Population-based identification of Hα-excess sources in the Gaia DR2 and IPHAS catalogues

Abstract

We present a catalogue of point-like Hα-excess sources in the Northern Galactic Plane. Our catalogue is created using a new technique that leverages astrometric and photomeric information from Gaia to select Hα-bright outliers in the INT Photometric Hα Survey of the Northern Galactic Plane (IPHAS), across the colour-absolute magnitude diagram. To mitigate the selection biases due to stellar population mixing and to extinction, the investigated objects are first partitioned with respect to their positions in the Gaia colour-absolute magnitude space, and in the Galactic coordinates space, respectively. The selection is then performed on both partition types independently. Two significance parameters are assigned to each target, one for each partition type. These represent a quantitative degree of confidence that the given source is a reliable Hα-excess candidate, with reference to the other objects in the corresponding partition. Our catalogue provides two flags for each source, both indicating the significance level of the Hα-excess. By analysing their intensity in the Hα narrow band, 28,496 objects out of 7,474,835 are identified as Hα-excess candidates with a significance higher than 3. The completeness fraction of the Hα outliers selection is between 3% and 5%. The suggested 5σ conservative cut yields a purity fraction of 81.9%.

arXiv comment20 pages, 23 figures

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• Mapping H$\alpha$-Excess Candidate Point Sources in the Southern Hemisphere Using S-PLUS Data
• The Enigma of Gaia18cjb: a Rare Hybrid of FUor and EXor?
• Hot white dwarf candidates from the IGAPS-GALEX cross-match
• Search for new Galactic Wolf-Rayet stars using Gaia DR3. I. Candidate selection and the follow-up of the bright sample
• XGAPS: a sub-arcsecond cross-match of Galactic Plane Surveys
• Spectroscopic follow-up of a sub-set of the Gaia/IPHAS catalogue of Hα-excess sources