![Page 1: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/1.jpg)
What’s going on with Dark Energy?
Bill CarithersAspen 2008
![Page 2: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/2.jpg)
I assume you all know:
Dark energy?
Type Ia
Off by 1060
“worst prediction in the history of science”
Why now?
![Page 3: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/3.jpg)
GR on a slide
Simplify, simplify… homogeneous, isotropic, perfect fluid (stress-energy tensor becomes diagonal)
a is the (expansion) scale factor = 1/(1+ z)H is Hubble factor
curvature termthen
![Page 4: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/4.jpg)
OK, two slides
For acceleration, w < -1/3, cosmological constant implies w = -1
Define: c = 3 H02 /8G where H0 is the current value of Hubble const
/ c for each component (I.e., baryons, dark matter, dark energy, radiation)
Caution about astro-speakH0 = (100 km/s/Mpc) h
€
H(a) = H0 Ωma3 + Ωdea
3(1+w ) + Ωka2
In a flat universe,
€
i
i
∑ =1
Define: equation of state,
€
w =p
ρ
€
=−4πGρ (1+ 3w)
![Page 5: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/5.jpg)
What is it that we actually measure?
Answer: detailed expansion history of the universe.
Need two ingredientsDistance (equivalent to time=age) Red shift
![Page 6: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/6.jpg)
The program
Measure a(t) with standard rulers, candlesStrategy 1: Assume GR and extract dark
energy equation of stateIs it -1 ?Does it vary? w = w0 + wa (1- a) ?Need multiple techniques to sort out the
degeneraciesStrategy 2: Measure growth of structureCompare the results of the two strategies
as a consistency check on GR
€
a•
a= H0 Ωma
3 + (1− Ωm )a3(1+w )
![Page 7: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/7.jpg)
Measuring red shift
The precise way--spectral linesBut… takes a long time!
Photometric redshiftsQuick but accuracy limited to z > .03
![Page 8: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/8.jpg)
BAO
baryons
baryons
photons
photons
150 Mpc
Thanks to Martin White for graphics
By here, photons have de-coupled and arefree-streaming to become CMBBaryons stall
![Page 9: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/9.jpg)
BAO first measurementSpectroscopic survey of 55000LRG’s from SDSS, <z> = 0.35(Eisenstein, et al. 2005)
Scaled correlation
BAO is same physics as CMB butmuch smaller effect and harder tomeasure so what’s the point?
The point is that it is at very different redshift, z<3 (CMB is z=1100)•Stake through the heart of curvature (or discovery!)•Relevant region for emergence of dark energy and relatively free of
astrophysical complications (galaxy counting exeriment)•Need sub-percent (spectrographic) accuracy on redshift-- photo-z
not good enough
![Page 10: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/10.jpg)
QuickTime™ and a decompressor
are needed to see this picture.
BAO future
QuickTime™ and a decompressor
are needed to see this picture.
Shameless plug
Baryon Oscillation Spectrographic Survey (BOSS)•Next step in SDSS •Big collaboration led by LBNL (David Schlegel)
Stage IV: ADEPT (a JDEM proposal) 1<z<2, 30,000 sq deg
![Page 11: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/11.jpg)
Weak gravitational lensing
![Page 12: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/12.jpg)
WL--geometry and structure
Thanks to Gary Bernstein
Measures expansion history andgrowth of structure
![Page 13: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/13.jpg)
WL tomography
z
dec
RA
From HST COSMOS field, Massey et al., 2007
![Page 14: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/14.jpg)
Dark energy current status
Assumes flat universe and constant w
Adding “all” the data:w0 = -1.04 ± 0.06
Still after all those years
![Page 15: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/15.jpg)
JDEM and BEPAC
NASA to NRC: “Which of these should go first(FY09)?”
NRC to NASA: “JDEM” (with LISA 2nd)
![Page 16: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/16.jpg)
BEPAC considered 3 JDEM candidates
ADEPTBAO for 1< z <2, 30000 sq deg
DESTINYIa SN using slitless spectrometerWeak lensing over 1000 sq deg
SNAP2000 well-measured Ia SN (imaging + spectro)Weak lensing over 4000 sq deg
BEPAC: importance of “other science”
![Page 17: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/17.jpg)
JDEM next steps
DOE and NASA working to formulate a call for proposals (Announcement of Opportunity[AO] in NASA-speak)
AO released in 2008Selection in 2009Launch in 2014
![Page 18: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/18.jpg)
… and in conclusion
![Page 19: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/19.jpg)
2008 2010 2012 2014 2016 2018 2020Ground based
PanStarrs
BOSS
DES
LSST
WFMOS/Subaru
WL, Sn
BAO
WL, Sn,clusters(with SPT)
BAO
WL, Sn
Space based
Planck
SNAP
LISA
CMBWL, Sn
GW
? wa , k =0|1+w0 |>.15
|wa | >.3Or
wa =0 &|1+w0 |>.03
wa =0|1+w0 |>.08
Bill’s crystal ball roadmap
Sensitivity to wa
![Page 20: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/20.jpg)
Breaking news
INTEGRAL 511 KeV high resolution map of galactic centerDoesn’t look good for dark matter annihilation, but seems tocorrelate with low mass X-ray binaries
![Page 21: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/21.jpg)
But wait, there’s more
Last week at the AAS meeting, NASA administrator Michael Griffin gave a speech where he revealed that, in response to the language in the Congressional Omnibus bill, he has asked BEPAC to rank JDEM against AMS
![Page 22: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/22.jpg)
Toolbox for surveying the expansion history
Red shiftStandard candle (luminosity
distance) from Type Ia SNStandard ruler (CMB and Baryon
Acoustic Oscillations)Weak gravitational lensingStandard siren (if I have time)
![Page 23: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/23.jpg)
WL--ellipticity to cosmology
Each “whisker” is an averaged measured galaxy ellipticity
photo-z goodenough
![Page 24: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/24.jpg)
WL --current status
Really just getting started. Not a huge impact on cosmology yetLong-term could be the most powerful technique
LCDM
![Page 25: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/25.jpg)
Gravitational waves as standard sirens
QuickTime™ and a decompressor
are needed to see this picture.
LISA
≈ 1% distance
Problem for redshiftPointing accuracy is poor105 galaxies in error box
Binary black hole inspiral is“absolutely calibrated” source strength
![Page 26: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/26.jpg)
BAO with neutral hydrogen
Or do a 21 cm survey
![Page 27: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/27.jpg)
CMB, a standard ruler
Flat space?
Moral 2: Unless you assume curvature is =0 on religious (read inflation) grounds,it is a complication so keep it in mind when you see results quoted
Moral: For CMB, there is a degeneracy betweenCurvature and knowledge of Hubble parameter
QuickTime™ and a decompressor
are needed to see this picture.
![Page 28: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/28.jpg)
No sensitivity to wa yet
QuickTime™ and a decompressor
are needed to see this picture.
![Page 29: What’s going on with Dark Energy? Bill Carithers Aspen 2008](https://reader035.vdocument.in/reader035/viewer/2022062809/56649f165503460f94c2bb54/html5/thumbnails/29.jpg)
€
a•
a= H0 Ωma
3 + (1− Ωm )a3(1+w )