We identify, categorize, and quantify alignment effects among host and satellite galaxies using a spectroscopically-confirmed, low-redshift (z<0.23) galaxy sample from the Sloan Digital Sky Survey Data Release 6. Consistent with other recent findings, we find that satellite galaxies (SGs) of red, centrally concentrated (elliptical) host galaxies (HGs) with radial velocity separation |Delta_V|<600 km/s preferentially reside near the projected major axes of their HGs. Among these, this preference is strongest for highly concentrated, red SGs. We find that fractional anisotropy increases with decreasing Δ_V and Delta_R and is nearly 40% greater among the closest SGs (Delta_R<250 kpc/h) relative to more distant (Delta_R>500 kpc/h) SGs. For highly concentrated SGs at small (<300 kpc/h) projected separation, we observe a strong radial (hostward) alignment signal in isophotal position angles (PAs) due to isophotal twisting and contamination that is not present when using galaxy model PAs. Among objects for which both isophotal and galaxy model PAs agree to <15 degrees, this elongation signal is significantly weaker. We also investigate the "Holmberg Effect," a well-known result wherein nearby (<40 kpc/h) SGs of large, inclined spiral HGs were seen to preferentially reside near the minor axes of their HGs. Survey limitations preclude a strict test of this effect using only SDSS spectroscopic galaxies. By adopting a looser set of cuts than those of Holmberg's study, we recover a comparable preference among faint blue SGs for the HG minor axis at marginal significance (~3 sigma). We conclude that several types of alignment likely exist among different galaxy populations, but that the observed nature and strength of alignment trends depend sensitively on both selection criteria and on the method used to determine galaxy orientation.
Based on galaxies from the Sloan Digital Sky Survey (SDSS) and subhalos in the corresponding reconstructed region from the constrained simulation of ELUCID, we study the alignment of central galaxies relative to their host groups in the group catalog, as well as the alignment relative to the corresponding subhalos in the ELUCID simulation. Galaxies in observation are matched to dark matter subhalos in the ELUCID simulation using a novel neighborhood abundance matching method. In observation, the major axes of galaxies are found to be preferentially aligned to the major axes of their host group…
It has been shown, both in simulations and observationally, that the tidal field of a large galaxy can torque its satellites such that the major axis of satellite galaxies points towards their hosts. This so-called `shape alignment' has been observed in isolated Milky Way-like galaxies but not in `Local Group'-like pairs. In this study, we investigate the shape alignment of satellite galaxies in galaxy pairs similar to the Local Group identified in the Sloan Digital Sky Survey Data Release 13 (SDSS DR13). By stacking tens of thousands of satellite galaxies around primary galaxy pairs, we find …
Spin alignments of spiral galaxies within the large-scale structure from SDSS DR7
利用Sloan数字巡天数据发布7（SDSS DR 7）和星系动物园2（GZ 2）中的一组旋涡星系，研究了旋涡星系的自旋轴与周围大尺度结构的排列，其特征是利用一定质量阈值以上的星系群数据重建的大尺度潮汐场.我们发现，只有自旋轴有微弱的倾向，是对齐（或垂直于）本地潮汐张量的中（或短）轴。信号是最强的\cluster环境中的所有三个特征值的本地潮汐张量是积极的。与N体模拟中得到的晕自旋与局域潮汐场的一致性相比，上述观测结果与晕内区自旋的一致性最好，表明盘物质追踪了内区暗物质晕的角动量.
