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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 stars.”
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.
See the full article here.
The NASA/ESA Hubble Space Telescope – with a little help from an amateur astronomer – has produced one of the best views yet of nearby spiral galaxy Messier 106. Located a little over 20 million light-years away, practically a neighbour by cosmic standards, Messier 106 is one of the brightest and nearest spiral galaxies to our own.
Despite its appearance, which looks much like countless other galaxies, Messier 106 hides a number of secrets. Thanks to this image, which combines data from Hubble with observations by amateur astronomers Robert Gendler and Jay GaBany, they are revealed as never before.
At its heart, as in most spiral galaxies, is a supermassive black hole, but this one is particularly active. Unlike the black hole at the centre of the Milky Way, which pulls in wisps of gas only occasionally, Messier 106’s black hole is actively gobbling up material. As the gas spirals towards the black hole, it heats up and emits powerful radiation. Part of the emission from the centre of Messier 106 is produced by a process that is somewhat similar to that in a laser – although here the process produces bright microwave radiation.
As well as this microwave emission from Messier 106’s heart, the galaxy has another startling feature – instead of two spiral arms, it appears to have four. Although the second pair of arms can be seen in visible light images as ghostly wisps of gas, as in this image, they are even more prominent in observations made outside of the visible spectrum, such as those using X-ray or radio waves.
Unlike the normal arms, these two extra arms are made up of hot gas rather than stars, and their origin remained unexplained until recently. Astronomers think that these, like the microwave emission from the galactic centre, are caused by the black hole at Messier 106’s heart, and so are a totally different phenomenon from the galaxy’s normal, star-filled arms.
The extra arms appear to be an indirect result of jets of material produced by the violent churning of matter around the black hole. As these jets travel through the galactic matter they disrupt and heat up the surrounding gas, which in turn excites the denser gas in the galactic plane and causes it to glow brightly. This denser gas closer to the centre of the galaxy is tightly-bound, and so the arms appear to be straight. However, the looser disc gas further out is blown above or below the disc in the opposite direction from the jet, so that the gas curves out of the disc — producing the arching red arms seen here.
Despite carrying his name, Messier 106 was neither discovered nor catalogued by the renowned 18th century astronomer Charles Messier. Discovered by his assistant, Pierre Méchain, the galaxy was never added to the catalogue in his lifetime. Along with six other objects discovered but not logged by the pair, Messier 106 was posthumously added to the Messier catalogue in the 20th century.
Amateur astronomer Robert Gendler retrieved archival Hubble images of M 106 to assemble a mosaic of the centre of the galaxy. He then used his own and fellow astrophotographer Jay GaBany’s observations of M 106 to combine with the Hubble data in areas where there was less coverage, and finally, to fill in the holes and gaps where no Hubble data existed.
The centre of the galaxy is composed almost entirely of Hubble data taken by the Advanced Camera for Surveys, Wide Field Camera 3, and Wide Field and Planetary Camera 2 detectors. The outer spiral arms are predominantly HST data colourised with ground-based data taken by Gendler’s and GaBany’s 12.5-inch and 20-inch telescopes, located at very dark remote sites in New Mexico, USA.
Gendler was a prizewinner in the recent Hubble’s Hidden Treasures image processing competition. Another prizewinner, André van der Hoeven, entered a different version of Messier 106, combining Hubble and NOAO data.
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
 Lasers work when light stimulates emission of more light from a cloud of excited gas, with the original light in effect being amplified (the word laser is an acronym for light amplification by the stimulated emission of radiation). The centre of M106 harbours a similar phenomenon called a maser (short for microwave amplification by the stimulated emission of radiation), in which microwave radiation, which is at longer wavelengths than visible light, is emitted. Note that unlike man-made lasers, which are designed to produce a narrow beam, astronomical masers shine in all directions.
Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), and R. Gendler (for the Hubble Heritage Team). Acknowledgment: J. GaBany
The Spitzer Space Telescope is a NASA mission managed by the Jet Propulsion Laboratory located on the campus of the California Institute of Technology and part of NASA’s Infrared Processing and Analysis Center.
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