Spatially resolved spectroscopy of planetary nebulae and their halos I. Five galactic disk objects

TL;DR

This study uses integral field spectroscopy to analyze the physical properties of halos around planetary nebulae in the galactic disk, providing new insights into mass loss processes during the late stages of stellar evolution.

Contribution

It is the first study to apply integral field spectroscopy to planetary nebula halos, improving data analysis techniques and correcting for observational effects to better understand mass loss.

Findings

Detected halos around planetary nebulae IC3568 and M2-2.

Measured halo radius of M2-2 to be 2.5 times larger than previously known.

Enhanced data analysis methods reduced errors in temperature measurements.

Abstract

Strong mass loss off stars at the tip of the asymptotic giant branch (AGB) profoundly affects properties of these stars and their surroundings, including the subsequent planetary nebula (PN) stage. With this study we wanted to determine physical properties of mass loss by studying weakly emitting halos, focusing on objects in the galactic disk. Halos surround the, up to several thousand times, brighter central regions of PNe. Young halos, specifically, still contain information of the preceeding final mass loss stage on the AGB. In the observations we used the method of integral field spectroscopy with the PMAS instrument. This is the first committed study of halos of PNe that uses this technique. We improved our data analysis by a number of steps. In a study of the influence of scattered light we found that a moderate fraction of intensities in the inner halo originate in adjacent regions. As we combine line intensities of distant wavelengths, and because radial intensity gradients are steep, we corrected for effects of differential atmospheric refraction. In order to increase the signal-to-noise of weak emission lines we introduced a dedicated method to bin spectra of individual spatial elements. We also developed a general technique to subtract telluric lines - without using separate sky exposures. By these steps we avoided introducing errors of several thousand Kelvin to our temperature measurements in the halo. For IC3568 we detected a halo. For M2-2 we found a halo radius that is 2.5 times larger... (abridged)