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We present a study of pixel Colour Magnitude Diagrams (pCMDs) for a sample of 69 nearby galaxies chosen to span a wide range of Hubble types. Our goal is to determine how useful a pixel approach is for studying galaxies according to their…

Astrophysics · Physics 2009-11-13 M. M. Lanyon-Foster , C. J. Conselice , M. R. Merrifield

The study of strong-lensing systems conventionally involves constructing a mass distribution that can reproduce the observed multiply-imaging properties. Such mass reconstructions are generically non-unique. Here, we present an alternative…

Astrophysics of Galaxies · Physics 2021-06-30 Philipp Denzel , Sampath Mukherjee , Prasenjit Saha

In order to obtain morphological information of unlabeled galaxies, we present an unsupervised machine-learning (UML) method for morphological classification of galaxies, which can be summarized as two aspects: (1) the methodology of…

Astrophysics of Galaxies · Physics 2022-02-02 C. C. Zhou , Y. Z. Gu , G. W. Fang , Z. S. Lin

We explore unsupervised machine learning for galaxy morphology analyses using a combination of feature extraction with a vector-quantised variational autoencoder (VQ-VAE) and hierarchical clustering (HC). We propose a new methodology that…

The large number of galaxies imaged by digital sky surveys reinforces the need for computational methods for analyzing galaxy morphology. While the morphology of most galaxies can be associated with a stage on the Hubble sequence,…

Instrumentation and Methods for Astrophysics · Physics 2013-09-17 Lior Shamir , Anthony Holincheck , John Wallin

In order to investigate the properties of large-scale structures of galaxies in the universe, we present an analysis of their spatial distribution at z$<$0.033. We used the LEDA extragalactic database containing over 1 million of galaxies…

Astrophysics · Physics 2015-01-27 Helene Courtois , Georges Paturel , Thierry Sousbie , Francesco Sylos Labini

We extend a recently developed galaxy morphology classification method, Quantitative Multiwavelength Morphology (QMM), to connect galaxy morphologies to their underlying physical properties. The traditional classification of galaxies…

Astrophysics of Galaxies · Physics 2015-05-18 D. B. Wijesinghe , A. M. Hopkins , B. C. Kelly , N. Welikala , A. J. Connolly

This paper addresses the challenge of spectral-spatial feature extraction for hyperspectral image classification by introducing a novel tensor-based framework. The proposed approach incorporates circular convolution into a tensor structure…

Computer Vision and Pattern Recognition · Computer Science 2024-12-10 Yuemei Ren , Liang Liao , Stephen John Maybank , Yanning Zhang , Xin Liu

Recent studies on Generative Adversarial Network (GAN) reveal that different layers of a generative CNN hold different semantics of the synthesized images. However, few GAN models have explicit dimensions to control the semantic attributes…

Computer Vision and Pattern Recognition · Computer Science 2021-08-10 Zhenliang He , Meina Kan , Shiguang Shan

Three-dimensional (3D) spectroscopy techniques are becoming more and more popular, producing an increasing number of large data cubes. The challenge of extracting information from these cubes requires the development of new techniques for…

Cosmology and Nongalactic Astrophysics · Physics 2014-03-28 T. V. Ricci , J. E. Steiner , R. B. Menezes

Classification of galaxies is traditionally associated with their morphologies through visual inspection of images. The amount of data to come renders this task inhuman and Machine Learning (mainly Deep Learning) has been called to the…

Astrophysics of Galaxies · Physics 2023-06-14 Didier Fraix-Burnet

Cosmological galaxy formation simulations can now produce rich and diverse ensembles of galaxy histories. These simulated galaxy histories, taken all together, provide an answer to the question "how do galaxies form?" for the models used to…

Astrophysics of Galaxies · Physics 2015-06-19 J. D. Cohn , Freeke van de Voort

Principal components analysis (PCA) is a classical method for the reduction of dimensionality of data in the form of n observations (or cases) of a vector with p variables. For a simple model of factor analysis type, it is proved that…

Statistics Theory · Mathematics 2009-01-29 Iain M Johnstone , Arthur Yu Lu

We develop a straightforward and quantitative two-step method for spectroscopically classifying galaxies from the low signal-to-noise (S/N) optical spectra typical of galaxy redshift surveys. First, using \chi^2-fitting of characteristic…

Astrophysics · Physics 2009-10-28 Dennis Zaritsky , Ann I. Zabludoff , Jeffrey A. Willick

We propose to use eigenvalue densities of unitary random matrix ensembles as mass distributions in gravitational lensing. The corresponding lens equations reduce to algebraic equations in the complex plane which can be treated analytically.…

Mathematical Physics · Physics 2018-03-12 Luis Martínez Alonso , Elena Medina

Principal Component Analysis (PCA) is being extensively used in Astronomy but not yet exhaustively exploited for variability search. The aim of this work is to investigate the effectiveness of using the PCA as a method to search for…

Instrumentation and Methods for Astrophysics · Physics 2018-04-04 M. I. Moretti , D. Hatzidimitriou , A. Karampelas , K. V. Sokolovsky , A. Z. Bonanos , P. Gavras , M. Yang

Galaxies of rare morphology are of paramount scientific interest, as they carry important information about the past, present, and future universe. Once a rare galaxy is identified, studying it more effectively requires a set of galaxies of…

Instrumentation and Methods for Astrophysics · Physics 2017-01-04 Lior Shamir

Estimating stellar masses for billions of galaxies in upcoming surveys requires methods that are both accurate and computationally efficient. We present a new approach using symbolic regression trained on a simulation to derive simple,…

We analyse synthetic galaxy spectra from the evolutionary models of Bruzual&Charlot and Fioc&Rocca-Volmerange using the method of Principal Component Analysis (PCA). We explore synthetic spectra with different ages, star formation histories…

Astrophysics · Physics 2009-10-30 S. Ronen , A. Aragon-Salamanca , O. Lahav

Gradually, the $\Lambda$CDM model starts to be challenged by observational data. Upcoming cosmological surveys will increase the number of detected galaxy clusters by several orders of magnitude. Therefore, shortly, clusters will provide…

Cosmology and Nongalactic Astrophysics · Physics 2022-08-25 E. Artis , J-B Melin , J. G. Bartlett , C. Murray