Baryon Acoustic Oscillations

1
Baryon Acoustic Oscillations

• SDSS, DES, WFMOS teams

2
Evidence for Dark Energy

• LSS
• CMB Sne
• Cluster baryon fractions
• ISW effect
• Lensing experiments (strong weak)
• Ages of ellipticals

3
Understanding Dark Energy
Observers Prospective

• We can make progress on questions
• Is DE just a cosmological constant (w(z)-1)?
• (Make better observations and push to higher z)
• Is DE a new form of matter (with negative
  effective pressure) or a breakdown of GR?
• (Study DE using different probes)
• But there are only two broad avenues
• Geometrical tests (SN, BAO)
• Growth of structure (ISW, lensing, clusters)

No compelling theory, must be observational driven
4
Massive Surveys
Need large surveys of the Universe to measure DE
accurately
SDSS / SDSS-II / AS2 SDSS SN
Survey Baryon Acoustic Oscillations
(BAO) Dark Energy Survey (DES) New SN
Survey WFMOS Future BAO measurements
5
SDSSwww.sdss.org
SDSSwww.sdss.org.uk/dr5
DR5 Million spectra, 8000 sq degs Extension
(2005-2008) Legacy, SNe, Galaxy
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Baryon Acoustic Oscillations
baryons
photons
Initial fluctuation in DM. Sound wave driven out
by intense pressure at 0.57c.
Courtesy of Martin White
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Baryon Acoustic Oscillations
baryons
photons
After 105 years, we reach recombination and
photons stream away leaving the baryons behind
Courtesy of Martin White
8
Baryon Acoustic Oscillations
baryons
photons
Photons free stream, while baryons remain still
as pressure is gone
Courtesy of Martin White
9
Baryon Acoustic Oscillations
baryons
photons
Photons almost fully uniform, baryons are
attracted back by the central DM fluctuation
Courtesy of Martin White
10
Baryon Acoustic Oscillations
baryons
photons
Fourier transform gives sinusoidal function
Today. Baryons and DM in equilibrium. The final
configuration is the original peak at the center
and an echo roughly 100Mpc in radius
Courtesy of Martin White
11
Baryon Acoustic Oscillations
Many superimposed waves. See them statistically

• Positions predicted once (physical) matter and
  baryon density known - calibrated by the CMB.
• Oscillations are sharp, unlike other features of
  the power spectrum

Daniel Eisenstein
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Baryon Acoustic Oscillations
?m0.24 best fit WMAP model
Miller et al. 2001, Percival et al. 2001,
Tegmark et al. 2001, 2006 Cole et al. 2005,
Eisenstein et al. 2005, Hutsi 2006, Blake et
al. 2006, Padmanabhan et al. 2006
WMAP3
Power spectrum of galaxy clustering. Smooth
component removed
Percival et al. 2006
SDSS DR5 520k galaxies
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Cosmological Constraints
Standard ruler (flat,h0.73,?b0.17)
99.74 detection
Percival et al. (2006)
h0.720.08 HST ?m0.2560.049-0.029
Best fit ?m0.26
Sullivan et al. (2003)
?m0.275h WMAP3 ?m0.2560.029-0.024
?mh2 WMAP3 ?m0.2560.019-0.023
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BAO with Redshift
Measure ratio of angular-diameter distance
between these redshifts (D0.35 /D0.2) D0.35
/D0.2 1.812 0.060 Flat ?CDM
1.67 Systematics (damping, BAO fitting) also
1???Next set of measurements will need to worry
about this
99.74 detection
z0.2
143k 465k
79k
z0.35
Percival et al. (2006)
Percival et al. 2007
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Cosmological Constraints
Flatness assumed, constant w
With CMB
Only D0.35 /D0.2
W
3?
1?
Favors wlt-1 at 1.4?
2?
?m
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Cosmological Constraints
Flatness assumed
?m 0.249 0.018 w -1.004 0.089
With CMB
Only D0.35 /D0.2
W
W
3?
1?
D0.35 /D0.2 1.66 0.01
2?
?m
?m
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Discrepancy! What Discrepancy?

• 2.4? difference between SN BAO. The BAO want
  more acceleration at zlt0.3 than predicted by
  zgt0.3 SNe (revisit with SDSS SNe)
• 1? possible from details of BAO damping - more
  complex then we thought
• Assumption of flatness and constant w needs to
  be revisited

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SDSS SN Survey

• Use the SDSS 2.5m telescope
• September 1 - November 30 of 2005-2007
• Scan 300 square degrees of the sky every 2 days
• Data reduced in less than 24hours
• Stripe82 (UKIDSS data)
• Many telescopes used for spectroscopic follow-up
  (NTT, NOT)

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Redshift and Cadence
325 spectro Ias 31 spectro probable Ias 80
photo Ias with host z 14 spectro Ib/c 30 spectro
II
Interval between observations of same object
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SN Rate
SNLS
SDSS
SN Rate (z lt 0.12) 2.9 ? 0.7stat ? 0.3syst
?10-5 (Mpc/h70)?3 yr?1
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After SDSSII (AS2)
Baryon Oscillation Spectroscopic Survey (BOSS)

