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Interstellar cloud
High velocity cloud
Observation data: J2000 epoch
Right ascension 17h 45.5m[1]
Declination −29° 24′[1]
Distance 27000 ly   (8300[2] pc)
Constellation Sagittarius
See also: Lists of nebulae

CO-0.40-0.22 is a high velocity compact gas cloud near the centre of the Milky Way. It is 200 light years away from the centre in the central molecular zone. The cloud is in the shape of ellipse. The differences in the velocity, termed velocity dispersion, of the gas is unusually high at 100 km/s. The velocity dispersion may be due to an intermediate-mass black hole with a mass of about 100,000 solar masses. If it exists, this black hole would be the second largest known in the Milky Way.[3] However, signature of presence of an IMBH was not detected by observations using the Atacama Large Millimeter/submillimeter Array. [4]

The molecular cloud has a mass of 4,000 solar masses. It is located at −0.40°, −0.22° galactic longitude and latitude. The cloud is 0.2° away from Sgr C to the galactic southeast. The gas is moving away from Earth at speeds ranging from 20 to 120 km/s. The spectral lines of carbon monoxide reveal that the gas is dense, and warm and fairly opaque.[2]

The gas cloud includes carbon monoxide and hydrogen cyanide molecules. Other molecules detected via microwave spectroscopy include cyanoacetylene, cyclopropenylidene, methanol, silicon monoxide, sulfur monoxide, carbon monosulfide, Thioformaldehyde, Hydrogen isocyanide, Formamide, and ions H2N+ and HCO+.[2]

The name followed the precedent set by CO-0.02-0.02, which is another high velocity compact cloud in the central molecular zone. Another example of this naming convention is CO–0.30–0.07.[2]


  1. ^ a b "GCM -0.40 -0.22". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 13 April 2018. 
  2. ^ a b c d Oka, Tomoharu; Mizuno, Reiko; Miura, Kodai; Takekawa, Shunya (28 December 2015). "Signature of an Iintermediate-Mass Black Hole in the Central Molecular Zone of Our Galaxy". The Astrophysical Journal. 816 (1): L7. arXiv:1512.04661Freely accessible. Bibcode:2016ApJ...816L...7O. doi:10.3847/2041-8205/816/1/L7. 
  3. ^ "Signs of second largest black hole in the Milky Way: Possible missing link in black hole evolution". 15 January 2016. Retrieved 16 January 2016. 
  4. ^ Tanaka, Kunihiko (April 2018), ALMA Images of the Host Cloud of the Intermediate-mass Black Hole Candidate CO-0.40-0.22* : No Evidence for Cloud-Black Hole Interaction, but Evidence for a Cloud-Cloud Collision, arXiv:1804.03661Freely accessible, Bibcode:2018ApJ...859...86T, doi:10.3847/1538-4357/aabd77