MIRIS Pa{\alpha} Galactic Plane Survey. II. The Catalog of Pa{\alpha} Emission-line Sources

TL;DR

This paper presents a comprehensive catalog of 1489 Pa{ extalpha} emission-line sources in the Galactic plane using MIRIS data, demonstrating the advantages of Pa{ extalpha} observations over H{ extalpha} and providing insights into H II regions and their ionizing sources.

Contribution

The study provides the first large-scale Pa{ extalpha} emission-line source catalog for the Galactic plane, enhancing the understanding of ionized regions through multi-wavelength comparison and flux analysis.

Findings

Identified 902 Pa{ extalpha} sources associated with H II regions.

Confirmed 619 new H II region candidates via Pa{ extalpha} or H{ extalpha} detection.

Estimated E(B-V) color excesses and Lyman continuum luminosities for selected sources.

Abstract

Using data from the MIRIS Pa{\alpha} Galactic Plane Survey (MIPAPS), we present a Pa{\alpha} 1.87 um line image of the entire Galactic plane within the latitude range of -3{\deg} < b < +3{\deg}, revealing numerous Pa{\alpha} features. Based on the MIPAPS Pa{\alpha} image and the WISE H II region catalog, we compile a catalog of 1489 Pa{\alpha} emission-line sources in the Galactic plane within 90{\deg} < l < 330{\deg}. By comparing our Pa{\alpha} images with H{\alpha} images constructed from the IPHAS and VPHAS+ survey data, we demonstrate the advantages of Pa{\alpha} line observations. We identify 902 Pa{\alpha} sources associated with H II regions, and newly confirm 619 H II region candidates as definitive H II regions through Pa{\alpha} or H{\alpha} detections. We also identify 261 extended and 326 point-like Pa{\alpha} sources not included in the WISE catalog, most of which have H{\alpha} 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{\alpha} and H{\alpha} fluxes, we estimate the E(B-V) color excesses derived from extended emissions for 138 Pa{\alpha} sources, showing good agreement with values obtained from spectrophotometry of ionizing stars in previous studies. Futhermore, we calculate total Lyman continuum luminosities for 42 Pa{\alpha} 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{\alpha} line observations and the benefits of combining multiple hydrogen recombination lines in exploring ionized regions.