The Hot and Clumpy Molecular Cocoon Surrounding the Ultracompact HII Region G5.89-0.39

Abstract

We present observations of CH3CN (12-11) emission at a resolution of 2" toward the shell-like ultracompact HII region G5.89-0.39 with the Submillimeter Array. The integrated CH3CN emission reveals dense and hot molecular cocoon in the periphery of the HII region G5.89-0.39, with a CH3CN deficient region roughly centered at G5.89-0.39. By analyzing the CH3CN emission using population diagram analysis, we find, for the first time, a decreasing temperature structure from 150 to 40 K with the projected distance from Feldt's star, which is thought to be responsible for powering the HII region. Our results further indicate that the majority of the heating energy in the observed dense gas is supplied by the Feldt's star. From the derived CH3CN column density profile, we conclude that the dense gas is not uniformly-distributed but centrally-concentrated, with a power-law exponent of 5.5 for r < 8000 AU, and 2.0 for 8000 AU < r < 20000 AU, where r is the distance to Feldt's star. The estimated large power index of 5.5 can be attributed to an enhancement of CH3CN abundance in the close vicinity of Feldt's star.

accepted for publication in The Astrophysical Journal Letters

References in corpus (8)

• The Submillimeter Array
• A CH3CN and HCO+ survey towards southern methanol masers associated with star formation
• A detailed study of the rotating toroids in G31.41+0.31 and G24.78+0.08
• Full-Polarization Observations of OH Masers in Massive Star-Forming Regions: I. Data
• Subarcsecond Submillimeter Imaging of the Ultracompact HII Region G5.89-0.39
• Evolution of Magnetic Fields in High Mass Star Formation: SMA dust polarization image of the UCHII region G5.89-0.39
• A High-Mass Protobinary System in the Hot Core W3(H2O)
• Mapping the Outflow from G5.89-0.39 in SiO(5-4)

Cited by in corpus (11)

• SMA millimeter observations of Hot Molecular Cores
• Spectroscopically resolved far-IR observations of the massive star-forming region G5.89--0.39
• Digging into the Interior of Hot Cores with ALMA (DIHCA). I. Dissecting the High-mass Star-Forming Core G335.579-0.292 MM1
• New Distance and Revised Natures of High Mass Star Formation in G5.89-0.39
• Extremely large and hot multilayer Keplerian disk around the O-type protostar W51N: The precursors of the HCHII regions?
• ALMA View of the Infalling Envelope around a Massive Protostar in S255IR SMA1
• Confirming the Explosive Outflow in G5.89 with ALMA
• The Extremely High-Velocity Outflow from the Luminous Young Stellar Object G5.89-0.39
• Gas vs. solid phase deuterated chemistry: HDCO and D${}_2$CO in massive star-forming regions
• SiO Outflows in the Most Luminous and Massive Protostellar Sources of the Southern Sky
• Evolutions of CH${}_3$CN abundance in molecular clumps