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A galaxy about 23 million light-years away
is the site of impressive, ongoing, fireworks. Rather than paper,
powder, and fire, this galactic light show involves a giant black hole,
shock waves, and vast reservoirs of gas.
NASA/CXC/JPL-Caltech/STScI/NSF/NRAO/VLA.Full image and caption
A composite image of the spiral galaxy NGC
4258 showing X-ray emission observed with NASA's Chandra X-ray
Observatory (blue) and infrared emission observed with NASA's Spitzer
Space Telescope (red and green).Image Credit: X-ray:
NASA/CXC/NASA/JPL-Caltech.Full image and caption - enlarge image
Celebrants this Fourth of July will enjoy the dazzling lights and
booming shock waves from the explosions of fireworks. A similarly styled
event is taking place in the galaxy Messier 106, as seen by NASA's
Spitzer Space Telescope, Chandra X-ray Observatory and the Herschel
Space Observatory. Herschel is a European Space Agency mission with
important NASA contributions.
Energetic jets, which blast from Messier 106's central black hole,
are heating up material in the galaxy and thus making it glow, like the
ingredients in a firework. The jets also power shock waves that are
driving gases out of the galaxy's interior.
Those gases constitute the fuel for churning out new stars. A new
study estimates the shock waves have already warmed and ejected
two-thirds of the gas from the center of Messier 106. With a reduced
ability to birth new stars, Messier 106 appears to be transitioning into
a barren, so-called lenticular galaxy full of old, red stars.
Lenticular galaxies are flat disks without prominent spiral arms.
"Jets from the supermassive black hole at the center of Messier 106
are having a profound influence on the available gas for making stars in
this galaxy," said Patrick Ogle, an astrophysicist at the Infrared
Processing and Analysis Center at the California Institute of Technology
in Pasadena, and lead author of a new paper describing the results.
"This process may eventually transform the spiral galaxy Messier 106
into a lenticular galaxy, depriving it of the raw material to form
Many galaxies contain a central black hole that actively "feeds" upon
nearby gas. Some of the material, as it draws toward the black hole,
dramatically speeds up and violently spews out as twin jets near the
black hole's poles. As one of the Milky Way's closest galactic
neighbors, Messier 106 offers a great opportunity for investigating
these high-powered jets. Messier 106 -- also known as NGC 4258 -- is
23.5 million light-years distant, and visible with binoculars in the
constellation Canes Venatici.
For the new study, researchers used data obtained with the Spitzer
infrared telescope before the observatory ran out of coolant in 2009, as
planned. The data amount to a map of the infrared light emitted by
heated-up hydrogen molecules in Messier 106. The warmed hydrogen is a
signature of the jet from the central black hole energizing the
surrounding disk of the galaxy.
Specifically, Spitzer saw warmed hydrogen in the two mysterious
spiral arms for which Messier 106 is famous. These arms are not like the
usual, star-filled spiral arms found in spiral galaxies, such as our
Milky Way. In previous research with Spitzer and Chandra, researchers
discovered that twin jets from the black hole spawned the anomalous
arms, which contain gas heated to millions of degrees that shines in
X-rays, detected by Chandra.
In the inner portions of the anomalous spiral arms, the Spitzer
infrared images have revealed the equivalent of 10 million times the
mass of the sun of molecular hydrogen heated to between about minus 20
and 1,400 degrees Fahrenheit (minus 28 and 760 degrees Celsius) by the
shock waves. Without the shock waves, this gas would be colder, likely a
few hundred degrees below zero, Fahrenheit.
From a direct comparison of the Chandra and Spitzer images, Ogle and
colleagues saw that there is a close connection between the gas that is
shocked to millions of degrees, seen by Chandra, and the bulk of denser
hydrogen gas heated to hundreds of degrees, seen by Spitzer. The jet is
surrounded by a cocoon of superhot gas, which drives shock waves into
the surrounding molecular hydrogen gas, like a firework popping off. The
molecular hydrogen then heats up, emits infrared light that Spitzer
records, and is cast out of the galaxy's gas-strewn interior.
The Herschel observations, meanwhile, pinned down the heat radiating
from dust grains that are mixed in with the galaxy's shock-heated gas.
"A relatively large amount of molecular gas emission compared to dust
emission confirms that shock-driven turbulence from the black hole jets
is heating the molecular gas," said paper co-author Philip Appleton of
the NASA Herschel Science Center at Caltech.
Spitzer and Herschel were also able to gauge the level of star-making
activity in Messier 106's central region. The little gas left there
supports a paltry star-formation rate of only 0.08 solar, or
sun-equivalent, masses per year (a robust pace runs to about three solar
masses per year). The star-formation rate in Messier 106's inner
quarters will continue to decline until the jets have ejected all of the
gas from the center of the galaxy, turning Messier 106 into an
over-the-hill lenticular galaxy.
"Our results demonstrate that these black hole jets can have a
significant impact on the evolution of their host galaxies, eventually
sterilizing them and making them bereft of the gas needed to form new
stars," said Ogle.
NASA's Jet Propulsion Laboratory, Pasadena, California, manages the
Spitzer Space Telescope mission for NASA's Science Mission Directorate,
Washington. In 2009, the telescope began its "warm" mission, which takes
advantage of the still-working, shortest-wavelength infrared channels
on the observatory. Science operations are conducted at the Spitzer
Science Center at Caltech. Spacecraft operations are based at Lockheed
Martin Space Systems Company, Littleton, Colorado. Data are archived at
the Infrared Science Archive housed at the Infrared Processing and
Analysis Center at Caltech. Caltech manages JPL for NASA.
Herschel is a European Space Agency mission, with science instruments
provided by consortia of European institutes and with important
participation by NASA. While the observatory stopped making science
observations in April 2013, after running out of liquid coolant, as
expected, scientists continue to analyze its data. NASA's Herschel
Project Office is based at JPL. JPL contributed mission-enabling
technology for two of Herschel's three science instruments. The NASA
Herschel Science Center, part of the Infrared Processing and Analysis
Center at Caltech, supports the U.S. astronomical community. Caltech
manages JPL for NASA.
NASA's Marshall Space Flight Center in Huntsville, Ala., manages the
Chandra program for NASA's Science Mission Directorate in Washington.
The Smithsonian Astrophysical Observatory in Cambridge, Mass., controls
Chandra's science and flight operations.