The VIMOS Public Extragalactic Redshift Survey (VIPERS). Unsupervised classification with photometric redshifts: a method to accurately classify large galaxy samples without spectroscopic information
Abstract
Techniques to classify galaxies solely based on photometry will be necessary for future large cosmology missions, such as Euclid or LSST. However, the precision of classification is always lower in photometric surveys and can be systematically biased with respect to classifications based upon spectroscopic data. We verified how precisely the detailed classification scheme introduced by Siudek et al. (2018, hereafter: S1) for galaxies at z~0.7 could be reproduced if only photometric data are available. We applied the Fisher Expectation-Maximization (FEM) unsupervised clustering algorithm to 54,293 VIPERS galaxies working in a parameter space of reliable photometric redshifts and 12 corresponding rest-frame magnitudes. The FEM algorithm distinguishes four main groups: (1) red, (2) green, (3) blue, and (4) outliers. Each group is further divided into 3, 3, 4, and 2 subclasses, respectively. The accuracy of reproducing galaxy classes using spectroscopic data is high: 92%, 84%, 96% for red, green, and blue classes, respectively, except for dusty star-forming galaxies. The presented verification of the photometric classification demonstrates that large photometric samples can be used to distinguish different galaxy classes at z > 0.5 with an accuracy provided so far only by spectroscopic data except for particular galaxy classes.
Keywords
Cite
@article{arxiv.1805.09905,
title = {The VIMOS Public Extragalactic Redshift Survey (VIPERS). Unsupervised classification with photometric redshifts: a method to accurately classify large galaxy samples without spectroscopic information},
author = {M. Siudek and K. Małek and A. Pollo and B. R. Granett and M. Scodeggio and T. Moutard and A. Iovino and L. Guzzo and B. Garilli and M. Bolzonella and S. de la Torre and U. Abbas and C. Adami and D. Bottini and A. Cappi and O. Cucciati and I. Davidzon and P. Franzetti and A. Fritz and J. Krywult and V. Le Brun and O. Le Fèvre and D. Maccagni and F. Marulli and M. Polletta and L. A. M. Tasca and R. Tojeiro and D. Vergani and A. Zanichelli and S. Arnouts and J. Bel and E. Branchini and J. Coupon and G. De Lucia and O. Ilbert and L. Moscardini and G. Zamorani and T. T. Takeuchi},
journal= {arXiv preprint arXiv:1805.09905},
year = {2018}
}
Comments
the letter submitted to MNRAS, 6 pages, 4 figures. Please contact Malgorzata Siudek ([email protected]) if you are interested in the catalogue