Low-density star cluster formation: discovery of a young faint fuzzy on the outskirts of the low-mass spiral galaxy NGC 247
Low-density star cluster formation: discovery of a young faint fuzzy on the outskirts of the low-mass spiral galaxy NGC 247
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低密度星团的形成：在低质量螺旋星系NGC 247的外围发现了一个年轻的微弱模糊星团
DOI：
10.1093/mnras/stac2898
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发表时间：
2022
影响因子：
4.8
通讯作者：
Cheng, Chloe M.
中科院分区：
文献类型：
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作者：
Romanowsky, Aaron J.;Larsen, Søren S.;Villaume, Alexa;Carlin, Jeffrey L.;Janz, Joachim;Sand, David J.;Strader, Jay;Brodie, Jean P.;Chakrabarti, Sukanya;Cheng, Chloe M.
在所有类型的星系中发现的经典球状星团的半光半径为rh = 2-4 pc，这与巨大分子云的致密核心的形成有关。一些老的星星团有更大的尺寸，目前还不清楚这些是否代表了一种根本不同的低密度星星团形成模式。我们报告了在附近的玉夫座星系群中的低质量螺旋星系NGC 247的外围发现了一个罕见的年轻的“暗淡模糊”星星团NGC 247-SC 1，并使用Keck光谱测量了它的径向速度。利用哈勃空间望远镜成像测量了该星团的半光半径为rh = 12 pc，光度为LV = 4 × 105 L/cm。我们绘制了星团恒星的色星等图，并与理论上的等时线进行了比较，发现其年龄为3.3亿年，金属丰度为[Z/H]<$−0.6，推断质量为M <$$> 9 × 104 M <$。蓝圈星星星等的宽度很窄，这意味着它的年龄跨度为1.5亿年，而没有发现古老的红巨星分支星，所以SC 1是一个单一的恒星群体，模几个无法解释的明亮的“红色掉队”星。SC 1似乎被潮汐碎片包围，在一个1.2kpc长的恒星细丝的末端，也有两个年龄相似的低质量，低密度的星团。我们探索这些不寻常的集群和他们的宿主星系的外部扰动的形成之间的联系，照亮了一个可能的通道，一些集群出生的大尺寸。
The classical globular clusters found in all galaxy types have half-light radii ofrh∼ 2–4 pc, which have been tied to formation in the dense cores of giant molecular clouds. Some old star clusters have larger sizes, and it is unclear if these represent a fundamentally different mode of low-density star cluster formation. We report the discovery of a rare, young ‘faint fuzzy’ star cluster, NGC 247-SC1, on the outskirts of the low-mass spiral galaxy NGC 247 in the nearby Sculptor group, and measure its radial velocity using Keck spectroscopy. We useHubble Space Telescopeimaging to measure the cluster half-light radius ofrh≃ 12 pc and a luminosity ofLV≃ 4 × 105L⊙. We produce a colour–magnitude diagram of cluster stars and compare to theoretical isochrones, finding an age of ≃300 Myr, a metallicity of [Z/H] ∼ −0.6 and an inferred mass ofM⋆≃ 9 × 104M⊙. The narrow width of blue-loop star magnitudes implies an age spread of ≲50 Myr, while no old red-giant branch stars are found, so SC1 is consistent with hosting a single stellar population, modulo several unexplained bright ‘red straggler’ stars. SC1 appears to be surrounded by tidal debris, at the end of an ∼2 kpc long stellar filament that also hosts two low-mass, low-density clusters of a similar age. We explore a link between the formation of these unusual clusters and an external perturbation of their host galaxy, illuminating a possible channel by which some clusters are born with large sizes.
WFC3/UVIS 光度转换
DOI：
--
发表时间：
2014
期刊：
影响因子：
--
作者：
K. Sahu;S. Deustua;E. Sabbi
通讯作者：
E. Sabbi