Alignment between satellite and central galaxies in the SDSS DR7: dependence on large-scale environment
卫星星系和中央星系之间的排列已经在观测和理论工作中得到了详细的研究。普遍接受的事实是，卫星优先居住在其中央星系的主轴上。然而，这种对齐的起源和大规模环境依赖性仍然是未知的。为了找出这些问题，我们使用SDSS DR 7构建的数据来研究这种对齐的大规模环境依赖性，重点是检查对齐对中央星系颜色的依赖性。我们发现一个非常强大的大规模的环境依赖的卫星中心对准组与蓝色的中心。结中蓝心的排列方向优先垂直于心的长轴，排列角度随环境变化而减小，即从结到空洞。对齐角度强烈依赖于中心的${}^{0.1}(g-r)$颜色。我们认为，卫星中心排列是大尺度结构内卫星吸积与宿主晕内星系演化竞争的结果。对于包含红色中心星系的星系团，星心排列主要由演化效应决定，而对于蓝色中心星系团，大尺度结构的作用更为重要，特别是在星系结中。我们的研究结果提供了一个解释如何在不同的大尺度环境中的卫星中心对准的形式。垂直的情况下，在集团和结与蓝色的中心也可能提供深入了解类似的极性安排，如银河系和半人马座A的卫星系统的形成。
Previous observations have suggested non-random distribution of spin directions of galaxies at scales far larger than the size of a supercluster. Here I use $\sim1.7\cdot10^5$ spiral galaxies from SDSS and $3.3\cdot10^4$ spiral galaxies from Pan-STARRS to analyze the distribution of galaxy spin patterns of spiral galaxies as observed from Earth. The analysis shows in both SDSS and Pan-STARRS that the distribution of galaxy spin directions forms a non-random pattern, and can be fitted to a dipole axis in probability much higher than mere chance. These observations agree with previous findings, …
Galaxies, as well as their satellites, are known to form within the cosmic web: the large, multi-scale distribution of matter in the universe. It is known that the surrounding large scale structure (LSS) can impact and influence the formation of galaxies, e.g. the spin and shape of haloes or galaxies are correlated with the LSS and the correlation depends on halo mass or galaxy morphology. In this work, we use group and filament catalogues constructed from the SDSS DR12 to investigate the correlation between satellite systems and the large scale filaments they are located in. We find that the …
We study the alignment of galaxies relative to their local environment in SDSS-DR8 and, using these data, we discuss evolution scenarios for different types of galaxies. We defined a vector field of the direction of anisotropy of the local environment of galaxies. We summed the unit direction vectors of all close neighbours of a given galaxy in a particular way to estimate this field. We found the alignment angles between the spin axes of disc galaxies, or the minor axes of elliptical galaxies, and the direction of anisotropy. The distributions of cosines of these angles are compared to the ra…
Intrinsic alignments of SDSS-III BOSS LOWZ sample galaxies
星系的内禀排列（IA），即星系形状彼此之间或与密度场的相关性，是弱透镜巡天的主要天体物理污染源。本文介绍了在0.16<z<0.36的红移范围内，利用SDSS-III BOSS LOWZ样品对星系进行0.1- 200 Mpc/h尺度的IA测量的结果。我们扩展了现有的IA测量光谱LRGs较低的光度，并表明，大规模IA的光度依赖性可以很好地描述了一个幂律。在有限的红移和颜色范围内，我们观察到没有显着的红移或颜色依赖的IA。我们使用星系-星系透镜测量了LOWZ星系的晕质量，并表明大尺度IA的质量依赖性也很好地描述了幂律。我们检测IA与质量和光度的尺度依赖性的变化，这强调了需要使用灵活的模板，以消除IA信号。我们还研究了IA的环境依赖性分裂成场星系和群星系，这是进一步分裂成卫星星系和中央星系的样本。我们发现，集团中央星系对准他们的晕在小尺度上，也对准了大尺度的潮汐场。我们还检测到的径向排列的卫星星系内的群体，这导致在一个零检测大规模的内在对准的卫星。这些结果可以用来构建更好的本征对准模型，以去除这种污染物的弱透镜信号。
Galaxy Clusters from the DESI Legacy Imaging Surveys. IV. Alignment of Member Galaxy Orientations at z < 0.5
Nanjing Normal University（南京师范大学）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交通大学李政道研究所）；University of Chinese Academy of Sciences（中国科学院大学）
B-field Orion Protostellar Survey (BOPS). IV: The Relative Orientation Between Magnetic Fields and Density Structures in Young Protostellar Envelopes
Guangxi University（广西大学）；Institut de Ciències de l’Espai (ICE-CSIC)（空间科学研究所）；Korea Astronomy and Space Science Institute（韩国天体空间科学研究所）；Institut d’Estudis Espacials de Catalunya (IEEC)（加泰罗尼亚空间研究学院）；Worcester State University（伍斯特州立大学）
We investigate the 3D spin alignment of galaxies with respect to the large-scale filaments using the MaNGA survey. The cosmic web is reconstructed from the Sloan Digital Sky Survey using Disperse and the 3D spins of MaNGA galaxies are estimated using the thin disk approximation with integral field spectroscopy kinematics. Late-type spiral galaxies are found to have their spins parallel to the closest filament's axis. The alignment signal is found to be dominated by low-mass spirals. Spins of S0-type galaxies tend to be oriented preferentially in perpendicular direction with respect to the fila…
