Their detailed maps show the ‘local’ cosmos out to a distance of 600 million light years, identifying all the major superclusters of galaxies and voids. They also provide important clues regarding the distribution of the mysterious ‘dark matter’ and ‘dark energy’ which are thought to account for up to 96% of the apparent mass of the Universe.
The reconstructed density fields in the supergalactic coordinates (SGX, SGY). In this coordinate system, the equator is aligned with the Virgo Cluster, Great Attractor and Perseus-Pisces superclusters. The main overdensities are Hydra-Centaurus (centre-left), Perseus-Pisces (centre-right), Shapley Concentration (upper left), Coma (upper-middle).
Within this vast volume, the most massive galaxy supercluster is 400 million light years away. It was named after its identifier, the American astronomer Harlow Shapley. The Shapley supercluster is so big that it takes light at least 20 million years to travel from its one end to the other. However, Shapley is not the only massive supercluster in our vicinity.
The Great Attractor supercluster, which is three times closer than Shapley, plays a bigger role in the motion of our Galaxy. According to the team, our Milky Way galaxy, its sister galaxy Andromeda and other neighbouring galaxies are moving towards the Great Attractor at an amazing speed of about a million miles per hour. The researchers also established that the Great Attractor is indeed an isolated supercluster and is not part of Shapley.
The new maps are based on the observation that, as the Universe expands, the colours of galaxies change as their emitted light waves are stretched or “redshifted”. By measuring the extent of this redshift, astronomers are able to calculate approximate distances to galaxies.
The new survey, known as the 2MASS Redshift Survey (2MRS), has combined two dimensional positions and colours from the Two Micron All Sky Survey (2MASS), with redshifts of 25,000 galaxies over most of the sky. These redshifts were either measured specifically for the 2MRS or they were obtained from an even deeper survey of the southern sky, the 6dF Galaxy Redshift Survey (6dFGS).
The great advantage of 2MASS is that it detects light in the near-infrared, at wavelengths slightly longer than the visible light. The near-infrared waves are one of the few types of radiation that can penetrate gases and dust and that can be detected on the Earth’s surface. Although the 2MRS does not probe as deeply into space as other recent narrow-angle surveys, it covers the entire sky.
Galaxy redshift surveys are only able to detect luminous matter. This luminous matter accounts for no more than a small fraction of the total matter in the Universe. The remainder is composed of a mysterious substance called ‘dark matter’ and an even more elusive component named ‘dark energy’.
“We need to map the distribution of dark matter rather than luminous matter in order to understand large-scale motions in our Universe,” explained Dr. Pirin Erdogdu (Nottingham University), lead author of the paper. “Fortunately, on large scales, dark matter is distributed almost the same way as luminous matter, so we can use one to help unravel the other.”
Her collaborator, Dr. Thomas Jarrett from Caltech, added, “The other advantage of observing in the near-infrared wavelength is the fact that it traces directly the luminous matter, and thus the dark matter, as well.”
“Our nearly two decade effort has produced the absolute best ever map of the nearby Universe,” said Prof. John Huchra of Harvard University. “With this we hope to elucidate the nature and disposition of dark matter and understand much, much more about our cosmological model and about galaxies themselves.”
In order to map the dark matter probed by the survey, the team used a novel technique borrowed from image processing. The method was partly developed by Prof. Ofer Lahav, a co-author of the paper and head of the astrophysics group at University College London. The technique utilizes the relationship between galaxy velocities and the total distribution of mass.
“It is like reconstructing the true street map of London just from a satellite image of London taken at night. The street lights, like the luminous galaxies, act as beacons of the underlying roads,” said Prof. Lahav.
"This extraordinarily detailed map of the Milky Way’s cosmic neighbourhood provides a benchmark against which theories for the formation of structure in the Universe can be tested,” commented Prof. Matthew Colless, director of the Anglo-Australian Observatory and leader of the 6dF Galaxy Survey.
“In the near future, the predicted motions derived from this map will be confronted with direct measurements of galaxies’ velocities obtained by the 6dF Galaxy Survey, providing a new and stringent test of cosmological models.”
Dr. Pirin Erdogdu | alfa
Study offers new theoretical approach to describing non-equilibrium phase transitions
27.04.2017 | DOE/Argonne National Laboratory
SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
27.04.2017 | Life Sciences
27.04.2017 | Physics and Astronomy
27.04.2017 | Earth Sciences