MIRIS Paα Galactic Plane Survey. I. Comparison with IPHAS Hα in ℓ = 96°–116°

Abstract

The Multipurpose InfraRed Imaging System (MIRIS) performed the MIRIS Pa α Galactic Plane Survey (MIPAPS), which covers the entire Galactic plane within the latitude range of at Pa α (1.87 μ m). We present the first result of the MIPAPS data extracted from the longitude range of –116.°3 and demonstrate the quality and scientific potential of the data by comparing them with H α maps obtained from the INT Photometric H α Survey (IPHAS) data. We newly identify 90 H ii region candidates in the WISE H ii region catalog as definite H ii regions by detecting the Pa α and/or H α recombination lines, out of which 53 H ii regions are detected at Pa α . We also report the detection of an additional 29 extended and 18 point-like sources at Pa α . We estimate the E ( B − V ) color excesses and total Lyman continuum luminosities for H ii regions by combining the MIPAPS Pa α and IPHAS H α fluxes. The E ( B − V ) values are found to be systematically lower than those estimated from point stars associated with H ii regions. Utilizing the MIPAPS Pa α and IPHAS H α images, we obtain an E ( B − V ) map for the entire region of the H ii region Sh2-131 with an angular size of ∼2.°5. The E ( B − V ) map shows not only numerous high-extinction filamentary features but also negative E ( B − V ) regions, indicating H α excess. The H α excess and systematic underestimation of E ( B − V ) are attributed to light scattered by dust.