Reduction of bar fraction in paired galaxies in the SDSS
Hebei Normal University（河北师范大学）；Shijiazhuang Key Laboratory of Astronomy and Space Science / Guoshoujing Institute of Astronomy, Hebei Normal University（石家庄天文与空间科学重点实验室/郭守敬天文台，河北师范大学）；Hebei Key Laboratory of Photophysics Research and Application（河北省光物理研究与应用重点实验室）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；Shanghai Key Lab for Astrophysics（上海市天体物理重点实验室）；Department of Astronomy, School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院天文学系）；State Key Laboratory of Dark Matter Physics, Tsung-Dao Lee Institute & School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院及李政道研究所暗物质物理全国重点实验室）
Warped Disk Galaxies: Alignment with the Large-Scale Tidal Field
Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）；University of Science and Technology of China（中国科学技术大学）；Zhejiang University（浙江大学）
We present measurements of the intrinsic alignments (IAs) of the star-forming gas of galaxies in the EAGLE simulations. Radio continuum imaging of this gas enables cosmic shear measurements complementary to optical surveys. We measure the orientation of star-forming gas with respect to the direction to, and orientation of, neighbouring galaxies. Star-forming gas exhibits a preferentially radial orientation-direction alignment that is a decreasing function of galaxy pair separation, but remains significant to $\gtrsim 1$ Mpc at $z=0$. The alignment is qualitatively similar to that exhibited by …
Magnetic fields are an important component of the interstellar medium (ISM) and exhibit strongly varying field strengths and a non-trivial correlation with the gas density. Its dynamical impact varies between individual regions of the ISM and correlates with the orientation of the field with respect to the gas structures. Using high-resolution magneto-hydrodynamical simulations of the ISM we explore the connection between the orientation of the field and the dynamical state of the gas. We find that the onset of gravitational instability in molecular gas above a density of $ρ\sim10^{-21}\,\math…
Spatial Orientation of Spin Vectors of Blue-shifted Galaxies
本文分析了5个$\,$ 987 SDSS星系的自旋矢量取向，它们的负红移从$-$ 87.6到$-$ 0.3 km $\,$ s $^{-1}$。用“位置角-倾角”方法，利用二维观测参数计算三维星系自转轴。我们的目标是研究蓝移星系空间取向的非随机效应。我们通过数值模拟生成了5个$\times$ 10个$^6$虚拟星系，以找到预期的各向同性分布。我们编写了MATLAB程序，方便了仿真过程，消除了过程中的人为误差。卡方，自相关，和傅立叶测试被用来检查在极角和方位角分布的星系旋转轴的非随机效应。一般来说，蓝移星系没有显示出星系旋转轴的优先排列。我们的结果支持星系角动量矢量随机取向的Hierarchy模型。然而，当地的影响指出，建议相邻星系之间的引力潮汐相互作用。
Aims.The main purpose of this study is to investigate aspects regarding the validity of the active galactic nucleus (AGN) unification paradigm (UP). In particular, we focus on the AGN host galaxies, which according to the UP should show no systematic differences depending on the AGN classification. Methods.For the purpose of this study, we used (a) the spectroscopic Sloan Digital Sky Survey (SDSS) Data Release (DR) 14 catalogue, in order to select and classify AGNs using emission line diagnostics, up to a redshift of z=0.2, and (b) the Galaxy Zoo Project catalogue, which classifies SDSS galaxi…
The distribution of spin directions of $\sim6.4\cdot10^4$ SDSS spiral galaxies with spectra was examined, and compared to the distribution of $\sim3.3\cdot10^4$ Pan-STARRS galaxies. The analysis shows a statistically significant asymmetry between the number of SDSS galaxies with opposite spin directions, and the magnitude and direction of the asymmetry changes with the direction of observation and with the redshift. The redshift dependence shows that the distribution of the spin direction of SDSS galaxies becomes more asymmetric as the redshift gets higher. Fitting the distribution of the gala…
