Continuum source catalog for the first APERTIF data release^★

¹ ASTRON, The Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
e-mail: kutkin@astron.nl
² Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
³ Astronomisches Institut der Ruhr-Universität Bochum (AIRUB), Universitätsstrasse 150, 44780 Bochum, Germany
⁴ Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
⁵ Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
⁶ CSIRO Astronomy and Space Science, Australia Telescope National Facility, PO Box 76, Epping, NSW 1710, Australia
⁷ Sydney Institute for Astronomy, School of Physics, University of Sydney, Sydney, New South Wales 2006, Australia
⁸ Anton Pannekoek Institute, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam, The Netherlands
⁹ Cahill Center for Astronomy, California Institute of Technology, Pasadena, CA, USA
¹⁰ Department of Physics, Virginia Polytechnic Institute and State University, 50 West Campus Drive, Blacksburg, VA 24061, USA
¹¹ Netherlands eScience Center, Science Park 140, 1098 XG Amsterdam, The Netherlands
¹² University of Oslo Center for Information Technology, PO Box 1059, 0316 Oslo, Norway
¹³ National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune 411007, Maharashtra, India

Received: 12 May 2022
Accepted: 20 July 2022

Abstract

The first data release from Apertif survey contains 3074 radio continuum images, covering a thousand square degrees of the sky. The observations were performed between August 2019 and July 2020. The continuum images were produced at a central frequency 1355 MHz, with a bandwidth of ~150 MHz and angular resolution of up to 10″. In this work, we introduce and apply a new method to obtain a primary beam model based on a machine-learning approach, namely, Gaussian process regression. The primary beam models obtained with this method have been published, along with the data products for the first Apertif data release. We applied the method to the continuum images, carried out a mosaicking process on their basis, and extracted the source catalog. The catalog contains 249672 radio sources, many of which have been detected for the first time at these frequencies. We cross-matched the coordinates with the NVSS, LOFAR/DR1/value-added, and LOFAR/DR2 catalogs – resulting in 44523, 22825, and 152824 common sources, respectively. The first sample provides a unique opportunity for detecting long-term transient sources, which have significantly changed their flux density over the past 25 yr. A combination of the second and the third samples provides valuable information on the spectral properties of the sources in addition to redshift estimates.