We introduce the first entire-sky catalog of the most isolated nearby galaxies with radial velocities VLG<3500 km/s. This kind of cosmic "orphans" amounts to 4% among all known galaxies within the same velocity range. We describe a criterion of isolation applied to select our sample, the "Local Orphan Galaxies", and discuss their basic optical and HI properties.
The largest galaxy systems in the cosmic web are superclusters, overdensity regions of galaxies, groups, clusters, and filaments. Low-density regions around superclusters are called basins of attraction or cocoons. In my talk I discuss the properties of galaxies, groups, and filaments in the A2142 supercluster and its cocoon at redshift $z \approx 0.09$. Cocoon boundaries are determined by the lowest density regions around the supercluster. We analyse the structure, dynamical state, connectivity, and galaxy content of the supercluster, and its high density core with the cluster A2142. We show …
我们研究了一组超星系团的形态从SDSS DR 7。我们从SDSS DR 7的一个限流星系样本中计算了超星系团的光度密度场,并选择了300个以上的超星系团进行研究。超星系团的形态用第四Minkowski泛函V3、形态特征(在shapefinder的K1-K2平面上的曲线)和形状参数(shapefinder的K1/K2比值)来描述。我们使用多维正态混合模型研究超星系团样本,并使用Abell星系团来识别我们的超星系团与已知的超星系团,并研究超星系团的大尺度分布。我们样本中的超星系团形成了三条超星系团链,其中之一就是斯隆长城。大多数超星系团都有类似于木星的整体形状。超星系团可以分为两类:较长的超星系团比较短的超星系团更明亮,更丰富,直径更大,精细结构更复杂。超星系团的精细结构可以分为四种主要的形态类型:蜘蛛、多蜘蛛、细丝和多分支细丝。我们提出了2D和3D分布的星系和丰富的群体,第四闵可夫斯基功能,和所有超星系团的形态签名。超星系团的形态差异很大,这表明它们的演化是不同的。需要对来自观测和模拟的更大样本的超星系团进行研究,以了解超星系团的形态多样性以及超星系团形态与其大尺度环境之间的可能联系。
Groups of dwarf galaxies in the Local supercluster
我们提出了一个研究仅由矮星系组成的星系群的项目。我们选择这样的结构,使用HyperLEDA和NED数据库与SDSS图像和POSS的数字副本上的视觉检查。这些组的特点是几十千秒差距的大小和视线速度色散约18公里/秒。我们的群体类似于Tully et al.(2006)的附近矮星的协会。这个特定的多矮星系群,如IZw 18,可能含有大量的暗物质。我们很可能在其组成部分合并之前的阶段看到它们。
The evolution of dwarf galaxies in the Coma supercluster
利用SDSS DR 7在500平方度区域的分光光度数据,研究后发座超星系团(z=0.023)中矮星系(~M*+2<M_z<M*+4)的演化。我们发现,在后发座超星系团中,红矮星主要集中在后发座和阿贝尔1367星系团的致密核心,以及嵌入连接它们的灯丝中的星系群中。然而,在后发座星系团和Abell 1367星系团的陷落区发现了后星爆(k+A)矮星,偶尔也在沿暗条嵌入的星系群中发现,这表明深势阱附近普遍存在的强速度场可能与导致矮星系后星爆阶段的机制密切相关。此外,后发座星系团中一些k+A矮星的蓝色,在其维里半径内发现,这表明这些星系中的恒星形成在过去的500 Myr中非常迅速地熄灭了。超星系团中60%以上的红矮星系的H_δ吸收角为0-3角,这表明在这些星系中有一个不可忽略的部分发生了一个主要的恒星形成事件,在最后一个Gyr内结束,使它们能够移动到红色序列。后发座超星系团中的蓝矮星系在EW(H_α)-EW(H_δ)平面上呈双峰分布,其中一个星系团在H_α中有很高的发射,在H_δ中也有一些发射。在EW(H_α)-EW(H_δ)平面上,蓝矮星和红矮星的一个子群重合,在H_δ上表现出吸收,在H_α上表现出相对较低的发射。我们认为,后者人口的很大一部分是被动矮星系的祖先,大量发现在低红移丰富的集群,如后发座的核心。
AKARI Observation of the North Ecliptic Pole (NEP) Supercluster at z = 0.087: mid-infrared view of transition galaxies
我们提出的中红外(MIR)的性质的星系内的超星系团在北极地区在z?0.087 AKARI卫星观测到的。我们使用的数据从AKARI NEP宽(5.4 deg 2)IR调查和星系演化研究(CLEVL)任务计划的集群。我们发现,近红外(3 μm)-中红外(11 μm)颜色可以作为一个指标,具体的恒星形成率和存在的中间年龄恒星星族。从MIR观测中发现,红序星系不仅由被动演化的红色早型星系组成,而且还包括1)“弱SFG”(盘控星系,其恒星形成速率比蓝云星系低\sim 4)和2)“中等MXG”(膨胀星系,其MIR尘埃辐射比正常的红色早型星系强)。这两个群体可能是一组过渡星系,从蓝色的、恒星形成的、晚型星系演变成红色的、静止的、早型星系。我们发现弱SFG在中等质量(1010 M \odot < M \star <1010.5 M \odot)时占优势,并且通常在类似于星系团外围的局部密度中发现。在这个质量范围内,有40%的超星系团成员星系可以被归类为弱SFG,但在任何星系密度下,它们的比例在更大的质量(M \star > 1010.5 M \odot)时会下降到< 10%。在1010 M \odot < M \star <1011 M \odot的红序星系中,中间MXG的比例也随着密度和质量的增加而减少。特别是,\sim 42%的红序列星系的早期型形态被归类为中等密度的中间MXG。这些结果表明,…
Multimodality of rich clusters from the SDSS DR8 within the supercluster-void network
