Problems in cosmology and the upcoming data avalanche !
Mike Hudson Physics and Astronomy mike.hudson@uwaterloo.ca
Cosmology As a Science
• Perhaps the fastest-moving field in Physics today … we are in the “Golden Age of Cosmology”
• Driven by observation, not theory
The building blocks: A Milky Way-like Galaxy
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Scale: 30 kpc = 100000 ly = 1021 m
Dark Matter Halo
300 kpc = 1 M lyr Dynamics indicates dark matter
What is it and how much is there?
CMB by Planck satellite 2013
N-body simulation of gravitational instability (Moore)
First Galaxies !
Hubble Ultradeep Field ! ! !
• 3 billion years to ~13 billion years ago ! !
• Seeing galaxies in the earliest stages of formation
Feedback
• It is commonly assumed that there must be
some form of “feedback” that heats the gas.
• Supernovae • Active Galactic Nuclei (AGN: black holes with accretion disks)
Composite of multi-wavelength images of the active galaxy M82. X-ray data recorded by Chandra appears here in blue; infrared light recorded by Spitzer appears in red; Hubble's observations of hydrogen emission appears in orange, and the bluest visible light appears in yellow-green.
Starburst galaxies eject winds
AGN can emit powerful jets
Jets blow “bubbles” in clusters From NASA press release
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This is a composite image of galaxy cluster MS0735.6+7421
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The optical view of the galaxy cluster, taken by the Hubble Space Telescope shows dozens of galaxies bound together by gravity. Diffuse, hot gas with a temperature of nearly 50 million degrees permeates the space between the galaxies. The gas emits X-rays, seen as blue in the image taken with the Chandra X-ray Observatory. The X-ray portion of the image shows enormous holes or cavities in the gas, each roughly 640,000 light-years in diameter -- nearly seven times the diameter of the Milky Way. The cavities are filled with charged particles gyrating around magnetic field lines and emitting radio waves shown in the red portion of image taken with the Very Large Array telescope. The cavities were created by jets of charged particles ejected at nearly light speed from a supermassive black hole weighing nearly a billion times the mass of our Sun lurking in the nucleus of the bright central galaxy. The jets displaced more than one trillion solar masses worth of gas. The power required to displace the gas exceeded the power output of the Sun by nearly ten trillion times in the past 100 million years.
Credit X-ray: NASA/CXC/Univ. Waterloo/B.McNamara Optical: NASA/ESA/STScI/Univ. Waterloo/B.McNamara Radio: NRAO/Ohio Univ./L.Birzan et al.
Challenges • Nature of Dark Matter and Dark Energy • How do galaxies form and evolve? • Feedback • Interactions • Star formation
The Coming Deluge of Data • Large-scale surveys will dominate the future of astronomy and cosmology
• EUCLID and WFIRST : European and NASA Satellites
• Ground-based: Large Synoptic Survey Telescope
LSST • 20,000 square degrees (half the sky) of the southern sky using an 8.4-meter ground-based telescope.
• Each patch of sky will be visited about 1000 times in ten years. • “The LSST leverages innovative technology in all subsystems: the
camera (3200 Megapixels, which will be the world's largest digital camera) … and data management (30 terabytes of data nightly, nearly instant alerts issued for objects that change in position or brightness).”
• Data will be public (Google) • Starting to take data ~2020 • Waterloo is a partner!
Data Analysis Challenges ! !
• GRavitatioanal lEnsing Accuracy Testing Challenge (GREAT)
• http://great3.projects.phys.ucl.ac.uk/ leaderboard/
Galaxy Zoo: Crowdsourced Morphologies
Summary • Broad range of problems and challenges
over a very wide range of physical and time scales.
• Upcoming data will be of unprecedented scale.
• New methods needed both to understand/ model the science and understand/reduce the data.