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A Simulation Of The Universe With Realistic Galaxies

December 29, 2014 Leave a comment

Credit: J. Schaye et al. 2015

Credit: J. Schaye et al. 2015

The simulations took several months to run at the “Cosmology Machine” in Durham and at “Curie” in Paris, among the largest computers used for scientific research in the U.K. and France, respectively. Astronomers can now use the results to study the development of galaxies from almost 14 billion years ago until now. The results will be published in Monthly Notices of the Royal Astronomical Society on 1 January.

or years, astronomers have studied the formation of galaxies using computer simulations, but with limited success. The galaxies that formed in previous simulations were often too massive, too small, too old and too spherical.

The galaxies formed in the EAGLE-simulation (Evolution and Assembly of GaLaxies and their Environments) are a much closer reflection of real galaxies thanks to the strong galactic winds, which blow away the gas supply needed for the formation of stars. EAGLE’s galaxies are lighter and younger because fewer stars form and they form later. In the EAGLE simulation these galactic winds – which are powered by stars, supernova explosions and supermassive black holes – are stronger than in earlier simulations.

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NASA’s Chandra Weighs Most Massive Galaxy Cluster In Distant Universe

December 18, 2014 Leave a comment

Credit: X-ray: NASA/CXC/INAF/P.Tozzi, et al; Optical: NAOJ/Subaru and ESO/VLT; Infrared: ESA/Herschel

Credit: X-ray: NASA/CXC/INAF/P.Tozzi, et al; Optical: NAOJ/Subaru and ESO/VLT; Infrared: ESA/Herschel

Using NASA’s Chandra X-ray Observatory, astronomers have made the first determination of the mass and other properties of a very young, distant galaxy cluster.

The Chandra study shows that the galaxy cluster, seen at the comparatively young age of about 800 million years, is the most massive known cluster with that age or younger. As the largest gravitationally- bound structures known, galaxy clusters can act as crucial gauges for how the Universe itself has evolved over time.

The galaxy cluster was originally discovered using ESA’s XMM-Newton observatory and is located about 9.6 billion light years from Earth. Astronomers used X-ray data from Chandra that, when combined with scientific models, provides an accurate weight of the cluster, which comes in at a whopping 400 trillion times the mass of the Sun. Scientists believe the cluster formed about 3.3 billion years after the Big Bang.

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An Unprecedented View Of Two Hundred Galaxies Of The Local Universe

October 2, 2014 Leave a comment

Galaxies are the result of an evolutionary process started thousands of million years ago, and their history is coded in their distinct components. The CALIFA project is intended to decode the galaxies’ history in a sort of galactic archaeology, through the 3D observations of a sample of six hundred galaxies. With this second data release corresponding to two hundred galaxies, the project reaches its halfway point with important results behind.

The CALIFA Project allows not only to inspect the galaxies in detail, but it also provides with data on the evolution of each particular galaxy with time: how much gas and when was it converted into stars along each phase of the galaxy’s life, and how did each region of the galaxies evolve along the more than ten thousand million years of cosmic evolution.

Thanks to the CALIFA data, the astronomers have been able to deduce the history of the mass, luminosity and chemical evolution of the CALIFA sample of galaxies, and thus they have found that more massive galaxies grow faster than less massive ones, and that they form their central regions before the external ones (inside-out mass assembly).

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Interactive Dark Matter Could Explain Milky Way’s Missing Satellite Galaxies

September 11, 2014 Leave a comment

Scientists believe they have found a way to explain why there are not as many galaxies orbiting the Milky Way as expected. Computer simulations of the formation of our galaxy suggest that there should be many more small galaxies around the Milky Way than are observed through telescopes.

This has thrown doubt on the generally accepted theory of cold dark matter, an invisible and mysterious substance that scientists predict should allow for more galaxy formation around the Milky Way than is seen.

Now cosmologists and particle physicists at the Institute for Computational Cosmology and the Institute for Particle Physics Phenomenology, at Durham University, working with colleagues at LAPTh College & University in France, think they have found a potential solution to the problem.

