Emission-line properties of the optical filaments of NGC 1275

被引:29
作者
Sabra, BM [1 ]
Shields, JC
Filippenko, AV
机构
[1] Ohio Univ, Dept Phys & Astron, Athens, OH 45701 USA
[2] Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA
基金
美国国家科学基金会;
关键词
cooling flows; galaxies : clusters : individual (Perseus); galaxies : individual (NGC 1275); galaxies : ISM;
D O I
10.1086/317793
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Extended nebular filaments are seen at optical wavelengths in NGC 1275, the central galaxy in the Perseus cluster. The agents responsible for the excitation of these filaments remain poorly understood. In this paper we investigate possible mechanisms for powering the filaments, using measurements from an extensive spectroscopic data set acquired at the Lick Observatory 3 m Shane telescope. The results show that the filaments are in an extremely low ionization and excitation state. The high signal-to-noise ratio of the spectra allows us to measure or place sensitive upper limits on weak but important diagnostic lines. We compare the observed line intensity ratios to the predictions of various ionization models, including photoionization by an active galactic nucleus, shock heating, stellar photoionization, and photoionization by the intracluster medium. We also investigate possible roles for cluster extreme-ultraviolet emission, and filtering of cluster soft X-ray emission by an ionized screen, in the energetics of the filaments. None of these mechanisms provides an entirely satisfactory explanation for the physical state of the nebulae. Heating and ionization by reconnection of the intracluster magnetic field remains a potentially viable alternative, which merits further investigation through Faraday rotation studies.
引用
收藏
页码:157 / 170
页数:14
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