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Astroinformatics of galaxies and quasars: a new general method for photometric redshifts estimation

Laurino, O. and D'Abrusco, R. and Longo, G. and Riccio, G. (2011) Astroinformatics of galaxies and quasars: a new general method for photometric redshifts estimation. Monthly Notices of the Royal Astronomical Society, 418 (4). pp. 2165-2195. ISSN 0035-8711. https://resolver.caltech.edu/CaltechAUTHORS:20120217-104557038

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Abstract

With the availability of the huge amounts of data produced by current and future large multiband photometric surveys, photometric redshifts have become a crucial tool for extragalactic astronomy and cosmology. In this paper we present a novel method, called Weak Gated Experts (WGE), which allows us to derive photometric redshifts through a combination of data mining techniques. The WGE, like many other machine learning techniques, is based on the exploitation of a spectroscopic knowledge base composed by sources for which a spectroscopic value of the redshift is available. This method achieves a variance σ^2(Δz) = 2.3 × 10^(−4) [σ^2(Δz) = 0.08, where Δz=z_(phot)−z_(spec)] for the reconstruction of the photometric redshifts for the optical galaxies from the Sloan Digital Sky Survey (SDSS) and for the optical quasars, respectively, while the root mean square (rms) of the Δz variable distributions for the two experiments is, respectively, equal to 0.021 and 0.35. The WGE provides also a mechanism for the estimation of the accuracy of each photometric redshift. We also present and discuss the catalogues obtained for the optical SDSS galaxies, for the optical candidate quasars extracted from the Data Release 7 of SDSS photometric data set (the sample of SDSS sources on which the accuracy of the reconstruction has been assessed is composed of bright sources, for a subset of which spectroscopic redshifts have been measured) and for optical SDSS candidate quasars observed by GALEX in the ultraviolet range. The WGE method exploits the new technological paradigm provided by the virtual observatory and the emerging field of astroinformatics.


Item Type:Article
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http://dx.doi.org/10.1111/j.1365-2966.2011.19416.xDOIUNSPECIFIED
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2966.2011.19416.x/abstractPublisherUNSPECIFIED
Additional Information:© 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 Royal Astronomical Society. Accepted 2011 July 10; Received 2011 June 17; in original form 2011 March 9. This work was made possible by the financial support of the US Virtual Astronomical Observatory, which is sponsored by the National Science Foundation and the National Aeronautics and Space Administration. This paper is based on work that took advantage of several technologies the authors would like to acknowledge. The WGE code is mostly based on the Fast Artificial Neural Network library. Most of the statistical code is implemented in R, while for data retrieval, analysis and publication, multiple tools, services and protocols developed by the International Virtual Observatory Alliance were used. In particular, all the catalogues derived from this publication will be published as standard Cone Search services through the VODance service hosted at the Italian Center for Astronomical Archives (IA2), Trieste Astronomical Observatory. TOPCAT (Taylor 2005) was used extensively in both its desktop version and its command line counterpart STILTS (Taylor 2006). The authors thank the anonymous reviewer for insightful comments that have helped to improve the paper.
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Funding AgencyGrant Number
US Virtual Astronomical ObservatoryUNSPECIFIED
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NASAUNSPECIFIED
Subject Keywords:methods: data analysis; techniques: photometric; catalogues; surveys; virtual observatory tools; cosmology: observations
Issue or Number:4
Record Number:CaltechAUTHORS:20120217-104557038
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20120217-104557038
Official Citation:Laurino, O., D’Abrusco, R., Longo, G. and Riccio, G. (2011), Astroinformatics of galaxies and quasars: a new general method for photometric redshifts estimation. Monthly Notices of the Royal Astronomical Society, 418: 2165–2195. doi: 10.1111/j.1365-2966.2011.19416.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:29360
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:17 Feb 2012 21:28
Last Modified:03 Oct 2019 03:40

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