A 22 GHz Baseline VLBI Survey of 142 AGN

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Session 8 -- Surveys and Cosmology
Display presentation, Monday, June 12, 1995, 9:20am - 6:30pm

[8.03] A 22 GHz Baseline VLBI Survey of 142 AGN

George Moellenbrock (Brandeis), Kenta Fujisawa (ISAS), R. Preston (JPL), L. Gurvits (JIVE/NFRA/ASC), R. Dewey (JPL/Princeton), H. Hirabayashi (ISAS), M. Inoue (NRO), D. Jauncey, V. Migenes (ATNF), D. Roberts (Brandeis), R. Schilizzi (JIVE/Leiden), S. Tingay (JPL/MSSS), A. Zensus (NRAO)

A sample of 142 compact (i.e., flat- or inverted-spectrum: $\alpha>-0.5$, $F_{\nu} \sim \nu ^\alpha$) active galactic nuclei with ${\delta > -40\deg}$ and 22 GHz total flux ${F_{22} > 1}$ Jy have been observed on baselines of 4400--10800 km (340--830 million wavelengths at 22 GHz) using NASA's 70m Deep Space Network antennas in Australia and California, Japan's 45m Nobeyama and 34m Kashima antennas, and the NRAO's 25m Mauna Kea and Brewster Very Long Baseline Array antennas. With an average of 7 4-minute scans per source, each source was observed on as many as three simultaneous baselines per scan. Structure information (for sources where sufficient data exists) on scales of $\sim$200--600 ${\mu}$as and lower limits on brightness temperature have been derived. This ``Pre-Launch Survey'' of 22 GHz correlated fluxes (visibilities for 95 sources) should prove useful in planning for mm-VLBI experiments and the low-sensitivity, high-brightness temperature limits of baselines to small orbiting antennas such as VSOP, a Japanese Space VLBI mission scheduled for launch in mid-late 1996. In addition, these results provide valuable observational data for statistical studies of AGN. Of particular interest is the prominence in this survey of the blazars that have been detected in $\gamma$-rays by CGRO/EGRET (e.g., see von Montigny {\it{et al.}}, 1995).

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