IGAPS: the merged IPHAS and UVEX optical surveys of the northern Galactic plane^⋆

¹ School of Physics, Astronomy & Mathematics, University of Hertfordshire, Hatfield AL10 9AB, UK
e-mail: m.monguio@icc.ub.edu
² Institut d’Estudis Espacials de Catalunya, Universitat de Barcelona (ICC-UB), Martí i Franquès 1, 08028 Barcelona, Spain
³ IGAM, Institute of Physics, University of Graz, Universitätsplatz 5/II, 8010 Graz, Austria
⁴ Department of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, UK
⁵ Bay Area Environmental Research Institute, PO Box 25 Moffett Field, CA 94035, USA
⁶ Department of Astrophysics/IMAPP, Radboud University, PO Box 9010 6500 GL Nijmegen, The Netherlands
⁷ Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
⁸ South African Astronomical Observatory, PO Box 9 Observatory 7935, South Africa
⁹ The Inter-University Institute for Data Intensive Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
¹⁰ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹¹ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
¹² Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
¹³ University of Warwick, Department of Physics, Gibbet Hill Road, Coventry CV4 7AL, UK
¹⁴ Department of Earth and Planetary Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
¹⁵ European Southern Observatory (ESO), Av. Alonso de Córdova 3107, 7630355 Vitacura, Santiago, Chile
¹⁶ Department of Physics and Astronomy, Texas Tech University, PO Box 41051 Lubbock, TX 79409, USA
¹⁷ Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106, USA
¹⁸ Department of Astronomy, University of California Berkeley, Berkeley, CA 94720, USA
¹⁹ The University of Hong Kong, Department of Physics, Hong Kong SAR, PR China
²⁰ Hamad Bin Khalifa University (HBKU), Qatar Foundation, PO Box 5825 Doha, Qatar
²¹ Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA
²² Isaac Newton Group, Apartado de correos 321, 38700 Santa Cruz de La Palma, Canary Islands, Spain
²³ Mollerlyceum, 4611DX Bergen op Zoom, The Netherlands
²⁴ Astrophysics Group, Keele University, Keele ST5 5BG, UK
²⁵ Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany
²⁶ Observatorio Astronómico, Universidad de Valencia, Calle Catedrático José Beltrán 2, 46980 Paterna, Spain
²⁷ Astrophysics Group, School of Physics, University of Bristol, Tyndall Av, Bristol BS8 1TL, UK
²⁸ Dr. Remeis-Sternwarte, Friedrich Alexander Universität Erlangen-Nürnberg, Sternwartstr 7, 96049 Bamberg, Germany
²⁹ Universidad Nacional Autónoma de México (UNAM), Instituto de Astronomía, Km 103 Carretera Tijuana, Ensenada, Mexico
³⁰ Department of Physics, Imperial College London, SW7 2AZ London, UK
³¹ Armagh Observatory and Planetarium, BT61 9DG Armagh, UK
³² LBT Observatory, University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85721-0009, USA
³³ Department of Physics, Shahid Bahonar University of Kerman, Kerman, Iran

Received: 10 December 2019
Accepted: 12 February 2020

Abstract

The INT Galactic Plane Survey (IGAPS) is the merger of the optical photometric surveys, IPHAS and UVEX, based on data from the Isaac Newton Telescope (INT) obtained between 2003 and 2018. Here, we present the IGAPS point source catalogue. It contains 295.4 million rows providing photometry in the filters, i, r, narrow-band Hα, g, and U_RGO. The IGAPS footprint fills the Galactic coordinate range, |b| < 5° and 30° < ℓ < 215°. A uniform calibration, referred to as the Pan-STARRS system, is applied to g, r, and i, while the Hα calibration is linked to r and then is reconciled via field overlaps. The astrometry in all five bands has been recalculated in the reference frame of Gaia Data Release 2. Down to i ∼ 20 mag (Vega system), most stars are also detected in g, r, and Hα. As exposures in the r band were obtained in both the IPHAS and UVEX surveys, typically a few years apart, the catalogue includes two distinct r measures, r_I and r_U. The r 10σ limiting magnitude is approximately 21, with median seeing of 1.1 arcsec. Between approximately 13th and 19th mag in all bands, the photometry is internally reproducible to within 0.02 mag. Stars brighter than r = 19.5 mag are tested for narrow-band Hα excess signalling line emission, and for variation exceeding |r_I − r_U| = 0.2 mag. We find and flag 8292 candidate emission line stars and over 53 000 variables (both at > 5σ confidence).