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The detection and characterization of filamentary structures in the cosmic web allows cosmologists to constrain parameters that dictates the evolution of the Universe. While many filament estimators have been proposed, they generally lack…

Cosmology and Nongalactic Astrophysics · Physics 2015-10-07 Yen-Chi Chen , Shirley Ho , Peter E. Freeman , Christopher R. Genovese , Larry Wasserman

This paper studies the linear convergence of the subspace constrained mean shift (SCMS) algorithm, a well-known algorithm for identifying a density ridge defined by a kernel density estimator. By arguing that the SCMS algorithm is a special…

Machine Learning · Statistics 2025-05-13 Yikun Zhang , Yen-Chi Chen

(abridged) In the last decade, the advent of enormous galaxy surveys has motivated the development of automated morphological classification schemes to deal with large data volumes. Existing automated schemes can successfully distinguish…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-20 Judy Y. Cheng , S. M. Faber , Luc Simard , Genevieve J. Graves , Eric D. Lopez , Renbin Yan , Michael C. Cooper

We construct a catalogue for filaments using a novel approach called SCMS (subspace constrained mean shift; Ozertem & Erdogmus 2011; Chen et al. 2015). SCMS is a gradient-based method that detects filaments through density ridges (smooth…

Cosmology and Nongalactic Astrophysics · Physics 2016-08-03 Yen-Chi Chen , Shirley Ho , Jon Brinkmann , Peter E. Freeman , Christopher R. Genovese , Donald P. Schneider , Larry Wasserman

We present a new non-parametric method to quantify morphologies of galaxies based on a particular family of learning machines called support vector machines. The method, that can be seen as a generalization of the classical CAS…

Astrophysics · Physics 2009-11-13 M. Huertas-Company , D. Rouan , L. Tasca , G. Soucail , O. Le Fevre

Low surface brightness substructures around galaxies, known as tidal features, are a valuable tool in the detection of past or ongoing galaxy mergers, and their properties can answer questions about the progenitor galaxies involved in the…

Astrophysics of Galaxies · Physics 2024-06-06 Alice Desmons , Sarah Brough , Francois Lanusse

We present an unsupervised machine learning technique that automatically segments and labels galaxies in astronomical imaging surveys using only pixel data. Distinct from previous unsupervised machine learning approaches used in astronomy…

Instrumentation and Methods for Astrophysics · Physics 2017-11-08 Alex Hocking , James E. Geach , Yi Sun , Neil Davey

Simulations of massive star formation predict the formation of discs with significant substructure, such as spiral arms and clumps due to fragmentation. Here we present a semi-analytic framework for producing synthetic observations of discs…

Automatic mammogram classification and mass segmentation play a critical role in a computer-aided mammogram screening system. In this work, we present a unified mammogram analysis framework for both whole-mammogram classification and…

Computer Vision and Pattern Recognition · Computer Science 2018-09-03 Rongzhao Zhang , Han Zhang , Albert C. S. Chung

Modern astronomy relies on massive databases collected by robotic telescopes and digital sky surveys, acquiring data in a much faster pace than what manual analysis can support. Among other data, these sky surveys collect information about…

Instrumentation and Methods for Astrophysics · Physics 2018-10-29 Evan Kuminski , Lior Shamir

In this paper we explore the use of spatial clustering algorithms as a new computational approach for modeling the cosmic web. We demonstrate that such algorithms are efficient in terms of computing time needed. We explore three distinct…

Instrumentation and Methods for Astrophysics · Physics 2022-09-14 Dimitrios Kelesis , Spyros Basilakos , Vicky Papadopoulou Lesta , Dimitris Fotakis , Andreas Efstathiou

The latticework structure known as the cosmic web provides a valuable insight into the assembly history of large-scale structures. Despite the variety of methods to identify the cosmic web structures, they mostly rely on the assumption that…

Cosmology and Nongalactic Astrophysics · Physics 2022-10-26 Yikun Zhang , Rafael S. de Souza , Yen-Chi Chen

The extraction of filamentary structure from a point cloud is discussed. The filaments are modeled as ridge lines or higher dimensional ridges of an underlying density. We propose two novel algorithms, and provide theoretical guarantees for…

Machine Learning · Statistics 2025-01-03 Wanli Qiao , Wolfgang Polonik

We investigate the power of the caustic technique for identifying substructures of galaxy clusters from optical redshift data alone. The caustic technique is designed to estimate the mass profile of galaxy clusters to radii well beyond the…

Cosmology and Nongalactic Astrophysics · Physics 2015-09-09 Heng Yu , Ana Laura Serra , Antonaldo Diaferio , Marco Baldi

Low surface brightness substructures around galaxies, known as tidal features, are a valuable tool in the detection of past or ongoing galaxy mergers. Their properties can answer questions about the progenitor galaxies involved in the…

Astrophysics of Galaxies · Physics 2023-07-12 Alice Desmons , Sarah Brough , Francois Lanusse

Ground-based optical surveys such as PanSTARRS, DES, and LSST, will produce large catalogs to limiting magnitudes of r > 24. Star-galaxy separation poses a major challenge to such surveys because galaxies---even very compact…

Instrumentation and Methods for Astrophysics · Physics 2015-06-05 Ross Fadely , David W. Hogg , Beth Willman

We present a novel method for automatically detecting and characterising semi-resolved star clusters: clusters where the observational point-spread function (PSF) is smaller than the cluster's radius, but larger than the separations between…

We develop an explicit model for the formation of the stellar halo from tidally disrupted, accreted dwarf satellites in the cold dark matter (CDM) framework, focusing on predictions testable with the Sloan Digital Sky Survey (SDSS) and…

Astrophysics · Physics 2009-10-31 James S. Bullock , Andrey V. Kravtsov , David H. Weinberg

In this paper we present a novel method to identify and characterize stellar clusters deeply embedded in a dark molecular cloud. The method is based on measuring stellar surface density in wide-field infrared images using star counting…

Instrumentation and Methods for Astrophysics · Physics 2017-11-29 Marco Lombardi , Charles J. Lada , Joao Alves

We derive the fraction of substructure in the Galactic halo using a sample of over 10,000 spectroscopically-confirmed halo giant stars from the LAMOST spectroscopic survey. By observing 100 synthetic models along each line of sight with the…

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