Physical Structure of Planetary Nebulae. Iii. the Large and Evolved Ngc 1360

NGC1360 is a large planetary nebula (PN) without an obvious shell morphology. We have analyzed Hα images and high-dispersion echelle spectra of NGC1360 in order to construct spatio-kinematic models and to determine its density distribution. The best-fit model indicates that NGC 1360 is a prolate ellipsoidal shell whose major axis is twice as long as its minor axis and is tilted by 60 with respect to the line of sight. The large kinematic age of the shell, ∼10,000 yr, and the low density of the nebula, ≤130 H-atom cm, imply that NGC1360 is an evolved PN and has begun to merge with the interstellar medium. The observed morphology and surface brightness profiles of NGC1360 can be described well as a thick shell with a Gaussian radial density profile without a sharp inner edge, indicating a lack of on-going compression by a fast stellar wind. The FLIERs observed in NGC1360 near the end of its major axis expand faster and are younger than the nebular shell. Subject headings: ISM: kinematics and dynamics – ISM: planetary nebulae: general – planetary nebulae: individual (NGC1360)