The warped nuclear disk of radio galaxy 3C 449
Date
2006Author
Tremblay, Grant
Quillen, Alice
Floyd, David
Noel-Storr, Jacob
Baum, Stefi
Axon, David
O'Dea, Christopher
Chiaberge, Marco
Macchetto, Duccio
Sparks, William
Miley, George
Capetti, Alessandro
Madrid, Juan
Perlman, Eric
Metadata
Show full item recordAbstract
Among radio galaxies containing nuclear dust disks, the bipolar jet axis is generally observed to be perpendicular to the disk major axis. The FR I radio source 3C 449 is an outlier to this statistical
majority, as it possesses a nearly parallel jet/disk orientation on the sky. We examine the 600 pc dusty disk in this galaxy with images from the Hubble Space Telescope. We find that a 1.6 µm/0.7 µm colormap of the disk exhibits a twist in its isocolor contours (isochromes). We model the colormap by integrating galactic starlight through an absorptive disk, and find that the anomalous twist in the isochromes can be reproduced in the model with a vertically thin, warped disk. The model predicts that the disk is nearly perpendicular to the jet axis within 100 pc of the nucleus. We discuss physical mechanisms capable of causing such a warp. We show that precessional models or a torque on the disk arising from a possible binary black hole in the AGN causes precession on a timescale that is
too long to account for the predicted disk morphology. However, we estimate that the pressure in the X-ray emitting interstellar medium is large enough to perturb the disk, and argue that jet-driven anisotropy in the excited ISM may be the cause of the warp. In this way, the warped disk in 3C 449 may be a new manifestation of feedback from an active galactic nucleus. (Refer to PDF file for exact formulas).