arXiv:0708.0428

Date: Thu, 2 Aug 2007 22:04:48 GMT (241kb)

Title: Progress Toward a VLBA Movie of the Jet Collimation Region in M87

Authors: R. C. Walker, C. Ly, W. Junor and P. E. Hardee

Categories: astro-ph

Comments: 7 pages, 3 figures. To be published in the proceedings of
"Extragalactic Jets: Theory and Observation from Radio to Gamma Ray", eds. T.
A. Rector and D. S. De Young (ASP Conf. Ser.)

\\
With its high black hole mass, proximity, and bright jet, M87 provides the
best prospect for a direct imaging study of the acceleration and collimation
region of a jet. Previous VLBI observations have shown an edge brightened
structure with a wide opening angle at small scales. An effort to measure
component speeds in this region using existing VLBA data at 43 GHz gave
tentative results of 0.25c to 0.4c but also indicated that faster sampling is
needed. Here we provide a progress report on a project to make a properly
sampled movie of motions in the inner jet using the VLBA at 43 GHz. A pilot
project during 2006 measured speeds of about 0.6c and was used to set a frame
interval of 3 weeks for the movie. The movie observations began in January
2007. Results from the pilot and from the first frame of the movie are
presented. The goal of the project is to provide observations of the structure
and dynamics of the jet on scales from under 100 to a few hundred Schwarzschild
radii that can be compared with expectations from theoretical studies and
numerical modeling.

\\ ( http://arxiv.org/abs/0708.0428 , 241kb)