Two new evolved bipolar planetary nebulae in the solar neighbourhood

We present AAO/UKST Hα+[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 Hα 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 ≃ +0.44 for RCW 24, and log N/O = +0.33 for RCW 69. Systemic velocities and |z| distances are V LSR =+5  km s⁻¹ and |z| ∼ 23 pc for RCW 24, and V LSR =−33  km s⁻¹ and only |z| ∼ 7 pc for RCW 69. Both PNe originated from massive progenitors (>2.0–2.5 M ⊙ ), as deduced from their chemical abundances, large ionized masses, small |z| 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.