HOT GAS ARMS IN COMA CLUSTER OF GALAXIES

FROM:  NASA,  
Clues to the Growth of the Colossus in Coma

A team of astronomers has discovered enormous arms of hot gas in the Coma cluster of galaxies by using NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton. These features, which span at least half a million light years, provide insight into how the Coma cluster has grown through mergers of smaller groups and clusters of galaxies to become one of the largest structures in the universe held together by gravity.

A new composite image, with Chandra data in pink and optical data from the Sloan Digital Sky Survey appearing in white and blue, features these spectacular arms. In this image, the Chandra data have been processed so extra detail can be seen.

The X-ray emission is from multimillion-degree gas and the optical data shows galaxies in the Coma Cluster, which contain only about one-sixth the mass in hot gas. Only the brightest X-ray emission is shown here, to emphasize the arms, but the hot gas is present over the entire field of view.

Researchers think that these arms were most likely formed when smaller galaxy clusters had their gas stripped away by the head wind created by the motion of the cluster through the hot gas, in much the same way that the headwind created by a roller coaster blows the hats off riders.

Coma is an unusual galaxy cluster because it contains not one, but two giant elliptical galaxies near its center. These two giant elliptical galaxies are probably the vestiges from each of the two largest clusters that merged with Coma in the past. The researchers also uncovered other signs of past collisions and mergers in the data.

From their length, and the speed of sound in the hot gas (about four million km/hr), the newly discovered X-ray arms are estimated to be about 300 million years old, and they appear to have a rather smooth shape. This gives researchers some clues about the conditions of the hot gas in Coma. Most theoretical models expect that mergers between clusters like those in Coma will produce strong turbulence, like ocean water that has been churned by many passing ships. Instead, the smooth shape of these lengthy arms points to a rather calm setting for the hot gas in the Coma cluster, even after many mergers.

Large-scale magnetic fields are likely responsible for the small amount of turbulence that is present in Coma. Estimating the amount of turbulence in a galaxy cluster has been a challenging problem for astrophysicists. Researchers have found a range of answers, some of them conflicting, and so observations of other clusters are needed.

Two of the arms appear to be connected to a group of galaxies located about two million light years from the center of Coma. One or both of these arms connects to a larger structure seen in the XMM-Newton data, and spans a distance or at least 1.5 million light years. A very thin tail also appears behind one of the galaxies in Coma. This is probably evidence of gas being stripped from a single galaxy, in addition to the groups or clusters that have merged there.

These new results on the Coma cluster, which incorporate over six days worth of Chandra observing time, will appear in the September 20, 2013, issue of the journal Science. The first author of the paper is Jeremy Sanders from the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. The co-authors are Andy Fabian from Cambridge University in the UK; Eugene Churazov from the Max Planck Institute for Astrophysics in Garching, Germany; Alexander Schekochihin from University of Oxford in the UK; Aurora Simionescu from Stanford University in Stanford, CA; Stephen Walker from Cambridge University in the UK and Norbert Werner from Stanford University in Stanford, CA.
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 controls Chandra's science and flight operations from Cambridge, Mass.

Credits: X-ray: NASA/CXC/MPE/J. Sanders et al; Optical: SDSS

IMMENSE POWER GENERATED BY SUPERMASSIVE BLACK HOLE

FROM: NASA

This composite image of a galaxy illustrates how the intense gravity of a supermassive black hole can be tapped to generate immense power. The image contains X-ray data from NASA's Chandra X-ray Observatory (blue), optical light obtained with the Hubble Space Telescope (gold) and radio waves from the NSF’s Very Large Array (pink).

This multi-wavelength view shows 4C+29.30, a galaxy located some 850 million light years from Earth. The radio emission comes from two jets of particles that are speeding at millions of miles per hour away from a supermassive black hole at the center of the galaxy. The estimated mass of the black hole is about 100 million times the mass of our Sun. The ends of the jets show larger areas of radio emission located outside the galaxy.

The X-ray data show a different aspect of this galaxy, tracing the location of hot gas. The bright X-rays in the center of the image mark a pool of million-degree gas around the black hole. Some of this material may eventually be consumed by the black hole, and the magnetized, whirlpool of gas near the black hole could in turn, trigger more output to the radio jet.

Most of the low-energy X-rays from the vicinity of the black hole are absorbed by dust and gas, probably in the shape of a giant doughnut around the black hole. This doughnut, or torus blocks all the optical light produced near the black hole, so astronomers refer to this type of source as a hidden or buried black hole. The optical light seen in the image is from the stars in the galaxy.

The bright spots in X-ray and radio emission on the outer edges of the galaxy, near the ends of the jets, are caused by extremely high energy electrons following curved paths around magnetic field lines. They show where a jet generated by the black hole has plowed into clumps of material in the galaxy (mouse over the image for the location of these bright spots). Much of the energy of the jet goes into heating the gas in these clumps, and some of it goes into dragging cool gas along the direction of the jet. Both the heating and the dragging can limit the fuel supply for the supermassive black hole, leading to temporary starvation and stopping its growth. This feedback process is thought to cause the observed correlation between the mass of the supermassive black hole and the combined mass of the stars in the central region or bulge or a galaxy.

