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Photometric redshifts (photo-z's) provide an alternative way to estimate the distances of large samples of galaxies and are therefore crucial to a large variety of cosmological problems. Among the various methods proposed over the years,…

Instrumentation and Methods for Astrophysics · Physics 2017-06-13 Stefano Cavuoti , Massimo Brescia , Valeria Amaro , Civita Vellucci , Giuseppe Longo , Crescenzo Tortora

We are pursuing a project to build a database of phase calibration sources suitable for Giant Metrewave Radio Telescope (GMRT). Here we present the first release of 45 low frequency calibration sources at 235 MHz and 610 MHz. These…

Instrumentation and Methods for Astrophysics · Physics 2016-10-19 Dharam V. Lal , Shilpa S. Dubal , Sachin S. Sherkar

This paper presents a catalogue of optimised pointings for differential photometry of 23,779 quasars extracted from the Sloan Digital Sky Survey (SDSS) Catalogue and a score for each indicating the quality of the Field of View (FoV)…

Astrophysics of Galaxies · Physics 2020-09-30 Oisín Creaner , Kevin Nolan , David Grennan , Niall Smith , Eugene Hickey

We present a new technique for creating mock catalogues of the individual stars that make up the accreted component of stellar haloes in cosmological simulations and show how the catalogues can be used to test and interpret observational…

Astrophysics of Galaxies · Physics 2014-11-27 Ben Lowing , Wenting Wang , Andrew Cooper , Rachel Kennedy , John Helly , Carlos Frenk , Shaun Cole

Difference imaging provides a new way to discover gravitationally lensed quasars because few non-lensed sources will show spatially extended, time variable flux. We test the method on lens candidates in the Sloan Digital Sky Survey (SDSS)…

The KiDS Strongly lensed QUAsar Detection project (KiDS-SQuaD) aims at finding as many previously undiscovered gravitational lensed quasars as possible in the Kilo Degree Survey. This is the second paper of this series where we present a…

We present a study of variable faint optical sources discovered by comparing the Sloan Digital Sky Survey (SDSS) and the Palomar Observatory Sky Survey (POSS) catalogs. We use SDSS measurements to photometrically recalibrate several…

Recent technological advances have led to a flood of new data on cosmology rich in information about the formation and evolution of the universe, e.g., the data collected in Sloan Digital Sky Survey (SDSS) for more than 200 million objects.…

Cosmology and Nongalactic Astrophysics · Physics 2009-02-25 Sabyasachi Mukhopadhyay , Sisir Roy , Sourabh Bhattacharya

We present mock catalogs created to support the interpretation of the CANDELS survey. We extract halos along past lightcones from the Bolshoi Planck dissipationless N-body simulations and populate these halos with galaxies using two…

We present the Lensed Mock Map Facility (LeMoMaF), a tool designed to perform mock weak lensing measurements on numerically simulated chunks of the universe. Coupling N-body simulations to a semi-analytical model of galaxy formation,…

We present the first edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 3814 objects (3000 discovered by the SDSS) in the initial SDSS public data release that have at least one emission line with a…

In this work we deal with the problem of simultaneous multifrequency detection of extragalactic point sources in maps of the Cosmic Microwave Background. We apply a linear filtering technique that uses spatial information and the…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 L. F. Lanz , D. Herranz , J. L. Sanz , J. González-Nuevo , M. López-Caniego

We propose a Multimodal Machine Learning method for estimating the Photometric Redshifts of quasars (PhotoRedshift-MML for short), which has long been the subject of many investigations. Our method includes two main models, i.e. the feature…

Astrophysics of Galaxies · Physics 2022-11-09 Shuxin Hong , Zhiqiang Zou , A-Li Luo , Xiao Kong , Wenyu Yang , Yanli Chen

We introduce a new method for estimating the covariance matrix for the galaxy correlation function in surveys of large-scale structure. Our method combines simple theoretical results with a realistic characterization of the survey to…

Cosmology and Nongalactic Astrophysics · Physics 2016-08-31 Ross O'Connell , Daniel Eisenstein , Mariana Vargas , Shirley Ho , Nikhil Padmanabhan

A non-parametric smoothing method is presented that reduces noise in multi-wavelength imaging data sets. Using Principle Component Analysis (hereafter PCA) to associate pixels according to their $ugriz$-band colors, smoothing is done over…

Instrumentation and Methods for Astrophysics · Physics 2015-03-17 James Pizagno

Ultra-faint dwarf galaxies, which can be detected as resolved satellite systems of the Milky Way, are critical to understanding galaxy formation, evolution, and the nature of dark matter, as they are the oldest, smallest, most metal-poor,…

Weak lensing has become a powerful tool for probing the matter distribution in the Universe and constraining cosmological parameters. This paper aims to explore the fast mock generation pipeline to obtain the covariance matrix of the…

Cosmology and Nongalactic Astrophysics · Physics 2025-06-17 Yiming Hu , Yu Yu

Weak lensing shear estimation typically results in per galaxy statistical errors significantly larger than the sought after gravitational signal of only a few percent. These statistical errors are mostly a result of shape-noise -- an…

Cosmology and Nongalactic Astrophysics · Physics 2020-01-08 Ofer M. Springer , Eran O. Ofek , Yair Weiss , Julian Merten

We have used the VLA FIRST survey and the APM catalog of the POSS-I plates as the basis for constructing a new radio-selected sample of optically bright quasars. This is the first radio-selected sample that is competitive in size with…

In this study, we investigate the morphology of galaxies in the TNG100 simulation by applying mock observation techniques and compare the results with the observational data from the Sloan Digital Sky Survey (SDSS). By employing a…

Astrophysics of Galaxies · Physics 2025-07-01 Jun-Yu Gong , Weipeng Lin , Lin Tang , Yanyao Lan
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