
%0 Journal Article
%A Francis, Paul J 
%A Webster, Rachel L 
%A Whiting, Matthew T 
%T The optical/near-IR colours of red quasars
%J Publications of the Astronomical Society of Australia
%D 2000/04/01
%V 17
%N 1
%P 56-71
%K 
%R https://doi.org/10.1071/AS00056
%U https://www.publish.csiro.au/paper/AS00056 
%X We present quasi-simultaneous multi-colour optical/near-IR photometry for 157 radio selected quasars, forming an unbiassed sub-sample of the Parkes Flat-Spectrum Sample. Data are also presented for 12 optically selected QSOs, drawn from the Large Bright QSO Survey. The spectral energy distributions of the radio- and optically-selected sources are quite different. The optically selected QSOs are all very similar: they have blue spectral energy distributions curving downwards at shorter wavelengths. Roughly 90% of the radio-selected quasars have roughly power-law spectral energy distributions, with slopes ranging from F_nu propotional to nu^0 to F_nu proportional to nu^-2. The remaining 10% have spectral energy distributions showing sharp peaks: these are radio galaxies and highly reddened quasars. Four radio sources were not detected down to magnitude limits of H ~ 19.6. These are probably high redshift (z >3) galaxies or quasars. We show that the colours of our red quasars lie close to the stellar locus in the optical: they will be hard to identify in surveys such as the Sloan Digital Sky Survey. If near-IR photometry is added, however, the red power-law sources can be clearly separated from the stellar locus: IR surveys such as 2MASS should be capable of finding these sources on the basis of their excess flux in the K-band. 
