Molecular and ionized gas in the central part of the bipolar planetary nebula NGC 6302

Naomi Hirano, Tatsuhiko Hasegawa, Francisca Kemper, Hyosun Kim, Mikako Matsuura, Oscar Morata, Alfonso Trejo-Cruz, Ronny Zhao-Geisler & Albert A. Zijlsyra

ASIAA, Taiwan

NGC 6302 is a remarkable planetary nebula (PN) with a butterfly shape. The central region of this PN was imaged in the 13CO 2-1, C18O 2-1, SO 56-45, H30alpha, and 1.3 mm continuum with the ALMA at an angular resolution of ~0.7". The 1.3 mm continuum and H30alpha images show a ring-like structure with a size of ~5" (6,000 AU) x 3" (3500 AU) near the base of the eastern lobe. The geometrical center of this ring does not coincide with the location of the central star, but is located at ~2" NE from the star. The 13CO image reveals four distinct kinematic features; (1) an expanding ring having a radius of ~7" (8200 AU) and a width of ~1" (1200 AU) at the waist of the nebula, 2) the outer limbs of the bipolar lobes, 3) several bullets moving outward, and 4) filamentary structures moving outward in the optical lobes. The expanding ring is also seen in the maps of C18O and SO. In all molecular lines, the southern part of the ring is missing. The molecular ring is inclined by ~75 deg. from the plane of the sky, and is expanding at a velocity of ~9 km/s. The timescale of this ring is estimated to be ~4300 yr. A comparison between molecular and ionized rings suggests that the location of the ionized ring corresponds to the inner edge of the molecular ring. The southern part of the molecular ring is missing probably because of the effect of ionization.

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