These images
highlight the most massive of the newly discovered compact galaxies
known as "red nuggets." The photo at left from the Sloan Digital Sky
Survey shows that the galaxy is so small it appears starlike. The higher
resolution photo at right from the Hubble Space Telescope reveals the
object's true, extended shape.
Credit: SDSS (left), NASA (right). High Resolution Image (jpg) - Low Resolution Image (jpg)
Credit: SDSS (left), NASA (right). High Resolution Image (jpg) - Low Resolution Image (jpg)
Cambridge, MA - In
2005 the Hubble Space Telescope spotted unusually small galaxies
densely packed with red stars in the distant, young universe. They were
nicknamed "red nuggets," not only because they are small and red but
also their existence challenged current theories of galaxy formation,
making them precious in astronomers' eyes.
Since no "red nuggets" were seen nearby, astronomers wondered why they
had disappeared over time. New research shows that they didn't disappear
completely. In fact, they were simply hidden within the data of
previous surveys.
Astronomers now realize these newfound compact galaxies could represent a
missing link between distant "red nuggets" and nearby elliptical
galaxies. They may light the evolutionary path to show how compact
galaxies age over time and reveal whether they become the "seeds" for
the monster ellipticals we see today.
To find them, astronomer Ivana Damjanov (Harvard-Smithsonian Center for
Astrophysics) and her colleagues searched databases from the Sloan
Digital Sky Survey. The "red nugget" galaxies are so small that they
appear like stars in photographs from ground-based telescopes. However,
their spectra give away their true nature.
"Looking for 'red nuggets' in the Sloan Digital Sky Survey was like
panning a riverbed, washing away silt and mud to uncover bits of gold,"
says Damjanov.
By sifting through the Sloan data, the team dug up more than 600 "red
nugget" candidates. They are located at distances of 2.5 to 5.7 billion
light-years from Earth.
Damjanov then investigated the Hubble Space Telescope database to find
photos of the patches of sky where those objects were located.
Serendipitous images of nine targets confirmed that they are as compact
as more distant "red nugget" galaxies. The most massive weigh up to 10
times more than the Milky Way, but are up to 10 times smaller than our
galaxy. As a result, they're called compact, massive galaxies.
"We think there are more of these red nuggets, or compact galaxies,
hidden in the universe, waiting to be discovered," says co-author Ho
Seong Hwang (Smithsonian Astrophysical Observatory).
The team's future plans include using the Hubble Space Telescope to
investigate more of these compact, massive galaxies to answer questions
like: Where do they live, near other galaxies or in the intergalactic
void? What is their internal structure?
Damjanov, a Menzel Fellow at the Harvard College Observatory, is lead author on the paper, which has been accepted for publication in The Astrophysical Journal Letters. Her co-authors are Igor Chilingarian, Ho Seong Hwang, and Margaret Geller (Smithsonian Astrophysical Observatory).
Headquartered in Cambridge, Mass., the
Harvard-Smithsonian Center for Astrophysics (CfA) is a joint
collaboration between the Smithsonian Astrophysical Observatory and the
Harvard College Observatory. CfA scientists, organized into six research
divisions, study the origin, evolution and ultimate fate of the
universe.
For more information, contact:
David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
daguilar@cfa.harvard.edu
Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463
cpulliam@cfa.harvard.edu
