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  • richardmitnick 10:02 am on January 31, 2019 Permalink | Reply
    Tags: , , , , , Blue Waters supercomputer-National Center for Supercomputing Applications, , , Dark matter halos, Georgia Tech,   

    From Georgia Institute of Technology via Manu: “Birth of Massive Black Holes in the Early Universe Revealed “ 


    From Manu Garcia, a friend from IAC.

    The universe around us.
    Astronomy, everything you wanted to know about our local universe and never dared to ask.

    23/1/19

    John Toon
    Phone: 404-894-6986
    E – mail: jtoon@gatech.edu

    From Georgia Institute of Technology

    Renaissance simulations
    1
    This image shows a light region 30,000 years simulation Renaissance, centered on a group of young galaxies generating radiation (white) and metals (green) while heating the surrounding gas. A halo of dark matter just outside this region hot forms three stars supermassive (box), each more than 1,000 times the mass of our sun. The stars quickly collapse into massive black holes, and eventually supermassive black holes, for thousands of millions of years. Credits: Advanced Visualization Laboratory, National Center for Supercomputing Applications.

    The light released around the first massive black holes in the universe is so intense that it is capable of reaching telescopes across the expanse of the universe. Incredibly, the light of the most distant black holes (or quasars) has been traveling toward us for more than 13 billion light years. However, we do not know how these monstrous black holes were formed.

    New research led by researchers at the Institute of Technology of Georgia, Dublin University , the State University of Michigan , the University of California at San Diego , the Supercomputing Center San Diego and IBM offers a new and extremely promising way to solve this cosmic enigma. The team showed that when galaxies are assembled extremely fast, sometimes violently, that can lead to the formation of very massive black holes. In these rare galaxies, normal star formation stops taking over the formation of black holes.

    The new study finds that massive black holes are formed in dense regions without stars that are growing rapidly, turning to the accepted belief that massive black hole formation was limited to regions bombarded by powerful radiation of nearby galaxies. The findings of the study based on simulation, published Jan. 23 in the journal Nature and backed by funding from the National Science Foundation, the European Union and NASA also found that massive black holes are much more common in the universe than than previously thought.

    2
    This image shows the interior light 30 years of a halo of dark matter in a
    group of young galaxies. The rotating gaseous disk is broken into three groups that
    collapse under their own gravity to form supermassive stars.
    Credit: John Wise, Georgia Institute of Technology.

    The key criteria to determine where massive black holes were formed during the infancy of the universe are related to the rapid growth of cloud pre-galactic gas which are the precursors of all current galaxies, which means that most of the supermassive black holes have a common origin that forms in this new scenario discovered, said John Wise , an associate professor Center for Relativistic Astrophysics School of Physics at Georgia Tech and corresponding author of the article. Dark matter collapses into halos that are the gravitational glue to all galaxies. The rapid early growth of these halos prevented the formation of stars that would have competed with black holes for gaseous matter to flow into the area.

    Dark matter halo. Image credit: Virgo consortium / A. Amblard / ESA

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    “In this study, we have discovered an entirely new mechanism that triggers the formation of massive black holes in halos of dark matter in particular,” Wise said. “Instead of just considering radiation, we need to observe how quickly halos grow. We do not need much physics to understand, just how dark matter is distributed and how gravity will affect it. The formation of a massive black hole requires being in a rare region with intense convergence of matter. ”

    When the research team found these sites formation of black holes in the simulation, they felt puzzled at first, said John Regan, a researcher at the Center for Astrophysics and Relativity at the University of Dublin. The paradigm was previously accepted that black holes may be formed only when exposed to high levels of radiation nearby.


    This display was made from the region “RarePeak” Renaissance in the simulations that follow the formation of 800 galaxies in too dense region of the universe when it was only 270 million years. Blue and red are neutral (cold) and ionized gas (hot). White shows where galaxies are creating ultraviolet light, heating the surrounding intergalactic gas. This simulation was run on Blue Waters supercomputer at the National Center for Supercomputing Applications (NCSA).
    Credit: JH Wise (Georgia Tech), BW O’Shea (Michigan State), ML Norman (UCSD), H. Xu (UCSD)

    U Illinois Urbana-Champaign Blue Waters Cray Linux XE/XK hybrid machine supercomputer

    “Previous theories suggested that this should only happen when sites were exposed to high levels of star formation that kill radiation,” he said. “As we go deeper, we saw that these sites were experiencing a period of extremely rapid growth. That was the key. Violent and turbulent nature of rapid assembly, violent shock of the foundations of the galaxy during the birth of the galaxy prevented the normal formation of stars and resulted in perfect conditions for the formation of black holes. This research changes the previous paradigm and opens a new area of research. ”

    The above theory was based on the intense ultraviolet radiation from a nearby galaxy to inhibit the formation of stars in the halo forming a black hole, said Michael Norman, director of the Supercomputing Center San Diego at UC San Diego and one of the authors. “While UV radiation continues to be a factor, our work has shown that it is not the dominant factor, at least in our simulations,” he said.

