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We report on the astrometric observations of the 22 GHz H2O masers in the high mass star-forming region G5.89-0.39 with VERA (VLBI Exploration of Radio Astrometry). Newly derived distance of 1.28^{+0.09}_{-0.08} kpc is the most precise and significantly nearer than previous values. We revised physical parameters and reconsidered nature of G5.89-0.39 based on the new distance as follows. (1) The ionizing star of the ultra compact (UC) HII region is a late O-type (O8 - 8.5) zero age main sequence (ZAMS) star, consistent with previously established limits based on its infrared spectral line emission. (2) Crescent-like maser alignment at the position of the O type ZAMS star may trace accretion disk (or its remnant), which suggests that the star is still young and before complete evaporation of circumstellar materials. (3) Although the revised mass for the east-west outflow has been reduced, it still quite large (100 Msun) which indicates that a significant fraction of the mass is entrained material and that the dynamical age significantly underestimates the actual outflow age. Our newly-derived distance emphasizes that G5.89-0.39 is one of the nearest targets to investigate ongoing high-mass star formation and evolution in a compact cluster containing a young O-type star.
The fine-structure line of [OI] at 63micron is an important diagnostic tool in different fields of astrophysics. However, our knowledge of this line relies on observations with low spectral resolution, and the real contribution of each component (PDR
I review theoretical models of star formation and how they apply across the stellar mass spectrum. Several distinct theories are under active study for massive star formation, especially Turbulent Core Accretion, Competitive Accretion and Protostella
We report 1.2 mm polarized continuum emission observations carried out with the Atacama Large Millimeter/submillimeter Array (ALMA) toward the high-mass star formation region G5.89-0.39. The observations show a prominent 0.2 pc north-south filamentar
We present the first subarcsecond submillimeter images of the enigmatic ultracompact HII region (UCHII) G5.89-0.39. Observed with the SMA, the 875 micron continuum emission exhibits a shell-like morphology similar to longer wavelengths. By using imag
Star formation is a multi-scale, multi-physics problem ranging from the size scale of molecular clouds ($sim$10s pc) down to the size scales of dense prestellar cores ($sim$0.1 pc) that are the birth sites of stars. Several physical processes like tu