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We calculate photometric redshifts from the Sloan Digital Sky Survey Data Release 2 Galaxy Sample using artificial neural networks (ANNs). Different input patterns based on various parameters (e.g. magnitude, color index, flux information)…

Astrophysics · Physics 2007-05-23 Lili Li , Yanxia Zhang , Yongheng Zhao , Dawei Yang

Deep Learning models have been increasingly exploited in astrophysical studies, yet such data-driven algorithms are prone to producing biased outputs detrimental for subsequent analyses. In this work, we investigate two major forms of…

Instrumentation and Methods for Astrophysics · Physics 2022-06-15 Q. Lin , D. Fouchez , J. Pasquet , M. Treyer , R. Ait Ouahmed , S. Arnouts , O. Ilbert

Based on the Sloan Digital Sky Survey Data Release 5 Galaxy Sample, we explore photometric morphology classification and redshift estimation of galaxies using photometric data and known spectroscopic redshifts. An unsupervised method,…

Astrophysics · Physics 2009-11-13 Yanxia Zhang , Lili Li , Yongheng Zhao

We present a simple method for evaluating the nonlinear biasing function of galaxies from a redshift survey. The nonlinear biasing is characterized by the conditional mean of the galaxy density fluctuation given the underlying mass density…

Astrophysics · Physics 2009-10-31 Yair Sigad , Enzo Branchini , Avishai Dekel

Estimating redshift is a central task in astrophysics, but its measurement is costly and time-consuming. In addition, current image-based methods are often validated on homogeneous datasets. The development and comparison of networks able…

Instrumentation and Methods for Astrophysics · Physics 2026-03-17 Alessandro Meroni , Nicolò Oreste Pinciroli Vago , Piero Fraternali

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

Measuring distances of cosmological sources such as galaxies, stars and quasars plays an increasingly critical role in modern cosmology. Obtaining the optical spectrum and consequently calculating the redshift as a distance indicator could…

Astrophysics of Galaxies · Physics 2022-01-13 Aidin Momtaz , Mohammad Hossein Salimi , Soroush Shakeri

We use machine learning to identify in color images of high-redshift galaxies an astrophysical phenomenon predicted by cosmological simulations. This phenomenon, called the blue nugget (BN) phase, is the compact star-forming phase in the…

We train deep learning models on thousands of galaxy catalogues from the state-of-the-art hydrodynamic simulations of the CAMELS project to perform regression and inference. We employ Graph Neural Networks (GNNs), architectures designed to…

Cosmology and Nongalactic Astrophysics · Physics 2023-02-10 Pablo Villanueva-Domingo , Francisco Villaescusa-Navarro

We present METAPHOR (Machine-learning Estimation Tool for Accurate PHOtometric Redshifts), a method able to provide a reliable PDF for photometric galaxy redshifts estimated through empirical techniques. METAPHOR is a modular workflow,…

Instrumentation and Methods for Astrophysics · Physics 2017-06-14 Valeria Amaro , Stefano Cavuoti , Massimo Brescia , Civita Vellucci , Crescenzo Tortora , Giuseppe Longo

We present photometric redshifts and associated probability distributions for all detected sources in the Extended Chandra Deep Field South (ECDFS). The work makes use of the most up-to-date data from the Cosmic Assembly Near-IR Deep Legacy…

Estimating redshifts from broadband photometry is often limited by how accurately we can map the colors of galaxies to an underlying spectral template. Current techniques utilize spectrophotometric samples of galaxies or spectra derived…

Instrumentation and Methods for Astrophysics · Physics 2025-03-11 John Franklin Crenshaw , Andrew J. Connolly

We train and apply convolutional neural networks, a machine learning technique developed to learn from and classify image data, to Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) imaging for the identification of potential strong…

Instrumentation and Methods for Astrophysics · Physics 2017-06-16 Colin Jacobs , Karl Glazebrook , Thomas Collett , Anupreeta More , Christopher McCarthy

All-sky radio surveys are set to revolutionise the field with new discoveries. However, the vast majority of the tens of millions of radio galaxies won't have the spectroscopic redshift measurements required for a large number of science…

Instrumentation and Methods for Astrophysics · Physics 2022-03-01 Kieran J. Luken , Ray P. Norris , Laurence A. F. Park , X. Rosalind Wang , Miroslav D. Filipovic

We describe an Artificial Neural Network (ANN) approach to classification of galaxy images and spectra. ANNs can replicate the classification of galaxy images by a human expert to the same degree of agreement as that between two human…

Astrophysics · Physics 2007-05-23 Ofer Lahav

Accurate photometric redshifts are calculated for nearly 200,000 galaxies to a 4.5 micron flux limit of ~13 uJy in the 8.5 deg^2 Spitzer/IRAC Shallow survey. Using a hybrid photometric redshift algorithm incorporating both neural-net and…

Accurate and reliable photometric redshift determination is one of the key aspects for wide-field photometric surveys. Determination of photometric redshift for galaxies, has been traditionally solved by use of machine-learning and…

Instrumentation and Methods for Astrophysics · Physics 2025-07-18 M. Garcia-Fernandez

We present a novel approach to analyzing astronomical spectral survey data using our non-linear extension of an online dictionary learning algorithm. Current and upcoming surveys such as SPHEREx will use spectral data to build a 3D map of…

Instrumentation and Methods for Astrophysics · Physics 2023-11-28 Sean Bryan , Ayan Barekzai , Delondrae Carter , Philip Mauskopf , Julian Mena , Danielle Rivera , Abel S. Uriarte , Pao-Yu Wang

We constrain the mass profile and orbital structure of nearby groups and clusters of galaxies. Our method yields the joint probability distribution of the density slope n, the velocity anisotropy beta, and the turnover radius r0 for these…

Astrophysics · Physics 2009-11-10 A. Mahdavi , M. J. Geller

Using a suite of self-similar cosmological simulations, we measure the probability distribution functions (PDFs) of real-space density, redshift-space density, and their geometric mean. We find that the real-space density PDF is…

Cosmology and Nongalactic Astrophysics · Physics 2022-04-27 Huanqing Chen , Nickolay Y. Gnedin , Philip Mansfield
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