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The NASA/ESA Hubble Space Telescope provides new evidence for dark matter around small galaxies
March 13, 2009The NASA/ESA Hubble Space Telescope has uncovered a strong new line of evidence that galaxies are embedded in halos of dark matter.
Peering into the tumultuous heart of the nearby Perseus galaxy cluster, Hubble discovered a large population of small galaxies that have remained intact while larger galaxies around them are being ripped apart by the gravitational tug of other galaxies.
The Hubble images provide further evidence that the undisturbed galaxies are enshrouded by a "cushion" of dark matter that protects them from their rough-and-tumble neighbourhood.
Dark matter is an invisible form of matter that accounts for most of the Universe's mass. Astronomers have deduced the existence of dark matter by observing its gravitational influence on normal matter, such as stars, gas and dust.
"We were surprised to find so many dwarf galaxies in the core of this cluster that were so smooth and round and had no evidence at all of any kind of disturbance," says astronomer Christopher Conselice of the University of Nottingham, UK, and leader of the team that made the Hubble observations. "These dwarfs are very old galaxies that have been in the cluster for a long time. So if something was going to disrupt them, it would have happened by now. They must be very, very dark-matter-dominated galaxies."
The dwarf galaxies may have an even higher amount of dark matter than spiral galaxies. "With these results, we cannot say whether the dark matter content of the dwarfs is higher than in the Milky Way Galaxy," Conselice says. "Although, the fact that spiral galaxies are destroyed in clusters, while the dwarfs are not, suggests that this is indeed the case."
First proposed about 80 years ago by Swiss astronomer Fritz Zwicky, dark matter is thought to be the glue that holds galaxies together. Astronomers suggest that dark matter provides a vital scaffolding for the Universe, forming a framework for the formation of galaxies through gravitational attraction.
Observations by Hubble's Advanced Camera for Surveys spotted 29 dwarf elliptical galaxies in the Perseus Cluster, located 250 million light-years away and one of the closest galaxy clusters to Earth. Of these galaxies, 17 are new discoveries.
Because dark matter cannot be seen, astronomers detected its presence through indirect evidence. The most common method is by measuring the velocities of individual stars or groups of stars as they move randomly in the galaxy or as they rotate around the galaxy. The Perseus Cluster is too far away for telescopes to resolve individual stars and measure their motions. So Conselice and his team derived a new technique for uncovering dark matter in these dwarf galaxies by determining the minimum additional mass contribution from dark matter that the dwarfs must have to protect them from being disrupted by the strong, tidal pull of gravity from larger galaxies.
Studying these small galaxies in detail was possible only because of the sharpness of Hubble's Advanced Camera for Surveys. Conselice and his team first spied the galaxies with the WIYN Telescope at Kitt Peak National Observatory. These observations, Conselice says, only hinted that many of the galaxies were smooth and therefore dark matter dominated. "Those ground-based observations could not resolve the galaxies, so we needed Hubble imaging to nail it," he says.
The Hubble results appeared in the 1 March issue of Monthly Notices of the Royal Astronomical Society.
Hubble Information Centre
Dark matter is an invisible form of matter that accounts for most of the Universe's mass. Astronomers have deduced the existence of dark matter by observing its gravitational influence on normal matter, such as stars, gas and dust.
"We were surprised to find so many dwarf galaxies in the core of this cluster that were so smooth and round and had no evidence at all of any kind of disturbance," says astronomer Christopher Conselice of the University of Nottingham, UK, and leader of the team that made the Hubble observations. "These dwarfs are very old galaxies that have been in the cluster for a long time. So if something was going to disrupt them, it would have happened by now. They must be very, very dark-matter-dominated galaxies."
The dwarf galaxies may have an even higher amount of dark matter than spiral galaxies. "With these results, we cannot say whether the dark matter content of the dwarfs is higher than in the Milky Way Galaxy," Conselice says. "Although, the fact that spiral galaxies are destroyed in clusters, while the dwarfs are not, suggests that this is indeed the case."
