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Photometric redshifts play an important role as a measure of distance for various cosmological topics. Spectroscopic redshifts are only available for a very limited number of objects but can be used for creating statistical models. A broad…

Instrumentation and Methods for Astrophysics · Physics 2016-08-30 Kai Lars Polsterer , Antonio D'Isanto , Fabian Gieseke

Photometric redshift uncertainties are a major source of systematic error for ongoing and future photometric surveys. We study different sources of redshift error caused by choosing a suboptimal redshift histogram bin width and propose…

Cosmology and Nongalactic Astrophysics · Physics 2017-05-02 Markus Michael Rau , Ben Hoyle , Kerstin Paech , Stella Seitz

Hyperspectral images, which store a hundred or more spectral bands of reflectance, have become an important data source in natural and social sciences. Hyperspectral images are often generated in large quantities at a relatively coarse…

Computer Vision and Pattern Recognition · Computer Science 2022-04-29 Kangning Cui , Ruoning Li , Sam L. Polk , James M. Murphy , Robert J. Plemmons , Raymond H. Chan

The Two-Micron All-Sky Survey (2MASS) has mapped out the low-redshift Universe down to $K_S\sim14$ mag. As its near-infrared photometry primarily probes the featureless Rayleigh-Jeans tail of galaxy spectral energy distributions,…

Astrophysics of Galaxies · Physics 2016-02-17 Mubdi Rahman , Brice Ménard , Ryan Scranton

We apply both a traditional `dropout' approach and a photometric redshift estimation technique to the Hubble Deep Field South data. We give a list of dropout selected z$\sim$3 objects, and show their images. We then discuss our photometric…

Astrophysics · Physics 2007-05-23 D. L. Clements

We show that current clustering observations of quasars and luminous AGN can be explained by a merger model augmented by feedback from outflows. Using numerical simulations large enough to study clustering out to 25 comoving h^{-1} Mpc, we…

Astrophysics · Physics 2011-02-11 Robert J. Thacker , Evan Scannapieco , H. M. P. Couchman , Mark Richardson

A new approach to estimating photometric redshifts - using Artificial Neural Networks (ANNs) - is investigated. Unlike the standard template-fitting photometric redshift technique, a large spectroscopically-identified training set is…

Astrophysics · Physics 2009-11-07 Andrew E. Firth , Ofer Lahav , Rachel S. Somerville

We introduce a new effective strategy to assign group and cluster membership probabilities $P_{mem}$ to galaxies using photometric redshift information. Large dynamical ranges both in halo mass and cosmic time are considered. The method…

Cosmology and Nongalactic Astrophysics · Physics 2016-11-09 Gianluca Castignani , Christophe Benoist

Given multiband photometric data from the SDSS DR6, we estimate galaxy redshifts. We employ a Random Forest trained on color features and spectroscopic redshifts from 80,000 randomly chosen primary galaxies yielding a mapping from color to…

In this paper, we address the problem of spectroscopic redshift estimation in Astronomy. Due to the expansion of the Universe, galaxies recede from each other on average. This movement causes the emitted electromagnetic waves to shift from…

Instrumentation and Methods for Astrophysics · Physics 2019-08-27 Radamanthys Stivaktakis , Grigorios Tsagkatakis , Bruno Moraes , Filipe Abdalla , Jean-Luc Starck , Panagiotis Tsakalides

We apply instance-based machine learning in the form of a k-nearest neighbor algorithm to the task of estimating photometric redshifts for 55,746 objects spectroscopically classified as quasars in the Fifth Data Release of the Sloan Digital…

We first present a catalogue of photometric redshifts for 14.68 million galaxies derived from the 7-band photometric data of Hyper Suprime-Cam Subaru Strategic Program and the Wide-field Infrared Survey Explorer using the nearest-neighbour…

Cosmology and Nongalactic Astrophysics · Physics 2020-11-20 Z. L. Wen , J. L. Han

We study the problem of applying spectral clustering to cluster multi-scale data, which is data whose clusters are of various sizes and densities. Traditional spectral clustering techniques discover clusters by processing a similarity…

Machine Learning · Computer Science 2020-06-09 Xiang Li , Ben Kao , Caihua Shan , Dawei Yin , Martin Ester

High-redshift clusters of galaxies are amongst the largest cosmic structures. Their properties and evolution are key ingredients to our understanding of cosmology: to study the growth of structure from the inhomogeneities of the cosmic…

Astrophysics · Physics 2007-05-23 A. Fernandez-Soto , J. Bland-Hawthorn , J. I. Gonzalez-Serrano , R. Carballo

SpectralNet is a graph clustering method that uses neural network to find an embedding that separates the data. So far it was only used with $k$-nn graphs, which are usually constructed using a distance metric (e.g., Euclidean distance).…

Machine Learning · Computer Science 2023-02-28 Mashaan Alshammari , John Stavrakakis , Adel F. Ahmed , Masahiro Takatsuka

Given the importance of clusters to the fields of cosmology and galaxy evolution, it is critical to understand how the cluster detection process affects (biases) ones scientific conclusions derived from a given cluster sample. I review the…

Astrophysics · Physics 2007-05-23 Marc Postman

The relationship between the clustering of dark matter and that of luminous matter is often described using the bias parameter. Here, we provide a new method to probe the bias of intermediate to high-redshift radio continuum sources for…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-12 Sean Passmoor , Catherine Cress , Andreas Faltenbacher , Russell Johnston , Mathew Smith , Ando Ratsimbazafy , Ben Hoyle

We present an empirical algorithm for obtaining photometric redshifts of quasars using 5-band Sloan Digital Sky Survey (SDSS) photometry. Our algorithm generates an empirical model of the quasar color-redshift relation, compares the colors…

The discrete distribution is often used to describe complex instances in machine learning, such as images, sequences, and documents. Traditionally, clustering of discrete distributions (D2C) has been approached using Wasserstein barycenter…

Machine Learning · Computer Science 2024-08-19 Zixiao Wang , Dong Qiao , Jicong Fan

In order to retrieve cosmological parameters from photometric surveys, we need to estimate the distribution of the photometric redshift in the sky with excellent accuracy. We use and apply three different machine learning methods to…

Cosmology and Nongalactic Astrophysics · Physics 2025-11-13 Elcio Abdalla , Filipe B. Abdalla , Alessandro Marins , Amilcar Queiroz , Rafael M. Ribeiro , Alex S. C. Souza