COSMOS survey Archives

June 29, 2016June 30, 2016 by Matt Williams

Professor Stephen Hawking Intends To Map The Known Universe

In honor of Dr. Stephen Hawking, the COSMOS center will be creating the most detailed 3D mapping effort of the Universe to date. Credit: BBC, Illus.: T.Reyes

Back in 1997, a team of leading scientists and cosmologists came together to establish the COSMOS supercomputing center at Cambridge University. Under the auspices of famed physicist Stephen Hawking, this facility and its supercomputer are dedicated to the research of cosmology, astrophysics and particle physics – ultimately, for the purpose of unlocking the deeper mysteries of the Universe.

Yesterday, in what was themed as a “tribute to Stephen Hawking”, the COSMOS center announced that it will be embarking on what is perhaps the boldest experiment in cosmological mapping. Essentially, they intend to create the most detailed 3D map of the early universe to date, plotting the position of billions of cosmic structures including supernovas, black holes, and galaxies.

This map will be created using the facility’s supercomputer, located in Cambridge’s Department of Applied Mathematics and Theoretical Physics. Currently, it is the largest shared-memory computer in Europe, boasting 1,856 Intel Xeon E5 processor cores, 31 Intel Many Integrated Core (MIC) co-processors, and 14.5 terabytes of globally shared memory.

*The COSMOS IX supercomputer. Credit: cosmos.damtp.cam.ac.uk*

The 3D will also rely on data obtained by two previous surveys – the ESA’s Planck satellite and the Dark Energy Survey. From the former, the COSMOS team will use the detailed images of the Cosmic Microwave Background (CMB) – the radiation leftover by the Big Ban – that were released in 2013. These images of the oldest light in the cosmos allowed physicists to refine their estimates for the age of the Universe (13.82 billion years) and its rate of expansion.

This information will be combined with data from the Dark Energy Survey which shows the expansion of the Universe over the course of the last 10 billion years. From all of this, the COSMOS team will compare the early distribution of matter in the Universe with its subsequent expansion to see how the two link up.

While cosmological simulations that looked at the evolution and large-scale structure of the Universe have been performed in the past – such as the Evolution and Assembly of GaLaxies and their Environments (EAGLE) project and the survey performed by the Institute for the Physics and Mathematics of the Universe at Tokyo University – this will be the first time where scientists compare data the early Universe to its evolution since.

The project is also expected to receive a boost from the deployment of the ESA’s Euclid probe, which is scheduled for launch in 2020. This mission will measure the shapes and redshifts of galaxies (looking 10 billion years into the past), thereby helping scientists to understand the geometry of the “dark Universe” – i.e. how dark matter and dark energy influence it as a whole.

*Artist impression of the Euclid probe, which is set to launch in 2020. Credit: ESA*

The plans for the COSMOS center’s 3D map are will be unveiled at the Starmus science conference, which will be taking place from July 2nd to 27th, 2016, in Tenerife – the largest of the Canary Islands, located off the coast of Spain. At this conference, Hawking will be discussing the details of the COSMOS project.

In addition to being the man who brought the COSMOS team together, the theme of the project – “Beyond the Horizon – Tribute to Stephen Hawking” – was selected because of Hawking’s long-standing commitment to physics and cosmology. “Hawking is a great theorist but he always wants to test his theories against observations,” said Prof. Shellard in a Cambridge press release. “What will emerge is a 3D map of the universe with the positions of billions of galaxies.”

Hawking will also present the first ever Stephen Hawking Medal for Science Communication, an award established by Hawking that will be bestowed on those who help promote science to the public through media – i.e. cinema, music, writing and art. Other speakers who will attending the event include Neil deGrasse Tyson, Chris Hadfield, Martin Rees, Adam Riess, Rusty Schweickart, Eric Betzig, Neil Turok, and Kip Thorne.

Professor Hawking, flanked by , announcing the launch of the Stephen Hawking Medal for Science Communication, Dec. 16th, 2015. Credit: — Professor Hawking and colleagues from the Royal Society announcing the launch of the Stephen Hawking Medal for Science Communication, Dec. 16th, 2015. Credit: starmus.com

Naturally, it is hoped that the creation of this 3D map will confirm current cosmological theories, which include the current age of the Universe and whether or not the Standard Model of cosmology – aka. the Lambda Cold Dark Matter (CDM) model – is in fact the correct one. As Hawking is surely hoping, this could bring us one step closer to a Theory of Everything!

Further Reading: Cambridge News

October 27, 2011December 24, 2015 by Tammy Plotner

Galaxy Interactions Could Cause Overweight Black Holes

Two examples of galaxy pairs in the COSMOS survey (courtesy of the Chandra X-ray Center). The Hubble Space Telescope images show galaxies undergoing a close encounter (shown in gold). X-rays, as detected by Chandra, indicate which of the two galaxies hosts an AGN. In addition, diffuse X-ray emission from hot gas is present thus highlighting that such galaxy associations tend to reside in galaxy groups, an environment of rapid galaxy and black hole growth.

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Yep. It’s true. Almost all galaxies are guilty of having a supermassive black hole in their centers. Some even tip the scales at millions – or even billions – of times more mass than the Sun. However, how they came to be so weighty is a true enigma. Thanks to research done by Dr. John Silverman (IPMU) and the international COSMOS team, the Chandra X-Ray Observatory and the European Southern Observatory’s Very Large Telescope have revealed that galaxy interactions may be responsible for the growth of supermassive black holes – and they’ve left behind some very important clues…

If you’re big – you’re big. As a general rule, supermassive black holes like to hang out in massive galaxies. Their mass is usually directly related to the central bulge. Now the consensus is that massive galaxies gained their girth (at least in part) by mergers and interactions with smaller galaxies. This act of cannibalism in galactic evolution has been postulated to explain how matter gathers toward the middle, eventually resulting in a supermassive black hole.

