CEA News, January 2023
XGAPS: a sub-arcsec cross-match of galactic plane surveys
A recent paper led by astronomers at the CEA presents a sub-arcsec cross-match of Gaia Data Release 3 (DR3) against the INT Galactic Plane Surveys (IGAPS) and the United Kingdom Infrared Deep Sky Survey (UKIDSS).
Left panel: Gaia-based absolute CMD of all cross-matched sources between Gaia and IGAPS.
Right panel: The recovered negative parallax “mirror sample” from the Gaia/IGAPS cross-match.
The resulting cross-match of Galactic Plane Surveys (XGAPS) provides additional precise photometry (URGO, g, r, i, Hα, J, H, and K) to the Gaia photometry. In building the catalogue, proper motions given in Gaia DR3 are wound back to match the epochs of the IGAPS constituent surveys (INT Photometric HαSurvey of the Northern Galactic Plane, IPHAS, and the UV-Excess Survey of the Northern Galactic Plane, UVEX) and UKIDSS, ensuring high-proper motion objects are appropriately cross-matched. The catalogue contains 33 987 180 sources. The requirement of >3σ parallax detection for every included source means that distances out to 1-1.5 kpc are well covered. In producing XGAPS, the authors have also trained a Random Forest classifier to discern targets with problematic astrometric solutions. Selection cuts based on the classifier results can be used to clean colour-magnitude and colour-colour diagrams in a controlled and justified manner, as well as producing subsets of astrometrically reliable targets. This paper provides XGAPS as a 111 column table. Uses of the catalogue include the selection of Galactic targets for multi-object spectroscopic surveys as well as identification of specific Galactic populations.