Correlation between excitation index and Eddington ratio in radio galaxies  

作　　者：Jing-Fu Hu Xin-Wu Cao Liang Chen Bei You 

机构地区：[1]Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China [2]Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China [3]Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, 210008 Nanjing, China [4]University of Chinese Academy of Sciences, Beijing 100049, China [5]Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Bartycka 18,00-716, Warsaw, Poland

出　　处：《Research in Astronomy and Astrophysics》2016年第9期23-30,共8页天文和天体物理学研究（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant Nos. 11173043 and 11233006);the Strategic Priority Research Program “the Emergence of Cosmological Structures” of the CAS (Grant No. XDB09000000);the CAS/SAFEA International Partnership Program for Creative Research Teams

摘　　要：We use a sample of 111 radio galaxies with redshift z 〈 0.3 to investigate their nuclear properties. The black hole masses of the sources in this sample are estimated with the velocity dispersion/luminosity of the galaxies, or the width of the broad-lines. We find that the excitation index, the relative intensity of low and high excitation lines, is correlated with the Eddington ratio for this sample. The size of the narrow-line region （NLR） was found to vary with ionizing luminosity as RNLR ∝ Lion^0.25 （Liu et al. 2013）. Using this empirical relation, we find that the correlation between the excitation index and the Eddington ratio can be reproduced by photoionization models. We adopt two sets of spectral energy distributions （SEDs）, with or without a big blue bump in ultraviolet as the ionizing continuum, and infer that the modeled correlation between the excitation index and the Eddington ratio is insensitive to the applied SED. This means that the difference between high excitation galaxies and low excitation galaxies is not caused by the different accretion modes in these sources. Instead, it may be caused by the size of the NLR.We use a sample of 111 radio galaxies with redshift z 〈 0.3 to investigate their nuclear properties. The black hole masses of the sources in this sample are estimated with the velocity dispersion/luminosity of the galaxies, or the width of the broad-lines. We find that the excitation index, the relative intensity of low and high excitation lines, is correlated with the Eddington ratio for this sample. The size of the narrow-line region （NLR） was found to vary with ionizing luminosity as RNLR ∝ Lion^0.25 （Liu et al. 2013）. Using this empirical relation, we find that the correlation between the excitation index and the Eddington ratio can be reproduced by photoionization models. We adopt two sets of spectral energy distributions （SEDs）, with or without a big blue bump in ultraviolet as the ionizing continuum, and infer that the modeled correlation between the excitation index and the Eddington ratio is insensitive to the applied SED. This means that the difference between high excitation galaxies and low excitation galaxies is not caused by the different accretion modes in these sources. Instead, it may be caused by the size of the NLR.

关 键 词：accretion  accretion disks -- black hole physics -- galaxies active 

分 类 号：P152[天文地球—天文学]