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arXiv 1104.3305astro-ph.CO
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量化的HI形态学V:室女星系团中的HI

Quantified HI Morphology V: HI Disks in the Virgo Cluster

B. W. Holwerda, N. Pirzkal, W. J. G. de Blok, W. van Driel

摘要:

我们探讨了室女星系团中氢原子盘的量化形态。这些星系在其Hi形态中显示出丰富的现象,例如,尾部、截断和扭曲。这些形态扰动与星系在稠密星系团环境中经历的冲压压力剥离和潮汐相互作用有关。为了量化HI盘的形态转换,我们计算了CAS,Gini和M20的形态参数和我们自己的GM,用于VIVA项目中的48个HI柱密度图中的51个星系。在相对低分辨率HI数据的这个空间中可以识别一些形态学现象。HI盘的截断可以通过浓度参数(C<1)清楚地识别,并且浓度也可以用于识别HI缺陷盘(1<C<5)。潮汐相互作用通常是确定使用这些形态参数的组合,适用于(光学)图像的星系。我们发现某些选择标准(Gini-M20、不对称性和修改的浓度-M20)仍然适用于粗略(~15”FWHM)VIVA HI数据。潮汐尾的现象可以用吉尼-M20标准(60%的星系有尾巴,但有同样多的污染物)合理地识别。冲压压力确实使HI盘进出我们的大多数相互作用标准:Vollmer等人(2009)确定的冲压压力序列跟踪进出其中一些标准(基于不对称性和Gini-M20选择,但不是基于浓度-M20或GM的标准)。因此,未来的搜索使用HI形态的相互作用应考虑冲压压力作为一种机制,干扰HI磁盘足以使他们出现的引力相互作用。一种机制将是从样品中去除所有HI缺陷(C<5)盘,因为这些盘已经经历了多于一种HI去除机制。

英文摘要:

We explore the quantified morphology of atomic hydrogen (HI) disks in the Virgo cluster. These galaxies display a wealth of phenomena in their Hi morphology, e.g., tails, truncation and warps. These morphological disturbances are related to the ram-pressure stripping and tidal interaction that galaxies undergo in this dense cluster environment. To quantify the morphological transformation of the HI disks, we compute the morphological parameters of CAS, Gini, and M20 and our own GM for 51 galaxies in 48 HI column density maps from the VIVA project. Some morphological phenomena can be identified in this space of relatively low resolution HI data. Truncation of the HI disk can be cleanly identified via the Concentration parameter (C<1) and Concentration can also be used to identify HI deficient disks (1<C<5). Tidal interaction is typically identified using combinations of these morphological parameters, applied to (optical) images of galaxies. We find that some selection criteria (Gini-M20, Asymmetry, and a modified Concentration-M20) are still applicable for the coarse (~15" FWHM) VIVA HI data. The phenomena of tidal tails can be reasonably well identified using the Gini-M20 criterion (60% of galaxies with tails identified but with as many contaminants). Ram-pressure does move HI disks into and out of most of our interaction criteria: the ram-pressure sequence identified by Vollmer et al. (2009) tracks into and out of some of these criteria (Asymmetry based and the Gini-M20 selections, but not the Concentration-M20 or the GM based ones). Therefore, future searches for interaction using HI morphologies should take ram-pressure into account as a mechanism to disturb HI disks enough to make them appear as gravitationally interacting. One mechanism would be to remove all the HI deficient (C<5) disks from the sample, as these have undergone more than one HI removal mechanism.

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