Ultra-luminous OH maser emission from an IRAS galaxy

Since the discovery1 in 1982 of intense hydroxyl (OH) maser emission from the infrared-luminous galaxy Arp 220, twenty similar sources have been found in single-dish radio searches2–7. These so-called OH megamasers are associated with infrared-luminous galaxies with far-infrared colour temperatures of about 50 K. Here we report the detection of luminous OH maser emission in the galaxy IRAS20100—4156. This galaxy, at redshift Z = 0.129, displays similar optical properties to Arp 220, but exceeds it in OH luminosity by well over an order of magnitude, making it the most luminous OH maser known. The existence of such luminous megamasers increases the volume of space accessible for their study by a factor of about 50.