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arXiv 1604.01883astro-ph.GA
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冲压压力剥离室女座螺旋NGC 4402和NGC 4522中尘埃结构和恒星的HST成像:从外部剥离到内部,采用密集云解耦

HST Imaging of Dust Structures and Stars in the Ram Pressure Stripped Virgo Spirals NGC 4402 and NGC 4522: Stripped from the Outside In with Dense Cloud Decoupling

A. Abramson, J. Kenney, H. Crowl, T. Tal

摘要:

我们描述和限制ISM结构的起源可能是由正在进行的ICM冲压压力剥离两个室女星系团螺旋,NGC 4522和NGC 4402,使用HST的尘埃消光和恒星的BVI图像,以及补充HI,Halalpha和无线电连续图像。这是迄今为止对ICM-ISM冲压压力剥离相互作用期间发生的物理过程、冲压压力剥离对多相、多密度ISM的影响以及冲压压力剥离尾部的形成和演变的最高分辨率研究。在尘埃消光中,我们看到了NGC 4402的前侧和NGC 4522的后侧;我们在两个星系中看到了不同类型的特征。NGC 4522经历了更强、更近的压力,并具有一些冲压压力剥离星系的水母形态特征。它的剥离的尾巴从盘平面向上延伸,尘埃和恒星在盘平面上方弯曲约2 kpc。一个运动学和形态学上不同的平面外臂的年轻,蓝色的恒星和ISM延伸以上的一个大部分剥离部分的磁盘,和它之间的磁盘平面是解耦的尘埃云。NGC 4402包含了长长的尘埃脊,这表明ISM的大部分正在被一次推出。这两个星系都含有偏振射电连续辐射的长脊,表明存在大尺度有序的磁场。我们认为,磁场可以将不同密度的气体结合在一起,导致附近不同密度的气体以相同的速度剥离,并产生大的、连贯的尘埃脊和隆起。许多因素在决定冲压压力形成何种结构时发挥作用:冲压压力强度和历史,星系内相对于前沿的位置,以及ISM中预先存在的可能被磁场束缚在一起的子结构。

英文摘要:

We describe and constrain the origins of ISM structures likely created by ongoing ICM ram pressure stripping in two Virgo Cluster spirals, NGC 4522 and NGC 4402, using HST BVI images of dust extinction and stars, as well as supplementary HI, Halpha, and radio continuum images. This is the highest-resolution study to date of the physical processes that occur during an ICM-ISM ram pressure stripping interaction, ram pressure stripping's effects on the multi-phase, multi-density ISM, and the formation and evolution of ram-pressure-stripped tails. In dust extinction, we view the leading side of NGC 4402 and the trailing side of NGC 4522; we see distinct types of features in both galaxies. NGC 4522 has experienced stronger, more recent pressure and has the jellyfish morphology characteristic of some ram pressure stripped galaxies. Its stripped tail extends up from the disk plane in continuous upturns of dust and stars curving ~2 kpc above the disk plane. A kinematically and morphologically distinct extraplanar arm of young, blue stars and ISM extends above a mostly-stripped portion of the disk, and between it and the disk plane are decoupled dust clouds. NGC 4402 contains long dust ridges, suggesting that large parts of the ISM are being pushed out at once. Both galaxies contain long ridges of polarized radio continuum emission indicating the presence of large-scale ordered magnetic fields. We propose that magnetic fields could bind together gas of different densities, causing nearby gas of different densities to be stripped at the same rate and creating the large, coherent dust ridges and upturns. A number of factors that play roles in determining what types of structures form as a result of ram pressure: ram pressure strength and history, the location within the galaxy relative to the leading side, and pre-existing substructure in the ISM that may be bound together by magnetic fields.

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