Motions in nearby galaxy cluster reveal presence of hidden superstructure

Sep 10, 2004
Motions in nearby galaxy cluster

A nearby galaxy cluster is facing an intergalactic headwind as it is pulled by an underlying superstructure of dark matter, according to new evidence from NASA's Chandra X-ray Observatory. Astronomers think most of the matter in the universe is concentrated in long large filaments of dark matter and that galaxy clusters are formed where these filaments intersect. The Marshall Center manages the Chandra program.

A nearby galaxy cluster is facing an intergalactic headwind as it is pulled by an underlying superstructure of dark matter, according to new evidence from NASA's Chandra X-ray Observatory. Astronomers think that most of the matter in the universe is concentrated in long large filaments of dark matter and that galaxy clusters are formed where these filaments intersect.

A Chandra survey of the Fornax galaxy cluster revealed a vast, swept-back cloud of hot gas near the center of the cluster. This geometry indicates that the hot gas cloud, which is several hundred thousand light years in length, is moving rapidly through a larger, less dense cloud of gas. The motion of the core gas cloud, together with optical observations of a group of galaxies racing inward on a collision course with it, suggests that an unseen, large structure is collapsing and drawing everything toward a common center of gravity.

"At a relatively nearby distance of about 60 million light years, the Fornax cluster represents a crucial laboratory for studying the interplay of galaxies, hot gas and dark matter as the cluster evolves." said Caleb Scharf of Columbia University in New York, NY, lead author of a paper describing the Chandra survey that was presented at an American Astronomical Society meeting in New Orleans, LA. "What we are seeing could be associated directly with the intergalactic gas surrounding a very large scale structure that stretches over millions of light years."

The infalling galaxy group, whose motion was detected by Michael Drinkwater of the University of Melbourne in Australia, and colleagues, is about 3 million light years from the cluster core, so a collision with the core will not occur for a few billion years. Insight as to how this collision will look is provided by the elliptical galaxy NGC 1404 that is plunging into the core of the cluster for the first time. As discussed by Scharf and another group led by Marie Machacek of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., the hot gas cloud surrounding this galaxy has a sharp leading edge and a trailing tail of gas being stripped from the galaxy.

"One thing that makes what we see in Fornax rather compelling is that it looks a lot like some of the latest computer simulations," added Scharf. "The Fornax picture, with infalling galaxies, and the swept back geometry of the cluster gas — seen only with the Chandra resolution and the proximity of Fornax — is one of the best matches to date with these high-resolution simulations."

Over the course of hundreds of millions of years, NGC 1404's orbit will take it through the cluster core several times, most of the gas it contains will be stripped away, and the formation of new stars will cease. In contrast, galaxies that remain outside the core will retain their gas, and new stars can continue to form. Indeed, Scharf and colleagues found that galaxies located in regions outside the core were more likely to show X-ray activity that could be associated with active star formation.

The wide-field and deep X-ray view around Fornax was obtained through ten Chandra pointings, each lasting about 14 hours. Other members of the research team were David Zurek of the American Museum of Natural History, New York, NY, and Martin Bureau, a Hubble Fellow currently at Columbia.

NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA's Office of Space Science, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

Additional information and images are available at: chandra.harvard.edu

Explore further: Observing the onset of a magnetic substorm

add to favorites email to friend print save as pdf

Related Stories

Evidence for supernovas near Earth

Aug 27, 2014

Once every 50 years, more or less, a massive star explodes somewhere in the Milky Way. The resulting blast is terrifyingly powerful, pumping out more energy in a split second than the sun emits in a million ...

Best view yet of merging galaxies in distant universe

Aug 26, 2014

Using the Atacama Large Millimeter/submillimeter Array, and other telescopes, an international team of astronomers has obtained the best view yet of a collision that took place between two galaxies when the ...

A possible signal from dark matter?

Aug 12, 2014

(Phys.org) —Galaxies are often found in groups or clusters, the largest known aggregations of matter and dark matter. The Milky Way, for example, is a member of the "Local Group" of about three dozen galaxies, ...

A spectacular landscape of star formation

Aug 20, 2014

This image, captured by the Wide Field Imager at ESO's La Silla Observatory in Chile, shows two dramatic star formation regions in the Milky Way. The first, on the left, is dominated by the star cluster NGC ...

Swirling electrons in the whirlpool galaxy

Aug 20, 2014

The whirlpool galaxy Messier 51 (M51) is seen from a distance of approximately 30 million light years. This galaxy appears almost face-on and displays a beautiful system of spiral arms.

Recommended for you

Observing the onset of a magnetic substorm

15 hours ago

Magnetic substorms, the disruptions in geomagnetic activity that cause brightening of aurora, may sometimes be driven by a different process than generally thought, a new study in the Journal of Geophysical Research: Space Ph ...

We are all made of stars

17 hours ago

Astronomers spend most of their time contemplating the universe, quite comfortable in the knowledge that we are just a speck among billions of planets, stars and galaxies. But last week, the Australian astronomical ...

ESA video: The ATV-5 Georges Lemaitre loading process

18 hours ago

This time-lapse video shows the ATV-5 Georges Lemaitre loading process and its integration on the Ariane 5 launcher before its transfer and launch to the International Space Station from Europe's Spaceport in Kourou, French ...

Raven soars through first light and second run

19 hours ago

Raven, a Multi-Object Adaptive Optics (MOAO) science demonstrator, successfully saw first light at the Subaru Telescope on the nights of May 13 and 14, 2014 and completed its second run during the nights ...

Titan's subsurface reservoirs modify methane rainfall

20 hours ago

(Phys.org) —The international Cassini mission has revealed hundreds of lakes and seas spread across the icy surface of Saturn's moon Titan, mostly in its polar regions. These lakes are filled not with water ...

User comments : 0