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arXiv · 1811.05267

G11.92-0.61 MM 1: A fragmented Keplerian disk surrounding a proto-O star

J. D. Ilee·C. J. Cyganowski·C. L. Brogan·T. R. Hunter·D. H. Forgan·T. J. Haworth·C. J. Clarke·T. J. Harries
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Abstract

We present high resolution ($\sim$300 au) Atacama Large Millimeter/submillimeter Array (ALMA) observations of the massive young stellar object G11.92-0.61 MM 1. We resolve the immediate circumstellar environment of MM 1 in 1.3 mm continuum emission and CH$_{3}$CN 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 $0.141'' \times 0.050''$ ($480\times170$ au). The gas kinematics toward MM 1a probed via CH$_{3}$CN trace a variety of scales. The lower energy $J=12-11$ $K=3$ line traces extended, rotating gas within the outflow cavity, while the $v$8=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 $40\pm5$ 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.

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J. D. Ilee, C. J. Cyganowski, C. L. Brogan, T. R. Hunter, D. H. Forgan, T. J. Haworth, C. J. Clarke, T. J. Harries. 2018-11-13. G11.92-0.61 MM 1: A fragmented Keplerian disk surrounding a proto-O star. https://doi.org/10.3847/2041-8213%2Faaeffc

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