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arXiv 2501.07286astro-ph.GA
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利用FAST比较MaNGA星系对中的全局HI与H$α$谱线轮廓

Comparison of Global HI and H$α$ Line Profiles in MaNGA Galaxy Pairs with FAST

Gaoxiang Jin, Y. Sophia Dai, Cheng Cheng, Cong Kevin Xu, Jia-Sheng Huang, Lihwai Lin

AI总结:

本研究利用FAST观测6个不同并合阶段、不同核活动的星系对,结合光学积分场光谱对比HI与Hα谱线,发现并合过程可推动不同相态气体混合对齐。

摘要:

我们开展了案例研究,对比6个星系对的全局HI与H$α$发射线轮廓。这6个星系对经筛选具有不同的核活动,其中2个包含活动星系核,且处于不同的并合阶段(并合前、并合中、并合后阶段各2个)。我们使用五百米口径球面射电望远镜(FAST)观测了它们的全局HI光谱,实现了约0.5 mJy的噪声水平。6个星系对系统中有5个明确探测到了HI发射(信噪比>10)。这6个星系对的HI占比和恒星形成效率与孤立星系相比没有偏离。在HI谱线轮廓方面,观测到了普遍存在的独特不对称性,表明星系相互作用对原子气体产生了扰动。并合系统的全局H$α$光谱由光学积分场光谱观测构建,通过对对应视向速度区间内的流量进行积分得到。H$α$光谱在并合前阶段往往呈现多成分,在并合后系统中呈现单成分谱线轮廓,而所有HI光谱无论并合阶段如何均呈现单成分谱线轮廓。HI与H$α$光谱的中心速度存在偏移,偏移量似乎从并合前星系对的>100 km/s降至并合后星系对的<10 km/s。这一趋势与如下情景一致:尽管原子气体和电离气体的分布与运动学特征存在显著差异,但并合过程可能有助于各类气体成分的混合并最终实现对齐。

英文摘要:

We present case studies comparing the global HI and H$α$ emission line profiles of six galaxy pairs. The six pairs are selected to have different nuclear activities, with two hosting an active galactic nucleus, and in different merging stages (two of each from pre-merging, merging, and post-merger stages). We observe their global HI spectra with the Five-hundred-meter Aperture Spherical radio Telescope (FAST), achieving a noise level of about 0.5 mJy. Five out of the six pair systems have secure detections of HI emissions (signal-to-noise ratio > 10). The HI fraction and star formation efficiency of the six pairs do not deviate from isolated galaxies. For the HI line profiles, common unique asymmetry is observed, indicating disturbances on the atomic gas from the galaxy interaction. The global H$α$ spectra of the merger systems are constructed from the optical integral field spectroscopic observations, by integrating the flux in corresponding line-of-sight velocity bins. The H$α$ spectra tend to show multiple components in the pre-merger phase, and single component line profiles in the post-merger systems, while all HI spectra show single component line profiles regardless of merger stages. The HI and H$α$ spectra show offsets in the central velocities, which appear to decrease from >100 km/s in the pre-merger pair to <10 km/s in post-merger pairs. This trend is consistent with the scenario that, despite the significantly different distribution and kinematics of the atomic and ionized gases, the merging process may contribute to the mixing and eventually align various gas contents.

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