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| Vela Molecular Ridge | |
|---|---|
| Name | Vela Molecular Ridge |
| Type | molecular cloud complex |
| Constellation | Vela |
| Distance | 700–2,000 pc |
| Mass | ~10^5–10^6 M☉ |
| Components | VMR A, VMR B, VMR C, VMR D |
Vela Molecular Ridge
The Vela Molecular Ridge is a massive association of molecular clouds and star-forming regions in the southern sky within the constellation of Vela. The complex contains numerous molecular clouds, young stellar objects, embedded clusters, H II regions, masers and supernova remnants, and it has been the target of multiwavelength surveys by observatories and missions across radio, infrared, submillimeter and X-ray bands. The region plays a significant role in studies of large-scale star formation, triggered star formation, and the interplay between massive stars and interstellar medium in the Milky Way.
The complex spans several degrees near the constellations Vela (constellation), Puppis, and Carina (constellation) and is associated with large-scale features such as the Gum Nebula, the Vela Supernova Remnant, and the Vela OB2 association. It contains high-mass star-forming sites comparable to regions like Orion Nebula, Carina Nebula, and RCW 38, and it is cataloged in molecular line surveys such as the Columbia Survey of CO, the NANTEN survey, and the CfA CO survey. Studies of the complex link observational resources including the IRAS point source catalog, the Spitzer Space Telescope, the Herschel Space Observatory, the WISE mission, the Chandra X-ray Observatory, and the Australia Telescope Compact Array.
The complex is subdivided into major cloud groups historically labeled A–D, comprising dark clouds, dense cores, filaments, and giant molecular clouds mapped in transitions of CO (carbon monoxide), 13CO, and C18O. Prominent embedded regions host compact H II regions cataloged in surveys of Sharpless (Sh 2) objects and radio continuum catalogs such as those produced by the Parkes Observatory and the Molonglo Observatory Synthesis Telescope. Key compact objects include infrared sources cataloged by IRAS, maser sites tied to 6.7 GHz methanol masers and water masers, and reflection nebulae similar to those listed in van den Bergh catalogues.
The complex contains embedded young clusters and associations with populations spanning Class 0 to Class III young stellar objects identified via near-infrared and mid-infrared photometry, X-ray emission, and spectroscopic follow-up by instruments on Very Large Telescope, Anglo-Australian Telescope, and Gemini Observatory. Massive young stellar objects and OB stars influence local feedback analogous to feedback seen in Trumpler 14, NGC 6611, and Westerlund 2. The region also hosts T Tauri stars, Herbig Ae/Be stars cataloged in optical and infrared studies, and candidate protostellar cores identified in submillimeter maps from facilities like APEX and JCMT.
Molecular line studies reveal broad linewidths, velocity gradients, and complex kinematic substructure traced by surveys using NANTEN, Mopra Telescope, and the Atacama Pathfinder Experiment. Observations of CO isotopologues, dense gas tracers such as NH3, N2H+, and HCN, and shock tracers like SiO indicate active accretion, outflows, and turbulence consistent with massive star formation. Kinematic links to expansion shells attributed to feedback from associations such as Vela OB2 and remnants like the Vela Supernova Remnant are identified through position–velocity analyses and comparisons with HI surveys like those from the Parkes Galactic All-Sky Survey.
Parallax, spectrophotometric, and kinematic measurements place subregions at distances ranging from roughly 700 parsecs to about 2 kiloparsecs, with notable uncertainties and line-of-sight confusion with features in the Carina–Sagittarius Arm and the Local Arm (Orion Spur). The historical subdivision into VMR A, VMR B, VMR C, and VMR D corresponds to cloud concentrations with differing radial velocities, masses, and star-forming properties; these subregions are often cross-referenced with catalogs of dark nebulae by Lynds (1962), H II regions in the Sharpless catalog, and radio recombination line studies.
The molecular complex was first characterized in CO surveys by groups using the Columbia University antenna and later mapped at higher resolution by NANTEN and millimeter arrays. Infrared detections in the IRAS era revealed numerous protostellar candidates, later followed by targeted observations with Spitzer, Herschel, and ground-based near-infrared cameras such as those on the 2MASS survey. Radio and maser searches were conducted with facilities including the Parkes Observatory, ATCA, and the Effelsberg 100-m Radio Telescope, while X-ray studies employing ROSAT and Chandra identified pre-main-sequence populations and high-energy feedback signatures.
The complex lies within a portion of the Milky Way influenced by large-scale structures including spiral-arm density waves associated with the Carina Arm, superbubbles like the Gum Nebula and the Local Bubble, and stellar associations such as Vela OB1 and Vela OB2. Its interaction with expanding shells and supernova ejecta from sources like the Vela Supernova Remnant and nearby massive clusters contributes to triggered star formation scenarios examined in the context of feedback-driven cloud compression studied for regions like IC 1396 and Sh2-284.
Category:Molecular clouds Category:Star-forming regions in the Milky Way