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

• 来源期刊: 天文和天体物理学研究
• 年，卷（期）: 2013,（8）
• 页码范围: 935-944
• 页数: 10页
• 语种: 英文

摘要

Ultra compact HⅡ (UCHII) G25.4NW is a bright IR source in the region of the inner Galaxy.New HⅠ images from the Very Large Array Galactic Plane Survey show clear absorption features associated with the UCHⅡ region up to 95 km s-1,and there are no other absorptions up to the tangential velocity.This reveals that G25.4NWhas a near-side distance of 5.7 kpc,and it is located in the region of the inner Galactic molecular ring.Using the new distance,the bolometric luminosity of G25.4NW is estimated as 105.6 L☉,which corresponds to an O6 star.It contains 460 M☉ of ionized gas.A high-resolution 13CO image from the Galactic Ring Survey reveals that G25.4NW is part of a more extended star-forming complex with about 104 M☉ of molecular gas.