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| RCW 106 | |
|---|---|
| Name | RCW 106 |
| Type | H II region |
| Epoch | J2000 |
| Distance | 3.6 kpc (approx.) |
| Constellation | Norma |
| Radius | ~40 pc (complex) |
| Other names | G333.6−0.2, Gum 48a |
RCW 106 is a large star-forming H II region and molecular cloud complex in the southern Milky Way notable for massive star formation and bright radio and infrared emission. The complex has been the subject of surveys using facilities such as the Australia Telescope Compact Array, Spitzer Space Telescope, Herschel Space Observatory, and the Atacama Pathfinder Experiment. It lies in a crowded Galactic plane field alongside other prominent complexes like the Carina Nebula, RCW 57, and the Vela Molecular Ridge.
RCW 106 is catalogued as an emission nebula in the southern RCW survey compiled by Rodgers, Campbell & Whiteoak and is identified with radio and infrared catalog entries such as G333.6−0.2 and entries in the Molonglo Observatory Synthesis Telescope and IRAS point source catalogs. The region hosts multiple embedded clusters comparable to those in Westerhout 49 and NGC 3603 and is often compared with the Orion Nebula and Eagle Nebula for studies of triggered star formation. Surveys by the Two Micron All Sky Survey and the Midcourse Space Experiment have revealed populations of young stellar objects (YSOs) and compact H II regions across the complex.
The RCW survey in the 1960s led by A. W. Rodgers and collaborators produced the optical identification; subsequent radio mapping by the Molonglo Observatory and the Parkes Observatory revealed strong free–free emission. Infrared observations by IRAS in the 1980s and follow-up with MSX and 2MASS in the 1990s identified candidate massive protostars, while higher-resolution imaging by Spitzer and spectroscopic follow-up with SOFIA and Herschel characterized the dust and gas properties. Millimeter and submillimeter line surveys with the Mopra Telescope, Atacama Pathfinder Experiment, and the Atacama Large Millimeter/submillimeter Array (ALMA) resolved giant molecular filaments and dense clumps similar to structures seen in Giant Molecular Cloud Complexes like W51 and Cygnus X.
The complex contains multiple massive molecular clouds traced in CO, HCO+, and NH3 lines, with total molecular mass estimates comparable to those of Giant Molecular Clouds such as Orion A. Dense cores within RCW 106 show signs of high-mass star formation with luminosities rivaling embedded clusters in Trumpler 14 and Trumpler 16. Ionized gas temperatures and electron densities measured via radio recombination lines resemble those in regions like S106 and M17. Observed maser species including water masers and methanol masers associate RCW 106 with sites of massive protostellar outflows akin to sources in W75N and Cepheus A.
RCW 106 lies in the southern sky in the constellation Norma within the inner portion of the Scutum–Centaurus Arm of the Milky Way, at a kinematic distance estimated from CO and HI velocities similar to distances used for G333.6−0.2. The complex is embedded in a high-column-density region of the Galactic plane near other prominent star-forming regions such as RCW 122 and the Norma Arm tangent, and it interacts with surrounding molecular gas and supernova remnants comparable to environments near W44 and IC 443. Extinction toward the core is high, producing strong mid- and far-infrared emission as seen in comparisons with NGC 6334 and NGC 6357.
RCW 106 serves as a nearby laboratory for studying high-mass star formation, cluster formation, and feedback processes similar to those investigated in Carina, W49A, and DR21. Its numerous compact H II regions and proto-clusters provide empirical constraints on theories advanced by researchers studying massive star formation in regions like Mon R2 and Sgr B2. The complex has been included in Galactic plane surveys by projects such as the Red MSX Source Survey, the Hi-GAL program, and the Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey, contributing to statistical comparisons of star formation efficiency, initial mass function, and triggered star formation associated with expanding bubbles seen in WISE imagery.
Observations of RCW 106 employ multiwavelength techniques: radio continuum mapping with facilities like the Australia Telescope Compact Array and the ATNF Parkes Observatory trace ionized gas; millimeter interferometry with ALMA and single-dish mapping with Mopra and APEX trace molecular gas; infrared imaging and spectroscopy with Spitzer, Herschel, and SOFIA reveal warm dust and spectral lines such as [C II] and [O I]; maser surveys with the Very Long Baseline Array and the Long Baseline Array (Australia) locate compact high-mass protostars; and near-infrared photometry from 2MASS and adaptive-optics observations with telescopes like the Very Large Telescope resolve embedded clusters. Complementary surveys by GLIMPSE and MIPSGAL situate RCW 106 within the broader context of Galactic plane structure mapped by missions such as Planck and the COBE legacy.