ALMA detection of Masers and Dasars in the Hydrogen Recombination Lines of the Planetary Nebula Mz3

TL;DR

This study used ALMA to detect hydrogen recombination lines in the planetary nebula Mz3, revealing maser amplification and stimulated absorption effects, providing insights into the nebula's ionized gas densities and velocity structure.

Contribution

First detection of masers and dasar effects in hydrogen recombination lines in Mz3 using ALMA, confirming laser amplification and constraining gas densities.

Findings

Detection of maser amplification in H30α line at high velocities.

Observation of dasar effect indicating low-density absorbing regions.

Identification of ionized gas with densities around 10^7 cm^-3.

Abstract

The hydrogen recombination lines H30$\alpha$, H40$\alpha$, H42$\alpha$, H50$\beta$ and H57$\gamma$ and the underlying bremsstrahlung continuum emission were detected with ALMA in the bipolar nebula Mz3. The source was not spatially resolved, but the velocity profile of the H30$\alpha$ line shows clear indication of maser amplification, confirming previous reports of laser amplification in the far infrared H recombination lines observed with Herschel Space Observatory. Comparison between the flux densities of the H50$\beta$, H40$\alpha$ and H42$\alpha$ lines show overcooling, or darkness amplification by stimulated absorption (dasar effect) at the LSR velocity of about $-25$ km s$^{-1}$, which constrains the density of the absorbing region to about 10$^3$ cm$^{-3}$. The H30$\alpha$ line, on the other hand, presents maser lines at LSR velocities of $-69$ and $-98$ km s$^{-1}$, which indicates ionized gas with densities close to 10$^7$ cm$^{-3}$. Although the source of emission was not resolved, it was possible to find the central position of the images for each velocity interval, which resulted in a well defined position-velocity distribution.