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arXiv 2302.04003astro-ph.GA
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类星体 I Zwicky 1 中心区域的分子气体动力学

Dynamics of Molecular Gas in the Central Region of the Quasar I$\,$Zwicky$\,$1

Qinyue Fei, Ran Wang, Juan Molina, Jinyi Shangguan, Luis C. Ho, Franz E. Bauer, Ezequiel Treister

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20 pages, 10 figures. Accepted for publication in ApJ
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AI总结：

本文利用 ALMA 的 CO 观测数据研究了类星体 I Zwicky 1 核周区域的分子气体分布与运动学，发现中心区域动力学较热，通过盘动力学建模限制 CO 到 H2 转换因子，并指出高速度色散源于 ISM 湍流压力与重力平衡，排除了 AGN 反馈的主导作用。

摘要：

我们利用收集到的阿塔卡马大型毫米波/亚毫米波阵列（ALMA）对一氧化碳（CO）发射的观测数据，研究了红移 z≈0.061 的类星体 I Zwicky 1 核周区域（半径 $\lesssim 2\,$kpc）的分子气体分布和运动学。在 $\sim0.36''$（对应于 $\sim\,400\,\rm pc$）的角分辨率下，宿主星系的子结构（包括核区分子气体盘、旋臂和致密的棒状结构）得到了分辨。我们基于 CO 图像立方体分析了气体运动学，获得了旋转曲线和速度色散的径向分布。速度色散在外部 CO 盘区域约为 $30\,\rm km\,s^{-1}$，并在半径 $\lesssim 1\,$kpc 处升至 $\gtrsim 100\,\rm km\,s^{-1}$，表明盘的中心区域在动力学上是热的。我们通过对冷气体盘动力学进行建模，限制了 CO 到 $\rm H_2$ 的转换因子 $α_{\rm CO}$。我们发现，在具备关于恒星和暗物质成分先验知识的情况下，该类星体宿主星系核周区域的 $α_{\rm CO}$ 值为 $1.55_{-0.49}^{+0.47}\,M_\odot\,\left(\rm K\,km\,s^{-1}\,pc^2\right)^{-1}$，该值介于超亮红外星系和银河系中报告的值之间。该类星体宿主星系中心 1$\,$kpc 区域具有显著的恒星形成活动，可被认定为一次核区星暴。我们进一步研究了中心区域的高速度色散。我们发现由气体速度色散推导出的 ISM 湍流压力与 ISM 的重力处于平衡状态。这反驳了来自 AGN 反馈的额外功率显著影响冷分子气体运动学的观点。

英文摘要：

We present a study of the molecular gas distribution and kinematics in the cicumnuclear region (radii $\lesssim 2\,$kpc) of the $z\approx0.061$ quasar I$\,$Zwicky$\,$1 using a collection of available Atacama Large Millimeter/submillimeter Array (ALMA) observations of the carbon monoxide (CO) emission. With an angular resolution of $\sim0.36''$ (corresponding to $\sim\,400\,\rm pc$), the host galaxy sub-structures including the nuclear molecular gas disk, spiral arms, and a compact bar-like component are resolved. We analyzed the gas kinematics based on the CO image cube and obtained the rotation curve and radial distribution of velocity dispersion. The velocity dispersion is about $30\,\rm km\,s^{-1}$ in the outer CO disk region and rises up to $\gtrsim 100\,\rm km\,s^{-1}$ at radius $\lesssim 1\,$kpc, suggesting that the central region of disk is dynamically hot. We constrain the CO-to-$\rm H_2$ conversion factor, $α_{\rm CO}$, by modeling the cold gas disk dynamics. We find that, with prior knowledge about the stellar and dark matter components, the $α_{\rm CO}$ value in the circumnuclear region of this quasar host galaxy is $1.55_{-0.49}^{+0.47}\,M_\odot\,\left(\rm K\,km\,s^{-1}\,pc^2\right)^{-1}$, which is between the value reported in ultra-luminous infrared galaxies and in the Milky-Way. The central 1$\,$kpc region of this quasar host galaxy has significant star formation activity, which can be identified as a nuclear starburst. We further investigate the high velocity dispersion in the central region. We find that the ISM turbulent pressure derived from the gas velocity dispersion is in equilibrium with the weight of the ISM. This argues against extra power from AGN feedback that significantly affects the kinematics of the cold molecular gas.

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