Examining Dark Energy With Dark Matter Lenses: The Large Synoptic Survey Telescope. Andrew R. Zentner University of Pittsburgh

Transcription

1 Examining Dark Energy With Dark Matter Lenses: The Large Synoptic Survey Telescope Andrew R. Zentner University of Pittsburgh 1

2 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

3 The Cosmic Energy Budget Normal Matter ΩBARYON = % Dark Energy ΩDE=0.70 Dark Matter ΩDM = % 70% 3

4 Dark Matter in the Coma Cluster of Galaxies Fritz Zwicky 4

5 Dark Matter in the Coma Cluster of Galaxies Fritz Zwicky Zwicky

6 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

7 Dark Matter in Disk Galaxies Velocities: Observed vs. Expected from Light Rotational Velocity V c (R) [km/s] Rotation Curve of F571!8 Baryonic Contribution 20 This problem of excessive rotation speeds is typical of disk galaxies R [kpc] Distance from Galactic Center 6

8 Dark Matter is Needed to Grow This... WMAP 7

9 ... into This Hubble Space Telescope Ultradeep Field 8

10 The Accelerating Universe 9

11 Dark Matter has become a fact of life, but there is something weirder 10

12 The Expanding Universe 11

13 The Expanding Universe The spectra of galaxies are shifted to longer wavelengths or redshifted 12

14 The Expanding Universe earlier time later time Einstein s theory of describes an expanding Universe 13

15 The Expanding Universe earlier time later time Wavelengths of light are stretched by the expansion, giving rise to the redshift 14

16 The Expanding Universe earlier time later time The amount of stretching, or redshift, gives the amount of cosmic expansion 14

17 The Expanding Universe earlier time later time For a given amount of expansion, or redshift, light travels farther in an accelerating Universe 14

18 Detecting Acceleration Type Ia Supernovae have a known intrinsic brightness, or luminosity 15

19 Acceleration Detected Supernovae with large redshifts are anomalously dim! cosmic acceleration! 16

20 Acceleration Detected The causative agent of acceleration has been dubbed Dark Energy, and we want to explore it 16

21 Dark Energy Is Weird! We Expect Bits of Matter to Pull Back On each Other due to gravity, SLOWING the expansion 17

22 Dark Energy Is Weird! Dark Energy Drives Ever Faster Expansion, Things Fly APART! 17

23 DEEPER, WIDER, FASTER 18

24 The Telescope and The LSST Survey 19

25 20

26 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

27 THE LSST: DESIGN A Truly Unique Mission Cost: $400 Million ( roughly 18 Iraq-hours) Three large mirrors, 8.4m primary (effective 6.7m) f/ field of view (enormous!) 3.2 Gigapixel Camera for 0.2 arcsec/pixel magnitude photometric precision 22

28 THE LSST: Mirror Construction mirror spinning began at 10:30PM March 28 23

29 THE LSST: Mirror The Furnace Was Opened July 23 to Reveal a Perfect Cast 24

30 LSST: The Site In Northern Chile C. Claver (NOAO) 25

31 LSST: The Survey Location: Northern Chile First Light: Fall , 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

32 The Power of LSST second exposures surveying power Etendue (m 2 deg 2 ) 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

33 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

34 A FLAGSHIP PROJECT OF THE LSST: Gravitational Lensing & Cosmic Acceleration 29

35 nasa HST 30

36 CFHT 31

37 Large Binocular Telescope 32

38 nasa HST 33

39 nasa HST 34

40 nasa HST 35

41 Lensing 36

42 A Gravitational Lens Image of Source actual source D LS : Lens-Source Distance D OL : Observer-Lens Distance 37

43 true galaxy position 38

44 ObserveD Galaxy Position 38

45 A Gravitational Lens Image of Source actual source D LS : Lens-Source Distance D OL : Observer-Lens Distance 39

46 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

47 There will be a Revolution 41

48 There will be a Revolution What will LSST actually teach us? 41

49 There will be a Revolution What will LSST actually teach us? 41

50 There will be a Revolution What will LSST actually teach us? The beauty of it is that we probably don t know! 41

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