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Register a new userALMA Band 3 polarimetric follow-up of a complete sample of faint PACO sources
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We present Atacama Large Millimeter/submillimiter Array (ALMA) high sensitivity ($sigma_P simeq 0.4,$mJy) polarimetric observations at $97.5,$GHz (Band 3) of a complete sample of $32$ extragalactic radio sources drawn from the faint Planck-ATCA Co-eval Observations (PACO) sample ($b<-75^circ$, compact sources brighter than $200,$mJy at $20,$GHz). We achieved a detection rate of $~97%$ at $3,sigma$ (only $1$ non-detection). We complement these observations with new Australia Telescope Compact Array (ATCA) data between $2.1$ and $35,$GHz obtained within a few months and with data published in earlier papers from our collaboration. Adding the co-eval GaLactic and Extragalactic All-sky Murchison widefield array (GLEAM) survey detections between $70,$ and $230,$MHz for our sources, we present spectra over more than $3$ decades in frequency in total intensity and over about $1.7$ decades in polarization. The spectra of our sources are smooth over the whole frequency range, with no sign of dust emission from the host galaxy at mm wavelengths nor of a sharp high frequency decline due, for example, to electron ageing. We do however find indications of multiple emitting components and present a classification based on the number of detected components. We analyze the polarization fraction behaviour and distributions up to $97,$GHz for different source classes. Source counts in polarization are presented at $95,$GHz.
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We present high sensitivity polarimetric observations in 6 bands covering the 5.5-38 GHz range of a complete sample of 53 compact extragalactic radio sources brighter than 200 mJy at 20 GHz. The observations, carried out with the Australia Telescope Compact Array (ATCA), achieved a 91% detection rate (at 5 sigma). Within this frequency range the spectra of about 95% of sources are well fitted by double power laws, both in total intensity and in polarisation, but the spectral shapes are generally different in the two cases. Most sources were classified as either steep- or peaked-spectrum but less than 50% have the same classification in total and in polarised intensity. No significant trends of the polarisation degree with flux density or with frequency were found. The mean variability index in total intensity of steep-spectrum sources increases with frequency for a 4-5 year lag, while no significant trend shows up for the other sources and for the 8 year lag. In polarisation, the variability index, that could be computed only for the 8 year lag, is substantially higher than in total intensity and has no significant frequency dependence.
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 $5sigma$) 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.
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We present SCUBA-2 follow-up of 61 candidate high-redshift Planck sources. Of these, 10 are confirmed strong gravitational lenses and comprise some of the brightest such submm sources on the observed sky, while 51 are candidate proto-cluster fields undergoing massive starburst events. With the accompanying Herschel-SPIRE observations and assuming an empirical dust temperature prior of $34^{+13}_{-9}$ K, we provide photometric redshift and far-IR luminosity estimates for 172 SCUBA-2-selected sources within these Planck overdensity fields. The redshift distribution of the sources peak between a redshift of 2 and 4, with one third of the sources having $S_{500}$/$S_{350} > 1$. For the majority of the sources, we find far-IR luminosities of approximately $10^{13},mathrm{L}_odot$, corresponding to star-formation rates of around $1000$ M$_odot mathrm{yr}^{-1}$. For $S_{850}>8$ mJy sources, we show that there is up to an order of magnitude increase in star-formation rate density and an increase in uncorrected number counts of $6$ for $S_{850}>8$ mJy when compared to typical cosmological survey fields. The sources detected with SCUBA-2 account for only approximately $5$ per cent of the Planck flux at 353 GHz, and thus many more fainter sources are expected in these fields.
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