JOINT XMM-NEWTON AND CHANDRA OBSERVATIONS OF THE NGC 1407/1400 COMPLEX: A TAIL OF AN EARLY-TYPE GALAXY AND A TALE OF A NEARBY MERGING GROUP
JOINT XMM-NEWTON AND CHANDRA OBSERVATIONS OF THE NGC 1407/1400 COMPLEX: A TAIL OF AN EARLY-TYPE GALAXY AND A TALE OF A NEARBY MERGING GROUP
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DOI：
10.1088/0004-637x/786/2/152
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发表时间：
2014-03
期刊：
影响因子：
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通讯作者：
Yuanyuan Su;L. Gu;Raymond E. White III;J. Irwin
中科院分区：
文献类型：
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作者：
Yuanyuan Su;L. Gu;Raymond E. White III;J. Irwin
以其明亮的中央星系NGC 1407为中心的附近星系群已经被先前的运动学研究认为是一个异常黑暗的系统。它还以拥有一个明亮的星系NGC 1400而闻名，该星系相对于群中心的径向速度很大（1200 km s−1）。以前的ROSAT X射线观测显示，在NGC 1400的东面有一个扩大的表面亮度增强区域。我们研究了NGC 1407/1400复合体的XMM-牛顿和钱德拉观测。我们发现，增强区域的温度和金属丰度是不同的（更冷，更富含金属）比周围的组气体，但与NGC 1400中的星际介质（ISM）是一致的。NGC 1400的相对速度足够大，以至于它的大部分ISM可能在穿过大气层时被冲压压力剥离。我们的结论是，增强区很可能是从NGC 1400的ISM剥离的热气体。我们使用NGC 1407群的总质量分布和其相关的停滞锋处的压力跃变来约束NGC 1400的运动。我们的结论是，NGC 1400是在视线范围内与马赫数为0.30 °。我们在这个复合体中没有检测到任何明显的激波特征，可能是因为NGC 1400的高视线运动。用一个XMM-牛顿指向相对松弛的NGC 1407东侧，我们推导出这群100 kpc以内的流体静力质量为101 × 1013 M。外推到维里半径（681 kpc）的总质量是3.8 × 1013 M，这使得这个群的质光比上限为10300。这表明NGC 1407星系群并不是一个异常黑暗的星系群。
The nearby group centered on its bright central galaxy NGC 1407 has been suggested by previous kinematic studies to be an unusually dark system. It is also known for hosting a bright galaxy, NGC 1400, with a large radial velocity (1200 km s−1) with respect to the group center. Previous ROSAT X-ray observations revealed an extended region of enhanced surface brightness just eastward of NGC 1400. We investigate the NGC 1407/1400 complex with XMM-Newton and Chandra observations. We find that the temperature and metallicity of the enhanced region are different (cooler and more metal rich) than those of the surrounding group gas but are consistent with those of the interstellar medium (ISM) in NGC 1400. The relative velocity of NGC 1400 is large enough that much of its ISM could have been ram pressure stripped while plunging through the group atmosphere. We conclude that the enhanced region is likely to be hot gas stripped from the ISM of NGC 1400. We constrain the motion of NGC 1400 using the pressure jump at its associated stagnation front and the total mass profile of the NGC 1407 group. We conclude that NGC 1400 is moving within ∼30° of the line of sight with Mach number . We do not detect any obvious shock features in this complex, perhaps because of the high line-of-sight motion of NGC 1400. With an XMM-Newton pointing on the relatively relaxed eastern side of NGC 1407, we derive a hydrostatic mass for this group of ∼1 × 1013 M☉ within 100 kpc. The total mass extrapolated to the virial radius (681 kpc) is 3.8 × 1013 M☉, which puts an upper limit of ∼300 on the mass-to-light ratio of this group. This suggests that the NGC 1407 group is not an unusually dark group.