THE PROTOCLUSTER G18.67+0.03: A TEST CASE FOR CLASS I CH3OH MASERS AS EVOLUTIONARY INDICATORS FOR MASSIVE STAR FORMATION

C. J. Cyganowski*, C. L. Brogan, T. R. Hunter, Q. Zhang, R. K. Friesen, R. Indebetouw, C. J. Chandler

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)

Abstract

We present high angular resolution Submillimeter Array and Karl G. Jansky Very Large Array observations of the massive protocluster G18.67+0.03. Previously targeted in maser surveys of GLIMPSE Extended Green Objects (EGOs), this cluster contains three Class I CH3OH maser sources, providing a unique opportunity to test the proposed role of Class I masers as evolutionary indicators for massive star formation. The millimeter observations reveal bipolar molecular outflows, traced by (CO)-C-13(2-1) emission, associated with all three Class I maser sources. Two of these sources (including the EGO) are also associated with 6.7 GHz Class II CH3OH masers; the Class II masers are coincident with millimeter continuum cores that exhibit hot core line emission and drive active outflows, as indicated by the detection of SiO(5-4). In these cases, the Class I masers are coincident with outflow lobes, and appear as clear cases of excitation by active outflows. In contrast, the third Class I source is associated with an ultracompact (UC) H II region, and not with Class II masers. The lack of SiO emission suggests that the 13CO outflow is a relic, consistent with its longer dynamical timescale. Our data show that massive young stellar objects (MYSOs) associated only with Class I masers are not necessarily young and provide the first unambiguous evidence that Class I masers may be excited by both young (hot core) and older (UC H II) MYSOs within the same protocluster.

Original languageEnglish
Article number20
Number of pages7
JournalAstrophysical Journal Letters
Volume760
Issue number2
DOIs
Publication statusPublished - 1 Dec 2012

Keywords

  • ISM: individual objects (G18.67+0.03)
  • ISM: jets and outflows
  • ISM: molecules
  • masers
  • stars: formation
  • techniques: interferometric
  • EXTENDED GREEN OBJECTS
  • METHANOL MASERS
  • FORMING REGIONS
  • LARGE ARRAY
  • GLIMPSE SURVEY
  • OUTFLOW
  • EGOS
  • ULTRACOMPACT
  • CATALOG
  • G5.89-0.39

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