Hard X-Ray Irradiation Potentially Drives Negative AGN Feedback by Altering Molecular Gas Properties
Hard X-Ray Irradiation Potentially Drives Negative AGN Feedback by Altering Molecular Gas Properties
复制标题
DOI：
10.3847/1538-4365/ac2891
复制
发表时间：
2021-09
期刊：
影响因子：
--
通讯作者：
T. Kawamuro;C. Ricci;T. Izumi;M. Imanishi;S. Baba;Dieu D. Nguyen;K. Onishi
中科院分区：
文献类型：
--
作者：
T. Kawamuro;C. Ricci;T. Izumi;M. Imanishi;S. Baba;Dieu D. Nguyen;K. Onishi
为了研究活动星系核(AGN)X射线辐照对星际介质(ISM)的作用，我们系统地分析了Chandra和Atalama大毫米/亚毫米阵列CO(J=2-1)的数据，这些数据来自于红移小于0.05的26个硬X射线(>；10keV)活动星系核。钱德拉通过Fe-Kα发射揭示了X射线辐照气体的分布，而CO(J=2-1)观测揭示了冷分子气体的分布。在高分辨率≲1“下，我们得到了核2”区和外环2“-4”区的Fe-Kα和CO(J=2-1)图，其中2“是我们大多数活动星系核的∼100-600pc。首先，聚焦于外部区域，我们得到了6个活动星系核在2α以上的Fe-Kσ发射。它们的大宽度(≳1keV)表明它们的起源是一种荧光过程。此外，通过比较Fe-Kα探测最显著的三个活动星系核的6-7keV/3-6keV比值和CO(J=2-1)图像，我们发现了一种可能的空间分离。这些都表明X射线辐照ISM的存在和ISM性质的变化。接下来，我们研究了核区，我们发现：(1)20-50keV光度随CO(J=2-1)光度增加；(2)CO(J=2-1)/HCN(J=1-0)光度比随20-50keV光度增加而增大，表明致密气体分数随X射线光度的降低而减小；(3)Fe-Kα-X射线连续谱光度比随分子气体质量的增加而减小。这可以用活动星系核的负反馈情景来解释：质量吸积率随着气体质量的增加而增加，同时活动星系核蒸发了一部分气体，这可能会影响恒星的形成。
To investigate the role of active galactic nucleus (AGN) X-ray irradiation on the interstellar medium (ISM), we systematically analyzed Chandra and Atacama Large Millimeter/submillimeter Array CO (J = 2–1) data for 26 hard X-ray (>10 keV) selected AGNs at redshifts below 0.05. While Chandra unveils the distribution of X-ray-irradiated gas via Fe-Kα emission, the CO (J = 2–1) observations reveal that of cold molecular gas. At high resolutions ≲1″, we derive Fe-Kα and CO (J = 2–1) maps for the nuclear 2″ region and for the external annular region of 2″–4″, where 2″ is ∼100–600 pc for most of our AGNs. First, focusing on the external regions, we find the Fe-Kα emission for six AGNs above 2σ. Their large equivalent widths (≳1 keV) suggest a fluorescent process as their origin. Moreover, by comparing the 6–7 keV/3–6 keV ratio, as a proxy of Fe-Kα, and CO (J = 2–1) images for three AGNs with the highest significant Fe-Kα detections, we find a possible spatial separation. These suggest the presence of X-ray-irradiated ISM and the change in the ISM properties. Next, examining the nuclear regions, we find that (1) the 20–50 keV luminosity increases with the CO (J = 2–1) luminosity; (2) the ratio of CO (J = 2–1)/HCN (J = 1–0) luminosities increases with 20–50 keV luminosity, suggesting a decrease in the dense gas fraction with X-ray luminosity; and (3) the Fe-Kα-to-X-ray continuum luminosity ratio decreases with the molecular gas mass. This may be explained by a negative AGN feedback scenario: the mass accretion rate increases with gas mass, and simultaneously, the AGN evaporates a portion of the gas, which possibly affects star formation.