Erosion of a dense molecular core by a strong outflow from a massive protostar

Abstract

We present Atacama Large Millimeter/submillimeter Array Band 3 observations of N${}_2$H${}^{+}$ (1-0) and CH${}_3$CN (5-4), as well as Band 7 observations of the H${}_2$CO molecular line emissions from the protostellar system GGD 27-MM2(E). Through position-velocity diagrams along and across the outflow axis, we study the kinematics and structure of the outflow. We also fit extracted spectra of the CH${}_3$CN emission to obtain the physical conditions of the gas. We use the results to discuss the impact of the outflow on its surroundings. We find that N${}_2$H${}^{+}$ emission traces a dense molecular cloud surrounding GGD 27-MM2(E). We estimate that the mass of this cloud is $\sim$13.3-26.5 M${}_{\odot }$. The molecular cloud contains an internal cavity aligned with the H${}_2$CO-traced molecular outflow. The outflow, also traced by $\mathrm{C}{\mathrm{H}}_3\mathrm{CN}$, shows evidence of a collision with a molecular core (MC), as indicated by the distinctive increases in the distinct physical properties of the gas such as excitation temperature, column density, line width, and velocity. This collision results in an X-shape structure in the northern part of the outflow around the position of the MC, which produces spray-shocked material downstream in the north of MC as observed in position-velocity diagrams both along and across of the outflow axis. The outflow has a mass of 1.7-2.1 M${}_{\odot }$, a momentum of 7.8-10.1 M${}_{\odot }$ km s${}^{-1}$, a kinetic energy of 5.0-6.6$\times 10^{44}$ erg, and a mass loss rate of 4.9--6.0$\times 10^{-4}$ M${}_{\odot }$ yr${}^{-1}$. The molecular outflow from GGD 27-MM2(E) significantly perturbs and erodes its parent cloud, compressing the gas of sources such as MC and ALMA 12. The feedback from this powerful protostellar outflow contributes to maintain the turbulence in the surrounding area.

14 pages, 8 figures. Accepted by A&A