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

Abstract

The hydrogen recombination lines H30$\hat{I}\pm$, H40$\hat{I}\pm$, H42$\hat{I}\pm$, H50${\hat{I}}^2$ and H57${\hat{I}}^3$ 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$\hat{I}\pm$ 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${\hat{I}}^2$, H40$\hat{I}\pm$ and H42$\hat{I}\pm$ 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$\hat{I}\pm$ 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.

Accepted for publication in The Astrophysical Journal