Messier 106 (left) with possible companion galaxy NGC 4217 (lower right)
Composite image of IR, x-ray, radio and visible light view (X-ray – blue, Optical – gold, IR – red, Radio – purple)
M106 has a water vapor megamaser (the equivalent of a laser operating in microwave instead of visible light and on a galactic scale) that is seen by the 22-GHz line of ortho-H2O that evidences dense and warm molecular gas. These water vapors give M106 its characteristic purple color. Water masers are useful to observe nuclear accretion disks in active galaxies. The water masers in M106 enabled the first case of a direct measurement of the distance to a galaxy and thereby providing an independent anchor for the cosmic distance ladder. M106 has a slightly warped, thin, almost edge-on Keplerian disc which is on a subparsec scale. It surrounds a central area with mass 4 × 107M⊙.
M106 has also played an important role in calibrating the cosmic distance ladder. Before, Cepheid variables from other galaxies could not be used to measure distances since they cover ranges of metallicities different from the Milky Way's. M106 contains Cepheid variables similar to both of the metallicities of the Milky Way and other galaxies' Cepheids. By measuring the distance of the Cepheids with metallicities similar to our galaxy, astronomers are able to recalibrate the other Cepheids with different metallicities, a key fundamental step in improving quantification of distances to other galaxies in the universe.
^Karachentsev, Igor D.; Karachentseva, Valentina E.; Huchtmeier, Walter K.; Makarov, Dmitry I. (2003). "A Catalog of Neighboring Galaxies". The Astronomical Journal. 127 (4): 2031–2068. Bibcode:2004AJ....127.2031K. doi:10.1086/382905.
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