JPLUS: Morphological star/galaxy classification by PDF analysis
Abstract
Aims: Our goal is to morphologically classify the sources identified in the images of the JPLUS early data release (EDR) as compact (stars) or extended (galaxies) using a dedicated Bayesian classifier.
Methods: JPLUS sources exhibit two distinct populations in the rband magnitude versus concentration plane, corresponding to compact and extended sources. We modelled the twopopulation distribution with a skewed Gaussian for compact objects and a lognormal function for the extended objects. The derived model and the number density prior based on JPLUS EDR data were used to estimate the Bayesian probability that a source is a star or a galaxy. This procedure was applied pointingbypointing to account for varying observing conditions and sky positions. Finally, we combined the morphological information from the g, r, and i broad bands in order to improve the classification of low signaltonoise sources.
Results: The derived probabilities are used to compute the pointingbypointing number counts of stars and galaxies. The former increases as we approach the Milky Way disk, and the latter are similar across the probed area. The comparison with SDSS in the common regions is satisfactory up to r 21, with consistent numbers of stars and galaxies, and consistent distributions in concentration and (gi) colour spaces.
Conclusions: We implement a morphological star/galaxy classifier based on probability distribution function analysis, providing meaningful probabilities for JPLUS sources to one magnitude deeper (r 21) than a classical Boolean classification. These probabilities are suited for the statistical study of 150 thousand stars and 101 thousand galaxies with 15 < r ≤ 21 present in the 31.7 deg^{2} of the JPLUS EDR. In a future version of the classifier, we will include JPLUS colour information from 12 photometric bands.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 February 2019
 DOI:
 10.1051/00046361/201732480
 arXiv:
 arXiv:1804.02673
 Bibcode:
 2019A&A...622A.177L
 Keywords:

 methods: data analysis;
 Galaxy: stellar content;
 galaxies: statistics;
 Astrophysics  Astrophysics of Galaxies
 EPrint:
 Submitted to Astronomy and Astrophysics. 14 pages, 16 figures, 1 tables. Comments are welcome. All extra figures and the number counts files will be available with the paper in press