21.02.2013 Views

Gas Disks and Supermassive Black Holes in Nearby Radio Galaxies

Gas Disks and Supermassive Black Holes in Nearby Radio Galaxies

Gas Disks and Supermassive Black Holes in Nearby Radio Galaxies

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

2.2.1 <strong>Radio</strong> properties<br />

<strong>Radio</strong> observations of the sample galaxies were obta<strong>in</strong>ed us<strong>in</strong>g both the Very Large Ar-<br />

ray (VLA; Wrobel, et al., <strong>in</strong> preparation) <strong>and</strong> the Very Large Basel<strong>in</strong>e Array (VLBA),<br />

descriptions of the radio morphology are given for each galaxy <strong>in</strong> §3.4. Xu et al. (2000)<br />

report the results of a program us<strong>in</strong>g the VLBA to observe 17 of the UGC FR-I sam-<br />

ple galaxies at 1.67 GHz. At a resolution of ∼ 10 × 4 mas, five galaxies showed only<br />

an unresolved radio core, 10 galaxies showed core-jet structures, <strong>and</strong> two galaxies<br />

showed tw<strong>in</strong>-jet structures. Compar<strong>in</strong>g the VLBA jets (on parsec scales) to the VLA<br />

jets (on kiloparsec scales) they found that the VLBA <strong>and</strong> VLA jets are well aligned<br />

<strong>and</strong> that the jet-to-counterjet surface brightness ratios, or the sidedness, decreases<br />

systematically with <strong>in</strong>creas<strong>in</strong>g distance along the jet. Xu et al. (2000) attribute the<br />

sidedness of the jets to the Doppler boost<strong>in</strong>g effect, <strong>and</strong> its decl<strong>in</strong>e to the deceleration<br />

of the jets.<br />

2.2.2 Optical properties<br />

A photometric analysis of the nuclei of the UGC FR-I sample galaxies was performed<br />

by Verdoes Kleijn et al. (1999), based on observations made us<strong>in</strong>g the WFPC2 <strong>in</strong>-<br />

strument on board HST (the photometric analyses of UGC 7115 <strong>and</strong> UGC 12064 are<br />

29

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!