scholarly journals Preferred Alignments of Angular Momentum Vectors of Galaxies in the SDSS Supercluster S[202-001+0084]

NUTA Journal ◽  
2019 ◽  
Vol 6 (1-2) ◽  
pp. 12-17
Author(s):  
Janak Ratna Malla ◽  
Binil Aryal ◽  
Walter Saurer
Keyword(s):  
Angular Momentum ◽  
Galaxy Formation ◽  
Particle Physics ◽  
Statistical Tests ◽  
Three Dimensional ◽  
Sloan Digital Sky Survey ◽  
Sky Survey ◽  
Hierarchy Model ◽  
Vector Orientation ◽  
Almost All

We present a study of spin vector orientation of 1331 SDSS (Sloan Digital Sky Survey) galaxies in SDSS Supercluster S[202-001+0084] having redshift 0.02 to 0.03. The data are provided by our collaborator, Institute of Astro-particle Physics, Innsbruck University, Austria. We have converted two dimensional data to three dimensional by Godlowskian Transformation. Our aim is to find out non-random effects in the preferred alignments of angular momentum vectors of galaxies. In general, no preferred alignments angular momentum vectors of galaxies are noticed, supporting Hierarchy model of galaxy formation. In almost all sub samples the 1st order Fourier coefficient suggests that the angular momentum vectors are randomly oriented but other statistical tests suggest anisotropic distribution probably due to the binning effect and gravitational shearing effect.

scholarly journals Spatial Orientation of Galaxies in Supercluster S[195+027+0022]

2019 ◽  
Vol 5 (1) ◽  
pp. 14-18
Author(s):  
J. R. Malla ◽  
B. Aryal ◽  
W. Saurer
Keyword(s):  
Galaxy Formation ◽  
Spatial Orientation ◽  
Three Dimensional ◽  
Position Angle ◽  
Sloan Digital Sky Survey ◽  
Spin Vector ◽  
Sky Survey ◽  
Hierarchy Model ◽  
Vector Orientation ◽  
Angle Method

We present a study of spin vector orientation of 1198 SDSS (Sloan Digital Sky Survey) galaxies in Super cluster S[195+027+0022] having red shift 0.07 to 0.09. The databases of these galaxies are taken from SDSS (Sloan Digital Sky Survey) 7th and 9th data release. We have converted two dimensional data to three-dimensional by Godlowskian Transformation using position angle-inclination angle method. We intend to find non-random effects in the spatial orientation of galaxies in Super cluster. No preferred alignment of angular momentum vectors (spin vector) is noticed, supporting Hierarchy model of galaxy formation.

scholarly journals Spatial orientation of galaxies in supercluster S[227+006+0078]

BIBECHANA ◽  
2020 ◽  
Vol 17 ◽  
pp. 117-122
Author(s):  
Janak Ratna Malla ◽  
Walter Saurer ◽  
Binil Aryal
Keyword(s):  
Galaxy Formation ◽  
Spatial Orientation ◽  
Three Dimensional ◽  
Position Angle ◽  
Sloan Digital Sky Survey ◽  
Spin Vector ◽  
Sky Survey ◽  
Hierarchy Model ◽  
Vector Orientation ◽  
Angle Method

We present a study of spin vector orientation of 1218 SDSS (Sloan Digital Sky Survey) galaxies in Supercluster S [227+006+0078] having redshift 0.07 to 0.09. The database of these galaxies is taken from SDSS (Sloan Digital Sky Survey) 7th and 9th data release. We have converted two dimensional data to three dimensional by Godlowskian Transformation using position angle-inclination angle method. We intend to find non-random effects in the spatial orientation of galaxies in the Supercluster.  No preferred alignment of angular momentum vectors is noticed, supporting Hierarchy model of galaxy formation. BIBECHANA 17 (2020) 117-122

scholarly journals Study of Spatial Orientation of Angular Momentum of z-Magnitude SDSS DR-13 Galaxies with Red Shift 0.50 to 0.53

