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arXiv 1801.06211astro-ph.GA
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神秘的(几乎)黑暗的星系后发座P:原子星际介质

The Enigmatic (Almost) Dark Galaxy Coma P: The Atomic Interstellar Medium

Catherine Ball, John M. Cannon, Lukas Leisman, Elizabeth A. K. Adams, Martha P. Haynes, Gyula I. G. Jozsa, Kristen B. W. McQuinn, John J. Salzer, Samantha Brunk… 展开作者

Catherine Ball, John M. Cannon, Lukas Leisman, Elizabeth A. K. Adams, Martha P. Haynes, Gyula I. G. Jozsa, Kristen B. W. McQuinn, John J. Salzer, Samantha Brunker, Riccardo Giovanelli, Gregory Hallenbeck, William Janesh, Steven Janowiecki, Michael G. Jones, Katherine L. Rhode

摘要:

我们提出了新的高分辨率HI谱线成像后发座P,在系统HI 1232 $+$ 20中最亮的HI源。这个表面亮度极低的星系在ALLENFA巡天中首次被确认为“(几乎)黑暗”天体:一个明显的河外HI源,在现有的光学巡天数据中没有明显的光学对应物(尽管在GALEX档案成像中检测到微弱的紫外线发射)。利用韦斯特博克综合射电望远镜和卡尔G。Jansky甚大阵,我们调查HI形态和运动学在各种物理尺度。HI形态不规则,仅达到质量表面密度的中等最大值(峰$σ_{\rm HI}\sim 10$ $M_{\odot}$ pc $^{-2}$)。较低表面亮度的气体延伸到大的径向距离,在1 $M_{\odot}$ pc $^{-2}$能级内测量的HI直径为4.0 $\pm$ 0.2 kpc。我们考虑GALEX远紫外观测和H $α$未探测到的HI气体质量表面密度和各种类型的恒星形成之间的关系进行量化。我们描述了昏迷P的复杂HI运动学空间分辨的位置-速度分析和三维建模。这两种分析方法都表明后发座P的运动学特征要么是两个HI盘的碰撞,要么是一个重大的撞击事件。彗差P与已知的M $_{\rm HI}$- D $_{\rm HI}$标度关系恰好一致(在3个$σ$内)。它要么对于其HI质量太大,要么对于其HI尺寸具有太低的HI质量,或者两个HI分量人为地扩展其HI尺寸。后发座P位于重子塔利-费舍尔关系的暗端的经验散射内,尽管HI动力学的复杂性使解释复杂化。后发座P的集体HI特征使其在附近宇宙的已知星系中不寻常。[删节]

英文摘要:

We present new high-resolution HI spectral line imaging of Coma P, the brightest HI source in the system HI 1232$+$20. This extremely low surface brightness galaxy was first identified in the ALFALFA survey as an "(Almost) Dark" object: a clearly extragalactic HI source with no obvious optical counterpart in existing optical survey data (although faint ultraviolet emission was detected in archival GALEX imaging). Using a combination of data from the Westerbork Synthesis Radio Telescope and the Karl G. Jansky Very Large Array, we investigate the HI morphology and kinematics at a variety of physical scales. The HI morphology is irregular, reaching only moderate maxima in mass surface density (peak $σ_{\rm HI}\sim 10$ $M_{\odot}$ pc$^{-2}$). Gas of lower surface brightness extends to large radial distances, with the HI diameter measured at 4.0$\pm$0.2 kpc inside the 1 $M_{\odot}$ pc$^{-2}$ level. We quantify the relationships between HI gas mass surface density and various types of star formation by considering GALEX far ultraviolet observations and H$α$ nondetections. We describe Coma P's complex HI kinematics using spatially resolved position-velocity analysis and three-dimensional modeling. Both methods of analysis suggest that Coma P's kinematics show signatures of either the collision of two HI disks or a significant infall event. Coma P is just consistent (within 3$σ$) with the known M$_{\rm HI}$ -- D$_{\rm HI}$ scaling relation. It is either too large for its HI mass, has too low an HI mass for its HI size, or the two HI components artificially extend its HI size. Coma P lies within the empirical scatter at the faint end of the baryonic Tully--Fisher relation, although the complexity of the HI dynamics complicates the interpretation. The collective HI characteristics of Coma P make it unusual among known galaxies in the nearby universe. [Abridged]

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