反向旋转气体压缩机的高环境--冷气团的气体吸积
The Hi Environment of Counter-rotating Gas Hosts: Gas Accretion from Cold Gas Blobs
摘要：
本文研究了三个含有反旋电离气体的早型棒星系NGC 128、NGC 3203和NGC 7332的HI性质和气体环境。每个星系都有一个或多个光学识别的星系，在50千秒差距的投影半径内有相似或未知的红移。使用HI合成成像数据，我们调查的假设，这些星系中的反旋转气体已从他们的邻居吸积。在NGC 128和NGC 3203中，我们分别发现了9.6e7和2.3e8 Msun的HI，几乎覆盖了所有物理上相连的矮伴星。无论是HI形态和运动学的潮汐相互作用的暗示。在NGC 7332中，我们没有发现任何直接关联的HI。相反，NGC 7339，一个在10千秒差距大小相当的邻居，被发现有8.9e8 Msun的HI气体。然而，在最近的一次单碟观测中，另一个研究小组发现了一个巨大的HI结构，它似乎是NGC 7339 HI盘的延伸，也覆盖了NGC 7332。因此，所有这些观测结果表明，HI气体正在从它们的同伴中吸积到这三个星系中，这可能是它们中心区域存在动力学解耦气体成分的原因。考虑到现有的研究在光学和HI中的微弱矮星系人口的不完整性，从冷气体斑点，可能是富含气体的矮星，吸积预计发生的频率甚至比从迄今为止观察到的情况下推断的更频繁。
英文摘要：
We probe the HI properties and the gas environments of three early-type barred galaxies harbouring counter-rotating ionized gas, NGC 128, NGC 3203 and NGC 7332. Each system has one or more optically-identified galaxy, at a similar or as yet unknown redshift within a 50 kpc projected radius. Using HI synthesis imaging data, we investigate the hypothesis that the counter-rotating gas in these galaxies has been accreted from their neighbours. In NGC 128 and NGC 3203, we find 9.6e7 and 2.3e8 Msun of HI, respectively, covering almost the entire stellar bodies of dwarf companions that appear physically connected. Both the HI morphology and kinematics are suggestive of tidal interactions. In NGC 7332, we do not find any directly-associated HI. Instead, NGC 7339, a neighbour of a comparable size at about 10 kpc, is found with 8.9e8 Msun of HI gas. More recently in a single dish observation, however, another group discovered a large HI structure which seems to be an extension of NGC 7339's HI disc and also covers NGC 7332. All these observations thus suggest that HI gas is being accreted in these three galaxies from their companions, which is likely responsible for the kinematically-decoupled gas component present in their central region. Considering the incompleteness of existing studies of the faint dwarf galaxy population both in the optical and in HI, accretion from cold gas blobs, presumably gas-rich dwarfs, is expected to occur even more frequently than what is inferred from such cases that have been observed to date.
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