These results were reported in two different papers. The first, which concentrated on the effects of the jets on the galaxy, is available online and was published in the May 10, 2012 issue of The Astrophysical Journal. It is led by Aneta Siemiginowska from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, MA and the co-authors are Łukasz Stawarz, from the Institute of Space and Astronautical Science in Yoshinodai, Japan; Teddy Cheung from the National Academy of Sciences in Washington, DC; Thomas Aldcroft from CfA; Jill Bechtold from University of Arizona in Tucson, AZ; Douglas Burke from CfA; Daniel Evans from CfA; Joanna Holt from Leiden University in Leiden, The Netherlands; Marek Jamrozy from Jagiellonian University in Krakow, Poland; and Giulia Migliori from CfA. The second, which concentrated on the supermassive black hole, is available online and was published in the October 20, 2012 issue of The Astrophysical Journal. It is led by Malgorzata Sobolewska from CfA, and the co-authors are Aneta Siemiginowska, Giulia Migliori, Łukasz Stawarz, Marek Jamrozy, Daniel Evans, and Teddy Cheung.

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 controls Chandra's science and flight operations from Cambridge, Mass.

Credits: X-ray: NASA/CXC/SAO/A. Siemiginowska et al; Optical: NASA/STScI; Radio: NSF/NRAO/VLA

THE DEAD STAR

FROM: NASA
Sizzling Remains of a Dead Star
This new view of the historical supernova remnant Cassiopeia A, located 11,000 light-years away, was taken by NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR. Blue indicates the highest energy X-ray light, where NuSTAR has made the first resolved image ever of this source. Red and green show the lower end of NuSTAR's energy range, which overlaps with NASA's high-resolution Chandra X-ray Observatory.

Light from the stellar explosion that created Cassiopeia A is thought to have reached Earth about 300 years ago, after traveling 11,000 years to get here. While the star is long dead, its remains are still bursting with action. The outer blue ring is where the shock wave from the supernova blast is slamming into surrounding material, whipping particles up to within a fraction of a percent of the speed of light. NuSTAR observations should help solve the riddle of how these particles are accelerated to such high energies

X-ray light with energies between 10 and 20 kiloelectron volts are blue; X-rays of 8 to 10 kiloelectron volts are green; and X-rays of 4.5 to 5.5 kiloelectron volts are red.

The starry background picture is from the Digitized Sky Survey.


Image credit: NASA/JPL-Caltech/DSS

 

A REALLY BIG BLACK HOLE

FROM:  NASA, BLACK HOLE

The black hole at the center of this galaxy is part of a survey of 18 of the biggest black holes in the universe. This large elliptical galaxy is in the center of the galaxy cluster PKS 0745-19, which is located about 1.3 billion light years from Earth.. X-ray data from NASA's Chandra X-ray Observatory are shown in purple and optical data from the Hubble Space Telescope are in yellow.

The researchers found that these black holes may be about ten times more massive than previously thought, with at least ten of them weighing between 10 and 40 billion times the mass of the sun.

All of the potential "ultramassive" black holes found in this study lie in galaxies at the centers of galaxy clusters containing huge amounts of hot gas. This hot gas produces the diffuse X-ray emission seen in the image. Outbursts powered by the central black holes create cavities in the gas preventing it from cooling and forming enormous numbers of stars. To generate the outbursts, the black holes must swallow large amounts of mass. Because the largest black holes can swallow the most mass and power the biggest outbursts, ultramassive black holes had already been predicted to exist to explain some of the most powerful outbursts seen. Credits: X-ray: NASA/CXC/Stanford/Hlavacek-Larrondo, J. et al; Optical: NASA/STScI

 

A PLACE WHERE STARS COME FROM

FROM: NASA

A Nearby Stellar Cradle
The Milky Way and other galaxies in the universe harbor many young star clusters and associations that each contain hundreds to thousands of hot, massive, young stars known as O and B stars. The star cluster Cygnus OB2 contains more than 60 O-type stars and about a thousand B-type stars. Deep observations with NASA’s Chandra X-ray Observatory have been used to detect the X-ray emission from the hot outer atmospheres, or coronas, of young stars in the cluster and to probe how these fascinating star factories form and evolve. About 1,700 X-ray sources were detected, including about 1,450 thought to be stars in the cluster. In this image, X-rays from Chandra (blue) have been combined with infrared data from NASA’s Spitzer Space Telescope (red) and optical data from the Isaac Newton Telescope (orange).

