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Upcoming wide-field spectroscopic surveys will observe galaxies in a range of cosmic web environments in and around galaxy clusters. In this paper, we test and quantify how successfully we will be able to identify the environment of…

We use a semi-analytic model of galaxy formation to study signatures of large-scale modulations in the star formation (SF) activity in galaxies. In order to do this we carefully define local and global estimators of the density around…

Astrophysics · Physics 2015-05-13 R. E. Gonzalez , N. D. Padilla

Cluster analysis is the distribution of objects into different groups or more precisely the partitioning of a data set into subsets (clusters) so that the data in subsets share some common trait according to some distance measure. Unlike…

Cosmology and Nongalactic Astrophysics · Physics 2013-09-17 Tuli De , Didier Fraix-Burnet , Asis Kumar Chattopadhyay

We use a sample of galaxies from the Two Micron All Sky Survey (2MASS) Extended Source Catalog to refine a matched filter method of finding galaxy clusters that takes into account each galaxy's position, magnitude, and redshift if…

Cosmology and Nongalactic Astrophysics · Physics 2012-03-08 Jeffrey A. Blackburne , Christopher S. Kochanek

Galaxies which fall into clusters as part of the same infall halo can retain correlations due to their shared origin. N-body simulations are used to study properties of such galaxy subgroups within clusters, including their richnesses and…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-28 J. D. Cohn

This work identifies the orientation of galaxies in the Galaxy zoo data set. The images are first identified by the number of principal components required to represent 99 percent of the variance of the image. K means clustering is used to…

Astrophysics of Galaxies · Physics 2020-10-27 Vijay Shankar A

Traditional studies of stellar clusters in external galaxies use surface photometry and therefore focus on systems that are still bright and compact enough to be separated from the stellar background. Consequently, the latter stages of…

Astrophysics · Physics 2007-05-23 Anne Pellerin , Martin Meyer , Jason Harris , Daniela Calzetti

Based on the photometric redshift catalog of Zou H. et al. (2019), we apply a fast clustering algorithm to identify 540,432 galaxy clusters at $z\lesssim1$ in the DESI legacy imaging surveys, which cover a sky area of about 20,000 deg$^2$.…

Astrophysics of Galaxies · Physics 2021-04-21 Hu Zou , Jinghua Gao , Xin Xu , Xu Zhou , Jun Ma , Zhimin Zhou , Tianmeng Zhang , Jundan Nie , Jiali Wang , Suijian Xue

The caustic technique measures the mass of galaxy clusters in both their virial and infall regions and, as a byproduct, yields the list of cluster galaxy members. Here we use 100 galaxy clusters with mass M200>=1E14 Msun/h extracted from a…

Cosmology and Nongalactic Astrophysics · Physics 2013-06-12 Ana Laura Serra , Antonaldo Diaferio

We describe a new open source package for calculating properties of galaxy clusters, including NFW halo profiles with and without the effects of cluster miscentering. This pure-Python package, cluster-lensing, provides well-documented and…

Instrumentation and Methods for Astrophysics · Physics 2016-12-14 Jes Ford , Jake VanderPlas

Clusters of galaxies are the most massive objects in the Universe and mapping their location is an important astronomical problem. This paper describes an algorithm (based on statistical signal processing methods), a software architecture…

Astrophysics · Physics 2015-05-26 Jeremy Kepner , Rita Kim

We present a self consistent method to perfom a joint analysis of Sunyaev-Zel'dovich and weak gravitational lensing observation of galaxy clusters. The spatial distribution of the cluster main constituents is described by a perturbative…

Astrophysics · Physics 2009-11-06 O. Doré , F. R. Bouchet , Y. Mellier , R. Teyssier

The detection of clusters of galaxies in large surveys plays an important part in extragalactic astronomy, and particularly in cosmology, since cluster counts can give strong constraints on cosmological parameters. X-ray imaging is in…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-03 V. G. Gurzadyan , F. Durret , T. Ghahramanyan , A. L. Kashin , H. G. Khachatryan , E. Poghosian

We describe an objective and automated method for detecting clusters of galaxies from optical imaging data. This method is a variant of the so-called `matched-filter' technique pioneered by Postman et al. (1996). With simultaneous use of…

Astrophysics · Physics 2009-10-30 Wataru Kawasaki , Kazuhiro Shimasaku , Mamoru Doi , Sadanori Okamura

With our previous study, the Super-k algorithm, we have introduced a novel way of piecewise-linear classification. While working on the Super-k algorithm, we have found that there is a similar, and simpler way to explain for obtaining a…

Machine Learning · Computer Science 2021-02-03 Rahman Salim Zengin , Volkan Sezer

Galaxy clusters are usually detected in blind optical surveys via suitable filtering methods. We present an optimal matched filter which maximizes their signal-to-noise ratio by taking advantage of the knowledge we have of their intrinsic…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-19 Fabio Bellagamba , Matteo Maturi , Takashi Hamana , Massimo Meneghetti , Satoshi Miyazaki , Lauro Moscardini

We present a proof of concept of a new galaxy group finder method, Markov graph Clustering (MCL; Van Dongen 2000) that naturally handles probabilistic linking criteria. We introduce a new figure of merit, the variation of information…

Astrophysics of Galaxies · Physics 2019-04-10 L. Stothert , P. Norberg , C. M. Baugh

In this paper, we present the tools used to search for galaxy clusters in the Kilo Degree Survey (KiDS), and our first results. The cluster detection is based on an implementation of the optimal filtering technique that enables us to…

Cosmology and Nongalactic Astrophysics · Physics 2017-02-08 M. Radovich , E. Puddu , F. Bellagamba , M. Roncarelli , L. Moscardini , S. Bardelli , A. Grado , F. Getman , M. Maturi , Z. Huang , N. Napolitano , J. McFarland , E. Valentijn , M. Bilicki

We have developed a new geometrical method for identifying and reconstructing a homogeneous and highly complete set of galaxy groups in the next generation of deep, flux-limited redshift surveys. Our method combines information from the…

Astrophysics · Physics 2009-11-07 Christian Marinoni , Marc Davis , Jeffrey A. Newman , Alison L. Coil

The effects of many physical processes in the intracluster medium of galaxy clusters imprint themselves in X-ray surface brightness images. It is therefore important to choose optimal methods for extracting information from and enhancing…

Cosmology and Nongalactic Astrophysics · Physics 2016-06-15 J. S. Sanders , A. C. Fabian , H. R. Russell , S. A. Walker , K. M. Blundell