66 research outputs found
A Study of Quasar Radio Emission from the VLA FIRST Survey
Using the most recent (1998) version of the VLA FIRST survey radio catalog,
we have searched for radio emission from 1704 quasars taken from the most
recent (1993) version of the Hewitt and Burbidge quasar catalog. These quasars
lie in the ~5000 square degrees of sky already covered by the VLA FIRST survey.
Our work has resulted in positive detection of radio emission from 389 quasars
of which 69 quasars have been detected for the first time at radio wavelengths.
We find no evidence of correlation between optical and radio luminosities for
optically selected quasars. We find indications of a bimodal distribution of
radio luminosity, even at a low flux limit of 1 mJy. We show that radio
luminosity is a good discriminant between radio loud and radio quiet quasar
populations, and that it may be inappropriate to make such a division on the
basis of the radio to optical luminosity ratio. We discuss the dependence of
the radio loud fraction on optical luminosity and redshift.Comment: 33 pages LaTeX, 10 figures, 2 tables. Accepted in the Astronomical
Journa
Seyfert 1 composite spectrum using SDSS Legacy survey data
We present a rest-frame composite spectrum for Seyfert 1 galaxies using spectra obtained from the 12th Data Release of the Sloan Digital Sky Survey. The spectrum is constructed by combining data from a total of 10112 galaxies, spanning a redshift range of 0β0.793. We produce an electronic table of the median and geometric mean composite Seyfert 1 spectrum. We measure the spectral index of the composite spectrum, and compare it with that of the composite quasar spectrum. We also measure the flux and width of the strong emission lines present in the composite spectrum. We compare the entire spectrum with the quasar spectrum in the context of the unification model for active galactic nuclei. The two composite spectra match extremely well in the blue part of the spectrum, while there is an offset in flux in the red portion of the spectrum
Seyfert 1 composite spectrum using SDSS Legacy survey data
We present a rest-frame composite spectrum for Seyfert 1 galaxies using spectra obtained from the 12th Data Release of the Sloan Digital Sky Survey. The spectrum is constructed by combining data from a total of 10112 galaxies, spanning a redshift range of 0β0.793. We produce an electronic table of the median and geometric mean composite Seyfert 1 spectrum. We measure the spectral index of the composite spectrum, and compare it with that of the composite quasar spectrum. We also measure the flux and width of the strong emission lines present in the composite spectrum. We compare the entire spectrum with the quasar spectrum in the context of the unification model for active galactic nuclei. The two composite spectra match extremely well in the blue part of the spectrum, while there is an offset in flux in the red portion of the spectrum
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