OH megamasers in IRAS galaxies.

Huge extragalactic hydroxyl masers have recently been discovered. These objects seem to belong to a very peculiar class and are called megamasers, regarding their high 1667 MHz OH line luminosity which can be greater than one thousand solar luminosities. Most of these galaxies were first detected by the IRAS satellite and are characterized by a strong far infrared luminosity. An OH and H I survey is carried out with the Nançay radio telescope and additional high resolution data (VLA and MERLIN) have been obtained. These observations provide essential data for a better understanding of these objects.