4 years ago

Characterization of polarimetric and total intensity behaviour of a complete sample of PACO radio sources in the radio bands.

Elisabetta Liuzzo, Marcella Massardi, Rosita Paladino, Jamie Stevens, Marco Tucci, Ronald David Ekers, Carlo Burigana, Anna Bonaldi, Laura Bonavera, Roberto Ricci, Viviana Casasola, Vincenzo Galluzzi, Luigi Toffolatti, Matteo Bonato, Joseph Russell Callingham, Marcos Lopez-Caniego, Tiziana Trombetti, Sperello di Serego Alighieri, Loretta Gregorini, Gianfranco De Zotti

We present high sensitivity ($\sigma_P \simeq 0.6\,$mJy) polarimetric observations in seven bands, from $2.1$ to $38\,$GHz, of a complete sample of $104$ compact extragalactic radio sources brighter than $200\,$mJy at $20\,$GHz. Polarization measurements in six bands, in the range $5.5-38\,$GHz, for $53$ of these objects were reported by \citet{Galluzzi2017}. We have added new measurements in the same six bands for another 51 sources and measurements at $2.1\,$GHz for the full sample of $104$ sources. Also, the previous measurements at $18$, $24$, $33$ and $38\,$GHz were re-calibrated using the updated model for the flux density absolute calibrator, PKS1934-638, not available for the earlier analysis. The observations, carried out with the Australia Telescope Compact Array (ATCA), achieved a $90\%$ detection rate (at $5\sigma$) in polarization. $89$ of our sources have a counterpart in the $72$ to $231\,$MHz GLEAM survey \citep{HurleyWalker2017}, providing an unparalleled spectral coverage of $2.7$ decades of frequency for these sources. While the total intensity data from $5.5$ to $38\,$GHz could be interpreted in terms of single component emission, a joint analysis of more extended total intensity spectra presented here, and of the polarization spectra, reveals that over $90\%$ of our sources show clear indications of at least two emission components. We interpret this as an evidence of recurrent activity. Our high sensitivity polarimetry has allowed a $5\,\sigma$ detection of the weak circular polarization for $\sim 38\%$ of the dataset, and a deeper estimate of $20\,$GHz polarization source counts than has been possible so far.

Publisher URL: http://arxiv.org/abs/1711.05373

DOI: arXiv:1711.05373v1

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