Various studies have laid claim to finding an alignment of the polarization vectors or radio jets of active galactic nuclei (AGN) over large distances, but these results have proven controversial and so far, there is no clear explanation for this observed alignment. To investigate this case further, we tested the hypothesis that the position angles of radio galaxies are randomly oriented in the sky by using data from the Low-Frequency Array (LOFAR) Two-metre Sky Survey (LoTSS). A sample of 7,555 double-lobed radio galaxies was extracted from the list of 318,520 radio sources in the first data …
Spatial correlations among proto-planetary disk orientations carry unique information on physics of multiple star formation processes. We select five nearby star-forming regions that comprise a number of proto-planetary disks with spatially-resolved images with ALMA and HST, and search for the mutual alignment of the disk axes. Specifically, we apply the Kuiper test to examine the statistical uniformity of the position angle (PA: the angle of the major axis of the projected disk ellipse measured counter-clockwise from the north) distribution. The disks located in the star-forming regions, exce…
The orientations of brightest cluster galaxies (BCGs) and their host clusters tend to be aligned, but the mechanism driving this is not clear. To probe the role of cluster mergers in this process, we quantify alignments of 38 BCGs in 22 clusters undergoing major mergers (up to $\sim 1$ Gyr after first pericenter). We find alignments entirely consistent with those of clusters in general. This suggests that alignments are robust against major cluster mergers. If, conversely, major cluster mergers actually help orient the BCG, such a process is acting quickly because the orientation is in place w…
Magnetic field alignment with dense cores in the transition between cloud and core scales
University of Toronto（多伦多大学）；Queen’s University（女王大学）；McGill University（麦吉尔大学）；David A. Dunlap Department of Astronomy and Astrophysics, University of Toronto（多伦多大学戴维·A·邓拉普天文学与天体物理学系）；Dunlap Institute for Astronomy and Astrophysics, University of Toronto（多伦多大学邓拉普天文学与天体物理学研究所）；National Astronomical Observatory of Japan, National Institute of Natural Sciences（日本国立自然科学研究院国立天文台）；Worcester State University（伍斯特州立大学）
It is known observationally that the major axes of galaxy clusters and their brightest cluster galaxies are roughly aligned with each other. To understand the origin of the alignment, we identify 40 cluster-sized dark matter (DM) haloes with masses higher than $5\times10^{13}~M_{\odot}$ and their central galaxies (CGs) at $z\approx 0$ in the Horizon-AGN cosmological hydrodynamical simulation. We trace the progenitors at 50 different epochs between $0<z<5$. We then fit their shapes and orientations with a triaxial ellipsoid model. While the orientations of both DM haloes and CGs change signific…
We define a sample of 200 protostellar outflows showing blue and redshifted CO emission in the nearby molecular clouds Ophiuchus, Taurus, Perseus and Orion to investigate the correlation between outflow orientations and local, but relatively large-scale, magnetic field directions traced by Planck 353 GHz dust polarization. At high significance (p~1e-4), we exclude a random distribution of relative orientations and find that there is a preference for alignment of projected plane of sky outflow axes with magnetic field directions. The distribution of relative position angles peaks at ~30deg and …
At the centre of a spherical and kinematically isotropic galaxy, the orientation of a massive binary black hole (BBH) orbit (i.e., the direction of the BBH orbital angular momentum) undergoes a random walk. If the stars in a spherical system have a non-zero total angular momentum, the BBH orbital orientation evolves towards aligning with the total stellar angular momentum direction. In this paper, we show that a triaxial galaxy has an alignment-erasing effect, that is, the alignment of the BBH orientations towards the galaxy rotation axis can be decreased significantly or erased. We also show …
