ESO 381-47，一个具有扩展的HI和恒星形成环的早型星系
ESO 381-47, an early-type galaxy with extended HI and a star forming ring
摘要：
ESO 381-47是一个具有扩展HI盘的早型星系。GALEX和极深光学图像显示，在光学体的远处有一个直径约为30 kpc的明显的恒星环，其最近的恒星形成速率为1.8 x 10^-4 Msun/yr/kpc^-2，这与其他新的结果相一致，这些新的结果探测到了旋涡星系外部低于传统肯尼库特关系的低水平恒星形成。这个星系的形态类似于最近发现的一类紫外线物体，称为扩展紫外线盘或XUV盘。在ATCA和VLA的CnB阵列中对该星系进行的新的HI观测表明，冷气体位于中央S 0星系周围的扩展（直径约90 kpc）环中。HI数据立方体可以很好地由翘曲环来建模。星系内部的微弱电离气体在运动学上与恒星脱钩，相反，它们表现出与HI环在较大半径处的旋转一致的速度。恒星环的峰值，如在光学和紫外线中看到的，相对于HI环的峰值稍微向内移位。我们讨论的方式，这种偏移可能是由一个径向密度波的传播通过现有的恒星盘，也许引发的星系碰撞在磁盘的中心，或可能是由于螺旋密度波成立于早期的磁盘太热，形成一个恒星酒吧。气体吸积和共振效应，由于酒吧，因为已经溶解也被认为是解释存在的恒星形成环中看到的GALEX和深光学数据。
英文摘要：
ESO 381-47 is an early type galaxy with an extended HI disk. GALEX and very deep optical images reveal a distinct stellar ring far outside the optical body with a diameter of ~30 kpc, which has undergone recent star formation at 1.8 x 10^-4 Msun/yr/kpc^-2, consistent with other new results which detect low level star formation below the traditional Kennicutt relation in the outer parts of spiral galaxies. The morphology of this galaxy resembles the recently identified class of ultraviolet objects called extended ultraviolet disks, or XUV-disks. New HI observations of this galaxy taken at the ATCA and in the CnB array at the VLA show that the cold gas lies in an extended (diameter ~90 kpc) ring around the central S0 galaxy. The HI data cube can be well modeled by a warped ring. The faint ionized gas in the inner parts of the galaxy is kinematically decoupled from the stars and instead appears to exhibit velocities consistent with the rotation of the HI ring at larger radius. The peak of the stellar ring, as seen in the optical and UV, is slightly displaced to the inside relative to the peak of the HI ring. We discuss the manner in which this offset could be caused by the propagation of a radial density wave through an existing stellar disk, perhaps triggered by a galaxy collision at the center of the disk, or possibly due to a spiral density wave set up at early times in a disk too hot to form a stellar bar. Gas accretion and resonance effects due to a bar which has since dissolved are also considered to explain the presence of the star forming ring seen in the GALEX and deep optical data.
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