2018/11/13 by J. D. Ilee, C. J. Cyganowski, C. L. Brogan +5 · 1 citation
Physics and Astronomy · #astro-ph.SR #astro-ph.GA
paper · pdf · doi:10.3847/2041-8213/aaeffc
8 pages, 3 figures, accepted for publication in ApJ Letters
arxiv created 2018/11/13 · arxiv updated 2018/12/26
We present high resolution (∼300 au) Atacama Large Millimeter/submillimeter Array (ALMA) observations of the massive young stellar object G11.92-0.61 MM 1. We resolve the immediate circumstellar environment of MM 1 in 1.3 mm continuum emission and CH3CN emission for the first time. The object divides into two main sources - MM 1a, which is the source of a bipolar molecular outflow, and MM 1b, located 0.57'' (1920 au) to the South-East. The main component of MM 1a is an elongated continuum structure, perpendicular to the bipolar outflow, with a size of 0.141'' × 0.050'' (480×170 au). The gas kinematics toward MM 1a probed via CH3CN trace a variety of scales. The lower energy J=12-11 K=3 line traces extended, rotating gas within the outflow cavity, while the v8=1 line shows a clearly-resolved Keplerian rotation signature. Analysis of the gas kinematics and dust emission shows that the total enclosed mass in MM 1a is 40±5 M\odot (where between 2.2-5.8 M\odot is attributed to the disk), while MM 1b is <0.6 M\odot. The extreme mass ratio and orbital properties of MM 1a and MM 1b suggest that MM 1b is one of the first observed examples of the formation of a binary star via disk fragmentation around a massive young (proto)star.