Does Diffuse Circumnuclear Gas around Sgr A^(*) Achieve Collisional Ionization Equilibrium or Remain Non-equilibrium Ionization?  

作　　者：Shu Niu Fu-Guo Xie Wei Sun Li Ji 

机构地区：[1]Key Laboratory for Research in Galaxies and Cosmology,Shanghai Astronomical Observatory,Chinese Academy of Sciences,Shanghai 200030,China [2]University of Chinese Academy of Sciences,Beijing 100049,China [3]Purple Mountain Observatory,Chinese Academy of Sciences,Nanjing 210023,China [4]Key Laboratory of Dark Matter and Space Astronomy,Chinese Academy of Sciences,Nanjing 210023,China

出　　处：《Research in Astronomy and Astrophysics》2023年第8期103-116,共14页天文和天体物理学研究（英文版）

基　　金：supported in part by the National SKA Program of China(No.2020SKA0110102);the National Natural Science Foundation of China(NSFC,Nos.12192220 and 12192223);the Youth Innovation Promotion Association of CAS(Y202064)。

摘　　要：The feeding and feedback processes at the vicinity of a supermassive black hole(BH)are essential for our understanding of the connection between supermassive BH and its host galaxy.In this work,we provide a detailed investigation,both observational and theoretical,on the diffuse(~2"-20",~0.08-0.8 pc)X-ray emission around Sgr A*.Over two-decade Chandra observations are gathered to obtain highest signal-to-noise to date.We find that,the line center of iron lines of the outer 8"-18"region,ε_(c)=6.65+0.02-0.03 keV,is comparable to that(ε_(c)=6.60+0.05-0.03 keV)of the inner 2"-5"region.This is somewhat unexpected,since the gas temperature decreases further away from the central BH.Based on a dynamical inflow-outflow model that considers the gas feeding by stellar winds from Wolf-Rayet stars,we calculate the X-ray spectrum based on both the conventional collisional ionization equilibrium(CIE)assumption,and the newly developed non-equilibrium ionization(NEI)assumption.We find that,theoretically gases within~8"-10"remain in a CIE state,outside of this radius they will be in the NEI state.A comparison of the properties of~6.6 keV iron lines between CIE and NEI is addressed.Interestingly,the NEI interpretation of outer region is supported by the Chandra line center ε_(c) measurements of this region.

关 键 词：X-rays diffuse background-galaxies active-Galaxy center-(galaxies:)quasars emission lines 

分 类 号：P145.8[天文地球—天体物理]