J/ApJ/732/45 VLA fluxes for AT20G radio galaxies (Sajina+, 2011)
High-frequency radio spectral energy distributions and polarization fractions of sources in an Atacama Cosmology Telescope survey field. Sajina A., Partridge B., Evans T., Stefl S., Vechik N., Myers S., Dicker S., Korngut P. <Astrophys. J., 732, 45 (2011)> =2011ApJ...732...45S
ADC_Keywords: Active gal. nuclei ; Galaxies, radio ; Radio continuum ; Polarization Keywords: galaxies: active - galaxies: jets - radio continuum: galaxies Abstract: We present flux densities and polarization percentages of 159 radio galaxies based on nearly simultaneous Very Large Array observations at four frequencies, 4.86, 8.46, 22.46, and 43.34GHz. This sample is selected from the high-frequency Australia Telescope 20GHz (AT20G) survey and consists of all sources with flux density S20GHz>40mJy in an equatorial field of the Atacama Cosmology Telescope (ACT) survey. For a subset of 25 of these sources, we used the Green Bank Telescope (GBT) to obtain 90GHz data. We find that, as expected, this sample consists of flatter spectrum and more compact or point-like sources than low-frequency-selected samples. In the K band, variability is typically ≲20%, although there are exceptions. The higher frequency data are well suited to the detection of extreme gigahertz peak spectrum sources. The inclusion of the 43GHz data causes the relative fraction of inverted spectrum sources to go down and of peaked spectrum sources to go up when compared with the AT20G survey results. The trend largely continues with the inclusion of the 90GHz data, although ∼10% of the sources with GBT data show a spectral upturn from 43GHz to 90GHz. The measured polarization fractions are typically <5%, although in some cases they are measured to be up to ∼20%. For sources with detected polarized flux in all four bands, about 40% of the sample, the polarization fractions typically increase with frequency. This trend is stronger for steeper spectrum sources as well as for the lower flux density sources. Description: Measurements in all four spectral bands were made at default VLA frequencies, centered at 43.34, 22.46, 8.46, and 4.86GHz. These are the Q, K, X, and C bands, respectively. The observations for the bulk of the sample were scattered over an interval from 2008 June 19 to September 6. For about one-third of the sample, the Q-band observations were made later on 2009 November 3 and 4. We also re-observed these sources in the K band in order to be able to estimate the level of variability between these two observing epochs (separated by 14-15 months). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 128 247 Flux densities and polarization percentages for the 159 radio galaxies table4.dat 49 25 GBT 90GHz measured and extrapolated fluxes
See also: J/ApJ/731/100 : 148GHz ACT extragalactic sources catalog (Marriage+, 2011) J/ApJ/718/587 : The Fermi-AT20G catalog (Mahony+, 2010) J/MNRAS/402/2403 : AT20G Survey Catalog (Murphy+, 2010) J/MNRAS/384/775 : Bright Source Sample of AT20G Survey (Massardi+, 2008) Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 14 A14 --- AT20G Source name (JHHMMSS+DDMMSS or HHMM+DDM for 3 calibrators) (1) 16 A1 --- m_AT20G [CJT] Source flag (C=Core, J=Jet, T=Total) (2) 18- 22 F5.3 --- z ? Redshift 24- 29 F6.1 mJy SC ? C band (4.86GHz) flux density 31- 34 F4.1 mJy e_SC ? Uncertainty in SC (3) 36- 41 F6.1 mJy SX ? X band (8.46GHz) flux density 43- 46 F4.1 mJy e_SX ? Uncertainty in SX (3) 48- 53 F6.1 mJy SK ? K band (22.46GHz) flux density 55- 58 F4.1 mJy e_SK ? Uncertainty in SK (3) 60- 65 F6.1 mJy SQ ? Q band (43.34GHz) flux density 67- 70 F4.1 mJy e_SQ ? Uncertainty in SQ (3) 72 A1 --- l_pC Limit flag on pC 74- 78 F5.2 % pC ? C band (4.86GHz) polarization fraction 80- 82 F3.1 % e_pC ? Uncertainty in pC (3) 84 A1 --- l_pX Limit flag on pX 85- 90 F6.3 % pX ? X band (8.46GHz) polarization fraction 92- 94 F3.1 % e_pX ? Uncertainty in pX (3) 96 A1 --- l_pK Limit flag on pK 98-102 F5.2 % pK ? K band (22.46GHz) polarization fraction 104-106 F3.1 % e_pK ? Uncertainty in pK (3) 108 A1 --- l_pQ Limit flag on pQ 110-115 F6.2 % pQ ? Q band (43.34GHz) polarization fraction 117-119 F3.1 % e_pQ ? Uncertainty in pQ (3) 121-128 A8 --- Class Class (GPS (GHz peak spectrum), Inverted or Upturned)
Note (1): The bulk of these data were taken in the Summer and early Fall of 2008 (see Table1 of the paper). For the subset of sources with K and Q-band observations in November 2009, these flux densities and polarization percentages are listed just below the 2008 values for the same source. Note (2): The jet(or lobe) photometry is quoted for J094123-014251, since for this source the northern jet corresponds to the AT20G position (see Figure 1). Note (3): The quoted uncertainties are the quadrature sum of the AIPS IMFIT fitting uncertainty (which is typically slightly larger than the rms) and our estimated systematic uncertainty. For the flux densities is the flux calibration uncertainty, which is equal to 1% for the C band, 0.7% for the X-band, 0.8% for the K-band, and 1% for the Q-band. For the polarization percentages we estimate an uncertainty (based on the measured spread in polarization of our calibrator sources) of 8% in the C-band, 6% in the X-band, 10% in the K-band and 8% in the Q-band.
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 14 A14 --- AT20G Source name (JHHMMSS+DDMMSS) 16- 21 F6.1 mJy S90m 90GHz measured flux 23- 27 F5.1 mJy e_S90m S90m uncertainty 29- 34 F6.1 mJy S90e ? 90GHz extrapolated flux (VLA SK) based on αKQ spectral index 36- 38 F3.1 --- Ratio [0.3/3]? Ratio of measured-to-expected flux densities 40- 45 F6.1 mJy S90e2 ? 90GHz extrapolated flux (SKx1.24) (1) 47- 49 F3.1 --- R2 [0.3/3.8]? Second ratio
Note (1): Our K-band flux densities may be underestimated compared with the AT20G survey flux densities. We test the effect of this by multiplying our K-band values by the median offset from the AT20G values, 1.22, and re-extrapolate to 90GHz. See section 6.7 for further explanations.
History: * 25-Oct-2012: From electronic version of the journal * 20-Dec-2012: Fixed 4 names in table4 to match those of table3! J073025-024125 J102834-023659 J121622-010753 J235725-015214
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 25-Oct-2012
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