FOR IMMEDIATE RELEASE December 3, 1996

CONTACT: Lydia Schindler (301) 405-4623; Heino Falcke (301) 405-3368

  University of Maryland, Max-Planck Institut Scientists Find
           Relativistic Jets, Black Holes in Quasars

COLLEGE PARK, MD -- Scientists from the University of Maryland at College Park
and the Max-Planck Institut fuer Radioastronomie in Bonn, Germany have found
strong evidence that the majority, if not all, quasars have a powerful
accelerator of relativistic plasma beams in their center. In a paper to be
published in the Astrophysical Journal Dec. 10, Heino Falcke of the University
of Maryland and Alok Patnaik and William Sherwood of the Max-Planck Institut
say that the formation of a relativistic outflow now seems to be the rule
rather than the exception in quasars. Falcke explains "This shows for the
first time that probably all quasars harbor a very similar engine: a black
hole, an accretion disk AND a relativistic jet."

     Quasars, the most luminous objects in the universe, are thought to be
powered by accretions disks around massive black holes. Because 10 percent of
these sources, so-called radio-loud quasars, also show well-collimated plasma
jets emanating from their nuclei at 99 percent of the speed of light, many
scientists believed that the unusual activity in quasars had to be powered by
an exotic object and not by something like a collection of stars. Yet, it
remained a mystery why the majority of quasars (radio-weak quasars) did not
seem to have these relativistic jets. Consequently, scientists questioned the
existence of a black hole in these sources.

      Falcke says that relativistic jets now appear to be intimately linked to
the presence of accretion disks and provide additional arguments that the
activity in quasars is due to a central black hole. In order to escape from
the region of its formation, any jet has to reach an initial outflow speed
large enough to leave the gravitational pull of the central object . Only
black holes require escape speeds close to the speed of light as they have
been deduced for quasars.

     The scientists made this discovery by studying a usually overlooked class
of quasars, with radio luminosities intermediate between radio-loud and
radio-quiet quasars. Using a technique where radio telescopes in different
countries are combined to give the resolution of a single telescope with the
diameter of a whole continent (Very-Long-Baseline-Interferome try/VLBI), they
found unusually bright and compact radio cores in these quasars whose radio
luminosity was apparently enhanced by relativistic Doppler boosting in a
relativistic jet.

     This effect is a consequence of Einstein's theory of relativity where
light is beamed toward the observer if an observer happens to look right into
a relativistic flow. The authors have very strong evidence that those
radio-intermediate quasars must be relativistically boosted radio-weak quasars
which happen to be preferentially oriented with respect to the earth. The
findings confirm earlier studies (The Astrophysical Journal Vol. 471, p.106,
Astronomy & Astrophy sics Vol. 298, p. 375) where the radio properties of
these specific sources were predicted. They imply that basically all quasars
should contain relativistic jets in their nuclei. Up until now, it was widely
believed that radio-weak quasars do not contain powerful jets at all and
therefore they were in a fundamental way different from radio-loud quasars.

     Further support for this interpretation comes from recently publicized
Hubble-Space-Telescope observations of the host galaxies of quasars which
revealed that at least one of the investigated quasars (PG1309+35) was hosted
by a spiral galaxy -- a galaxy similar to the Milky Way. So far, relativistic
jets have only been discovered in elliptical galaxies , the hosts of
radio-loud quasars.

     The discovery can also have far-ranging implications for other fields in
astronomy, since relativistic jets are primary sources for high-energy x-ray
and gamma-ray emission, which are currently studied by several satellite
missions. The new findings suggest that the number of extragalactic gamma-ray
sources that can be found with future, more sensitive missions could be larger
by a factor of 10 with respect to earlier measurements.

Note: The complete paper can be found at
http://www.astro.umd.edu/~hfalcke/publications.html#riqvlbi

                  Lydia Schindler
                  University Relations, University of Maryland
                  voice: 301/405-4623; fax: 301/314-9344
                  lschindl@umdacc.umd.edu