New maser measurements trace detail in active galactic core

The roiling cores of many active galaxies are difficult to see in detail because of surrounding gas and interstellar dust. Smithsonian astronomers announced Jan. 12, 2006, however, a first-time measurement that may help to better trace the structure of these unusual regions.

Elizabeth M. L. Humphreys and other Harvard-Smithsonian Center for Astrophysics (CfA) research team members presented the first detection at millimeter and submillimeter wavelengths of extragalactic water maser emission in the core of active galaxy NGC 3079 in their paper at the 207th meeting of the American Astronomical Society in Washington, D. C.

“Detections of water masers at these wavelengths will provide a unique new means of determining the physical conditions near the center of active galactic nuclei (AGN), where supermassive black holes are believed to lie,” said Humphreys.

The team measured radiation from compact radio sources known as H2O (water) masers using the Smithsonian Astrophysical Observatory’s Submillimeter Array and the James Clerk Maxwell Telescope, both on Mauna Kea, Hawaii.

Masers amplify and beam radio-wave emission similar to the way lasers emit light. Masers can occur in nature in interstellar space. In our own galaxy, water molecules near hot, newly formed stars can absorb energy and then emit radio waves with centimeter wavelengths, creating the brightest spectral lines in the radio universe. In active galaxies, it is processes related to black holes rather than stars that heat the molecules.