From: baalke@kelvin.jpl.nasa.gov (Ron Baalke)
Subject: HST Discovers Double Nucleus in Core of Active Galaxy
News-Software: VAX/VMS VNEWS 1.41    
Keywords:  HST
Organization: Jet Propulsion Laboratory
Date: Thu, 7 Jan 1993 17:12:00 GMT

Paula Cleggett-Haleim
Headquarters, Washington, D.C.               January 7, 1993
(Phone:  202/358-0883)         

Jim Elliott
Goddard Space Flight Center, Greenbelt, Md.
(Phone:  301/286-6256)

Ray Villard
Space Telescope Science Institute, Baltimore
(Phone:  410/338-4757)

RELEASE:  93-006

HUBBLE  DISCOVERS A DOUBLE NUCLEUS IN CORE OF ACTIVE GALAXY

     Astronomers, using the Hubble Space Telescope, now 
believe that a galaxy they have observed for a decade 
actually is composed of two merged galaxies and that the 
collision has provided new fuel for a massive black hole 
which is spewing out a jet of gas and other matter 240,000 
light-years long.

     The galaxy is Markarian 315 located about 500 million 
light-years from Earth.  The collision and refueling theory 
emerged after the Hubble Telescope revealed that the galaxy 
has a double nucleus or two core-like regions.

     The brighter core-like region is believed to harbor the 
massive black hole which accounts for the tremendous amounts 
of energy produced by the galaxy.  The fainter nucleus is 
considered to be the surviving core of a galaxy that recently 
merged into Markarian 315.

     "The galaxy's active core presumably harbors a black 
hole which has been re-fueled by the galactic collision," 
said Dr. Jack MacKenty, Assistant Scientist at the Space 
Telescope Science Institute in Baltimore.

     "The Hubble images provide support for the theory that 
the jet-like feature may be a 'tail' of gas stretched out by 
tidal forces between the two galaxies as they interacted," 
explained Dr. MacKenty, Assistant Scientist at the Space 
Telescope Science Institute.

     "The jet feature is most likely a remnant of a merger 
between Markarian 315 and a smaller galaxy," said MacKenty.  
This observation best explains the extraordinary 240,000-
light-year long jet-like feature of Markarian 315.  

     An image of the core of Markarian 315, taken with the 
Hubble Space Telescope's Wide Field and Planetary Camera 
shows a second, fainter nucleus located approximately 6,000 
light-years (or 2 arc seconds in angular separation) from the 
galaxy's bright central nucleus.  One light-year equals 
approximately 5.8 trillion miles (9.3 trillion km).

     Galaxy mergers may be one mechanism for driving gas deep 
into the heart of a galaxy, astronomers believe.  This raw 
material fuels massive black holes, theorized to be the 
"central engines" in Seyfert galaxies and other active 
galaxies.

     The Hubble Space Telescope's high spatial resolution 
allows astronomers to probe the cores of Seyfert galaxies in 
unprecedented detail.  In exposures taken with ground-based 
telescopes, the companion nucleus is drowned out by the 
brighter Seyfert nucleus. 

     The report on this discovery is by Drs. John MacKenty 
and Andrew Wilson of the Space Telescope Science Institute, 
Baltimore; Richard Griffiths of The Johns Hopkins University, 
Baltimore; and Susan Simkin of Michigan State University, 
East Lansing.  The report was delivered at the 181st Meeting 
of the American Astronomical Society meeting in Phoenix, 
Ariz.  

     The Hubble Space Telescope is a project of international 
cooperation between NASA and the European Space Agency.

- end -


NOTE TO EDITORS:  A photograph to illustrate this story is 
available by calling NASA's Broadcast and Imaging Branch on 
202/358-1900.

             Color:   92-HC-733              B&W:   92-H-794
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    /_ /|  /____/ \  /_ /|     Ron Baalke         | baalke@kelvin.jpl.nasa.gov
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