2021 ◽  
Vol 26 (1) ◽  
pp. 1-7
Author(s):  
Shiv Narayan Yadav ◽  
Santosh Kumar Sah
Keyword(s):  
Angular Momentum ◽  
Statistical Tests ◽  
Three Dimensional ◽  
Red Shift ◽  
Angular Momentum Vector ◽  
Initial Alignment ◽  
Chi Square ◽  
Local Anisotropy ◽  
Hierarchy Model ◽  
Merging Process

The spatial orientations of 142,929 SDSS DR-13, z- magnitude galaxies having red shift 0.50 to 0.53 have been analyzed. The main goal of this work is to examine the orientation of the angular momentum of galaxies within the given redshift limit in the framework of three different scenarios 'Hierarchy model', 'Pancake model', and the 'Primordial vorticity model'.  By using Godlowskian transformation the two-dimensional data were converted into three-dimensional data (polar and azimuthal angles). The expected isotropy distribution curves were obtained by removing the selection effects and performing a random simulation to generate 107 virtual galaxies by using Matlab 2015a. Three statistical tests of Chi-square, autocorrelation, and Fourier were used to compare the expected isotropic data with observed. The data classified into nine subsamples having each of one magnitude size. In general, the results supported the Hierarchy model. The model advocates random orientations of angular. However, a local anisotropy observed in few subsamples suggested a gravitational tidal interaction between neighboring galaxies, an early-merging process in which the angular momentum vector distorts the initial alignment of nearby galaxies.

scholarly journals A Study of R-Magnitude Dependence in Spatial Orientation of Spin Vectors of SDSS DR-7 Galaxies of Redshift 0.10 < Z < 0.11

2020 ◽  
Vol 13 (13) ◽  
pp. 42-45
Author(s):  
Shiv Narayan Yadav
Keyword(s):  
Galaxy Formation ◽  
Spatial Orientation ◽  
Three Dimensional ◽  
Simulation Method ◽  
Sloan Digital Sky Survey ◽  
Spin Vector ◽  
Local Anisotropy ◽  
Charge Coupled Device ◽  
Rotation Axes ◽  
Sky Survey

We present a study of spin vector orientations of 44749 r-magnitude SDSS (Sloan Digital Sky Survey) galaxies having redshift 0.10 to 0.11. The r -magnitudes are observed through 616.5 nm CCD (charge coupled device) filter attached to SDSS telescope located at New Mexico, USA. We have converted two dimensional data to three dimensional galaxy rotation axes. Our aim is to find out non-random effects in the spatial orientation of galaxies. In addition, we wanted to check r-magnitude dependence in the spatial orientation. The expected isotropy distribution curves are obtained by removing the selection effects and performing a random simulation method. In general, spin vector orientations of galaxies is found to be random, supporting Hierarchy model of galaxy formation. A local anisotropy is observed in few samples suggesting a gravitational tidal interaction between neighbor galaxies.

scholarly journals Spatial orientations of angular momentum vectors of galaxies in Supercluster S [173+014+0082]

BIBECHANA ◽  
2021 ◽  
Vol 18 (1) ◽  
pp. 26-32
Author(s):  
Janak Ratna Malla ◽  
Walter Saurer ◽  
B Aryal
Keyword(s):  
Angular Momentum ◽  
Galaxy Formation ◽  
Three Dimensional ◽  
Position Angle ◽  
Sloan Digital Sky Survey ◽  
Chi Square ◽  
Isotropic Distribution ◽  
The Galaxy ◽  
Inclination Angles ◽  
Chi Square Test

