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We present a new approach to obtaining photometric redshifts using a kernel learning technique called Support Vector Machines (SVMs). Unlike traditional spectral energy distribution fitting, this technique requires a large and…

Astrophysics · Physics 2009-11-10 Yogesh Wadadekar

We present a new cluster detection algorithm designed for finding high-redshift clusters using optical/infrared imaging data. The algorithm has two main characteristics. First, it utilises each galaxy's full redshift probability function,…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 Caroline van Breukelen , Lee Clewley

Obtaining accurately calibrated redshift distributions of photometric samples is one of the great challenges in photometric surveys like LSST, Euclid, HSC, KiDS, and DES. We present an inference methodology that combines the redshift…

Cosmology and Nongalactic Astrophysics · Physics 2021-12-09 M. M. Rau , C. B. Morrison , S. J. Schmidt , S. Wilson , R. Mandelbaum , Y. Y. Mao

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

We use CFHTLS deep optical data, WIRCam Deep Survey (WIRDS) NIR data and XMM data to identify z>1.1 clusters in the CFHTLS D1 and D4 fields. Counterparts to such clusters can not be identified without deep NIR data and as such the total of…

Using the 2MASS Photometric Redshift catalogue we perform a number of statistical tests aimed at detecting possible departures from statistical homogeneity and isotropy in the large-scale structure of the Universe. Making use of the angular…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-23 David Alonso , Ana Isabel Salvador , Francisco Javier Sánchez , Maciej Bilicki , Juan García-Bellido , Eusebio Sánchez

We have identified a large-scale structure at z~0.73 in the COSMOS field, coherently described by the distribution of galaxy photometric redshifts, an ACS weak-lensing convergence map and the distribution of extended X-ray sources in a…

We present the first results of our application of photometric redshifts to the study of galaxy populations in high-redshift clusters. For this survey, we are examining a sample of galaxy clusters at z > 0.6 which have already been…

Astrophysics · Physics 2007-05-23 L. M. Lubin , R. J. Brunner

I review the current status of studies of the large-scale structure of the Universe using redshift surveys of galaxies and clusters of galaxies. I first summarise the advances we have made in our knowledge of the cosmography of the z<0.2…

Astrophysics · Physics 2007-05-23 Luigi Guzzo

New observations of high-redshift objects are crucial for the improvement of the standard $\Lambda$CDM cosmological model and our understanding of the Universe. One of the main directions of modern observational cosmology is the analysis of…

Cosmology and Nongalactic Astrophysics · Physics 2020-11-24 Maxim Nikonov , Mikhail Chekal , Stanislav Shirokov , Andrey Baryshev , Vladimir Gorokhov

Adami et al. (2010) have detected several cluster candidates at z>0.5 as part of a systematic search for clusters in the Canada France Hawaii Telescope Legacy Survey, based on photometric redshifts. We focus here on two of them, located in…

Astrophysics of Galaxies · Physics 2015-06-23 C. Adami , E. S. Cypriano , F. Durret , V. Le Brun , G. B. Lima Neto , N. Martinet , F. Perez , B. Rouze , L. Sodré

We describe a new method of combining optical and infrared photometry to select Luminous Red Galaxies (LRGs) at redshifts $z > 0.6$. We explore this technique using a combination of optical photometry from CFHTLS and HST, infrared…

Astrophysics of Galaxies · Physics 2015-04-27 Abhishek Prakash , Timothy C. Licquia , Jeffrey A. Newman , Sandhya M. Rao

We study the potential of weak lensing surveys to detect clusters of galaxies, using a fast Particle Mesh cosmological N-body simulation algorithm specifically tailored to investigate the statistics of these mass-selected clusters. In…

Astrophysics · Physics 2009-11-10 Joseph F. Hennawi , David N. Spergel

Context. We present an estimation of cosmological parameters with clusters of galaxies. Aims. We constrain the $\Omega_m$, $\sigma_8$, and $w$ parameters from a stand-alone sample of X-ray clusters detected in the 50 deg$^2$ XMM-XXL survey…

We apply a matched-filter cluster detection algorithm to the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) i-band data for the Deep-1, Deep-2, Deep-3 and Deep-4 fields covering a total of 4square degrees. To test the implemented…

Astrophysics · Physics 2009-11-11 L. F. Olsen , C. Benoist , A. Cappi , S. Maurogordato , A. Mazure , E. Slezak , C. Adami , C. Ferrari , F. Martel

We present photometric redshifts for an uniquely large and deep sample of 522286 objects with i'_{AB}<25 in the Canada-France Legacy Survey ``Deep Survey'' fields, which cover a total effective area of 3.2 deg^2. We use 3241 spectroscopic…

Because of the 3D nature of galaxies, an algorithm for constructing spatial density distribution models of galaxies on the basis of galaxy images has many advantages over surface density distribution approximations. We present a method for…

Cosmology and Nongalactic Astrophysics · Physics 2015-10-28 E. Tempel , A. Tamm , R. Kipper , P. Tenjes

The new generation of deep photometric surveys requires unprecedentedly precise shape and photometry measurements of billions of galaxies to achieve their main science goals. At such depths, one major limiting factor is the blending of…

At high redshift, due to both observational limitations and the variety of galaxy morphologies in the early universe, measuring galaxy structure can be challenging. Non-parametric measurements such as the CAS system have thus become an…

Astrophysics of Galaxies · Physics 2021-09-08 C. Tohill , L. Ferreira , C. J. Conselice , S. P. Bamford , F. Ferrari