Properties of the UCHII region G25.4NW and its associated molecular cloud

Abstract

UCHII G25.4NW is a bright IR source in the inner Galaxy region. New HI images from the VLA Galactic Plane Survey (VGPS) show clear absorption features associated with the UCHII region up to 95 km s${}^{-1}$, and there is not any other absorptions up to the tangential velocity. It reveals that G25.4NW is at a near-side distance of 5.7 kpc, and it is located in the inner Galactic molecular ring region. Using the new distance, the bolometric luminosity of G25.4NW is estimated as $10^{5.6}{L}_{\odot }$, which corresponds to an O6 star. It contains 460 $M_{\odot }$ of ionized gas. High-resolution ${}^{13}$CO image from the Galactic Ring Survey (GRS) reveals that G25.4NW is part of a more extended star-formation complex with about $10^4{M}_{\odot }$ molecular gas.

9 pages, 5 figures, published in RAA

References in corpus (7)

• The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
• The VLA Galactic Plane Survey
• Resolution of the Distance Ambiguity for Galactic HII Regions
• The Distance and Age of the SNR Kes 73 and AXP 1E 1841-045
• Infall and outflow detections in a massive core JCMT 18354-0649S
• Supersonic turbulence in the cold massive core JCMT 18354-0649S
• High Resolution Mid-Infrared Imaging of Radio Ultra-Compact HII Regions

Cited by in corpus (5)

• The SOFIA Massive (SOMA) Star Formation Survey. IV. Isolated Protostars
• Probing the initial conditions of high-mass star formation -- IV. Gas dynamics and NH${}_2$D chemistry in high-mass precluster and protocluster clumps
• Probing the initial conditions of high-mass star formation. III. Fragmentation and triggered star formation
• Unraveling the inner substructure of new candidate hub-filament system in the HII region G25.4NW
• Surveying the Giant HII Regions of the Milky Way with SOFIA: IV. Sgr D, W42, and a Reassessment of the Giant HII Region Census