M106 (NGC 4258) is a spiral galaxy in the constellation Canes Venatici. It was discovered by Pierre Méchain in 1781. M106 is at a distance of about 22 to 25 million light-years away from Earth. It is also a Seyfert II galaxy, which means that due to x-rays and unusual emission lines detected, it is suspected that part of the galaxy is falling into a supermassive black hole in the center.
M106 has a water vapor maser that is seen by the 22-GHz line of ortho-H2O that evidences dense and warm molecular gas. Water masers are useful to observe nuclear accretion disks in active galaxies. M106 has a slightly warped, thin, almost edge-on Keplerian disk which is on a subparsec scale. It surrounds a central area with mass four × 107M⊙
Composite of IR, x-ray, radio and visible light view (X-ray - blue, Optical - gold, IR - red, Radio - purple; Image credit: NASA/CXC/University of Maryland)