MIRIS Pa<i>α</i> Galactic Plane Survey. II. The Catalog of Pa<i>α</i> Emission-line Sources

Abstract Using data from the MIRIS Pa α Galactic Plane Survey (MIPAPS), we present a Pa α 1.87 μ m line image of the entire Galactic plane within the latitude range of −3° ≲ b ≲ +3°, revealing numerous Pa α features. Based on the MIPAPS Pa α image and the Wide-field Infrared Survey Explorer (WISE) H ii region catalog, we compile a catalog of 1489 Pa α emission-line sources in the Galactic plane within 90° ≤ ℓ ≤ 330°. By comparing our Pa α images with H α images constructed from the IPHAS and VPHAS+ survey data, we demonstrate the advantages of Pa α line observations. We identify 902 Pa α sources associated with H ii regions, and newly confirm 619 H ii region candidates as definitive H ii regions through Pa α or H α detections. We also identify 261 extended and 326 pointlike Pa α sources not included in the WISE catalog, most of which have H α counterparts in the IPHAS or VPHAS+ images. A search of the SIMBAD database indicates that these sources originate from diverse object types. By measuring Pa α and H α fluxes, we estimate the E ( B − V ) color excesses derived from extended emissions for 138 Pa α sources, showing good agreement with values obtained from spectrophotometry of ionizing stars in previous studies. Furthermore, we calculate total Lyman continuum luminosities for 42 Pa α sources, providing constraints on the distances to H ii regions and the spectral types of their ionizing stars. These results highlight the scientific potential of Pa α line observations and the benefits of combining multiple hydrogen recombination lines in exploring ionized regions.