010) epochs to discriminate between candidate High-Frequency Peakers (HFPs) and candidate blazars. The HFPs picked up by our selection criteria have spectral peaks >10GHz in the observer frame and turn out to be rare (<0.5% of the S20GHz>=200mJy sources), consistent with the short duration of this phase implied by the "youth" scenario.