Tracing the Physical Conditions in Active Galactic Nuclei with Time-Dependent Chemistry

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• 作者：Rowin Meijerink ; Marco Spaans ; Inga Kamp ; Giambattista Aresu ; Wing-Fai Thi ; Peter Woitke
• 刊名：Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：October 3, 2013
• 年：2013
• 卷：117
• 期：39
• 页码：9593-9604
• 全文大小：957K
• 年卷期：v.117,no.39(October 3, 2013)
• ISSN：1520-5215

文摘

We present an extension of the code ProDiMo that allows for a modeling of processes pertinent to active galactic nuclei and to an ambient chemistry that is time dependent. We present a proof-of-concept and focus on a few astrophysically relevant species, e.g., H⁺, H₂⁺, and H₃⁺; C⁺ and N⁺; C and O; CO and H₂O; OH⁺, H₂O⁺, and H₃O⁺; and HCN and HCO⁺. We find that the freeze-out of water is strongly suppressed and that this affects the bulk of the oxygen and carbon chemistry occurring in the active galactic nucleus (AGN). The commonly used AGN tracer HCN/HCO⁺ is strongly time-dependent, with ratios that vary over orders of magnitude for times longer than 10⁴ years. Through Atacama large millimeter array observations this ratio can be used to probe how the narrow-line region evolves under large fluctuations in the supermassive black hole accretion rate. Strong evolutionary trends, on time scales of 10⁴鈥?0⁸ years are also found in species such as H₃O⁺, CO, and H₂O. These reflect, respectively, time-dependent effects in the ionization balance, the transient nature of the production of molecular gas, and the freeze-out/sublimation of water.