Kinematical Analysis of a Sample of Bipolar Planetary Nebulae

TL;DR

This study analyzes the kinematics of various bipolar planetary nebulae, revealing velocity ranges and ages, and compares observations with theoretical models emphasizing magnetic fields and stellar rotation as collimation mechanisms.

Contribution

It provides empirical measurements of expansion velocities and inclination angles across diverse bipolar PNe, and validates theoretical models involving magnetic fields and stellar rotation.

Findings

Equatorial velocities are low to medium (3-16 km/s).

Polar velocities range from 18 to 100 km/s.

No nebulae are younger than approximately 1000 years.

Abstract

We present the kinematics of a sample of bipolar planetary nebulae (PNe) which cover a wide range of observed morphologies and collimation degrees, from bipolar PNe with a marked equatorial ring and wide lobes to highly collimated objects. We use an empirical model in order to derive the expansion velocity, collimation degree, and inclination angle of the PN with respect to the plane of the sky. The equatorial expansion velocities measured in the objects in our sample are always in the low to medium range (3-16km/s),while their polar expansion velocities range from low to very high (18-100 km/s). None of the objects in our sample, even those that show an extreme collimation degree, seem to be (kinematically) younger than ~1000 yr. We compare our results with the state-of-the-art theoretical models for the formation of bipolar PNe. We find good agreement between the observed expansion velocities and numerical models that use magnetic fields with stellar rotation as collimation mechanism.