Image Credit: NASA

COLLISION OF A GALACTIC PROPORTION

FROM: NASASpacecraft Image Mashup Shows Galactic Collision

This new composite image from the Chandra X-ray Observatory, the Hubble Space Telescope, and the Spitzer Space Telescope shows two colliding galaxies more than a 100 million years after they first impacted each other. The continuing collision of the Antennae galaxies, located about 62 million light years from Earth, has triggered the formation of millions of stars in clouds of dusts and gas

SHOCK-WAVE

FROM:  NASA
Using observations from NASA's Chandra X-ray Observatory, researchers have obtained the first X-ray evidence of a supernova shock wave breaking through a cocoon of gas surrounding the star that exploded. This discovery may help astronomers understand why some supernovas are much more powerful than others. On Nov. 3, 2010, a supernova was discovered in the galaxy UGC 5189A, located about 160 million light years away. Using data from the All Sky Automated Survey telescope in Hawaii taken earlier, astronomers determined this supernova exploded in early October 2010. This composite image of UGC 5189A shows X-ray data from Chandra in purple and optical data from Hubble Space Telescope in red, green and blue. SN 2010jl is the very bright X-ray source near the top of the galaxy. A team of researchers used Chandra to observe this supernova in December 2010 and again in October 2011. The supernova was one of the most luminous that has ever been detected in X-rays. In the first Chandra observation of SN 2010jl, the X-rays from the explosion's blast wave were strongly absorbed by a cocoon of dense gas around the supernova. This cocoon was formed by gas blown away from the massive star before it exploded. In the second observation taken almost a year later, there is much less absorption of X-ray emission, indicating that the blast wave from the explosion has broken out of the surrounding cocoon. The Chandra data show that the gas emitting the X-rays has a very high temperature -- greater than 100 million degrees Kelvin – strong evidence that it has been heated by the supernova blast wave. In a rare example of a cosmic coincidence, analysis of the X-rays from the supernova shows that there is a second unrelated source at almost the same location as the supernova. These two sources strongly overlap one another as seen on the sky. This second source is likely to be an ultraluminous X-ray source, possibly containing an unusually heavy stellar-mass black hole, or an intermediate mass black hole. Image Credit: X-ray: NASA/CXC/Royal Military College of Canada/P.Chandra et al); Optical: NASA/STScI

GALACTIC COLLISION

FROM:  NASA
Using a combination of powerful observatories in space and on the ground, astronomers have observed a violent collision between two galaxy clusters in which so-called normal matter has been wrenched apart from dark matter through a violent collision between two galaxy clusters.

Finding another system that is further along in its evolution than the Bullet Cluster gives scientists valuable insight into a different phase of how galaxy clusters -- the largest known objects held together by gravity -- grow and change after major collisions.

Researchers used observations from NASA's Chandra X-ray Observatory and Hubble Space Telescope as well as the Keck, Subaru and Kitt Peak Mayall telescopes to show that hot, X-ray bright gas in the Musket Ball Cluster has been clearly separated from dark matter and galaxies.

In this composite image, the hot gas observed with Chandra is colored red, and the galaxies in the optical image from Hubble appear as mostly white and yellow. The location of the majority of the matter in the cluster (dominated by dark matter) is colored blue. When the red and the blue regions overlap, the result is purple as seen in the image. The matter distribution is determined by using data from Subaru, Hubble and the Mayall telescope that reveal the effects of gravitational lensing, an effect predicted by Einstein where large masses can distort the light from distant objects.

In addition to the Bullet Cluster, five other similar examples of merging clusters with separation between normal and dark matter and varying levels of complexity, have previously been found. In these six systems, the collision is estimated to have occurred between 170 million and 250 million years earlier.

In the Musket Ball Cluster, the system is observed about 700 million years after the collision. Taking into account the uncertainties in the age estimate, the merger that has formed the Musket Ball Cluster is two to five times further along than in previously observed systems. Also, the relative speed of the two clusters that collided to form the Musket Ball cluster was lower than most of the other Bullet Cluster-like objects.

The special environment of galaxy clusters, including the effects of frequent collisions with other clusters or groups of galaxies and the presence of large amounts of hot, intergalactic gas, is likely to play an important role in the evolution of their member galaxies. However, it is still unclear whether cluster mergers trigger star formation, suppress it, or have little immediate effect. The Musket Ball Cluster holds promise for deciding between these alternatives.

The Musket Ball Cluster also allows an independent study of whether dark matter can interact with itself. This information is important for narrowing down the type of particle that may be responsible for dark matter. No evidence is reported for self-interaction in the Musket Ball Cluster, consistent with the results for the Bullet Cluster and the other similar clusters.

The Musket Ball Cluster is located about 5.2 billion light years away from Earth. A paper describing these results was led by Will Dawson from University of California, Davis and was published in the March 10, 2012 issue of The Astrophysical Journal Letters. The other co-authors were David Wittman, M. James Jee and Perry Gee from UC Davis, Jack Hughes from Rutgers University in NJ, J. Anthony Tyson, Samuel Schmidt, Paul Thorman and Marusa Bradac from UC Davis, Satoshi Miyazaki from the Graduate University for Advanced Studies (GUAS) in Tokyo, Japan, Brian Lemaux from UC Davis, Yousuke Utsumi from GUAS and Vera Margoniner from California State University, Sacramento.

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 controls Chandra's science and flight operations from Cambridge, Mass.