VLA Observations of Compact Symmetric Objects

Compact symmetric objects (CSOs) are a type of radio source less than 1 kpc in size with symmetrical jet emission. They are important to study because they may have the ability to strongly influence their host galaxies and may emit radio lobes periodically through multiple epochs of activity, which can be seen on >1 kpc scales. However, they are often confused for compact steep spectrum (CSS) and gigahertz-peaked spectrum (GPS) sources in the literature due to their similarities with these types of sources and the ease of classifying them by spectra rather than morphology. To develop a more comprehensive catalog of CSOs, we have searched through about 200 publications for mentions of CSOs, CSSs, and GPSs and classified over 2000 sources as confirmed CSOs, candidates worth VLBI followup, candidates not worth followup, or rejected sources. Using the Very Large Array (VLA), we observed about 220 sources, which consists of the candidates worth VLBI followup plus some additional less likely candidate sources. In addition to using the VLA to learn more about the larger scale structure of these potential CSOs, since CSOs generally possess the ideal properties of phase calibrators at arcsecond scales, this information can be included in the VLA calibrator manual.