Sgr B2(N): A bipolar outflow and rotating hot core revealed by ALMA

Abstract

We present the results of SiO (2-1) and SO2 (12-13) line observations of Sgr B2(N) made with the Atacama Large Millimeter/submillimeter Array (ALMA) at an angular resolution of ~2arcsec. Our analysis of the SiO and SO2 line emission reveals a bipolar molecular outflow in an east-west direction whose driving source is located at K2. In addition, SO2 line core shows a north-south velocity gradient most probably indicating a hot core of molecular gas rotating around K2. Fractional abundances of SO2 and SiO (X(SO2) and X(SiO), respectively) in the outflowing molecular gas are derived from comparisons with the C18O emission. Assuming an excitation temperature of 100+-50 K, we calculate X(SO2) = 2.3X10^-8 and X(SiO) = 1.2X10^-9. The outflow from SgrB2(N) K2 is characterized as a young (5X10^3yr) and massive (~2000Msun), but moderately collimated (~60deg) outflow. We also report a possible detection of the SiO (v=2, J=2-1) maser emission from the position of K2. If confirmed, it would make Sgr B2(N) the 4th star forming region associated with SiO masers.Comment: 31 pages, 8 figures, ApJ accepted for publicatio