Writing in the journal Monthly Notices of the Royal Astronomical Society, the scientists suggest that dark matter particles, as well as feeling the force of gravity, could have interacted with photons and neutrinos in the young Universe, causing the dark matter to scatter.

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Hawaii Scientist Maps, Names Laniakea, Our Home Supercluster Of Galaxies

September 3, 2014 Leave a comment

University of Hawaii at Manoa astronomer R. Brent Tully, who recently shared the 2014 Gruber Cosmology Prize and the 2014 Victor Ambartsumian International Prize, has led an international team of astronomers in defining the contours of the immense supercluster of galaxies containing our own Milky Way. They have named the supercluster “Laniakea,” meaning “immense heaven” in Hawaiian. The paper explaining this work is the cover story of the September 4 issue of the prestigious journal Nature.

Galaxies are not distributed randomly throughout the universe. Instead, they are found in groups, like our own Local Group, that contain dozens of galaxies, and in massive clusters containing hundreds of galaxies, all interconnected in a web of filaments in which galaxies are strung like pearls. Where these filaments intersect, we find huge structures, called “superclusters.” These structures are interconnected, but they have poorly defined boundaries.

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Mapping Dark Matter, 4.5 Billion light Years Away


Credit: ESA/Hubble, NASA, HST Frontier Fields

Credit: ESA/Hubble, NASA, HST Frontier Fields

Using the NASA/ESA Hubble Space Telescope, an international team of astronomers have mapped the mass within a galaxy cluster more precisely than ever before. Created using observations from Hubble’s Frontier Fields observing programme, the map shows the amount and distribution of mass within MCS J0416.1–2403, a massive galaxy cluster found to be 160 trillion times the mass of the Sun.

The detail in this ‘mass map’ was made possible thanks to the unprecedented depth of data provided by new Hubble observations, and the cosmic phenomenon known as strong gravitational lensing. The team, led by Dr Mathilde Jauzac of Durham University in the UK and the Astrophysics & Cosmology Research Unit in South Africa, publish their results in the journal Monthly Notices of the Royal Astronomical Society.

Measuring the amount and distribution of mass within distant objects in the Universe can be very difficult. A trick often used by astronomers is to explore the contents of large clusters of galaxies by studying the gravitational effects they have on the light from very distant objects beyond them. This is one of the main goals of Hubble’s Frontier Fields, an ambitious observing programme scanning six different galaxy clusters — including MCS J0416.1–2403.

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Hubble Shows Farthest Lensing Galaxy Yields Clues To Early Universe


Credit: NASA, ESA, K.-V. Tran (Texas A&M University), and K. Wong (Academia Sinica Institute of Astronomy & Astrophysics)

Credit: NASA, ESA, K.-V. Tran (Texas A&M University), and K. Wong (Academia Sinica Institute of Astronomy & Astrophysics)

Astronomers using NASA’s Hubble Space Telescope have unexpectedly discovered the most distant cosmic magnifying glass, produced by a monster elliptical galaxy. Seen here as it looked 9.6 billion years ago, this monster elliptical galaxy breaks the previous record holder by 200 million years. These “lensing” galaxies are so massive that their gravity bends, magnifies, and distorts light from objects behind them, a phenomenon called gravitational lensing.

The object behind the cosmic lens is a tiny spiral galaxy undergoing a rapid burst of star formation. Its light has taken 10.7 billion years to arrive here. Seeing this chance alignment at such a great distance from Earth is a rare find.

Locating more of these distant lensing galaxies will offer insight into how young galaxies in the early universe built themselves up into the massive dark-matter-dominated galaxies of today. Dark matter cannot be seen, but it accounts for the bulk of the universe’s matter.

“When you look more than 9 billion years ago in the early universe, you don’t expect to find this type of galaxy-galaxy lensing at all,” explained lead researcher Kim-Vy Tran of Texas A&M University in College Station. “It’s very difficult to see an alignment between two galaxies in the early universe.”

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