    The research was based on the Renaissance Simulation suite, a set of 70 terabytes of data created in the supercomputer Blue Waters between 2011 and 2014 to help scientists understand how the universe evolved during its early years. To learn more about specific regions where it is likely that massive black holes are developed, researchers examined data from simulation and found ten halos specific dark matter that should have formed stars because of its mass but only contained a dense cloud of gas. Using TACC Stampede2 supercomputer, they returned to simulate two of these halos, each about 2,400 light-years in diameter, at a much higher resolution to understand the details of what was happening 270 million years after the Big Bang.

    TACC DELL EMC Stampede2 supercomputer

    Simulation of the Renaissance: Return to the normal region.

    This display in two parts by the Advanced Visualization Lab at the National Center for Supercomputing Applications begins shortly after the Big Bang and shows the evolution of the first galaxies in the universe during the first 400 million years, in increments of about 4 million years . The second part of the display stops time at the mark of 400 million years and makes the viewer revise the different variables that are displayed: dense gas filaments, bags of high temperature ionized gas and ultraviolet light. Credit: JH Wise (Georgia Tech), BW O’Shea (Michigan State), ML Norman (UCSD), H. Xu (UCSD)

    “It was only in these regions too dense universe that saw the formation of these black holes,” Wise said. “Dark matter creates most of gravity, and then the gas falls into the gravitational potential, which can form stars or a massive black hole.”

    Renaissance simulations are the most complete simulation of the early stages of the gravitational assembly pristine gas composed of hydrogen and helium and cold dark matter which leads to the formation of the first stars and galaxies. They use a technique known as adaptive mesh refinement to approach dense groups forming stars or black holes. In addition, covering a region of the early universe large enough to form thousands of objects, a requirement if you are interested in rare objects, as is the case here. “The high resolution, physical rich and the large sample collapsed halos were necessary to achieve this result,” Norman said.

    The improved resolution of the simulation carried out for two candidate regions allowed scientists to see the turbulence and gas inlet and clumps of matter formed as the precursors of the black hole began to condense and turn. Its growth rate was dramatic.

    “Astronomers observe supermassive black holes that have become a billion solar masses in 800 million years,” Wise said. “Doing that required an intense mass convergence in the region. It is expected in regions where galaxies were forming in very early times. ”

    Another aspect of the research is that the halos that give rise to black holes may be more common than previously believed.

    “An exciting component of this work is the discovery that these types of halos, though rare, can be common enough,” said Brian O’Shea, a professor at Michigan State University. “We predict that this scenario happen enough to be the source of the most massive black holes that are observed both in the early Universe as galaxies today.”

    Future work with these simulations will analyze the life cycle of these galaxies forming massive black holes, studying the formation, growth and evolution of the first massive black holes over time. “Our next goal is to investigate the future evolution of these exotic objects. Where are these black holes today? Can we detect evidence of them in the local Universe or gravitational waves?” Asked Regan.

    For these new responses, the research team and others can return to the simulations.

    “Renaissance Simulations are rich enough so that they can make other discoveries using already calculated data,” Norman said. “For this reason, we have created a public file containing SDSC Laboratory simulations of the Renaissance where others can solve their own questions.”

    This research was supported by the National Science Foundation through the PHY-1430152, AST-1514700, AST-161 433 and OAC-1835213 grants, subsidies NASA NNX12AC98G, 147 NNX15AP39G and NNX17AG23G, and the theory of Hubble HST -AR-13261.01, -AR-14315.001 HST and HST-AR-14326. This project has received funding of research and innovation program Horizon 2020 the European Union under Grant Agreement No 699941 (Marie Sklodowska-Curie Actions – “SmartStars). The simulation was performed at the Blue Waters supercomputer operated by the National Center for Supercomputing Applications (NCSA) supported PRAC allocation by the NSF (ACI award-0,832,662, 1,238,993 and ACI ACI-1514580). Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsoring organizations.

    Laboratory simulations of the Renaissance: https://rensimlab.github.io

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    The Georgia Institute of Technology, commonly referred to as Georgia Tech, is a public research university and institute of technology located in the Midtown neighborhood of Atlanta, Georgia. It is a part of the University System of Georgia and has satellite campuses in Savannah, Georgia; Metz, France; Athlone, Ireland; Shenzhen, China; and Singapore.

    The school was founded in 1885 as the Georgia School of Technology as part of Reconstruction plans to build an industrial economy in the post-Civil War Southern United States. Initially, it offered only a degree in mechanical engineering. By 1901, its curriculum had expanded to include electrical, civil, and chemical engineering. In 1948, the school changed its name to reflect its evolution from a trade school to a larger and more capable technical institute and research university.

