Polarization properties of OH emission in planetary nebulae

TL;DR

This study investigates the polarization and magnetic fields of OH emissions in planetary nebulae, revealing new detections, magnetic field estimates, and insights into early nebula evolution through polarization analysis.

Contribution

It provides the first interferometric polarization observations of OH in planetary nebulae, including new detections and magnetic field estimates, advancing understanding of early nebula magnetic properties.

Findings

Significant polarization detected in multiple nebulae.

Magnetic fields estimated between 0.8 and 24 mG.

New detection of 1720 MHz OH emission in Vy 2-2.

Abstract

We present interferometric, full-polarization observations of the four ground-state transitions of OH, toward five confirmed and one candidate OH-emitting planetary nebulae (OHPNe). OHPNe are believed to be very young PNe, and information on their magnetic fields (provided by their polarization) could be key to understand the early evolution of PNe. We detect significant circular and linear polarization in four and two objects, respectively. Possible Zeeman pairs are seen in JaSt 23 and IRAS 17393-2727, resulting in estimates of magnetic field strengths between 0.8 and 24 mG. We also report the new detection of OH emission at 1720 MHz toward Vy 2-2, making it the third known PN with this type of emission. We suggest that younger PNe have spectra dominated by narrow maser features and higher degrees of polarization. Shock-excited emission at 1720 MHz seems to be more common in PNe than in early evolutionary phases, and could be related to equatorial ejections during the early PN phase.