- ID:
- ivo://ia2.inaf.it/hosted/laurino2011/cqsophotoz
- Title:
- Laurino et al 2011 Catalog of WGE photometric redshifts for SDSS candidate quasars
- Date:
- 13 Mar 2019 11:56:43
- Publisher:
- IA2
- Description:
- The Sloan Digital Sky Survey (SDSS) has observed more than a quarter of the sky over eight years of operations, obtaining multicolor photometry and spectroscopy for ~ 1 million of galaxies. A catalog of photometric redshifts for ~ 2 millions quasars with magnitude r < 20.7 extracted from the SDSS DR7 dataset (D'Abrusco et al, 2009) is provided here. The photometric redshifts and the uncertainty of the estimates for each sources have been calculated using the Weak Gated Expert (WGE) method. The WGE (Laurino et al., submitted to MNRAS) is based on the exploitation of the spectroscopic redshifts for a subset of photometric sources and derives photometric redshifts through a combination of data mining techniques. This method can be applied to different classes of extragalactic sources and is scalable. A set of observational parameters used for the evaluation of photometric redshifts, the estimated photometric redshifts values and some of the most common observational parameters retrieved from the SDSS database have been included in the catalog for the sake of simplicity.
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- ID:
- ivo://ia2.inaf.it/hosted/laurino2011/cqsophotozOptUV
- Title:
- Laurino et al 2011 Catalog of WGE photometric redshifts (optical+UV) for SDSS candidate quasars
- Date:
- 13 Mar 2019 11:56:54
- Publisher:
- IA2
- Description:
- The Sloan Digital Sky Survey (SDSS) has observed more than a quarter of the sky over eight years of operations, obtaining multicolor photometry and spectroscopy for ~ 1 million of galaxies, and the GALEX survey is the ultraviolet counterpart of the SDSS. A catalog of photometric redshifts (evaluated using optical and ultraviolet photometry) for ~150000 candidate quasars with magnitude r < 20.7, extracted from the SDSS DR7 dataset (D'Abrusco et al, 2009) and with GALEX counterparts, is provided here. The photometric redshifts and the uncertainty of the estimates for each source have been calculated using the Weak Gated Expert (WGE) method. The WGE (Laurino et al., submitted to MNRAS) is based on the exploitation of the spectroscopic redshifts for a subset of photometric sources and derives photometric redshifts through a combination of data mining techniques. This method can be applied to different classes of extragalactic sources and is scalable. A set of observational parameters used for the evaluation of photometric redshifts, the estimated photometric redshifts values and some of the most common observational parameters retrieved from the SDSS and GALEX databases have been included in the catalog for the sake of simplicity.
- ID:
- ivo://ia2.inaf.it/hosted/dabrusco2009/cqso
- Title:
- [TEST] DAbrusco et al 2009 Catalogue of SDSS Quasar candidates
- Date:
- 13 Mar 2019 11:56:22
- Publisher:
- IA2
- Description:
- [TEST] We present a method for the photometric selection of candidate quasars in multiband surveys. The method makes use of a priori knowledge derived from a subsample of spectroscopic confirmed quasi-stellar objects (QSOs) to map the parameter space. The disentanglement of QSOs candidates and stars is performed in the colour space through the combined use of two algorithms, the probabilistic principal surfaces and the negative entropy clustering, which are for the first time used in an astronomical context. Both methods have been implemented in the VONEURAL package on the Astrogrid Virtual Observatory platform. Even though they belong to the class of the unsupervised clustering tools, the performances of the method are optimized by using the available sample of confirmed quasars and it is therefore possible to learn from any improvement in the available `base of knowledge'. The method has been applied and tested on both optical and optical plus near-infrared data extracted from the visible Sloan Digital Sky Survey (SDSS) and infrared United Kingdom Infrared Deep Sky Survey-Large Area Survey public data bases. In all cases, the experiments lead to high values of both efficiency and completeness, comparable if not better than the methods already known in the literature. A catalogue of optical candidate QSOs extracted from the SDSS Data Release 7 Legacy photometric data set has been produced and is publicly available at the URL http://voneural.na.infn.it/qso.html.
