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[*] The Nuclei of Nearby Low Luminosity Radio Loud Galaxies
Xu C., Baum S.A., Verdoes Kleijn G.A., de Zeeuw P.T., O'Dea C.P., van der Marel R.P., Carollo C.M.
2000 (AAS Meeting 196, 62.04)
© 2000. The American Astronomical Society. All Rights Reserved.


We present results from a study of the nuclei of a complete sample of 21 nearby UGC low luminosity radio galaxies, using VLBA and VLA radio data and WFPC2 and STIS optical data (see also AAS abstracts Baum et al. and Verdoes Kleijn et al.).

The radio observations show that the sidedness distribution of the radio jets is consistent with Doppler boosting with a typical Lorentz factor gamma=5. The fading of the jets is consistent with adiabatic jet expansion losses. The optical imaging indicates that the galaxies typically resemble normal ellipticals except for the presence of small (approx. 1 arcsec) central disks or lanes of dust and emission gas. Disks have outlines which closely resemble ellipses, while lanes are warped filaments. Disks are invariably well aligned with the stellar major axis while lanes are not. We describe possible scenarios to explain these differences. Half of the nuclei show unresolved nuclear blue emission. We argue this is synchrotron emission from the inner jet. The STIS spectral observations form an on-going program. So far ten targets have been observed. Multiple-slit high resolution spectra are obtained to infer to what extent the emission gas moves on circular orbits, and hence provide a measurement of the mass of the central black hole. In a few cases low resolution spectra are obtained to determine emission-line ratios to constrain the ionization mechanism of the gas: photo- or shock-ionization.

Combining the results from radio and optical data we present preliminary results on: (1) the jet orientation, physics and bulk outflow speed of the radio plasma, (2) the relationship between black hole mass, radio luminosity, optical line and nuclear continuum fluxes, (3) limits on the mass accretion rate, (4) the relationship between BL Lac objects and low luminosity radio galaxies.


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Last modified October 9, 2000.
Roeland van der Marel, marel@stsci.edu.
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