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Institut für Astronomie und Astrophysik

Abteilung Astronomie

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Preprint Kd/98

Principal components analysis of a sample of radio-loud AGN - radio, optical and X-ray properties

Fabian Rother and Rüdiger Staubert

Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Waldhäuser Str. 64, D-72076 Tübingen, Germany

1999, Highlights in X-ray Astronomy, ed. B. Aschenbach, MPE Report, in press

Abstract. We have analyzed a sample of 160 radio-loud quasars and BL Lac objects (alpha_ro > 0.4) detected in pointed ROSAT/PSPC observations using a principal components analysis (PCA). We find that 85% of the variations of the radio, optical and X-ray properties (luminosities, spectral indices, fluxes, broadband spectral indices, redshift) can be explained by the first two principal components: the luminosity of the central engine (accretion rate and mass of the central black hole) and the combined spectral form in the radio and X-ray energy band. Additionally, we find that flat radio spectrum objects have a flatter X-ray spectrum than steep radio spectrum objects and that their difference in alpha_x is independent of redshift.

Key words: -

Paper (40k gzip'ed Postscript including figures)

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Jürgen Barnstedt (barnstedt AT astro.uni-tuebingen.de)
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