The spin vector orientation of 1302 SDSS (Sloan Digital Sky Survey) galaxies in Supercluster S[173+014+0082] having redshift 0.076 to 0.091 has been analysed. The positions, position angles and inclination angles of galaxies are used to convert two-dimensional observed parameters into three-dimensional angular momentum vectors of the galaxy using the `position angle-inclination' method. The expected isotropic distribution curves are determined performing numerical simulation by generating 107 virtual galaxies. The observed distribution is compared with the expected isotropic distribution curves using three statistical tools namely Chi-square test, auto-correlation test and Fourier test. Redshift map is studied and found that the distributions fit with the Gaussian. No preferred alignment of angular momentum vectors is noticed, supporting Hierarchy model of galaxy formation. BIBECHANA 18 (2021) 26-32  

scholarly journals A New Catalog of Isolated Galaxies

2009 ◽  
Vol 5 (S267) ◽  
pp. 464-464
Author(s):  
J. A. Vázquez-Mata ◽  
H. M. Hernández-Toledo ◽  
Changbom Park ◽  
Yun-Young Choi
Keyword(s):  
Galaxy Formation ◽  
Environmental Effects ◽  
Comparative Studies ◽  
Sloan Digital Sky Survey ◽  
Selection Algorithm ◽  
Isolated Galaxies ◽  
Galaxy Formation And Evolution ◽  
Sky Survey ◽  
Data Release ◽  
Formation And Evolution

We present a new catalog of isolated galaxies (coined as UNAM–KIAS) obtained through an automated systematic search. The 1520 isolated galaxies were found in ~ 1.4 steradians of the sky in the Sloan Digital Sky Survey Data Release 5 (SDSS DR5) photometry. The selection algorithm was implemented from a variation of the criteria developed by Karachentseva (1973), with full redshift information. This new catalog is aimed to carry out comparative studies of environmental effects and constraining the currently competing scenarios of galaxy formation and evolution.

scholarly journals GALAXY CLUSTERING TOPOLOGY IN THE SLOAN DIGITAL SKY SURVEY MAIN GALAXY SAMPLE: A TEST FOR GALAXY FORMATION MODELS

2010 ◽  
Vol 190 (1) ◽  
pp. 181-202 ◽  
Author(s):  
Yun-Young Choi ◽  
Changbom Park ◽  
Juhan Kim ◽  
J. Richard Gott ◽  
David H. Weinberg ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Sloan Digital Sky Survey ◽  
Galaxy Clustering ◽  
Main Galaxy ◽  
Sky Survey ◽  
Galaxy Sample

scholarly journals How dark are filaments in the cosmic web?

2020 ◽  
Vol 498 (3) ◽  
pp. 3158-3170
Author(s):  
Tianyi Yang ◽  
Michael J Hudson ◽  
Niayesh Afshordi
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
Weak Lensing ◽  
Sky Survey ◽  
Mass Fractions ◽  
The Masses ◽  
Red Galaxies

ABSTRACT The cold dark matter model predicts that dark matter haloes are connected by filaments. Direct measurements of the masses and structure of these filaments are difficult, but recently several studies have detected these dark-matter-dominated filaments using weak lensing. Here we study the efficiency of galaxy formation within the filaments by measuring their total mass-to-light ratios and stellar mass fractions. Specifically, we stack pairs of luminous red galaxies (LRGs) with a typical separation on the sky of 8 h−1 Mpc. We stack background galaxy shapes around pairs to obtain mass maps through weak lensing, and we stack galaxies from the Sloan Digital Sky Survey to obtain maps of light and stellar mass. To isolate the signal from the filament, we construct two matched catalogues of physical and non-physical (projected) LRG pairs, with the same distributions of redshift and separation. We then subtract the two stacked maps. Using LRG pair samples from the Baryon Oscillation Spectroscopic Survey at two different redshifts, we find that the evolution of the mass in filament is consistent with the predictions from perturbation theory. The filaments are not entirely dark: Their mass-to-light ratios (M/L = 351 ± 137 in solar units in the rband) and stellar mass fractions (Mstellar/M = 0.0073 ± 0.0030) are consistent with the cosmic values (and with their redshift evolutions).

scholarly journals A spectroscopic survey of Abell 1703: is it a rare relaxed cluster hosting a radio halo or a usual merging system?

