Mathematics – Logic
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004aas...20514301d&link_type=abstract
American Astronomical Society Meeting 205, #143.01; Bulletin of the American Astronomical Society, Vol. 36, p.1584
Mathematics
Logic
Scientific paper
We have constructed a large sample of edge brightened, double lobed radio sources (FR2 hereafter), selected from the optical Sloan Digital Sky Survey Data Release 3 (DR3) preliminary quasar list and the FIRST radio survey. Unlike positional matching strictly on the quasar position, which would severely bias against lobe-dominated radio sources which do not happen to have a detected core component, we have used the actual radio environment of each quasar. Plausible radio source configurations are ranked according to the distance from the quasar position, component flux densities, and an inferred lobe opening angle. This ranking process does not care whether a radio core is present at the optical position, and is rather effective in picking up FR2 sources above the background. About 2% of our quasar sample of ˜ 50 000 have double lobed radio sources associated with them.
With this sample, which for the first time is large, unbiased, and uniform enough, we present new results on the occurrence of radio activity among quasars, the relative radio morphological make-up of the radio quasar population, and the implications the observed core-to-lobe flux density ratios have on unification models involving viewing angles. In addition, we present results correlating the (optical) environment of the quasar with the shape of the radio source; in particular the lobe-opening angle which tends to be 180 degrees in the unperturbed, straight case. We find, however, a significant fraction of our FR2 sample to be bent, with angles as small as 100 degrees.
Only with the advent of large scale surveys, like the SDSS and FIRST in this case, can we begin to address the nature of rare phenomena; rare either due to low levels of occurrence, or to their relatively short time-scales. The quasars and their associated radio emission are a prime example of this.
Becker Robert H.
de Vries Willem H.
White Richard L.
Xanthopoulos Emily
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