我们研究了SDSS DR 8中的星系团的多峰性与它们所处环境的关系。作为集群环境,我们考虑的全球光度密度场,超星系团成员,超星系团形态。我们使用3D正常的混合模型,Dressler-Shectman测试,和集群的主星系的特有的速度作为集群的多模态的签名。我们通过计算光度密度场来研究星系团周围的环境密度,寻找星系团所在的超星系团。我们用Minkowski泛函确定了超团簇的形态,并比较了不同形态超团簇中团簇的性质。本文应用主成分分析法研究了团簇的多峰参数与环境的关系。我们发现,多模态集群居住在更高的密度环境比单峰集群。超团簇中的团簇比孤立的团簇有更高的概率具有子结构。超星系团可以分为两种主要的形态类型,蜘蛛和细丝。蜘蛛状超星系团中的星系团比丝状超星系团中的星系团具有更高的主星系亚结构和更大的特有速度的概率。最明亮的星系团位于高密度的富超星系团核心。七个最明亮的星团中有五个和七个最多峰的星团中有五个位于蜘蛛型超星团中;七个最单峰的星团中有四个位于顺从型超星团中。我们的研究表明,超星系团作为高密度环境的作用的重要性,影响星系系统的性质在其中。
We report a promising candidate for a distant supercluster at z $\sim 1.1$ in the Dark Energy Survey Science Verification data. We examine smoothed semi-3D galaxy density maps in various photo-z slices. Among several overdense regions, in this work we report the most significant one as having a $3σ$ overdensity at a redshift of $\sim1.1$, over a $\sim160$ Mpc scale, much larger than the regular cluster scale (several Mpc). The shape of the supercluster is not circular in the sky projection. Therefore, we regard the point of maximum overdensity as the center for quantitative measurements. Two d…
We study the dynamical state and properties of galaxies and groups in the supercluster SClA2142 that has a collapsing core, to understand its possible formation and evolution. We find the substructure of galaxy groups using normal mixture modelling. We have used the projected phase space (PPS) diagram, spherical collapse model, clustercentric distances, and magnitude gap between the brightest galaxies in groups to study the dynamical state of groups and to analyse group and galaxy properties. We compared the alignments of groups and their brightest galaxies with the supercluster axis. The supe…
We study the properties, connectivity, and galaxy content of groups and filaments in the low-density region (cocoon) around A2142 supercluster (SClA2142). We traced the SClA2142 cocoon boundaries by the lowest luminosity-density regions that separate SClA2142 from other superclusters. We determined galaxy filaments and groups in the cocoon and analysed the connectivity of groups, the high density core (HDC) of the supercluster, and the whole of the supercluster. We compared the distribution and properties of galaxies with different star-formation properties in the supercluster and in the cocoo…
High-density cores (HDCs) of galaxy superclusters that embed rich clusters and groups of galaxies are the earliest large objects to form in the cosmic web, and the largest objects that may collapse in the present or future. We study the dynamical state and possible evolution of the HDCs in the BOSS Great Wall (BGW) superclusters at redshift $z \approx 0.5$ in order to understand the growth and evolution of structures in the Universe. We derived the density contrast values for the spherical collapse model in a wide range of redshifts and used these values to study the dynamical state and possib…
