DEEP VERY LARGE ARRAY RADIO CONTINUUM SURVEYS OF GLIMPSE EXTENDED GREEN OBJECTS (EGOs)

C. J. Cyganowski*, C. L. Brogan, T. R. Hunter, E. Churchwell

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

49 Citations (Scopus)

Abstract

We present the results of deep, high angular resolution Very Large Array surveys for radio continuum emission toward a sample of 14 GLIMPSE Extended Green Objects (EGOs). Identified as massive young stellar object (MYSO) outflow candidates based on their extended 4.5 um emission in Spitzer images, the EGOs in our survey sample are also associated with 6.7 GHz Class II and/or 44 GHz Class I CH3OH masers. No continuum is detected at 3.6 or 1.3 cm toward the majority (57%) of our targets (median rms ~0.03 and 0.25 mJy/beam). Only two EGOs are associated with optically thin emission consistent with ultracompact/compact H II regions. Both of these sources exhibit cm-wavelength multiplicity, with evidence that one of the less-evolved members may be driving the 4.5 um outflow. Most of the other cm-wavelength EGO counterparts are weak (< ~1 mJy), unresolved, undetected at 1.3 cm, and characterized by intermediate spectral indices consistent with hypercompact (HC) H II regions or ionized winds or jets. One EGO centimeter (cm) counterpart, likely an optically thick HC H II region, is detected only at 1.3 cm and is associated with hot core line emission and H2O and 6.7 GHz CH3OH masers. The results of our exceptionally sensitive survey indicate that EGOs signify an early stage of massive star formation, before photoionizing feedback from the central MYSO significantly influences the (proto) cluster environment. Actively driving outflows (and so, presumably, actively accreting), the surveyed EGOs are associated with significant clump-scale gas reservoirs, providing sufficient material for sustained, rapid accretion.

Original languageEnglish
Article number56
Number of pages18
JournalAstrophysical Journal
Volume743
Issue number1
DOIs
Publication statusPublished - 10 Dec 2011

Keywords

  • infrared: ISM
  • ISM: jets and outflows
  • radio continuum: ISM
  • stars: formation
  • techniques: interferometric
  • STAR-FORMING REGIONS
  • H-II REGIONS
  • SPECTRAL ENERGY-DISTRIBUTIONS
  • YOUNG STELLAR OBJECTS
  • ULTRACOMPACT HII-REGIONS
  • METHANOL MASER SURVEY
  • GALACTIC PLANE
  • MASSIVE STARS
  • PHYSICAL-PROPERTIES
  • RECOMBINATION LINE

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