    Today, Georgia Tech is organized into six colleges and contains about 31 departments/units, with emphasis on science and technology. It is well recognized for its degree programs in engineering, computing, industrial administration, the sciences and design. Georgia Tech is ranked 8th among all public national universities in the United States, 35th among all colleges and universities in the United States by U.S. News & World Report rankings, and 34th among global universities in the world by Times Higher Education rankings. Georgia Tech has been ranked as the “smartest” public college in America (based on average standardized test scores).

    Student athletics, both organized and intramural, are a part of student and alumni life. The school’s intercollegiate competitive sports teams, the four-time football national champion Yellow Jackets, and the nationally recognized fight song “Ramblin’ Wreck from Georgia Tech”, have helped keep Georgia Tech in the national spotlight. Georgia Tech fields eight men’s and seven women’s teams that compete in the NCAA Division I athletics and the Football Bowl Subdivision. Georgia Tech is a member of the Coastal Division in the Atlantic Coast Conference.

     
  • richardmitnick 2:03 pm on March 25, 2016 Permalink | Reply
    Tags: , , , Dark matter halos   

    From AAS NOVA: “Simulating Halos with the Caterpillar Project” 

    AASNOVA

    American Astronomical Society

    25 March 2016
    Susanna Kohler

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016
    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    The Caterpillar Project is a beautiful series of high-resolution cosmological simulations. The goal of this project is to examine the evolution of dark-matter halos like the Milky Way’s, to learn about how galaxies like ours formed. This immense computational project is still in progress, but the Caterpillar team is already providing a look at some of its first results.
    Lessons from Dark-Matter Halos

    Why simulate the dark-matter halos of galaxies? Observationally, the formation history of our galaxy is encoded in “galactic fossil record” clues, like the tidal debris from disrupted satellite galaxies in the outer reaches of our galaxy, or chemical abundance patterns throughout our galactic disk and stellar halo.

    But to interpret this information in a way that lets us learn about our galaxy’s history, we need to first test galaxy formation and evolution scenarios via cosmological simulations. Then we can compare the end result of these simulations to what we observe today.

    1
    This figure illustrates the difference that mass resolution makes. In the left panel, the mass resolution is 1.5*10^7 solar masses per particle. In the right panel, the mass resolution is 3*10^4 solar masses per particle [Griffen et al. 2016]

    A Computational Challenge

    Due to how computationally expensive such simulations are, previous N-body simulations of the growth of Milky-Way-like halos have consisted of only one or a few halos each. But in order to establish a statistical understanding of how galaxy halos form — and find out whether the Milky Way’s halo is typical or unusual! — it is necessary to simulate a larger number of halos.

    In addition, in order to accurately follow the formation and evolution of substructure within the dark-matter halos, these simulations must be able to resolve the smallest dwarf galaxies, which are around a million solar masses. This requires an extremely high mass resolution, which adds to the computational expense of the simulation.

    First Outcomes

    These are the challenges faced by the Caterpillar Project, detailed in a recently published paper led by Brendan Griffen (Massachusetts Institute of Technology). The Caterpillar Project was designed to simulate 70 Milky-Way-size halos (quadrupling the total number of halos that have been simulated in the past!) at a high mass resolution (10,000 solar masses per particle) and time resolution (5 Myr per snapshot). The project is extremely computationally intense, requiring 14 million CPU hours and 700 TB of data storage!

    2
    Mass evolution of the first 24 Caterpillar halos (selected to be Milky-Way-size at z=0). The inset panel shows the mass evolution normalized by the halo mass at z=0, demonstrating the highly varied evolution these different halos undergo. [Griffen et al. 2016]

    In this first study, the Griffen and collaborators show the end states for the first 24 halos of the project, evolved from a large redshift to today (z=0). They use these initial results to demonstrate the integrity of their data and the utility of their methods, which include new halo-finding techniques that recover more substructure within each halo.

    The first results from the Caterpillar Project are already enough to show clear general trends, such as the highly variable paths the different halos take as they merge, accrete, and evolve, as well as how different their ends states can be. Statistically examining the evolution of these halos is an important next step in providing insight into the origin and evolution of the Milky Way, and helping us to understand how our galaxy differs from other galaxies of similar mass. Keep an eye out for future results from this project!

    Bonus

    Check out this video of how the first 24 Milky-Way-like halos from the Caterpillar simulations form. Seeing these halos evolve simultaneously is an awesome way to identify the similarities and differences between them.


    Access mp4 video here .

    Citation

    Brendan F. Griffen et al 2016 ApJ 818 10. doi:10.3847/0004-637X/818/1/10
    If you access the science paper, you can see who is on the science team and the astronomical assets used in the study.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
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