We present AAO/UKST Hα+[N II] narrow-band imagery and low- and medium-resolution optical spectroscopy of RCW24 and RCW69. These nebulae were previously classified as HII 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 RCW24 and 1.3 ± 0.2 kpc for RCW69. Both objects have enhanced nitrogen abundances, with log N/O≃+0.44 for RCW24, and log N/O =+0.33 for RCW 69. Systemic velocities and |z| distances are VLSR = +5 kms⁻¹ and |z| ~23 pc for RCW 24, and VLSR = −33 km s⁻¹ and only |z| ~7 pc for RCW 69. Both PNe originated from massive progenitors (>2.0–2.5M⊙), 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.
- stars, AGB and post-AGB
- planetary nebulae