IGAPS: the merged IPHAS and UVEX optical surveys of the northern Galactic plane
M. Monguió, R. Greimel, J. E. Drew, Geert Barentsen, P. Groot, M. J. Irwin, J. Casares, B. T. Gänsicke, Philip J. Carter, J. M. Corral-Santana, N. P. Gentile-Fusillo, S. Greiss, L. M. van Haaften, Mark Hollands, David Jones, Thomas Kupfer, Christopher J. Manser, D. N. A. Murphy, Anna F. McLeod, T. Oosting, Q. A. Parker, S. Pyrzas, P. Rodríguez-Gil, Jan van Roestel, Simone Scaringi, P. Schellart, Odette Toloza, O. Văduvescu, L. van Spaandonk, K. Verbeek, N. J. Wright, J. Eislöffel, J. Fabregat, A. Harris, R. A. H. Morris, S. Phillipps, R. Raddi, L. Sabin, Y. C. Unruh, J. S. Vink, R. Wesson, A. Cardwell, A. de Burgos, R. K. Cochrane, Saeed Doostmohammadi, Teo Močnik, H. Stoev, L. Suárez-Andrés, Vlad Tudor, T. G. Wilson, Tarik Zegmott
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 H α , 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 H α 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 H α . 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 10 σ 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 H α 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 > 5 σ confidence).