Massive Expanding Torus and Fast Outflow in Planetary Nebula NGC 6302

• Published in: The Astrophysical journal 2008-02, Vol.673 (2), p.934-941
• Main Authors: Dinh-V-Trung, Bujarrabal, ValentÍn, Castro-Carrizo, Arancha, Lim, Jeremy, Kwok, Sun
• Format: Article
• Language: English
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/524373

We present interferometric observations of super(12)CO and super(13)CO J = 2 1 emission from the butterfly-shaped, young planetary nebula NGC 6302. The high angular resolution and high sensitivity achieved in our observations allow us to resolve the nebula into two distinct kinematic components: (1) a massive expanding torus seen almost edge-on and oriented in the north-south direction (roughly perpendicular to the optical nebula axis), which exhibits very complex and fragmented structure; and (2) high-velocity molecular knots moving at more than 20 km s super(-1) and located in the optical bipolar lobes. These knots show a linear position-velocity gradient (Hubble-like flow), which is characteristic of fast molecular outflow in young planetary nebulae. From the low but variable super(12)CO/ super(13)CO J = 2-1 line intensity ratio, we conclude that the super(12)CO J = 2 1 emission is optically thick over much of the nebula. Using the optically thinner line super(13)CO J = 2-1, we estimate a total molecular gas mass of similar to 0.1 M [unk], comparable to the ionized gas mass; the total gas mass of the NGC 6302 nebula, including the massive ionized gas from the photon dominated region, is found to be similar to 0.5 M [unk]. From radiative transfer modeling, we infer that the torus is seen at an inclination angle of 75 degree with respect to the plane of the sky, and is expanding at a velocity of 15 km s super(-1). Comparison with recent observations of molecular gas in NGC 6302 is also discussed.