Hydra I星团（Abell 1060）核心漫射恒星光的非混合运动学和起源
The unmixed kinematics and origins of diffuse stellar light in the core of the Hydra I cluster (Abell 1060)
摘要：
弥散的团内光（ICL）和cD星系晕被认为是起源于星系的演化和分裂。我们提出了一个在长蛇座I星系团核心的ICL的运动学研究，使用行星状星云（PNs）作为示踪剂。我们使用VLT-UT 1上的FORS 2多缝成像光谱仪，在长蛇座I中央100 x 100 kpc ^2的区域中探测到了56个与漫射光相关的PN。我们测量了它们的[OIII]星等、天空位置和速度分布（LOSVD），并与附近星系的相空间分布进行了比较。探测到的PNs的光度函数与在~50 Mpc距离处的预期一致。它们的数密度比预期的低4倍，我们讨论了热ICM对PN的冲压压力剥离作为可能的解释之一。PNs的LOSVD直方图是高度非高斯的和多峰的：它由一个宽的中心分量占主导地位，在星系团的平均速度附近的sigma约为500 km/s，并在1800 km/s和5000 km/s处显示出另外两个较窄的峰值。其主要成分与NGC 3311的团内晕向外延伸大致一致，较早的研究表明，NGC 3311在半径>50”时的速度色散约为470 km/s。在中心100 x 100 kpc ^2的区域中不存在速度在这个范围内的Galerkin，并且可能在更早的时候被破坏以形成这个分量。在5000 km/s的LOSVD的第二个峰值中的PNs在空间上和速度上与MSIS场中的一组矮星系一致。他们可能会追踪这些星系正在发生的潮汐破裂的碎片。Hydra核心的大部分漫射光仍然没有相位混合。ICL和NGC 3311周围的动态热cD晕的建立正在进行中，通过星系的吸积物质落入星系团核心并与其势阱发生潮汐相互作用。
英文摘要：
Diffuse intracluster light (ICL) and cD galaxy halos are believed to originate from galaxy evolution and disruption. We present a kinematic study of the ICL in the Hydra I cluster core, using planetary nebulas (PNs) as tracers. We used multi-slit imaging spectroscopy with FORS2 on VLT-UT1 to detect 56 PNs associated with diffuse light in the central 100 x 100 kpc^2 of Hydra I. We measured their [OIII] magnitudes, sky positions, and velocity distribution (LOSVD), and compared with the phase-space distribution of nearby galaxies. The luminosity function of the detected PNs is consistent with that expected at a distance of ~50 Mpc. Their number density is ~4 times lower for the light seen than expected, and we discuss ram pressure stripping of the PNs by the hot ICM as one of the possible explanations. The LOSVD histogram of the PNs is highly non-Gaussian and multipeaked: it is dominated by a broad central component with sigma~500 km/s at around the average velocity of the cluster, and shows two additional narrower peaks at 1800 km/s and 5000 km/s. The main component is broadly consistent with the outward continuation of the intracluster halo of NGC 3311, which was earlier shown to have a velocity dispersion of ~470 km/s at radii of >50". Galaxies with velocities in this range are absent in the central 100 x 100 kpc^2 and may have been disrupted earlier to build this component. The PNs in the second peak in the LOSVD at 5000 km/s are coincident spatially and in velocities with a group of dwarf galaxies in the MSIS field. They may trace the debris from the ongoing tidal disruption of these galaxies. Most of the diffuse light in the core of Hydra is still not phase-mixed. The build-up of ICL and the dynamically hot cD halo around NGC 3311 are ongoing, through the accretion of material from galaxies falling into the cluster core and tidally interacting with its potential well.
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