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arXiv 1507.01723astro-ph.GA
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探测室女星系团的低表面亮度矮星系群

Probing the Low Surface Brightness Dwarf Galaxy Population of the Virgo Cluster

J. I. Davies, L. J. M. Davies, O. C. Keenan

摘要:

我们使用了下一代室女座巡天(NGVS)的公开数据来研究室女星系团的矮星系人口,这超出了以前的发现。我们首先屏蔽和平滑数据,然后使用对象检测算法Sextractor来进行我们的初始矮星系选择。然后对所有候选人进行目视检查,以去除伪影和重复。我们推导Sextractor参数,以最好地选择低表面亮度星系使用g波段中心表面亮度值为22.5至26.0等平方角秒和指数尺度长度为3.0 - 10.0角秒,以确定443个簇矮星系-其中303个是新的检测。这些新探测到的表面密度随着距离星团中心的半径而减小。我们还将我们的选择算法应用于“背景”,非集群,字段,并找到零检测。结合起来,这使我们相信我们已经分离出了一个星团矮星系群。我们能够探测到的物体范围是有限的,因为较小尺度的星系与背景混淆,而较大的星系被探测算法分成许多较小的物体。使用以前的调查数据结合我们的数据,我们发现一个微弱的终端斜率的光度函数为-1.35+/-0.03,这并没有显着不同,以前发现的室女星系团,但有点陡于场星系的斜率。没有证据表明暗端斜率陡到足以与星系形成模型相对应,除非这些模型调用强反馈过程或使用温暖的暗物质。

英文摘要:

We have used public data from the Next Generation Virgo Survey (NGVS) to investigate the dwarf galaxy population of the Virgo cluster beyond what has previously been discovered. We initially mask and smooth the data, and then use the object detection algorithm Sextractor to make our initial dwarf galaxy selection. All candidates are then visually inspected to remove artefacts and duplicates. We derive Sextractor parameters to best select low surface brightness galaxies using g band central surface brightness values of 22.5 to 26.0 mag sq arc sec and exponential scale lengths of 3.0 - 10.0 arc sec to identify 443 cluster dwarf galaxies - 303 of which are new detections. These new detections have a surface density that decreases with radius from the cluster centre. We also apply our selection algorithm to 'background', non-cluster, fields and find zero detections. In combination, this leads us to believe that we have isolated a cluster dwarf galaxy population. The range of objects we are able to detect is limited because smaller scale sized galaxies are confused with the background, while larger galaxies are split into numerous smaller objects by the detection algorithm. Using data from previous surveys combined with our data, we find a faint end slope to the luminosity function of -1.35+/-0.03, which does not significantly differ to what has previously been found for the Virgo cluster, but is a little steeper than the slope for field galaxies. There is no evidence for a faint end slope steep enough to correspond with galaxy formation models, unless those models invoke either strong feedback processes or use warm dark matter.

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