Examining Dark Energy With Dark Matter Lenses: The Large Synoptic Survey Telescope Andrew R. Zentner University of Pittsburgh 1
Overview The contents of the Universe The accelerating Universe and Dark Energy! The Large Synoptic Survey Telescope (LSST) Survey Gravitational Lensing and the LSST program to uncover the nature of Dark Energy 2
The Cosmic Energy Budget Normal Matter ΩBARYON = 0.04 4% Dark Energy ΩDE=0.70 Dark Matter ΩDM = 0.26 26% 70% 3
Dark Matter in the Coma Cluster of Galaxies Fritz Zwicky 4
Dark Matter in the Coma Cluster of Galaxies Fritz Zwicky Zwicky 1937 4
Dark Matter in the Andromeda Galaxy Vera Rubin The rotation speed of the Andromeda disk (~250 km/s) is much larger than expected from its light output (Rubin & Ford 1970) 5
Dark Matter in Disk Galaxies Velocities: Observed vs. Expected from Light Rotational Velocity V c (R) [km/s] 160 140 120 100 80 60 40 Rotation Curve of F571!8 Baryonic Contribution 20 This problem of excessive rotation speeds is typical of disk galaxies 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 R [kpc] Distance from Galactic Center 6
Dark Matter is Needed to Grow This... WMAP http://map.gsfc.nasa.gov 7
... into This Hubble Space Telescope Ultradeep Field 8
The Accelerating Universe 9
Dark Matter has become a fact of life, but there is something weirder 10
The Expanding Universe 11
The Expanding Universe The spectra of galaxies are shifted to longer wavelengths or redshifted 12
The Expanding Universe earlier time later time Einstein s theory of describes an expanding Universe 13
The Expanding Universe earlier time later time Wavelengths of light are stretched by the expansion, giving rise to the redshift 14
The Expanding Universe earlier time later time The amount of stretching, or redshift, gives the amount of cosmic expansion 14
The Expanding Universe earlier time later time For a given amount of expansion, or redshift, light travels farther in an accelerating Universe 14
Detecting Acceleration Type Ia Supernovae have a known intrinsic brightness, or luminosity 15
Acceleration Detected Supernovae with large redshifts are anomalously dim! cosmic acceleration! 16
Acceleration Detected The causative agent of acceleration has been dubbed Dark Energy, and we want to explore it 16
Dark Energy Is Weird! We Expect Bits of Matter to Pull Back On each Other due to gravity, SLOWING the expansion 17
Dark Energy Is Weird! Dark Energy Drives Ever Faster Expansion, Things Fly APART! 17
DEEPER, WIDER, FASTER 18
The Telescope and The LSST Survey 19
20
THE LSST: WIDE, DEEP, & FAST Primary mirror diameter Field of view 10 m 0.2 degrees W. M. Keck Telescopes 3.5 degrees LSST 8.4 m 21
THE LSST: DESIGN A Truly Unique Mission Cost: $400 Million ( roughly 18 Iraq-hours) Three large mirrors, 8.4m primary (effective 6.7m) f/1.2 3.5 field of view (enormous!) 3.2 Gigapixel Camera for 0.2 arcsec/pixel 0.001 magnitude photometric precision 22
THE LSST: Mirror Construction mirror spinning began at 10:30PM March 28 23
THE LSST: Mirror The Furnace Was Opened July 23 to Reveal a Perfect Cast 24
LSST: The Site In Northern Chile C. Claver (NOAO) 25
LSST: The Survey Location: Northern Chile First Light: Fall 2014 2, 15 second exposures on each visit Cover the entire half sky (20,000 sq. deg.) every 3-5 days, (rinse) and repeat Lifetime: about 10 years Gather images of 10 Billion galaxies, many more than 100 times fainter than with the Sloan Digital Sky Survey 2 TB of data every hour! 26
The Power of LSST 320 15 second exposures surveying power Etendue (m 2 deg 2 ) 280 240 200 160 120 80 2000 Exposures per Field Covering 1/2 of sky 40 0 LSST PS4 PS1 Subaru CFHT SDSS MMT DES x0.3 4m VST VISTA IR SNAP x2 Endorsed by the National Academy of Sciences 27
LSST will determine the orbits of all Near Earth Objects larger than 150m across This demanding project requires mapping the entire visible sky down to 24 th magnitude every few days, with individual exposures of less than 15 seconds An Aside 28
A FLAGSHIP PROJECT OF THE LSST: Gravitational Lensing & Cosmic Acceleration 29
nasa HST 30
CFHT 31
Large Binocular Telescope 32
nasa HST 33
nasa HST 34
nasa HST 35
Lensing 36
A Gravitational Lens Image of Source actual source D LS : Lens-Source Distance D OL : Observer-Lens Distance 37
true galaxy position 38
ObserveD Galaxy Position 38
A Gravitational Lens Image of Source actual source D LS : Lens-Source Distance D OL : Observer-Lens Distance 39
The Upshot Is... With the power of LSST, we could measure the cosmic shearing of as many as 10 Billion galaxies! Such a measurement could increase the precision of measurements of cosmic acceleration a hundredfold! This is our best shot at a revolution in our understanding of cosmic acceleration and the Dark Energy 40
There will be a Revolution 41
There will be a Revolution What will LSST actually teach us? 41
There will be a Revolution What will LSST actually teach us? 41
There will be a Revolution What will LSST actually teach us? The beauty of it is that we probably don t know! 41
http://www.lsst.org 42