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| M-0.02-0.07 (50 km/s cloud) | |
|---|---|
| Name | M-0.02-0.07 (50 km/s cloud) |
| Type | Molecular cloud |
| Epoch | J2000 |
| Constellation | Sagittarius |
| Distance | ~8.2 kpc |
| Coordinates | Galactic center |
M-0.02-0.07 (50 km/s cloud) is a prominent molecular cloud located in the central molecular zone near the Galactic center. The cloud is often referred to by its approximate radial velocity and is closely associated with the supernova remnant Sgr A East and the complex environment surrounding Sgr A*. Studies of the cloud connect research from observatories such as the Atacama Large Millimeter/submillimeter Array, the Very Large Array, and space missions like the Spitzer Space Telescope and Chandra X-ray Observatory.
M-0.02-0.07 lies within the central molecular zone near Sgr A*, Sgr A East, Sgr B2, Sgr C, and adjacent to the Circumnuclear Disk and Arches Cluster, showing dense gas tracers such as CO isotopologues, HCN, HCO+, NH3, and SiO in observations from facilities including ALMA, VLA, IRAM 30m, OVRO, and the Nobeyama Radio Observatory. The cloud has been a focus for investigations by teams from institutions like the Max Planck Institute for Radio Astronomy, the National Radio Astronomy Observatory, the Harvard-Smithsonian Center for Astrophysics, and Japanese radio astronomy groups.
Located within a few parsecs of Sgr A* in the longitude-latitude coordinate designation used for the Galactic center, M-0.02-0.07 has a projected separation from Sgr A East and overlaps emission from the 50 km/s molecular cloud complex known in surveys by Bally, Morris, Güsten, and collaborators. The cloud's mass estimates, derived from CO and dust continuum using assumptions tied to results from the Herschel Space Observatory and Planck, place it at 10^4–10^5 solar masses, with densities probed by HCN and NH3 inversion transitions indicating n(H2) up to 10^5–10^6 cm−3 in clumps studied by teams at Princeton University and The University of Tokyo.
The name reflects a characteristic radial velocity near +50 km/s measured in single-dish surveys by Dame et al., Oka et al., and follow-up interferometric mapping by S. Yusef-Zadeh teams using the VLA and ALMA. Spectral line studies reveal broad linewidths and multiple velocity components attributed to cloud-cloud collisions, tidal shearing from the supermassive black hole at Sgr A*, and shocks associated with Sgr A East; these phenomena have been modeled in dynamical analyses by researchers from Columbia University and Caltech. Position–velocity diagrams constructed from CO J=1–0, J=3–2, and higher J observations show gradients and high-velocity wings consistent with interactions reported by groups including M. G. Burton and F. Yusef-Zadeh.
M-0.02-0.07 shows rich chemistry with detections of CO, 13CO, C18O, HCN, HCO+, CS, NH3, SiO, CH3OH, HNCO, HC3N, and shock tracers identified by surveys using ALMA, the IRAM 30m, and the Green Bank Telescope. Enhanced abundances of SiO and CH3OH point to shock processing attributed to interactions with Sgr A East and local turbulence studied by chemists at Leiden Observatory and University of Manchester. Isotopic ratios inferred from 13C and 18O lines link the cloud to Galactic center chemical evolution work by Wilson, Rood, and subsequent studies at institutions such as the Max Planck Institute for Astronomy.
The spatial and kinematic overlap with Sgr A East has led to interpretations that parts of the cloud are impacted by the expansion of the supernova remnant, as argued in papers from teams including Maeda, Coil & Ho, and Yusef-Zadeh et al.. Shock-excited masers and nonthermal radio continuum at interfaces with the remnant have been reported by observers using the VLA, the Very Long Baseline Array, and the Effelsberg 100-m Radio Telescope, while X-ray enhancements in observations by Chandra X-ray Observatory and XMM-Newton suggest high-energy irradiation from past activity of Sgr A* or local accelerators studied by groups at MIT and Stanford University. Tidal forces from the central potential modeled by Philipp Hopkins-style dynamics and analytic treatments by Stahler-style approaches help explain filamentary morphologies seen in high-resolution maps by ALMA and the Submillimeter Array.
Embedded compact sources and candidate star-forming clumps within M-0.02-0.07 have been identified in mid-infrared imaging from Spitzer Space Telescope and far-infrared continuum from Herschel Space Observatory, with radio recombination line and free–free continuum searches by VLA teams finding few classical H II regions compared to similar-mass clouds in the Galactic disk studied by Kennicutt and Lada. Studies by researchers at University of California, Berkeley and University of Leeds suggest inhibited star formation likely due to high turbulence, strong magnetic fields measured in Zeeman studies by Crutcher and colleagues, and external compression from Sgr A East; nevertheless, maser detections by MERLIN and compact dense cores imaged by ALMA imply ongoing, possibly triggered, low-efficiency star formation linked to scenarios developed by Kruijssen and Longmore.
M-0.02-0.07 has been surveyed across the electromagnetic spectrum: radio and millimeter via ALMA, VLA, IRAM 30m, GBT, SMA, and Nobeyama; infrared via Spitzer Space Telescope, SOFIA, and Herschel Space Observatory; and X-ray via Chandra X-ray Observatory and XMM-Newton. Analyses from collaborations including teams at Harvard-Smithsonian Center for Astrophysics, Max Planck Institute for Radio Astronomy, National Astronomical Observatory of Japan, and CSIRO have produced spectral-line catalogs, dust continuum maps, polarization measurements, and kinematic models that continue to refine understanding of the cloud's role in the central molecular zone and its interaction with major Galactic center structures such as Sgr A* and Sgr A East.