AutoSourceID-Classifier. Star-Galaxy Classification using a Convolutional Neural Network with Spatial Information

arXiv (Cornell University)

Abstract

Aims. Traditional star-galaxy classification techniques often rely on feature estimation from catalogues, a process susceptible to introducing inaccuracies, thereby potentially jeopardizing the classification's reliability. Certain galaxies, especially those not manifesting as extended sources, can be misclassified when their shape parameters and flux solely drive the inference. We aim to create a robust and accurate classification network for identifying stars and galaxies directly from astronomical images. By leveraging convolutional neural networks (CNN) and additional information about the source position, we aim to accurately classify all stars and galaxies within a survey, particularly those with a signal-to-noise ratio (S/N) near the detection limit. Methods. The AutoSourceID-Classifier (ASID-C) algorithm developed here uses 32x32 pixel single filter band source cutouts generated by the previously developed ASID-L code. ASID-C utilizes CNNs to distinguish these cutouts into stars or galaxies, leveraging their strong feature-learning capabilities. Subsequently, we employ a modified Platt Scaling calibration for the output of the CNN. This technique ensures that the derived probabilities are effectively calibrated, delivering precise and reliable results. Results. We show that ASID-C, trained on MeerLICHT telescope images and using the Dark Energy Camera Legacy Survey (DECaLS) morphological classification, outperforms similar codes like SourceExtractor. ASID-C opens up new possibilities for accurate celestial object classification, especially for sources with a S/N near the detection limit. Potential applications of ASID-C, like real-time star-galaxy classification and transient's host identification, promise significant contributions to astronomical research.

Authors 12

1. Fiorenzo Stoppa

   Radboud University Nijmegen

   Affiliation as printed

   : Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands

   : Department of Mathematics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands

2. Saptashwa Bhattacharyya

   University of Nova Gorica

   Affiliation as printed

   : Center for Astrophysics and Cosmology, University of Nova Gorica, Vipavska 13, SI-5000 Nova Gorica, Slovenia

3. Paul M. Vreeswijk

   Radboud University Nijmegen

   Affiliation as printed

   : Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands

4. S. Caron

   Radboud University Nijmegen · National Institute for Subatomic Physics

   Affiliation as printed

   : High Energy Physics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands

   : Nikhef, Science Park 105, 1098 XG Amsterdam, the Netherlands

5. Gabrijela Zaharijaš

   University of Nova Gorica · Institute for Fundamental Physics of the Universe

   Affiliation as printed

   : Center for Astrophysics and Cosmology, University of Nova Gorica, Vipavska 13, SI-5000 Nova Gorica, Slovenia

   : Institute for Fundamental Physics of the Universe, Via Beirut 2, 34151 Trieste, Italy

6. S. Bloemen

   Radboud University Nijmegen

   Affiliation as printed

   : Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands

7. G. Principe

   University of Trieste · University of Cape Town · Istituto Nazionale di Fisica Nucleare, Sezione di Trieste · South African Astronomical Observatory

   Affiliation as printed

   Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch, 7701, South Africa :

   Dipartimento di Fisica, Universitá di Trieste, I-34127 Trieste, Italy

   Erlangen Centre for Astroparticle Physics, Nikolaus-Fiebiger-Str. 2, Erlangen 91058, Germany

   Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste, Italy

   South African Astronomical Observatory, P.O. Box 9, Observatory, 7935, South Africa

8. Dmitry V. Malyshev

   University of Trieste · University of Cape Town · Istituto Nazionale di Fisica Nucleare, Sezione di Trieste · South African Astronomical Observatory

   Affiliation as printed

   Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch, 7701, South Africa :

   Dipartimento di Fisica, Universitá di Trieste, I-34127 Trieste, Italy

   Erlangen Centre for Astroparticle Physics, Nikolaus-Fiebiger-Str. 2, Erlangen 91058, Germany

   Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste, Italy

   South African Astronomical Observatory, P.O. Box 9, Observatory, 7935, South Africa

9. Veronika Vodeb

   University of Nova Gorica

   Affiliation as printed

   : Center for Astrophysics and Cosmology, University of Nova Gorica, Vipavska 13, SI-5000 Nova Gorica, Slovenia

10. P. Groot

    Radboud University Nijmegen

    Affiliation as printed

    : Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands

11. E. Cator

    Radboud University Nijmegen

    Affiliation as printed

    : Department of Mathematics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands

12. Gijs Nelemans Aachen SRON (Netherlands) Netherlands Institute for Space Research

    Radboud University Nijmegen · Space Research Organisation Netherlands · KU Leuven

    Affiliation as printed

    : Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands

    : Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium

    : SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, NL-3584 CA Utrecht, The Netherlands