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Description
The Planck-ATCA Co-eval Observations (PACO) project collected data between 4.5 and 40 GHz for 482 sources selected within the Australia Telescope 20-GHz (AT20G) catalog and observed with the Australia Telescope Compact Array (ATCA). Observations were done almost simultaneously with the Planck satellite, in the period between 2009 July and 2010 August. In this paper, the authors present and discuss the data for the complete sample of 159 sources with AT20G flux densities > 200 mJy in the South Ecliptic Pole (SEP) region. The Planck Early Release Compact Source Catalogue (ERCSC) contains 57 of their sources. A comparison between the PACO catalog and the ERCSC confirms that the reliability of the latter is better than 95%. The missing ERCSC sources are typically associated with the Large Magellanic Cloud, the Milky Way or are otherwise extended. The spectral analysis of the PACO faint catalog shows a spectral steepening of the sources at high frequencies, confirming the results obtained from the PACO bright sample (the HEASARC PACOBSCAT table). A comparison with AT20G measurements, carried out, on average, a few years earlier, has demonstrated that, on these time-scales, these sources show a rather high variability with an rms amplitude of approximately 40% at 20 GHz. The source spectral properties are found not to vary substantially with flux density, except for an increase in the fraction of steep spectrum sources at fainter flux densities. These data also allow the authors to extend by a factor of ~ 5 downwards in flux density the source counts at ~ 33 and ~ 40 GHz obtained from the ERCSC. This allows the authors to substantially improve their control on the contribution of unresolved extragalactic sources to the power spectrum of small-scale fluctuations in cosmic microwave background (CMB) maps. The PACO faint sample, presented in this paper, is made up of 159 sources with 20-GHz flux densities >= 200 mJy in the SEP region (ecliptic latitude < -75 degrees) and with 3h < RA < 9h, Dec. < -30 degrees. Near the Ecliptic Poles, Planck's scan circles intersect. Therefore, the area is covered many times, and Planck's sensitivity is maximal in these regions. A full description of the PACO project and of its main goals is given in Massardi et al. (2011, MNRAS, 415, 1597). The aims specific to the PACO faint sample are as follows: (i) Extend to fainter flux densities the characterization of radio source spectra from 4.5 GHz to the Planck frequency range; (ii) Extend the determination of source counts at ~ 33 and ~ 40 GHz obtained from the analysis of the ERCSC downwards in flux density by a factor of ~ 5. Going down in flux density is important to control the contamination of CMB maps by faint radio sources. This table contains the catalog of 674 observations of 152 of the 159 sources that comprise the 'faint PACO sample'. Thus, each row in this table corresponds to a specific observation of a source, and there can be several rows for any source, corresponding to different observations. The ATCA observations were made in 6 2-GHz wide observing bands: 4732 - 6780 MHz, 8232 - 10280 MHz, 17232 - 19280 MHz, 23232 - 25280 MHz, 32232 - 34280 MHz and 38232 - 40280 MHz. In order to properly define the detailed source spectral behavior, the authors have split each 2-GHz band into 4 x 512 MHz sub-bands, and calibrated each sub-band independently. Thus, for each observation, the flux density at 24 frequencies is given. The frequency identifier in the flux density appears (at least to this HEASARC scientist) to be the lower frequency of the sub-band rather than its central frequency. In order to provide the easiest way to extrapolate the observed counts or model predictions from one frequency to another, the authors have modeled the observed source spectra. As their observations covered a wide frequency range from 4.5 to 40 GHz over which a single power law is not enough to describe the spectral behavior of the sources, they studied the spectra of the 174 point-like sources in this sample by fitting the observed data with a double power law of the form S<sub>nu</sub> = S<sub>0</sub>/[(nu/nu<sub>0</sub>)<sup>-a</sup> + (nu/nu<sub>0</sub>)<sup>-b</sup>], where nu is the frequency, S<sub>nu</sub> is the flux density in Jy, and S<sub>0</sub>, nu<sub>0</sub>, a and b are free parameters. The authors considered only those sources for which they had at least four data points for each of the 2 x 2 GHz bands considered. When observations at more than one epoch were available, the authors chose the one with the greatest number of data points. Full details of the fitting procedure are given in Section 3.1 of Massardi et al. (2011, MNRAS, 415, 1597) and Section 4 of the reference paper. This table was created by the HEASARC in January 2014 based on the machine-readable version of the Paco faint catalog from the reference paper which was obtained from the CDS (their catalog J/MNRAS/416/559 file catalog.dat). This is a service provided by NASA HEASARC .
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