First proposed about 80 years ago by Swiss astronomer Fritz Zwicky, dark matter is thought to be the glue that holds galaxies together. Astronomers suggest that dark matter provides a vital scaffolding for the Universe, forming a framework for the formation of galaxies through gravitational attraction.
Observations by Hubble's Advanced Camera for Surveys spotted 29 dwarf elliptical galaxies in the Perseus Cluster, located 250 million light-years away and one of the closest galaxy clusters to Earth. Of these galaxies, 17 are new discoveries.
Because dark matter cannot be seen, astronomers detected its presence through indirect evidence. The most common method is by measuring the velocities of individual stars or groups of stars as they move randomly in the galaxy or as they rotate around the galaxy. The Perseus Cluster is too far away for telescopes to resolve individual stars and measure their motions. So Conselice and his team derived a new technique for uncovering dark matter in these dwarf galaxies by determining the minimum additional mass contribution from dark matter that the dwarfs must have to protect them from being disrupted by the strong, tidal pull of gravity from larger galaxies.
Studying these small galaxies in detail was possible only because of the sharpness of Hubble's Advanced Camera for Surveys. Conselice and his team first spied the galaxies with the WIYN Telescope at Kitt Peak National Observatory. These observations, Conselice says, only hinted that many of the galaxies were smooth and therefore dark matter dominated. "Those ground-based observations could not resolve the galaxies, so we needed Hubble imaging to nail it," he says.
The Hubble results appeared in the 1 March issue of Monthly Notices of the Royal Astronomical Society.
Hubble Information Centre
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When Europe's comet chaser Rosetta swings by Earth tomorrow for a critical gravity assist, tracking data will be collected to precisely measure the satellite's change in orbital energy. The results could help unravel a cosmic mystery that has stumped scientists for two decades.
Precise picture of early Universe supports 'dark matter' theory
A detailed picture of the seeds of structures in the universe has been unveiled by an international team co-led by a Cardiff University scientist.
Iowa State researchers contribute to discovery of gamma rays from starburst galaxy
Iowa State University astrophysicists contributed to the recent discovery that a galaxy quickly creating new stars is also a source of high energy gamma rays.
Science at the Petascale: Roadrunner Results Unveiled
The world's fastest supercomputer, Roadrunner, at Los Alamos National Laboratory has completed its initial "shakedown" phase doing accelerated petascale computer modeling and simulations of a variety of unclassified, fundamental science projects.
A solution to Darwin's 'mystery of the mysteries' emerges from the dark matter of the genome
Biological species are often defined on the basis of reproductive isolation. Ever since Darwin pointed out his difficulty in explaining why crosses between two species often yield sterile or inviable progeny (for instance, mules emerging from a cross between a horse and a donkey), biologists have struggled with this question.
Scientists use world's fastest supercomputer to model origins of the unseen universe
Understanding dark energy is the number one issue in explaining the universe, according to Salman Habib, of the Laboratory's Nuclear and Particle Physics, Astrophysics and Cosmology group.
Jumping genes, gene loss and genome dark matter
In research published today by Nature, an international team describes the finest map of changes to the structure of human genomes and a resource they have developed for researchers worldwide to look at the role of these changes in human disease.
Prototype developed to detect dark matter
A team of researchers from the University of Zaragoza (UNIZAR) and the Institut d'Astrophysique Spatiale (IAS, in France) has developed a "scintillating bolometer", a device that the scientists will use in efforts to detect the dark matter of the Universe, and which has been tested at the Canfranc Underground Laboratory in Huesca, Spain.
James Webb Space Telescope Begins to Take Shape at Goddard
NASA's James Webb Space Telescope is starting to come together. A major component of the telescope, the Integrated Science Instrument Module structure, recently arrived at NASA Goddard Space Flight Center in Greenbelt, Md. for testing in the Spacecraft Systems Development and Integration Facility.
Queen's physicist unlocking the mysteries of neighbouring galaxies
An international team of astronomers, including Queen's University physicist Larry Widrow, have uncovered evidence of a nearby cosmic encounter.
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