We take a close look at the galaxies in the Coma Supercluster and assess the role of the environment (in the form of cluster, group and supercluster filament) in their evolution, in particular examining the role of groups. We characterise the groups according to intrinsic properties such as richness and halo mass, as well as their position in the supercluster and proximity to the two rich clusters, Abell 1656 (Coma) and Abell 1367. We devise a new way of characterising the local environment using a kernel density estimator. We find that apart from the dominant effects of the galaxy mass, the e…
The characterization of the internal structure of the superclusters of galaxies (walls, filaments and knots where the clusters are located) is paramount for understanding the formation of the Large Scale Structure and for outlining the environment where galaxies evolved in the last Gyr. (i) To detect the compact regions of high relative density (clusters and rich groups of galaxies); (ii) to map the elongated structures of low relative density (filaments, bridges and tendrils of galaxies); (iii) to characterize the galaxy populations on filaments and study the environmental effects they are su…
It has long been established but seldom noticed that we are in a region at least 170 Mpc across in which different types of galaxies show different degrees of alignment with the plane of the de Vaucouleurs Local Supercluster. While clusters of galaxies and radio galaxies at redshifts less than 0.02 are concentrated at low supergalactic latitudes, the most luminous galaxies in the infrared, LIRGs, show little correlation with this plane. The most luminous early-type galaxies are concentrated at low supergalactic latitudes, but similarly luminous spirals are not noticeably so. The cross-correlat…
Dissecting the Perseus-Pisces supercluster observed with CFHT-MegaCam: Exploring late-type galaxy shape alignments within the local cosmic web
Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM(巴黎萨克雷大学、巴黎西岱大学、法国原子能和替代能源委员会、法国国家科学研究中心、天体物理学和信息学实验室);Institute for Astronomy, University of Hawaii(夏威夷大学天文学研究所)
We present a database and velocity catalogue towards the region of the Shapley Supercluster based on 18,146 measured velocities for 10,719 galaxies in the approximately 300 square degree area between 12h 43mn 00s < R.A. < 14h 17mn 00s and -23° 30' 00" < Dec < -38° 30' 00". The data catalogue contains velocities from the literature found until 2015. It also includes 5,084 velocities, corresponding to 4,617 galaxies, observed by us at Las Campanas and CTIO observatories and not reported individually until now. Of these, 2,585 correspond to galaxies with no other previously published velocity mea…
We investigate the distribution and velocity field of galaxies situated in a band of 100 by 20 degrees centered on M87 and oriented along the Local supercluster plane. Our sample amounts 2158 galaxies with radial velocities less than 2000 km/s. Of them, 1119 galaxies (52%) have distance and peculiar velocity estimates. About 3/4 of early-type galaxies are concentrated within the Virgo cluster core, most of the late-type galaxies in the band locate outside the virial radius. Distribution of gas-rich dwarfs with $M_{\rm H\,I} > M_*$ looks to be insensitive to the Virgo cluster presence. Among 50…