AVID：一个近主次后并的晚型矮星系位于一个规律旋转的HI盘下（VCC 693）
AVID: A Near-Major Post-Merger of Late-Type Dwarfs beneath a Regularly Rotating HI Disk (VCC 693)
AI总结：
研究通过高分辨率观测和模拟分析VCC 693的并合遗迹，发现其由近主次并合形成，HI气体形成规律旋转盘，星系结构与普通矮星系相似。
摘要：
在星系团边缘，中等高的星系密度和速度分散有利于相互作用和合并，这些事件在星系进入团前影响其演化。对矮星系这一阶段的观测研究仍然很少。我们通过原子气体在Virgo相互作用矮星系（AVID）项目中的观测数据，对VCC 693的合并遗迹进行了高分辨率研究。我们通过联合分析VLBA和FAST HI发射线观测，以及互补的光学成像和光谱学，探讨了VCC 693的起源以及合并对其恒星形成和结构的影响。我们利用流体动力学模拟来帮助解释观测结果。我们的分析倾向于一个近主次合并，两个矮星系的恒星质量比为3:1-4:1，其中一个是可能气体贫乏的先驱体（即温和的合并）。VCC 693的光学外观由系统中的复杂潮汐结构主导，而HI气体已沉降到一个规则旋转的盘中。与类似质量的矮星系相比，中心的恒星形成和气体相金属licity有所增强。VCC 693的总恒星形成率、HI气体含量和HI到光学大小比与类似质量的普通矮星系大致一致，尽管略低。将HI旋转曲线分解为恒星和暗物质部分表明了高晕浓度，这表明合并后松弛成更中心突出的配置。与最近的两个AVID合并后系统研究相结合，这些结果支持了即使主矮星系合并也能产生整体恒星结构与普通矮星系难以区分的残余物的观点，并且星团边缘的环境效应可以促进温和或混合的合并，构成了银河预处理的重要部分。
英文摘要：
On the periphery of galaxy clusters, moderately high galaxy densities and velocity dispersions favour interactions and mergers that influence galaxy evolution prior to cluster infall. Observational studies of this phase in dwarfs remain rare. We present a high-resolution study of the merger remnant VCC 693 in the outskirts of Virgo cluster, using observations from the Atomic gas in Virgo Interacting Dwarf galaxies (AVID) project. We explore the origin of VCC 693 and the consequences of the merger on its star formation and structure through a joint analysis of VLA and FAST HI emission line observations, together with complementary optical imaging and spectroscopy. We employ hydrodynamical simulations to help interpret the observations. Our analysis favours a near-major merger between two dwarfs with a stellar mass ratio of 3:1-4:1, with one likely gas-poor progenitor (i.e., a damp merger). The optical appearance of VCC 693 is dominated by complex tidal structures throughout the system, whereas the HI gas has settled to a regular rotating disk. Compared with similar-mass dwarfs, the central star formation and gas-phase metallicity are moderately enhanced. The global star formation rate, HI gas content, and HI-to-optical size ratio of VCC 693 are broadly consistent with those of typical dwarfs of similar mass, albeit somewhat lower. Decomposition of the HI rotation curve into baryonic and dark matter indicates a high halo concentration, suggesting post-merger relaxation into a more centrally peaked configuration. Together with two recent studies of AVID post-merger systems, these results support the view that even major dwarf mergers can produce remnants with overall stellar structures indistinguishable from ordinary dwarfs, and that the environmental effects in cluster outskirts can promote damp or mixed mergers, constituting an integral part of galactic pre-processing.
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