How do we determine this? One way is to take a closer look at galaxies currently in merger as compared to ones in isolation. While the concept is easy, carrying out the test hasn’t been. A supermassive black hole leaves visual observations “blinded by the light” while a quasar can effectively “outshine” an entire host galaxy, leaving an interactor almost impossible to detect. But, like a bulging waistline, such interactions should distort the overall contours of the galaxy.

Now the COSMOS team might have an answer to the riddle.. by assuming a galaxy is interacting if it has a nearby neighbor. It’s a test that can happen without needing to know if distortion is present in optical images. What makes it possible are accurate distance measurements of about 20,000 galaxies in the COSMOS field as provided by the zCOSMOS redshift survey with the European Southern Observatory’s Very Large Telescope. Isolated galaxies are used to give a comparison sample to lay the foundation as to whether an active galactic nucleus is common to interacting galaxies. With help from NASA’s Chandra Observatory, X-ray observations pinpoint galaxies which host an AGN. The X-ray emission signature dominates in growing SMBHs and X-rays are capable of cutting through the gas and dust of star-forming regions.

In their report to The Astrophysical Journal the team states that galaxies in close pairs are twice as likely to harbor AGNs as compared to galaxies in isolation. This answer may prove that beginning galaxy interactions can lead to “enhanced black hole growth”. Because it’s not a drastically common occcurrance, it means that only about 20% of SMBHs that break the scale happen via a merger event and that “final coalescence” might also play a role.

One thing we do know is that galaxies and their black holes, like people and their waistlines, all get a little heavier with time.

Original Story Source: Institute for Physics and Mathematics of the Univserse.

March 26, 2010December 24, 2015 by Nancy Atkinson

Hubble Confirms Cosmic Acceleration with Weak Lensing

This image shows a smoothed reconstruction of the total (mostly dark) matter distribution in the COSMOS field, created from data taken by the NASA/ESA Hubble Space Telescope and ground-based telescopes.Credit: NASA, ESA, P. Simon (University of Bonn) and T. Schrabback (Leiden Observatory)

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Need more evidence that the expansion of the Universe is accelerating? Just look to the Hubble Space Telescope. An international team of astronomers has indeed confirmed that the expansion of the universe is accelerating. The team, led by Tim Schrabback of the Leiden Observatory, conducted an intensive study of over 446,000 galaxies within the COSMOS (Cosmological Evolution Survey) field, the result of the largest survey ever conducted with Hubble. In making the COSMOS survey, Hubble photographed 575 slightly overlapping views of the same part of the Universe using the Advanced Camera for Surveys (ACS) onboard the orbiting telescope. It took nearly 1,000 hours of observations.

In addition to the Hubble data, researchers used redshift data from ground-based telescopes to assign distances to 194,000 of the galaxies surveyed (out to a redshift of 5). “The sheer number of galaxies included in this type of analysis is unprecedented, but more important is the wealth of information we could obtain about the invisible structures in the Universe from this exceptional dataset,” said co-author Patrick Simon from Edinburgh University.

In particular, the astronomers could “weigh” the large-scale matter distribution in space over large distances. To do this, they made use of the fact that this information is encoded in the distorted shapes of distant galaxies, a phenomenon referred to as weak gravitational lensing. Using complex algorithms, the team led by Schrabback has improved the standard method and obtained galaxy shape measurements to an unprecedented precision. The results of the study will be published in an upcoming issue of Astronomy and Astrophysics.

The meticulousness and scale of this study enables an independent confirmation that the expansion of the Universe is accelerated by an additional, mysterious component named dark energy. A handful of other such independent confirmations exist. Scientists need to know how the formation of clumps of matter evolved in the history of the Universe to determine how the gravitational force, which holds matter together, and dark energy, which pulls it apart by accelerating the expansion of the Universe, have affected them. “Dark energy affects our measurements for two reasons. First, when it is present, galaxy clusters grow more slowly, and secondly, it changes the way the Universe expands, leading to more distant — and more efficiently lensed — galaxies. Our analysis is sensitive to both effects,” says co-author Benjamin Joachimi from the University of Bonn. “Our study also provides an additional confirmation for Einstein’s theory of general relativity, which predicts how the lensing signal depends on redshift,” adds co-investigator Martin Kilbinger from the Institut d’Astrophysique de Paris and the Excellence Cluster Universe.

The large number of galaxies included in this study, along with information on their redshifts is leading to a clearer map of how, exactly, part of the Universe is laid out; it helps us see its galactic inhabitants and how they are distributed. “With more accurate information about the distances to the galaxies, we can measure the distribution of the matter between them and us more accurately,” notes co-investigator Jan Hartlap from the University of Bonn. “Before, most of the studies were done in 2D, like taking a chest X-ray. Our study is more like a 3D reconstruction of the skeleton from a CT scan. On top of that, we are able to watch the skeleton of dark matter mature from the Universe’s youth to the present,” comments William High from Harvard University, another co-author.

The astronomers specifically chose the COSMOS survey because it is thought to be a representative sample of the Universe. With thorough studies such as the one led by Schrabback, astronomers will one day be able to apply their technique to wider areas of the sky, forming a clearer picture of what is truly out there.

Source: EurekAlert

Paper: Schrabback et al., ‘Evidence for the accelerated expansion of the Universe from weak lensing tomography with COSMOS’, Astronomy and Astrophysics, March 2010,