Core radio and optical emission in nearby FR I radio galaxies

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Title: Core radio and optical emission in nearby FR I radio galaxies
Author: Kleijn, Gijs; Baum, Stefi; de Zeeuw, P. Tim; O'Dea, Christopher
Abstract: In this paper we analyze the relation between radio, optical continuum and Ha +[N ii] emission from the cores of a sample of 21 nearby Fanaroff and Riley type I galaxies as observed with the VLBA and HST. The emission arises inside the inner tens of parsecs of the galaxies. Core radio emission is observed in 19/20 galaxies, optical core continuum emission is detected in 12/21 galaxies and Ha+[N ii] core emission is detected in 20/21 galaxies. We confirm the recently detected linear correlation between radio and optical core emission in FR I galaxies and show that both core emissions also correlate with central Ha+[N ii] emission. The tight correlations between radio, optical, and Ha+[N ii] core emission constrain the bulk Lorentz factor to y~ 2–5 and y <~ 2 for a continuous jet and a jet consisting of discrete blobs, respectively, assuming jet-viewing angles in the range 30° –90° . Radio and optical core emissions are likely to be synchrotron radiation from the inner jet, possibly with a significant contribution from emission by an accretion disk and/or flow. Elliptical galaxies with LINER nuclei without large-scale radio jets seem to follow the core emission correlations found in FR I galaxies. This suggests that the central engines could be very similar for the two classes of active galactic nuclei (Refer to PDF file for exact formulas).
Description: Also archived in: arXiv: astro-ph/0112356 v2 18 Dec 2001
Record URI: http://hdl.handle.net/1850/1777
Date: 2002-03

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