| Abstract : | Near-infrared HI recombination lines are known to be indicators of the accretion and outflow activities in YSOs. They are formed in distinct regions around a YSO such as accretion columns, circumstellar disk, disk wind, and outflows. To understand the physical conditions of the HI recombination region, we analyze APOGEE H-band spectra which contain Brackett 11-20 emission lines. We identified 1418 sources showing the Brackett series in emission from Data Release 17. The sources were classified based on photometry and Gaia DR3 astrometry, mainly into Classical Be, HAeBe, and T-Tauri stars. Further, the spectra were visually checked to identify metallic lines, especially FeII and [FeII]. We perform a comparative case-B recombination analysis using Brackett series flux measurements with the theoretical values from Storey & Hummer and Kwan & Fischer models. For the first time, we present a homogenous study of Brackett decrement analysis discussing the physical conditions of line emitting medium in different types of emission-line stars. |
