New Haven, Conn. — Despite a decade of efforts to find flaws in the unification
theory of active galaxies, the theory correctly explains the exotic phenomena of
accreting supermassive black holes, a Yale astronomer said today.

"Furthermore, the striking parallels between normal and active galaxies that
have become apparent in the last few years," said Meg Urry, professor of physics
at Yale and director of the Yale Center for Astronomy and Astrophysics, "suggest
that there is a larger ‘Grand Unification’ at play. Apparently every galaxy goes
through an active phase."

Urry spoke at the American Astronomical Society meeting in Nashville, Tenn.

Urry said the Grand Unification theory predicts what objects should appear in
very deep multi-wavelength views of the universe. "Most of the active galaxies
in the early universe have been hidden from view until now," she said. "We
predict there are far more hidden black holes than brightly shining active
galaxies."

New multi-wavelength surveys involving unique space observatories provide a way
to test the Grand Unification theory, she said. Three of the National
Aeronautics and Space Administration (NASA) space observatories — the Hubble
Space Telescope and the Chandra X-Ray Observatory, both already in orbit, and
the Space Infrared Telescope Facility, due to be launched in August — are
critically important because they allow very deep imaging from far-infrared to
X-ray wavelengths, where active galaxies and star-forming galaxies radiate most
of their energy. Preliminary results from the first two observatories are
encouraging.

"The new challenge is to understand in detail how galaxy formation — the
gravitational collapse of a galaxy — is tied to star formation in that galaxy
and to accretion onto the black hole at its center," she said. "Now we think all
these processes are happening simultaneously, in the same objects. As a galaxy
forms and collapses under the weight of its own gravity, it stimulates both
intense star formation and the dumping of gas and stars onto the seed black hole
at the center of the gravitational potential well."

"The galaxy starts collapsing, makes stars and makes an active nucleus," Urry
said. "The violent events of this collapse dump matter onto the black hole and
this releases a lot of energy. All these wild things are happening at once."

EDITORS: A cartoon illustrating the unification paradigm for active galaxies
(not to scale), is available at
http://www.yale.edu/opa/assets/images/releases/20030520_cover.jpg (124KB)
It shows the supermassive black hole and the accretion disk (pink) of matter
falling toward the black hole. PHOTO CREDIT: Meg Urry (Yale) and John Godfrey
(STScI). Copyright PASP, reprinted by permission of the author. This photograph
can be obtained after 4:30 P.M. EST, May 26, 2003.