2020 ◽  
Vol 492 (2) ◽  
pp. 2405-2417 ◽  
Author(s):  
W Boschin ◽  
M Girardi ◽  
F Gastaldello
Keyword(s):  
Gravitational Lensing ◽  
Statistical Tests ◽  
Galaxy Cluster ◽  
Theoretical Models ◽  
Sloan Digital Sky Survey ◽  
Cluster Galaxies ◽  
Radio Halo ◽  
Sky Survey ◽  
Galaxies Kinematics ◽  
First Moment

ABSTRACT We present the study of the internal dynamics of the intriguing galaxy cluster Abell 1703, a system hosting a probable giant radio halo whose dynamical status is still controversial. Our analysis is based on unpublished spectroscopic data acquired at the Italian Telescopio Nazionale Galileo and data publicly available in the literature. We also use photometric data from the Sloan Digital Sky Survey. We select 147 cluster members and compute the cluster redshift 〈z〉 ∼ 0.277 and the global line-of-sight velocity dispersion σv ∼ 1300 km s−1. We infer that Abell 1703 is a massive cluster: M200 ∼ 1–2 × 1015 M⊙. The results of our study disagree with the picture of an unimodal, relaxed cluster as suggested by previous studies based on the gravitational lensing analysis and support the view of a perturbed dynamics proposed by recent works based on Chandra X-ray data. The first strong evidence of a dynamically disturbed cluster comes from the peculiarity of the BCG velocity with respect to the first moment of the velocity distribution of member galaxies. Moreover, several statistical tests employed to study the cluster galaxies kinematics find significant evidence of substructure, being Abell 1703 composed by at least two or three subclumps probably caught after the core–core passage. In this observational scenario, the suspected existence of a radio halo in the centre of this cluster is not surprising and well agrees with the theoretical models describing diffuse radio sources in clusters.

scholarly journals Gathering and Analyzing Surface Parameters for Diet Identification Purposes

Technologies ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 75 ◽  
Author(s):  
Arthur Francisco ◽  
Noël Brunetière ◽  
Gildas Merceron
Keyword(s):  
Statistical Tests ◽  
Three Dimensional ◽  
Training Data ◽  
Group Differences ◽  
Eighth Order ◽  
Surface Parameters ◽  
Knowing That ◽  
Order Polynomial ◽  
Almost All ◽  
Numerical Representations

Modern surface acquisition devices, such as interferometers and confocal microscopes, make it possible to have accurate three-dimensional (3D) numerical representations of real surfaces. The numerical dental surfaces hold details that are related to the microwear that is caused by food processing. As there are numerous surface parameters that describe surface properties and knowing that a lot more can be built, is it possible to identify the ones that can separate taxa based on their diets? Until now, the candidates were chosen from among those provided by metrology software, which often implements International Organization for Standardization (ISO) parameters. Moreover, the way that a parameter is declared as diet-discriminative differs from one researcher to another. The aim of the present work is to propose a framework to broaden the investigation of relevant parameters and subsequently a procedure that is based on statistical tests to highlight the best of them. Many parameters were tested in a previous study. Here, some were dropped and others added to the classical ones. The resulting set is doubled while considering two derived surfaces: the initial one minus a second order and an eighth order polynomial. The resulting surfaces are then sampled—256 samples per surface—making it possible to build new derived parameters that are based on statistics. The studied dental surfaces belong to seven sets of three or more groups with known differences in diet. In almost all cases, the statistical procedure succeeds in identifying the most relevant parameters to reflect the group differences. Surprisingly, the widely used Area-scale fractal complexity (Asfc) parameter—despite some improvements—cannot differentiate the groups as accurately. The present work can be used as a standalone procedure, but it can also be seen as a first step towards machine learning where a lot of training data is necessary, thus making the human intervention prohibitive.

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