Abstract
We have classified a sample of 37,492 objects from SDSS into QSOs, galaxies and stars using photometric data over five wave bands (u, g, r, i and z) and UV GALEX data over two wave bands (near-UV and far-UV) based on a template fitting method. The advantage of this method of classification is that it does not require any spectroscopic data and hence the objects for which spectroscopic data is not available can also be studied using this technique. In this study, we have found that our method is consistent by spectroscopic methods given that their UV information is available. Our study shows that the UV colours are especially important for separating quasars and stars, as well as spiral and starburst galaxies. Thus it is evident that the UV bands play a crucial role in the classification and characterization of astronomical objects that emit over a wide range of wavelengths, but especially for those that are bright at UV. We have achieved the efficiency of 89% for the QSOs, 63% for the galaxies and 84% for the stars. This classification is also found to be in agreement with the emission line diagnostic diagrams.
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Acknowledgements
The authors would like to thank the anonymous reviewers for their critical comments that have helped us in improving the paper. This work was supported by the Department of Science and Technology (DST), Ministry of Science and Technology, Government of India, New Delhi, India under Grant No. SR/S2/HEP-050/2012. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the participating institutions, the National Science Foundation, and the US Department of Energy Office of Science. The SDSS-III website is http://www.sdss3.org/. In the present work, data from SDSS and GALEX have been used. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University. GALEX is a NASA mission managed by Jet Propulsion Laboratory. This work is based on data from GALEX-GR6 and the authors acknowledge GALEX and NASA for their support. One of the authors (SBG) thanks the Inter-University Centre for Astronomy and Astrophysics, Pune for Associateship.
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Anjum, A., Das, M., Murthy, J. et al. Template-based classification of SDSS-GALEX point sources. J Astrophys Astron 39, 61 (2018). https://doi.org/10.1007/s12036-018-9552-3
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DOI: https://doi.org/10.1007/s12036-018-9552-3