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arXiv 2108.03231astro-ph.GA
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陨落之后:解析星暴后星系中的分子气体

After The Fall: Resolving the Molecular Gas in Post-Starburst Galaxies

Adam Smercina, John-David T. Smith, K. Decker French, Eric F. Bell, Daniel A. Dale, Anne M. Medling, Kristina Nyland, George C. Privon, Kate Rowlands, Fabian Wa… 展开作者

Adam Smercina, John-David T. Smith, K. Decker French, Eric F. Bell, Daniel A. Dale, Anne M. Medling, Kristina Nyland, George C. Privon, Kate Rowlands, Fabian Walter, Ann I. Zabludoff

摘要:

后星暴(PSB),或“E+ A”,星系代表了一个快速过渡阶段之间的主要,丰富的气体合并和气体贫乏,静止的早期类型的星系。令人惊讶的是,许多PSB已经被证明拥有重要的星际介质(ISM),尽管理论预测大多数恒星形成气体应该在活动星系核或恒星爆发驱动的外流中排出。到目前为止,这个幸存的ISM的解析属性仍然未知。我们提出了高分辨率的ALMA连续和CO(2 $-$ 1)的观测在6个气体和灰尘丰富的PSB,揭示了第一次的空间和运动学结构的ISM次千秒差距尺度。我们发现了非常紧凑的分子库,尘埃和气体的表面密度与(超)明亮的红外星系中发现的密度相媲美。我们观察到的空间和运动学的干扰,在所有的来源,有些还显示盘状运动。气体内部的湍流压力估计超过正常恒星形成盘至少2个数量级,并与在局部相互作用星系(如银河系)中发现的湍流气体相媲美。虽然这种高湍流压力的来源仍然不确定,我们认为,在PSB的潮汐中断事件(TDEs)的高发病率可能发挥作用。这些PSB的湍流中央分子库中的恒星形成受到抑制,形成恒星的效率仅为具有类似气体表面密度的星暴星系的10%。在这些星系中,恒星形成的“下降”并不是由于完全的气体排出或重新分布而促成的。相反,这张高分辨率的PSB ISM视图表明,它们剩余的致密气体储层中的恒星形成受到显着湍流加热的抑制。

英文摘要:

Post-starburst (PSB), or 'E+A', galaxies represent a rapid transitional phase between major, gas-rich mergers and gas-poor, quiescent early-type galaxies. Surprisingly, many PSBs have been shown to host a significant interstellar medium (ISM), despite theoretical predictions that the majority of star-forming gas should be expelled in AGN- or starburst-driven outflows. To-date, the resolved properties of this surviving ISM have remained unknown. We present high resolution ALMA continuum and CO(2$-$1) observations in six gas- and dust-rich PSBs, revealing for the first time the spatial and kinematic structure of their ISM on sub-kpc scales. We find extremely compact molecular reservoirs, with dust and gas surface densities rivaling those found in (ultra-)luminous infrared galaxies. We observe spatial and kinematic disturbances in all sources, with some also displaying disk-like kinematics. Estimates of the internal turbulent pressure in the gas exceed those of normal star-forming disks by at least 2 orders of magnitude, and rival the turbulent gas found in local interacting galaxies, such as the Antennae. Though the source of this high turbulent pressure remains uncertain, we suggest that the high incidence of tidal disruption events (TDEs) in PSBs could play a role. The star formation in these PSBs' turbulent central molecular reservoirs is suppressed, forming stars only 10% as efficiently as starburst galaxies with similar gas surface densities. "The fall" of star formation in these galaxies was not precipitated by complete gas expulsion or redistribution. Rather, this high-resolution view of PSBs' ISM indicates that star formation in their remaining compact gas reservoirs is suppressed by significant turbulent heating.

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