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A. B. Peck (NRAO/NMIMT), G. B. Taylor (NRAO)
One of the most important problems in the study of active galaxies (AG) is understanding the detailed geometry, physics, and evolution of the central engines and their environments. The leading models involve an accretion disk and torus around a central dense object, thought to be a black hole. Much of this torus should be comprised of atomic gas, detectable in absorption toward the bright inner radio jets. The class of AG known as Compact Symmetric Objects (CSOs) is of particular importance because a very high fraction of these sources have detectable HI in the central parsecs. This HI can be observed using the VLBA with high enough angular resolution to map the velocity field of the circumnuclear gas. This velocity field provides important constraints on the models of the central engines in AG. In the few CSOs available for study thus far, the gas kinematics on parsec scales is complicated. All exhibit multiple components of HI absorption, and the width of the lines varies greatly. It is clear that a more comprehensive sample is required to fully understand the nature of the circumnuclear gas in these objects. We have identified ~10 new CSOs from radio continuum observations for the VLBA Calibrator Survey, increasing the number of known CSOs by about 50%.
We present VLBA images of these compact sources at several frequencies, as well as the spectral index maps which confirm their identification as CSOs.
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