NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-26 T03:29:12 PDT
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For refcode 2006A&A...445..465R:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
2006A&A...445..465R High-frequency radio observations of the Kuhr sample and the epoch-dependent luminosity function of flat-spectrum quasars R. Ricci, I. Prandoni, C. Gruppioni, R. J. Sault and G. De Zotti Received 8 July 2005 / Accepted 6 September 2005 We discuss our ATCA 18.5 and 22 GHz flux density measurements of Southern extragalactic sources in the complete 5 GHz sample of Kuhr et al. (1981, A&AS, 45, 367). The high frequency (5-18.5 GHz) spectral indices of steep-spectrum sources for which we have 18.5 GHz data (66% of the complete sample) are systematically steeper than the low frequency (2.7-5 GHz) ones, with median {alpha}^5^_2.7_ = 0.76, median {alpha}^18.5^_5_ = 1.18 ( S_{nu} is proportional to_ {nu}^-^{alpha}), and median steepening {DELTA}{alpha} = 0.32, and there is evidence of an anti-correlation of {DELTA}{alpha}^18.5^_5_ with luminosity. The completeness of 18.5 GHz data is much higher (89%) for flat-spectrum sources (mostly quasars), which also exhibit a spectral steepening: median {alpha}^5^_2.7_=-0.14, median {alpha}^18.5^_5_ = 0.16 ( S_{nu} is proportional to_ {nu}^-^{alpha}), and median {DELTA}{alpha} = 0.19. Taking advantage of the almost complete redshift information on flat-spectrum quasars, we have estimated their 5 GHz luminosity function in several redshift bins. The results confirm that their radio luminosity density peaks at z_peak_ ~= 2.5 but do not provide evidence for deviations from pure luminosity evolution as hinted at by other data sets. A comparison of our 22 GHz flux densities with WMAP K-band data for flat-spectrum sources suggests that WMAP flux densities may be low by a median factor of ~= 1.2. The extrapolations of 5 GHz counts and luminosity functions of flat-spectrum radio quasars using the observed distribution of the 5-18.5 GHz spectral indices match those derived directly from WMAP data, indicating that the high frequency WMAP survey does not detect any large population of FSRQs with anomalous spectra. Key words: radio continuum: general, galaxies: nuclei, quasars: general, galaxies: luminosity function, mass function
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