Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Key theory of galaxy formation no longer conflicts with observations

09.06.2004


Astrophysicists led by the University of Chicago’s Andrey Kravtsov have resolved an embarrassing contradiction between a favored theory of how galaxies form and what astronomers see in their telescopes.



Astrophysicists base their understanding of how galaxies form on an extension of the big bang theory called the cold dark matter theory. In this latter theory, small galaxies collide and merge, inducing bursts of star formation that create the different types of massive and bright galaxies that astronomers see in the sky today. (Dark matter takes its name from the idea that 85 percent of the total mass of the universe is made of unknown matter that is invisible to telescopes, but whose gravitational effects can be measured on luminous galaxies.)

This theory fits some key data that astrophysicists have collected in recent years. Unfortunately, when astrophysicists ran supercomputer simulations several years ago, they ended up with 10 times more dark matter satellites--clumps of dark matter orbiting a large galaxy--than they expected.


"The problem has been that the simulations don’t match the observations of galaxy properties," said David Spergel, professor of astrophysics at Princeton University. "What Andrey’s work represents is a very plausible solution to this problem."

Kravtsov and his collaborators found the potential solution in new supercomputer simulations they will describe in a paper that will appear in the July 10 issue of the Astrophysical Journal. "The solution to the problem is likely to be in the way the dwarf galaxies evolve," Kravtsov said, referring to the small galaxies that inhabit the fringes of large galaxies.

In general, astrophysicists believe that formation of very small dwarf galaxies should be suppressed. This is because gas required for continued formation of stars can be heated and expelled by the first generation of exploding supernovae stars. In addition, ultraviolet radiation from galaxies and quasars that began to fill the universe approximately 12 billion years ago heats the intergalactic gas, shutting down the supply of fresh gas to dwarf galaxies.

In the simulations, Kravtsov, along with Oleg Gnedin of the Space Telescope Science Institute and Anatoly Klypin of New Mexico State University, found that some of the dwarf galaxies that are small today have been more massive in the past and could gravitationally collect the gas they need to form stars and become a galaxy.

"The systems that appear rather feeble and anemic today could, in their glory days, form stars for a relatively brief period," Kravtsov said. "After a period of rapid mass growth, they lost the bulk of their mass when they experienced strong tidal forces from their host galaxy and other galaxies surrounding them."

This galactic "cannibalism" persists even today, with many of the "cannibalized" dwarf galaxies becoming satellites orbiting in the gravitational pull of larger galaxies.

"Just like the planets in the solar system surrounding the sun, our Milky Way galaxy and its nearest neighbor, the Andromeda galaxy, are surrounded by about a dozen faint ’dwarf’ galaxies," Kravtsov said. "These objects were pulled in by the gravitational attraction of the Milky Way and Andromeda some time ago during their evolution."

The simulations had succeeded where others had failed because Kravtsov’s team analyzed simulations that were closely spaced in time at high resolution. This allowed the team to track the evolution of individual objects in the simulations. "This is rather difficult and is not often done in analyses of cosmological simulations. But in this case it was the key to recognize what was going on and get the result," Kravtsov said.

The result puts the cold dark matter scenario on more solid ground. Scientists had attempted to modify the main tenets of the scenario and the properties of dark matter particles to eliminate the glaring discrepancy between theory and observation of dwarf galaxies. "It turns out that the proposed modifications introduced more problems than they solved," Kravtsov said.


The simulations were performed at the National Center for Supercomputer Applications, University of Illinois at Urbana-Champaign, with grants provided by the National Science Foundation and the National Aeronautics and Space Administration.

Steve Koppes | EurekAlert!
Further information:
http://www-news.uchicago.edu/

More articles from Physics and Astronomy:

nachricht Engineering team images tiny quasicrystals as they form
18.08.2017 | Cornell University

nachricht Astrophysicists explain the mysterious behavior of cosmic rays
18.08.2017 | Moscow Institute of Physics and Technology

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>