孤立星系CIG 292中的HI不对称
HI asymmetries in the isolated galaxy CIG 292
摘要：
利用扩展甚大阵（EVLA）D阵观测了CIG 292的中性氢（HI）21厘米谱线，CIG 292是一个孤立的SA（s）b星系，距离约为24.3Mpc。从以前的HI单碟观测，该星系被认为有一个轻度不对称的HI轮廓（A_flux =1.23 { \pm }0.3）。我们的EVLA观测结果表明，尽管HI向北延伸的距离比向南延伸的距离多16%，但在光学中心以南（接近速度）的HI投影比在北部（后退速度）多12%。投射到光盘中的HI一定在HI弛豫时间（~ 10^8年）内受到了扰动，这意味着这不可能是由三个最近的伴星中的任何一个引起的，因为它们的距离（~ 0.5Mpc）太大了。在我们的视野和速度范围内，既没有发现高密度伴星系，也没有发现潮汐尾。我们的运动学数据表明，内部窝藏一个椭圆形的扭曲，而外部区域显示出适度的翘曲的迹象。因此，HI全球轮廓中的轻微不对称实际上掩盖了该星系中气体和恒星形成区域的二维分布中更强的不对称性。由于星系是孤立的，这必须主要是由于与其形成和长期演化有关的过程。
英文摘要：
We present Expanded Very Large Array (EVLA) D-array observations in the 21-cm line of neutral hydrogen (HI) of CIG 292, an isolated SA(s)b galaxy at a distance of ~ 24.3Mpc. From previous HI single dish observations the galaxy was known to have a mildly asymmetric HI profile (A_flux =1.23 {\pm}0.3). Our EVLA observations show there is ~ 12% more HI projected South of the optical centre (approaching velocities) than in the North (receding velocities), despite the HI extending ~ 16% further to the North than the South. The HI projected within the optical disk must have been perturbed within the HI relaxation time (~ 10^8 yr) which implies that this can not have been caused by any of the three nearest companions, as their distance (~ 0.5Mpc) is too large. Neither HI-rich companions nor tidal tails were found within our field of view and velocity range covered. Our kinematical data suggest that the inner part harbors an oval distortion whereas the outer regions show signs of a modest warp. The mild asymmetry in the HI global profile thus actually masks stronger asymmetries in the two-dimensional distributions of gas and star forming regions in this galaxy. Since the galaxy is isolated, this must predominantly be due to processes related to its formation and secular evolution.
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