2025AJ....170..121N

We present a near-infrared spectroscopic and imaging analysis of the star-forming region IRAS 16475-4609, based on TripleSpec/SOAR spectroscopy and NEWFIRM/CTIO imaging, complemented by archival radio and submillimeter data. Our spectroscopic analysis indicates that the central source is an early B-type star (B0-B0.7 V) powering a compact H II region characterized by strong H I and He I recombination lines, and molecular H₂ emission. We derive a distance of 3.51 ± 0.74 kpc, consistent with the position of the Scutum-Crux near arm at a Galactic longitude of ∼340^∘. At this distance, the ionized gas traced by Brγ emission has a radius of 0.27 ± 0.06 pc, placing the source in a transition phase between ultracompact and compact H II regions. From radio data, we estimate an ionizing photon flux of N_Ly = (2.3 ± 0.3) × 10⁴⁷ photons s^–1, and an electron temperature of T_e = (5.4 ± 0.2) × 10³ K for the ionized gas. The analysis also reveals an obscured high-density molecular clump SW of the H II region, coincident with an ATLASGAL submillimeter peak, indicating a potential site of ongoing and triggered star formation as the ionization front advances into the surrounding molecular material. These results suggest that IRAS 16475-4609 is a young high-mass star-forming region with stellar feedback actively shaping its environment, offering valuable insight into the early evolution of compact H II regions.