Two new evolved bipolar planetary nebulae in the solar neighbourhood

We present AAO/UKST H alpha+[N II] narrow-band imagery and low- and medium-resolution optical spectroscopy of RCW 24 and RCW 69. These nebulae were previously classified as H II regions, but we now show them to be two of the largest and nearest bipolar Type I PNe yet discovered. Distances were estimated using extinction-distance and kinematic methods, and via a new H alpha surface brightness-radius relation. The adopted distances are 1.0 +/- 0.3 kpc for RCW 24 and 1.3 +/- 0.2 kpc for RCW 69. Both objects have enhanced nitrogen abundances, with log N/O similar or equal to +0.44 for RCW 24, and log N/O = +0.33 for RCW 69. Systemic velocities and vertical bar z vertical bar distances are V-LSR= +5 km s(-1) and vertical bar z vertical bar similar to 23 pc for RCW 24, and V-LSR = -33 km s(-1) and only vertical bar z vertical bar similar to 7 pc for RCW 69. Both PNe originated from massive progenitors (> 2.0-2.5 M-circle dot), as deduced from their chemical abundances, large ionized masses, small vertical bar z vertical bar distances, low peculiar velocities and relatively hot central stars. These two objects form an important addition to the small sample of evolved bipolar PNe in the solar neighbourhood.