Chandra Observations of Gas Stripping in the Elliptical Galaxy NGC 4552 in the Virgo Cluster

Chandra Observations of Gas Stripping in the Elliptical Galaxy NGC 4552 in the Virgo Cluster
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DOI：
10.1086/503350
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发表时间：
2005-08
期刊：
The Astrophysical Journal
影响因子：
--
通讯作者：
M. Machacek;C. Jones;W. Forman;P. Nulsen;P. Nulsen
M. Machacek;C. Jones;W. Forman;P. Nulsen;P. Nulsen
中科院分区：
其他
文献类型：
--
作者：
M. Machacek;C. Jones;W. Forman;P. Nulsen;P. Nulsen

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我们使用 54.4 ks 钱德拉观测来研究 NGC 4552 (M89)（处女座星系团中的一个椭圆星系）中的冲压压力剥离。 0.5-2 keV 波段的钱德拉图像显示，银河系中心以北的表面亮度为 3.1 kpc，有一个尖锐的前缘，平均密度 ne ~ × 10-3 cm-3 的冷尾部（kT = 0.51 keV）向银河系南部延伸约 10 kpc，以及两个从前缘向南延伸的 3-4 kpc 发射角。这些都是由于 NGC 4552 穿过周围室女座 ICM 的运动而导致星系气体超音速冲压压力剥离的特征。拟合前缘的表面亮度分布和光谱，我们发现边缘内的星系气体比周围的处女座 ICM [kT = 2.2 keV 和 ne = (3.0 ± 0.3) × 10-4 cm-3] 更冷 (kT = 0.43 keV) 和更密集 (ne ~ 0.010 cm-3)。对于 0.5 Z☉ 的星系气体金属丰度，自由流动的 ICM 和星团气体之间在驻点处的最终压力比约为 7.6，这表明 NGC 4552 正在以相对于天空平面与我们成 θ ~ 35° ± 7° 的角度以 v ~ 1680 km s-1（马赫 2.2）的速度超音速穿过星团。
We use a 54.4 ks Chandra observation to study ram pressure stripping in NGC 4552 (M89), an elliptical galaxy in the Virgo Cluster. Chandra images in the 0.5-2 keV band show a sharp leading edge in the surface brightness 3.1 kpc north of the galaxy center, a cool (kT = 0.51 keV) tail with mean density ne ~ × 10-3 cm-3 extending ~10 kpc to the south of the galaxy, and two 3-4 kpc horns of emission extending southward away from the leading edge. These are all features characteristic of supersonic ram pressure stripping of galaxy gas, due to NGC 4552's motion through the surrounding Virgo ICM. Fitting the surface brightness profile and spectra across the leading edge, we find the galaxy gas inside the edge is cooler (kT = 0.43 keV) and denser (ne ~ 0.010 cm-3) than the surrounding Virgo ICM [kT = 2.2 keV and ne = (3.0 ± 0.3) × 10-4 cm-3]. The resulting pressure ratio between the free-streaming ICM and cluster gas at the stagnation point is ~7.6 for galaxy gas metallicities of 0.5 Z☉, which suggests that NGC 4552 is moving supersonically through the cluster with a velocity v ~ 1680 km s-1 (Mach 2.2) at an angle ξ ~ 35° ± 7° toward us with respect to the plane of the sky.