不同环境中镓的不对称成因比较研究。II。近红外观测
Comparative Study of Asymmetry Origin of Galaxies in Different Environments. II. Near-Infrared observations
摘要：
在这两个分析的第二篇论文中，我们提出了近红外（NIR）的形态和不对称性的研究中发现的92个星系在不同的密度环境中的样本：星系在紧凑的集团（HCG），孤立的星系对（KPGs），孤立的星系（KIGs）。这两项研究都被证明有助于确定星系相互作用的影响。在近红外光谱中，星系在HCG、KPG和KIG中的性质比它们在光学中的性质更相似。这是因为近红外波段追踪的是较老的恒星星族，它们形成得更早，比年轻的恒星族更松弛。然而，我们发现在KPG和HCG样品的相互作用相关的不对称性。在HCG中，非对称星系的比例甚至高于我们在光学中发现的比例。在KPGs中，相互作用看起来像是最近发生的事件，而在HCGs中，星系在形态上更加进化，并显示出表明它们遭受更频繁相互作用的特性。关键的区别似乎是在HCG中没有恒星形成;虽然相互作用在KPG中产生强烈的恒星形成，但我们在HCG中没有看到这种效应。这与干合并假说（Coziol & Plauchu-Frayn 2007）是一致的;致密星系群（CG）中星系之间的相互作用是在没有气体存在的情况下发生的。如果这些气体是在恒星形成过程中消耗掉的（用来建造众多早期星系的凸起），那么HCG可能在KPG之前的某个时候就开始相互作用了。另一方面，CG中的干相互作用条件表明星系处于合并轨道上，因此这样的系统也不可能老得多。[删节]
英文摘要：
In this second paper of two analyses, we present near-infrared (NIR) morphological and asymmetry studies performed in sample of 92 galaxies found in different density environments: galaxies in Compact Groups (HCGs), Isolated Pairs of Galaxies (KPGs), and Isolated Galaxies (KIGs). Both studies have proved useful for identifying the effect of interactions on galaxies. In the NIR, the properties of the galaxies in HCGs, KPGs, and KIGs are more similar than they are in the optical. This is because the NIR band traces the older stellar populations, which formed earlier and are more relaxed than the younger populations. However, we found asymmetries related to interactions in both KPG and HCG samples. In HCGs, the fraction of asymmetric galaxies is even higher than what we found in the optical. In the KPGs the interactions look like very recent events, while in the HCGs galaxies are more morphologically evolved and show properties suggesting they suffered more frequent interactions. The key difference seems to be the absence of star formation in the HCGs; while interactions produce intense star formation in the KPGs, we do not see this effect in the HCGs. This is consistent with the dry merger hypothesis (Coziol & Plauchu-Frayn 2007); the interaction between galaxies in compact groups, (CGs), is happening without the presence of gas. If the gas was spent in stellar formation (to build the bulge of the numerous early-type galaxies), then the HCGs possibly started interacting sometime before the KPGs. On the other hand, the dry interaction condition in CGs suggests that the galaxies are on merging orbits, and consequently such system cannot be that much older either. [abridge]
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