The hot, warm and cold gas in Arp 227 – an evolving poor group
The hot, warm and cold gas in Arp 227 – an evolving poor group
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DOI：
10.1111/j.1365-2966.2006.10179.x
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发表时间：
2006-05
影响因子：
4.8
通讯作者：
R. Rampazzo;P. Alexander;C. Carignan;M. Clemens;H. Cullen;O. Garrido;M. Marcelin;K. Sheth;G. Trinchieri
中科院分区：
文献类型：
--
作者：
R. Rampazzo;P. Alexander;C. Carignan;M. Clemens;H. Cullen;O. Garrido;M. Marcelin;K. Sheth;G. Trinchieri
阿普227代表了一个位于低密度环境中的相互作用的混合星系对的原型。我们在X射线、Hα、HI和CO带研究了该对的气体性质。我们还检测到两个额外的成员组在HI这表明对构成一个松散的群体的主导成员。HI分布显示了连接螺旋成员NGC 470和透镜状成员NGC 474的气体尾部，表明这两个主要成员目前正在发生相互作用。Hα辐射揭示了NGC 470中心存在次级分量，叠加在追踪星系旋转的主分量上。后者映射了一个几乎未受扰动的速度场。占主导地位的，几乎不受干扰的趋势的运动学证实了CO的观测，但仅限于银河系的中心。NGC 470的X射线光度与“正常”螺旋星系相当。另一方面，NGC 474非常缺乏气体，在Hα中没有检测到。它的X射线光度与离散源预期发射的低端一致。阿普227作为一个松散的星系群，显示出星系间相互作用的几个特征。我们的观察表明，在螺旋伴侣的整体运动的相互作用的签名的存在。正在进行的相互作用只有在NGC 470的HI外晕中才能清楚地看到。虽然NGC 474的大壳层系统可能与吸积事件有关，但NGC 470中心的Hα剖面中的次级成分可能是由于与伴星的相互作用。NGC 470的低X射线光度似乎是动态年轻系统的一个特征。所有上述证据都表明，阿普227是一个处于演化早期阶段的演化星系群，其驱动力是暗星系的吸积和NGC 470和474之间持续的大规模相互作用。
Arp 227 represents a prototypical example of an interacting mixed pair of galaxies located in a low-density environment. We investigate the gas properties of the pair in the X-ray, Hα, HI and CO bands. We also detect two additional members of the group in HI which indicates that the pair constitutes the dominant members of a loose group. The HI distribution shows a tail of gas that connects the spiral member, NGC 470, to the lenticular, NGC 474, showing that the two main members are currently undergoing interaction. The Hα emission reveals the presence of secondary components at the centre of NGC 470, superposed on the main component tracing the rotation of the galaxy. This latter maps a nearly unperturbed velocity field. The dominant, nearly unperturbed trend of the kinematics is confirmed by CO observations, although restricted to the centre of the galaxy. The X-ray luminosity of NGC 470 is comparable with that of a `normal' spiral galaxy. NGC 474 on the other hand is very gas-poor and has not been detected in Hα. Its X-ray luminosity is consistent with the low end of the expected emission from discrete sources. Arp 227 as a loose group shows several signatures of galaxy-galaxy interaction. Our observations suggest the presence of signatures of interaction in the overall kinematics of the spiral companion. The ongoing interaction is clearly visible only in the outer HI halo of NGC 470. While the large shell system of NGC 474 could be associated with an accretion event, the secondary components in the Hα profile in the centre of NGC 470 could be due to the interaction with the companion. The low X-ray luminosity of NGC 470 seems to be a characteristic of dynamically young systems. All the above evidence suggest that Arp 227 is an evolving group in the early phase of its evolution and that its drivers are the accretion of faint galaxies and the ongoing large-scale interaction between NGC 470 and 474.