Galaxy groups and clouds in the local (z∼ 0.01) Universe
Galaxy groups and clouds in the local (z∼ 0.01) Universe
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本地 (z~ 0.01) 宇宙中的星系群和云
DOI：
10.1111/j.1365-2966.2010.18071.x
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发表时间：
2010
影响因子：
4.8
通讯作者：
I. Karachentsev
中科院分区：
文献类型：
--
作者：
D. Makarov;I. Karachentsev
我们给出了本地超星系团及其周围的395个附近星系群的全天星表。这些群及其关联是在距离S−1 15°、径向速度Vlg<；3500公里的10个914个星系中确定的。我们的群发现算法要求群成员位于其零速面内。据此，我们假定单个星系的质量与它们的总K带光度成正比，M/LK=6M⊙/L⊙。
我们小组的样本，其中每个小组有n个≥4成员，其特征如下：平均投影半径<R>=268kpc，径向速度弥散σV=74km离S−1，K波段光度LK=1.2×10~(11)⊙，维里质量M_vir=2.4×10~(12)M⊙和MP=3.3×10~(12)M⊙。考虑到测量误差，中位数质量减少了30%。97%的已确定群体的穿越时间不超过宇宙时间13.7 Gyr，中位数为3.8 Gyr。
我们研究了这些群的不同性质，特别是处女座和福尔纳克斯的已知附近的群和星团。我们大约四分之一的星系可以归类为化石星系，在那里，占主导地位的星系的亮度至少是其他星系成员的10倍。
总体而言，我们的算法识别出54%的星系是星系群的成员。加上三重系统和对，它们聚集了本地宇宙82%的K波段光。在假设H0=73 kM的情况下，我们得到了Ωm=0.08±0.02的物质密度局域值，它明显小于标准的∼−模型中的宇宙值0.28。Ωm的整体和局域量之间的差异可能是由于暗物质分量的存在与银河系的维里质量无关。
We present an all-sky catalogue of 395 nearby galaxy groups revealed in the Local Supercluster and its surroundings. The groups and their associations are identified among 10 914 galaxies at |b| > 15° with radial velocities VLG < 3500 km s−1. Our group-finding algorithm requires the group members to be located inside their zero-velocity surface. Hereby, we assume that individual galaxy masses are proportional to their total K-band luminosities, M/LK= 6 M⊙/L⊙.
The sample of our groups, where each group has n≥ 4 members, is characterized by the following medians: mean projected radius 〈R〉= 268 kpc, radial velocity dispersion σV= 74 km s−1, K-band luminosity LK= 1.2 × 1011 L⊙, virial and projected masses Mvir= 2.4 × 1012 and Mp= 3.3 × 1012 M⊙, respectively. Accounting for measurement error reduces the median masses by 30 per cent. For 97 per cent of identified groups the crossing time does not exceed the cosmic time, 13.7 Gyr, with the median at 3.8 Gyr.
We examine different properties of the groups, in particular of the known nearby groups and clusters in Virgo and Fornax. About a quarter of our groups can be classified as fossil groups where the dominant galaxy is at least 10 times brighter than the other group members.
In total, our algorithm identifies 54 per cent of galaxies to be members of groups. Together with triple systems and pairs they gather 82 per cent of the K-band light in the local Universe. We have obtained the local value of matter density to be Ωm= 0.08 ± 0.02 within a distance of ∼40 Mpc assuming H0= 73 km s−1 Mpc−1. It is significantly smaller than the cosmic value, 0.28, in the standard ΛCDM model. The discrepancy between the global and local quantities of Ωm may be caused by the existence of a dark matter component unrelated to the virial masses of the galaxy systems.