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Photometric redshifts for Quasars in multi band Surveys
- Publication Year :
- 2013
- Publisher :
- arXiv, 2013.
-
Abstract
- MLPQNA stands for Multi Layer Perceptron with Quasi Newton Algorithm and it is a machine learning method which can be used to cope with regression and classification problems on complex and massive data sets. In this paper we give the formal description of the method and present the results of its application to the evaluation of photometric redshifts for quasars. The data set used for the experiment was obtained by merging four different surveys (SDSS, GALEX, UKIDSS and WISE), thus covering a wide range of wavelengths from the UV to the mid-infrared. The method is able i) to achieve a very high accuracy; ii) to drastically reduce the number of outliers and catastrophic objects; iii) to discriminate among parameters (or features) on the basis of their significance, so that the number of features used for training and analysis can be optimized in order to reduce both the computational demands and the effects of degeneracy. The best experiment, which makes use of a selected combination of parameters drawn from the four surveys, leads, in terms of DeltaZnorm (i.e. (zspec-zphot)/(1+zspec)), to an average of DeltaZnorm = 0.004, a standard deviation sigma = 0.069 and a Median Absolute Deviation MAD = 0.02 over the whole redshift range (i.e. zspec<br />38 pages, Submitted to ApJ in February 2013; Accepted by ApJ in May 2013
- Subjects :
- catalog
Cosmology and Nongalactic Astrophysics (astro-ph.CO)
Radio galaxy
media_common.quotation_subject
FOS: Physical sciences
Astrophysics
Astrophysics::Cosmology and Extragalactic Astrophysics
Standard deviation
Photometry (optics)
quasars: general
survey
Median absolute deviation
catalogs, galaxies: distances and redshifts, methods: data analysis, quasars: general, surveys, DIGITAL-SKY-SURVEY, 7TH DATA RELEASE, FUNCTION MINIMIZATION, CONJUGATE GRADIENTS, GALAXIES, SDSS, EVOLUTION, SELECTION, EXPLORER, MISSION
Instrumentation and Methods for Astrophysics (astro-ph.IM)
media_common
Physics
Astronomy and Astrophysics
Quasar
Redshift
galaxies: distances and redshift
Space and Planetary Science
Sky
Outlier
Astrophysics - Instrumentation and Methods for Astrophysics
Astrophysics - Instrumentation and Methods for Astrophysic
methods: data analysi
Astrophysics - Cosmology and Nongalactic Astrophysics
Subjects
Details
- Database :
- OpenAIRE
- Accession number :
- edsair.doi.dedup.....5cd285ee9379adc862734cac1b1d6585
- Full Text :
- https://doi.org/10.48550/arxiv.1305.5641