Chandra Observation of Diffuse Gas and Lmxbs in the Elliptical Galaxy Ngc 4649 (m60)
Chandra Observation of Diffuse Gas and Lmxbs in the Elliptical Galaxy Ngc 4649 (m60)
复制标题
钱德拉对椭圆星系 Ngc 4649 (m60) 中扩散气体和 Lmxb 的观测
DOI：
--
复制
发表时间：
2003
期刊：
影响因子：
--
通讯作者：
J. Irwin
中科院分区：
文献类型：
--
作者：
S. Randall;C. Sarazin;J. Irwin
我们给出了X射线明亮的E2椭圆星系NGC4649的Chandra X射线观测结果。除了明亮的漫反射发射，我们还解析了165个离散源，其中大部分可能是低质量X射线双星(LMXB)。在以前的研究中发现，分辨光源的光度函数符合破缺的幂定律。在NGC4697和NGC1553中，爆裂亮度相当于1.4M⊙中子星的爱丁顿光度。对这一结果的一种可能的解释是，在破裂上方具有亮度的源是吸积黑洞，而在破裂下面的源主要是吸积中子星。分解源的总X射线谱符合硬幂定律，而漫反射谱则需要硬成分和软成分，这可能是由于相对较软的扩散气体和较硬的未分辨源所致。我们还在NGC4649中心附近的漫反射发射中找到了结构的证据。具体地说，银河系中心似乎有明亮的发射“手指”，在银河系中心有一个5英尺长的条形。这些手指在形态上类似于椭圆星系冷却流动的二维流体动力学模拟中看到的径向特征，尽管它们的其他性质与特定模拟的预测不匹配，但我们得出结论，径向手指可能是由于热的流出气体和较冷的流入气体的对流运动所致。该条形与中心扩展射电源重合；我们得出结论，该条形可能是由未被探测到的低光度活动星系核(AGN)的扩散气体中的弱激波引起的。
We present a Chandra X-ray observation of the X-ray bright E2 elliptical galaxy NGC 4649. In addition to bright diffuse emission, we resolve 165 discrete sources, most of which are presumably low-mass X-ray binaries (LMXBs). As found in previous studies, the luminosity function of the resolved sources is well-fit by a broken power-law. In NGC 4697 and NGC 1553, the break lumi-nosity was comparable to the Eddington luminosity of a 1.4 M ⊙ neutron star. One possible interpretation of this result is that those sources with luminosities above the break are accreting black holes and those below are mainly accreting neutron stars. The total X-ray spectrum of the resolved sources is well-fit by a hard power-law, while the diffuse spectrum requires a hard and a soft component , presumably due to the relatively soft diffuse gas and the harder unresolved sources. We also find evidence for structure in the diffuse emission near the center of NGC 4649. Specifically, there appear to be bright " fingers " of emission extending from the center of the galaxy and a 5 ′′ long bar at the center of the galaxy. The fingers are morphologically similar to radial features seen in two-dimensional hydrodynamic simulations of cooling flows in elliptical galaxies, and although their other properties do not match the predictions of the particular simulations used we conclude that the radial fingers might be due to convective motions of hot outflowing gas and cooler inflowing gas. The bar is coincident with the central extended radio source; we conclude that the bar may be caused by weak shocks in the diffuse gas from an undetected low-luminosity active galactic nucleus (AGN).