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首页> 外文期刊>The Astrophysical journal >NEUTRAL HYDROGEN ASSOCIATED WITH SHELLS AND OTHER FINE STRUCTURE IN NGC 2865: A DYNAMICALLY YOUNG ELLIPTICAL?
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NEUTRAL HYDROGEN ASSOCIATED WITH SHELLS AND OTHER FINE STRUCTURE IN NGC 2865: A DYNAMICALLY YOUNG ELLIPTICAL?

机译：NGC 2865中与壳和其他精细结构相关的中性氢：动态年轻的椭圆形？

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摘要

We report the discovery of neutral hydrogen in a second elliptical galaxy with shells, NGC 2865. Very Large Array images reveal an association between the neutral hydrogen (H I) and the fine structure (shells, tails, and loops) in the galaxy. Similar to what we previously observed in NGC 5128 (Centaurus A), most of the 6 x 10~8 h~(-2) solar mass of cold gas is found in a broken ring in the outer regions of NGC 2865 (beyond 1/2D_(25)) and is displaced to the outside of the shells and loops. The measured velocities cover a range of 500 km s"1 around the systemic velocity. The velocity field of the outer H I has the same sense and magnitude (and line of nodes) as that of the stars in the elliptical body. Although NGC 2865 appears to be a relaxed elliptical galaxy, deep images, photometry, and spectroscopy suggest that the galaxy might be the recent (less than 7 Gyr) product of a major disk-disk merger—a "dynamically young elliptical." Our H I data support this hypothesis. Nevertheless, the association between gas and stellar fine structure, with gas displaced outward from the stars in projected position, implies gas motions not predicted by any of the current merger scenarios. Using the H I ring and assuming nearly circular motion, we measure M/L_B at large radii (4 x 1/2D_(25)). We find M/L_B = 33 ± 4 h, a factor of 5 greater than the value of M/L_B found for the central regions, indicating the presence of a dark halo.
机译：我们报道了在另一个带有壳的椭圆星系NGC 2865中发现中性氢的情况。非常大的阵列图像揭示了中性氢（HI）与星系中精细结构（壳，尾和环）之间的联系。与我们先前在NGC 5128（半人马座A）中观察到的类似，冷气的6 x 10〜8 h〜（-2）太阳质量中的大多数在NGC 2865外部区域的破裂环中发现（超过1 / 2D_（25）），并移至壳和环的外部。测得的速度围绕系统速度覆盖了500 km s“ 1的范围。外部HI的速度场与椭圆体中的恒星具有相同的方向和大小（以及节点线）。尽管出现了NGC 2865作为一个放松的椭圆星系，深层图像，光度法和光谱学表明，该星系可能是大型磁盘磁盘合并的最新产品（小于7 Gyr），即“动态年轻的椭圆形”。 。然而，气体与恒星精细结构之间的联系，即气体以投射位置从恒星向外移动，暗示着目前任何合并情况都无法预测的气体运动。使用HI环并假设近似圆周运动，我们测量M /大半径（4 x 1 / 2D_（25））的L_B我们发现M / L_B = 33±4 h，比中心区域的M / L_B值大5倍，表明存在暗处光环。

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