arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2006.15041astro-ph.GA
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NGC 1068中CS的ALMA观察:化学和激发

ALMA observations of CS in NGC 1068: chemistry and excitation

M. Scourfield, S. Viti, S. Garcia-Burillo, A. Saintonge, F. Combes, A. Fuente, C. Henkel, A. Alonso-Herrero, N. Harada, S. Takano, T. Nakajima, S. Martin, M. Kr… 展开作者

M. Scourfield, S. Viti, S. Garcia-Burillo, A. Saintonge, F. Combes, A. Fuente, C. Henkel, A. Alonso-Herrero, N. Harada, S. Takano, T. Nakajima, S. Martin, M. Krips, P. P. van der Werf, S. Aalto, A. Usero, K. Kohno

摘要:

我们目前的结果从阿塔卡马大型毫米/亚毫米阵列(ALMA)的CS从附近的星系NGC 1068($\sim14$ Mpc)的观测。这个塞弗特2型棒星系拥有一个环核盘(CND,$r\sim200$ pc)和一个星暴环(SB环,$r\sim1.3$ kpc)。这些高分辨率地图($\sim0.5$ ",$\sim35$ pc)使我们能够分析星系中的特定子区域,并调查线强度比和物理条件的差异,特别是CND和SB环之间的差异。局部热力学平衡(LTE)分析的气体被用来计算CS密度在每个子区域,然后进行非LTE分析,使用辐射传输代码RADEX,以适应观测和约束气体温度,CS柱密度和氢密度。最后,化学代码UCLCHEM用于重建气体,从而深入了解其起源和化学历史。CND中氢的密度被发现是$\geq10^5$ cm $^{-2}$,虽然精确的值各不相同,在活动星系核达到$10^6$ cm $^{-2}$。SB环两臂的情况似乎彼此相似,但发现的密度($\sim10^4$ cm $^{-2}$)低于CND。CND的温度从东向西升高,总体上也高于SB环。这些建模方法表明,需要多相气体成分,以适应观测到的星系发射。跨SLED的更大数量的高分辨率转变可以允许进一步约束条件,特别是在SB环中。

英文摘要:

We present results from Atacama Large Millimeter/submillimeter Array (ALMA) observations of CS from the nearby galaxy NGC 1068 ($\sim14$ Mpc). This Seyfert 2 barred galaxy possesses a circumnuclear disc (CND, $r\sim200$ pc) and a starburst ring (SB ring, $r\sim1.3$ kpc). These high-resolution maps ($\sim0.5$", $\sim35$ pc) allow us to analyse specific sub-regions in the galaxy and investigate differences in line intensity ratios and physical conditions, particularly those between the CND and SB ring. Local thermodynamic equilibrium (LTE) analysis of the gas is used to calculate CS densities in each sub-region, followed by non-LTE analysis conducted using the radiative transfer code RADEX to fit observations and constrain gas temperature, CS column density and hydrogen density. Finally, the chemical code UCLCHEM is used to reconstruct the gas, allowing an insight into its origin and chemical history. The density of hydrogen in the CND is found to be $\geq10^5$ cm$^{-2}$, although exact values vary, reaching $10^6$ cm$^{-2}$ at the AGN. The conditions in the two arms of the SB ring appear similar to one another, though the density found ($\sim10^4$ cm$^{-2}$) is lower than in the CND. The temperature in the CND increases from east to west, and is also overall greater than found in the SB ring. These modelling methods indicate the requirement for multi-phase gas components in order to fit the observed emission over the galaxy. A larger number of high resolution transitions across the SLED may allow for further constraining of the conditions, particularly in the SB ring.

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