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

*Corresponding author for this work

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We present high-resolution (~300 au) Atacama Large Millimeter/submillimeter Array 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 southeast. 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 (where between 2.2 and 5.8 M is attributed to the disk), while MM 1b is <0.6 M . 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.
Original languageEnglish
Article numberL24
Number of pages6
JournalAstrophysical Journal Letters
Issue number2
Publication statusPublished - 14 Dec 2018


  • Accretion, accretion disks
  • ISM: individual objects (G11.92-0.61)
  • Stars: formation
  • Stars: protostars
  • Submillimeter: ISM
  • Systems


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