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Description
We present a study of protocluster subsample IRAS 16445-4459 using high-resolution ALMA band 6 (λ ~ 1.3 mm) QUARKS survey selected for UC H II regions traced by the H30α Radio recombination line (RRL) and meerKAT 1.3 GHz observation G340.248-00.046 to investigate the excitation mechanism of the H30α RRL in the high-mass forming region. The source reveals the detection of the RRL indicating ionized dense gas region. This detection exhibits diverse physical properties from its radio continuum with core mass of 918 ( M_\odot ). at 100K and 446M⊙ at 200K, its ionizing photon rate S = 1.05 * 1047 s-1 (log S = 48.02) corresponds to the total Lyman continuum output of small young stellar cluster containing several early O-type or early B-type stars which is typical of a compact or embedded H II region in active star-forming complex. The hydrogen column density ranges between 2.59 (at 100K) and 1.26 cm-2 (at 200K). Detection of the H30α radio recombination line in this region reveals a single-Gaussian profile with a peak amplitude of 0.567±0.017 Jy/beam and a centroid velocity of −127.2±0.3 km/s. The velocity dispersion is σ=10.5±0.5 km/s, yielding a FWHM of 24.6±1.1 km/s, and a baseline offset of −0.056±0.015 Jy/beam. These H30α line characteristics indicate the presence of ionized gas with significant turbulent or bulk motions, possibly tracing a compact HII region or thermal jet associated with massive star formation. The line’s width and velocity features are consistent with ionized gas dynamics in energetic star-forming environments, supporting its origin in an active, embedded massive protostellar core.
| Stream | Science or Engineering |
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