ACS天炉座星团巡天。VI。天炉座星系团早型星系核
The ACS Fornax Cluster Survey. VI. The Nuclei of Early-Type Galaxies in the Fornax Cluster
摘要：
天炉座星系团巡天（英语：Fornax Cluster Survey）是哈勃太空望远镜的一项计划，利用ACS的F475 W和F850 LP带通对天炉座星系团中的43个早期星系进行成像。我们采用1D和2D技术来表征这些星系中的恒星核的性质，定义为中心的“光度过剩”相对于Sersic模型适合于底层主机。我们发现72+/-13%的样本（31个星系）是成核的，只有三个核偏离星系光心超过0.5”，大多数核的颜色比它们的宿主更蓝。观察到的核更大，更明亮，比典型的天炉座球状星团，并遵循不同的结构标度关系。将我们的结果与ACS室女星系团巡天的结果进行比较，发现属于这些不同环境的原子核的性质有惊人的相似之处。我们简要地回顾了各种拟议的形成模型，并得出结论，在我们的样本中的低质量星系，最重要的机制，核增长可能是通过动力学摩擦的恒星团的下落，而对于更高质量的星系，气体吸积引发的合并，吸积和潮汐扭矩可能占主导地位，这两个过程的相对重要性变化顺利作为星系质量的函数。在我们的样本中，一些中等质量的星系显示出其内部结构的复杂性，这可能是通过平行形成通道产生的“混合核”的特征。
英文摘要：
The Advanced Camera for Surveys (ACS) Fornax Cluster Survey is a Hubble Space Telescope program to image 43 early-type galaxies in the Fornax cluster, using the F475W and F850LP bandpasses of the ACS. We employ both 1D and 2D techniques to characterize the properties of the stellar nuclei in these galaxies, defined as the central "luminosity excesses" relative to a Sersic model fitted to the underlying host. We find 72+/-13% of our sample (31 galaxies) to be nucleated, with only three of the nuclei offset by more than 0.5" from their galaxy photocenter, and with the majority of nuclei having colors bluer than their hosts. The nuclei are observed to be larger, and brighter, than typical Fornax globular clusters, and to follow different structural scaling relations. A comparison of our results to those from the ACS Virgo Cluster Survey reveals striking similarities in the properties of the nuclei belonging to these different environments. We briefly review a variety of proposed formation models and conclude that, for the low-mass galaxies in our sample, the most important mechanism for nucleus growth is probably infall of star clusters through dynamical friction, while for higher mass galaxies, gas accretion triggered by mergers, accretions and tidal torques is likely to dominate, with the relative importance of these two processes varying smoothly as a function of galaxy mass. Some intermediate-mass galaxies in our sample show a complexity in their inner structure that may be the signature of "hybrid nuclei" that arose through parallel formation channels.
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