局部体积螺旋星系中的恒星潮汐流：中等孔径望远镜的初步观测
Stellar Tidal Streams in Spiral Galaxies of the Local Volume: A Pilot Survey with Modest Aperture Telescopes
摘要：
[摘要]在星系形成的层次框架内，微小的合并和潮汐相互作用预计将塑造今天所有的大星系。因此，大多数看似正常的盘状星系应该被空间扩展的恒星“潮汐特征”所包围，表面亮度低。作为对这种相互作用特征的初步调查的一部分，我们对局部体积中的8个孤立旋涡星系进行了超深宽视场成像，数据是在小型（D=0.1- 0.5 m）机器人望远镜上拍摄的，这些望远镜提供了精确的表面亮度灵敏度（μ V）~28.5$ mag/arcsec ^[2]。这一初步的观测工作导致在这些星系周围的晕中发现了六个以前未被发现的广泛（~30 kpc）的恒星结构，可能是潮汐破坏卫星的碎片。此外，我们确认和澄清几个巨大的恒星过密度以前在文献中报道，但从来没有以前解释为潮汐流。即使是这个星系的试点样本，也表现出这些扩展恒星特征的惊人多样的形态特征：类似于银河系周围人马座流的巨大圆形特征，遥远的外壳和远离主恒星体的巨大潮汐碎片云，以及从星系盘中出现的喷流状特征。与现有的模拟设置在一个拉姆达冷暗物质宇宙学的定性比较表明，在这个试点调查中检测到的恒星形态的异常变化与这些模拟中看到的相匹配。这些潮汐功能周围的“正常”盘星系和形态匹配的模拟共同存在构成了新的证据，这些理论模型也适用于大量的其他银河系质量盘星系在本地卷。
英文摘要：
[Abridged] Within the hierarchical framework for galaxy formation, minor merging and tidal interactions are expected to shape all large galaxies to the present day. As a consequence, most seemingly normal disk galaxies should be surrounded by spatially extended stellar 'tidal features' of low surface brightness. As part of a pilot survey for such interaction signatures, we have carried out ultra deep, wide field imaging of 8 isolated spiral galaxies in the Local Volume, with data taken at small (D=0.1-0.5m) robotic telescopes that provide exquisite surface brightness sensitivity (mu_V)~28.5$ mag/arcsec^2). This initial observational effort has led to the discovery of six previously undetected extensive (to ~30 kpc) stellar structures in the halos surrounding these galaxies, likely debris from tidally disrupted satellites. In addition, we confirm and clarify several enormous stellar over-densities previously reported in the literature, but never before interpreted as tidal streams. Even this pilot sample of galaxies exhibits strikingly diverse morphological characteristics of these extended stellar features: great circle-like features that resemble the Sagittarius stream surrounding the Milky Way, remote shells and giant clouds of presumed tidal debris far beyond the main stelar body, as well as jet-like features emerging from galactic disks. A qualitative comparison with available simulations set in a Lambda-Cold Dark Matter cosmology shows that the extraordinary variety of stellar morphologies detected in this pilot survey matches that seen in those simulations. The common existence of these tidal features around 'normal' disk galaxies and the morphological match to the simulations constitutes new evidence that these theoretical models also apply to a large number of other Milky Way-mass disk galaxies in the Local Volume.
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