UKIDSS银河平面巡天观测到的银河长条
The long Galactic bar as seen by UKIDSS Galactic Plane Survey
摘要：
在过去的十年中，有一系列的结果支持银河系中存在一个长而薄的棒的假设，其半长为4.5 kpc，位置角约为45度。这显然是一个非常不同的结构，从三轴凸起的银河系，这是更厚，更短，并占主导地位的恒星计数在|l| <10度。本文分析了银河系内部的恒星分布，以探讨是否存在银河系中两个三轴或棒状结构的明确证据。通过使用红团人口作为银河系结构的示踪剂，我们确定了银河系内部的表观形态。UKIDSS银河平面巡天的更深和更高空间分辨率的近红外测光使我们能够使用面内数据，即使在最里面的银河系，一个区域的源混淆是一个主导的影响，使其不可能使用其他近红外数据库，如2 MASS或TCS-CAIN。我们表明，以前获得的结果与使用红丛巨星与UKIDSS GPS的面内数据证实。有两种不同的结构共存于内银道面：一个位置角为23.60+-2.19度，可以从银道中心追踪到l=10度（银道凸起），另一个位置角更大，为42.44+-2.14度，在l=28度附近结束（银道长条）。
英文摘要：
Over the last decade there have been a series of results supporting the hypothesis of the existence of a long thin bar in the Milky Way with a half-length of 4.5 kpc and a position angle of around 45 deg. This is apparently a very different structure from the triaxial bulge of the Galaxy, which is thicker and shorter and dominates the star counts at |l|<10 deg. In this paper, we analyse the stellar distribution in the inner Galaxy to see if there is clear evidence for two triaxial or bar-like structures in the Milky Way. By using the red-clump population as a tracer of Galactic structure, we determine the apparent morphology of the inner Galaxy. Deeper and higher spatial resolution NIR photometry from the UKIDSS Galactic Plane Survey allows us to use in-plane data even at the innermost Galactic longitudes, a region where the source confusion is a dominant effect that makes it impossible to use other NIR databases such as 2MASS or TCS-CAIN. We show that results previously obtained with using the red-clump giants are confirmed with the in-plane data from UKIDSS GPS. There are two different structures coexisting in the inner Galactic plane: one with a position angle of 23.60+-2.19 deg that can be traced from the Galactic Centre up to l=10 deg (the Galactic bulge), and other with a larger position angle of 42.44+-2.14 deg, that ends around l=28 deg (the long Galactic bar).
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