OPACOS: OVRO Post-AGB CO (1-0) Emission Survey. I. Data and Derived Nebular Parameters

Abstract

We have performed interferometric observations of the ¹²CO (J = 1-0) emission in a sample of 27 objects spanning different evolutionary stages from the late asymptotic giant branch (late-AGB), through the post-AGB (pAGB) phase, and to the planetary nebula (PN) stage, but dominated by pAGB objects and young PNs (>=81%). In this paper (the first in a series) we present our maps and main nebular properties derived for the whole sample. Observations were performed with the Caltech Millimeter Array at the Owens Valley Radio Observatory. The angular resolution obtained in our survey ranges between 2farcs3 and 10farcs7. The ¹³CO and C¹⁸O (J = 1-0) transitions as well as the 2.6 mm continuum emission have also been observed in several objects. The detection statistics in the ¹²CO, ¹³CO, C¹⁸O transitions and 2.6 mm continuum are 89%, 83%, 0%, and 37%, respectively. We report first detections of ¹²CO (J = 1-0) emission in 13 targets and confirm emission from several previous marginal detections. The molecular envelope probed by ¹²CO (J = 1-0) emission is extended for 18 (out of 24) sources; envelope asymmetries and/or velocity gradients are found in most extended objects. Our data have been used to derive accurate target coordinates and systemic velocities and to characterize the envelope size, morphology, and kinematics. We also provide an estimate of the total molecular mass and the fraction of it contained in fast flows, lower limits to the linear momentum and to the isotopic ¹²C/¹³C ratio, as well as the AGB mass-loss rate and timescale for sources with extended CO emission.