A new study using NASA’s Chandra X-ray Observatory has tracked two pairs of supermassive black holes in dwarf galaxies on collision courses, as discussed in our latest press release. This is the first evidence for such an impending encounter, providing scientists with important information about the growth of black holes in the early Universe.
By definition, dwarf galaxies contain
stars with a total mass less than 3 billion Suns — or about 20 times less than
the Milky Way. Astronomers have long suspected that dwarf galaxies merge,
particularly in the relatively early Universe, in order to grow into the larger
galaxies seen today. However, current technology cannot observe the first
generation of dwarf galaxy mergers because they are extraordinarily faint at
their great distances. Another tactic — looking for dwarf galaxy mergers closer
by — had not been successful to date.
The new study overcame these challenges by
implementing a systematic survey of deep Chandra X-ray observations and
comparing them with infrared data from NASA’s Wide Infrared Survey Explorer
(WISE) and optical data from the Canada-France-Hawaii Telescope (CFHT).
Chandra was particularly valuable for this
study because material surrounding black holes can be heated up to millions of
degrees, producing large amounts of X-rays. The team searched for pairs of
bright X-ray sources in colliding dwarf galaxies as evidence of two black
holes, and discovered two examples.
One pair is in the galaxy cluster Abell
133 located 760 million light-years from Earth, seen in the composite image on
the left. Chandra X-ray data is in pink and optical data from CFHT is in blue.
This pair of dwarf galaxies appears to be in the late stages of a merger, and
shows a long tail caused by tidal effects from the collision. The authors of
the new study have nicknamed it “Mirabilis” after an endangered species of
hummingbird known for their exceptionally long tails. Only one name was chosen
because the merger of two galaxies into one is almost complete. The two Chandra
sources show X-rays from material around the black holes in each galaxy.
The other pair was discovered in Abell
1758S, a galaxy cluster about 3.2 billion light-years away. The composite image
from Chandra and CFHT is on the right, using the same colors as for Mirabilis.
The researchers nicknamed the merging dwarf galaxies “Elstir” and “Vinteuil,”
after fictional artists from Marcel Proust's "In Search of Lost
Time". Vinteuil is the galaxy on the top and Elstir is the galaxy on the
bottom. Both have Chandra sources associated with them, again from X-rays from
material around the black holes in each galaxy. The researchers think these two
have been caught in the early stages of a merger, causing a bridge of stars and
gas to connect the two colliding galaxies from their gravitational interaction.
The details of merging black holes and
dwarf galaxies may provide insight to our Milky Way’s own past. Scientists
think nearly all galaxies began as dwarf or other types of small galaxies and
grew over billions of years through mergers. Follow-up observations of these
two systems will allow astronomers to study processes that are crucial for
understanding galaxies and their black holes in the earliest stages of the
Universe.
A paper describing these results is being
published in the latest issue of The Astrophysical Journal and is available here. The authors of the study are Marko Micic, Olivia
Holmes, Brenna Wells, and Jimmy Irwin, all from the University of Alabama at
Tuscaloosa.
NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
Image credit: X-ray: NASA/CXC/Univ. of
Alabama/M. Micic et al.; Optical: International Gemini
Observatory/NOIRLab/NSF/AURA
Read more
from NASA's Chandra X-ray Observatory.
For more Chandra images, multimedia and
related materials, visit: http://www.nasa.gov/chandra
Source: NASA's
Chandra Discovers Giant Black Holes on Collision Course | NASA
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