This
artist's impression shows galaxy WISE J224607.55-052634.9, the most
luminous galaxy ever discovered. A new study using data from the Atacama
Large Millimeter/submillimeter Array (ALMA) shows that this galaxy is
syphoning dust and other material from three of its smaller galactic
neighbors. (NRAO/AUI/NSF) S. Dagnello. › Full image and caption
The most
luminous galaxy ever discovered is cannibalizing not one, not two, but at least
three of its smaller neighbors, according to a new study published
today (Nov. 15) in the journal Science and coauthored by scientists
from NASA's Jet Propulsion Laboratory in Pasadena, California. The material that
the galaxy is stealing from its neighbors is likely contributing to its uber-brightness,
the study shows.
Discovered by NASA's space-based Wide-field Infrared Survey
Explorer (WISE) in 2015,
the galaxy, called WISE
J224607.55-052634.9, is
by no means the largest or most massive galaxy we know of, but it radiates at 350
trillion times the luminosity of the Sun. If all galaxies were positioned an
equal distance from us, WISE J224607.55-052634.9 (or W2246-0526 for short)
would be the brightest.
New
observations using the
Atacama Large Millimeter/submillimeter Array (ALMA) in Chile reveal distinct
trails of dust being pulled from three smaller galaxies into W2246-0526. The
trails contain about as much material as the smaller galaxies themselves, and it's
unclear whether those galaxies will escape their current fate or will be
completely consumed by their luminous neighbor.
This image, created using radio
data from the Atacama Large Millimeter/submillimeter Array (ALMA), shows
W2246-0526 as it syphons material away from three smaller galaxies.
W2246-0526 and one of its companions are in the center; the second
galaxy is above them; the third is to the lower left. Image Credit: ALMA
(ESO/NAOJ/NRAO); S. Dagnello (NRAO/AUI/NSF)
. Larger view
Most of W2246-0526's
record-breaking luminosity comes
not only from stars, but also a collection of hot gas and dust concentrated
around the center of the galaxy. At the heart of this cloud is a supermassive
black hole, recently determined to be 4 billion times more massive than the Sun.
In the intense gravity, matter falls toward the black hole at high speeds,
crashing together and heating up to millions of degrees, causing the material
to shine with incredible brilliance. Galaxies that contain these types of luminous,
black-hole-fueled structures are known as quasars.
Like any
engine on Earth, W2246-0526's enormous energy output requires an equally high
fuel input. In this case, that means gas and dust to form stars and to
replenish the cloud around the central black hole. The new study shows that the
amount of material being accreted by WJ2246-0526 from its neighbors is
enough to replenish what is being consumed, thereby sustaining the galaxy's tremendous
luminosity.
"It is possible that this feeding frenzy has already been
ongoing for some time, and we expect the galactic feast to continue for at
least a few hundred million years," said Tanio Diaz-Santos of the Universidad Diego Portales in
Santiago, Chile, lead author of the study.
In the new
study, the scientists used images from ALMA - a collection of individual radio
antennas that work together as single telescope - to identify the dusty trails
of material. The position of the accretion trails strongly suggests they contain
material flowing between W2246-0526 and the other galaxies. In addition, the
trails exhibit the right morphology - that is, the shape of the trails is
consistent with how the material should flow if it is being pulled from one
galaxy into another.
This annotated image made using
radio data from the Atacama Large Millimeter/submillimeter Array (ALMA)
shows how W2246-0526 is being fed by three companion galaxies (C1, C2,
and C3). A large tidal tail connects C2 with the main galaxy; dust
bridges connect the other two galaxies to W2246-0526. Image Credit: T.
Diaz-Santos et al.; N. Lira; ALMA (ESO/NAOJ/NRAO) .Larger view
This kind of
galactic cannibalism is not uncommon. Astronomers have previously observed
galaxies merging with or accreting matter from their neighbors in the nearby
universe. For example, the pair
of galaxies collectively known as "the Mice" are so named because
each has a long, thin tail of accreting material stretching away from it.
W2246-0526 is
the most distant galaxy ever found to be accreting material from multiple
sources. The light from W2246-0526 took 12.4 billion years to reach us, so
astronomers are seeing the object as it was when our universe was only a tenth
of its present age of 13.8 billion years. At that distance, the streams of
material falling into W2246-0526 are particularly faint and difficult to
detect. The study relies on 2.5 hours of observation time using 40 of ALMA's 12-meter
radio dishes.
"We knew
from previous data that there were three companion galaxies, but there was no
evidence of interactions between these neighbors and the central source,"
said Diaz-Santos. "We weren't looking for cannibalistic behavior and
weren't expecting it, but this deep dive with the ALMA observatory makes it
very clear."
W2246-0526
falls into a special category of particularly luminous quasars known as hot,
dust-obscured galaxies, or Hot DOGs. Astronomers think that most quasars get
some of their fuel from external sources. One possibility is that these objects
receive a slow trickle of material from the space between galaxies. Another is
that they feed in bursts by eating up other galaxies, which appears to be
occurring with W2246-0526. It's unclear whether W2246-0526 is representative of
other obscured quasars (those with their central engines obscured by thick
clouds of dust) or if it is a special case.
"This galaxy may be one of a kind, because it's nearly
twice as luminous as any other galaxy we've found with WISE and it formed very
early in the universe's history," said Peter Eisenhardt, JPL project scientist
for WISE and a coauthor on the new paper. "But we've discovered many other
galaxies with WISE that are similar to this one: distant, dusty and thousands
of times more luminous than typical galaxies are today. So with W2246-0526, we
may be seeing what goes on during a key stage in the evolution of galaxies and
obscured quasars."
Ultimately, the galaxy's gluttony may only lead to
self-destruction. Scientists hypothesize that obscured quasars that gather too
much material around them end up vomiting gas and dust back out through the
galaxy. This onslaught of material halts the formation of new stars,
essentially pushing the galaxy into retirement while other galaxies continue to
renew themselves with the birth of new stars.
A companion study about W2246-0526, published on
Nov. 14 in the Astrophysical Journal, provided the mass measurement
for the supermassive black hole at the galaxy's center - 4 billion times the
mass of the Sun. This mass is large, but the extreme luminosity of W2246-0526
was thought to require a supermassive black hole with a mass at least three
times larger, according to the paper authors. Solving this apparent
contradiction will require more observations.
The
Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy
facility, is a partnership of the European Southern Observatory (ESO), the U.S.
National Science Foundation (NSF) and the National Institutes of Natural
Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is
funded by ESO on behalf of its Member States, by NSF in cooperation with the
National Research Council of Canada (NRC) and the Ministry of Science and
Technology (MOST) in Taiwan and by NINS in cooperation with the Academia Sinica
(AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).
NASA's
Jet Propulsion Laboratory in Pasadena, California, managed and operated WISE
for NASA's Science Mission Directorate in Washington. The spacecraft operated
until 2011. In September 2013, WISE was reactivated, renamed NEOWISE and
assigned a new mission to assist NASA's efforts to identify potentially
hazardous near-Earth objects.
News Media Contact
Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
626-808-2469
calla.e.cofield@jpl.nasa.gov
Charles Blue
NRAO Public Information Officer
434-296-0314
cblue@nrao.edu
Source: JPL-Caltech/News
