High-resolution Hα imaging of the northern Galactic plane and the IGAPS image database

¹ IGAM, Institute of Physics, University of Graz, Universitätsplatz 5/II, 8010 Graz, Austria
e-mail: rgreimel@gmail.com
² School of Physics, Astronomy & Mathematics, University of Hertfordshire, Hatfield AL10 9AB, UK
³ Department of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, UK
⁴ Institut d’Estudis Espacials de Catalunya, Universitat de Barcelona (ICC-UB), Martí i Franquès 1, 08028 Barcelona, Spain
⁵ Universitat Politècnica de Catalunya, Departament de Física, c/Esteve Terrades 5, 08860 Castelldefels, Spain
⁶ Isaac Newton Group, Apartado de correos 321, 38700 Santa Cruz de La Palma, Canary Islands, Spain
⁷ Bay Area Environmental Research Institute, PO Box 25 Moffett Field, CA 94035, USA
⁸ Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany
⁹ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
¹⁰ Astrophysics Group, School of Physics, University of Bristol, Tyndall Av, Bristol BS8 1TL, UK
¹¹ School of Physics, University of Exeter, Exeter EX4 4QL, UK
¹² Instituto de Astronomía, Universidad Nacional Autónoma de México (UNAM), AP 106, Ensenada, 22800 BC, Mexico
¹³ Astrophysics Group, Keele University, Keele ST5 5BG, UK
¹⁴ Department of Astrophysics/IMAPP, Radboud University, PO Box 9010 6500 GL Nijmegen, The Netherlands
¹⁵ Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
¹⁶ South African Astronomical Observatory, PO Box 9 Observatory 7935, South Africa
¹⁷ The Inter-University Institute for Data Intensive Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
¹⁸ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹⁹ Centro Astronómico Hispano-Alemán, Observatorio de Calar Alto, Sierra de los Filabres s/n, 04550 Gérgal, Almeria, Spain
²⁰ The University of Hong Kong, Department of Physics, Hong Kong SAR, PR China
²¹ The Laboratory for Space Research, Cyberport 4, Hong Kong SAR, PR China
²² Department of Physics, University of Durham, South Road, Durham DH1 3LE, UK
²³ Jodrell Bank Centre for Astrophysics, Alan Turing Building, Manchester M13 9PL, UK

Received: 31 March 2021
Accepted: 12 July 2021

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. It captures the entire northern Galactic plane within the Galactic coordinate range |b|< 5° and 30° < ℓ < 215°. From the beginning, the incorporation of narrow-band Hα imaging has been a unique and distinctive feature of this effort. Alongside a focused discussion of the nature and application of the Hα data, we present the IGAPS world-accessible database of images for all five survey filters, i, r, g, U_RGO, and narrow-band Hα, observed on a pixel scale of 0.33 arcsec and at an effective (median) angular resolution of 1.1−1.3 arcsec. The background, noise, and sensitivity characteristics of the narrow-band Hα filter images are outlined. Typical noise levels in this band correspond to a surface brightness at full ∼1 arcsec resolution of around 2 × 10⁻¹⁶ erg cm⁻² s⁻¹ arcsec⁻². Illustrative applications of the Hα data to planetary nebulae and Herbig-Haro objects are outlined and, as part of a discussion of the mosaicking technique, we present a very large background-subtracted narrow-band mosaic of the supernova remnant Simeis 147. Finally, we lay out a method that exploits the database via an automated selection of bright ionised diffuse interstellar emission targets for the coming generation of wide-field massive-multiplex spectrographs. Two examples of the diffuse Hα map output from this selection process are presented and compared with previously published data.