• Measure distance to 1 at z0.35 and z0.6
• 10000 deg2 with 1.5m LRGs to 0.2ltzlt0.8
• 160k quasars at 2.3ltzlt2.8
• Starting 2009
• h to 1 with SDSS SNe

2SLAQ (www.2slaq.info)
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Conclusions

• SDSS BAO measures are delivering sub 10
  measurements of cosmological parameters
• 2? discrepancy with SNe? Curvature / w(z)? Eager
  to test with SDSS SNe
• SDSS plans to continue until 2014 with definitive
  BAO measurement at zlt0.7

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Future Dark Energy Survey

• DETF Terminology
• Stage II are experiments going on now (most are
  still limited by statistics and systematics)
• Stage III are next generation (before end of
  decade). Investigate systematics and gain factor
  of gt3
• Stage IV are next decade and gain factor of 10

Trotta Bower PPARC Report / Peacock et al.
report from ESA/ESO WG
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DETF Report (Kolb et al)
138 pages condensed to this column
SN BAO - safe, but only 100 improvement CL
WL - risky, but big gains
Clear recommendation to do multiple measurement
with one being the growth of structure to test GR
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Dark Energy Survey (DES)

• 5000 sq deg multiband (g,r,i,z) survey of SGP
  using CTIO Blanco with a new wide-field camera
• 9 sq deg time domain search for SNe
• Cluster counts from opticalSPT
• Weak lensing maps
• SNe Ia distance measurement study from 1400 SNe
• Galaxy angular power spectrum for 300 million
  galaxies
• Each will independently constrain the dark energy
  eqn of state lt10
• DES on-sky by 2010

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The Dark Energy Survey UK Consortium (I)
PPARC funding O. Lahav (PI), P. Doel, M.
Barlow, S. Bridle, S. Viti, J. Weller (UCL),
R. Nichol (Portsmouth), G. Efstathiou, R.
McMahon, W. Sutherland (Cambridge), J.
Peacock (Edinburgh) Submitted a proposal to
PPARC in February 2005 requesting 1.5 M for
the DES optical design. In March 2006, PPARC
Council announced that it will seek
participation in DES. (II) SRIF3 funding
R. Nichol, R. Crittenden, R. Maartens, W.
Percival (ICG Portsmouth) K. Romer, A. Liddle
(Sussex) Funding the optical glass blanks for
the UCL DES optical work These scientists will
work together through the UK DES Consortium and
are collaborating with the Spanish DES Consortium

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DES Photo-zs

• DES science relies on good photometric estimates
  of the 300 million expected galaxies

Simulated DES
griz
grizJK
Simulated DESVISTA
ANNz Collister Lahav 2005, Abdalla et al.
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DES VISTA VST
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DES Forecasts
DETF FoM

• Nearly factor of 5 improvement in FoM
• These predictions include systematic errors as
  well

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WFMOS

• Proposed MOS on Subaru via an international
  collaboration of Gemini and Japanese astronomers
• 1.5deg FOV with 4500 fibres feeding 10 low-res
  spectrographs and 1 high-res spectrograph
• 20000 spectra a night (2dfGRS at z1 in 10
  nights)
• DE science, Galactic archeology, galaxy formation
  studies and lots of ancillary science from
  database
• Design studies underway on-sky by 2013
• Next Generation VLT instruments meetings in
  Garching
• Combine with an imager and do SDSS at z1

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WFMOS baseline

• Top-level design performance guidelines for WFMOS
• Wavelength range 0.391.0µm
• Field of view 1.5deg diameter
• Spectral resolution R 100030,000 (or 40,000)
• Simultaneous targets 4000 - 5000

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A bit of history.

• WFMOS was a proposed second-generation Gemini
  instrument that emerged from the Aspen process
• Before that, it was the KAOS conceptual
  instrument http//www.noao.edu/kaos/
• Originally for Gemini, sharing of Gemini/Subaru
  resources was recognized in 2004
• WFMOS underwent a feasibility study (Barden et
  al. 2005 Bassett, Nichol Eisenstein 2006),
  completed in March 2005. Fully reviewed and
  recommended WFMOS move to full concept design
  review
• Subaru/Gemini DE meeting in Hawaii in November
  2005 (over 80 participants from Japan, UK, US,
  Australia, Canada). Recent GA science meeting.
• Two teams have formed and submitted proposals for
  WFMOS Concept Design To start in earnest in 2007
• PPARC Council commitment of up to 18M for the
  UK share of the Gemini 'Aspen' programme, the
  full commitment being contingent on the Wide
  Field Multi Object Spectrograph (WFMOS)
  instrument proceeding.

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DE Science
Measure BAO at z1 and z3 to determine w(z)
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WFMOS LegacyFacility instrument
(Glazebrook et al. 2005)

• Galaxy Evolution Every galaxy in Coma (Mr lt -11)
• IGM and Quasars Simultaneously observing QSOs
  and galaxies in the same fields
• Calibrate photo-zs LSST and DES require gt a few
  105 unbiased redshifts (Abdalla et al. 2007)

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WFMOS LegacyArchival science

• Few thousand z1 SNe detected via their
  spectroscopy
• Alcock-Paczsynki test (Yamamoto et al. 2004,
  Matsubara 2004)
• High-z cluster counts (Newman et al. 2002)
• Reciprocity relation dA/dL (1z)2
  (Bassett Kunz 2004)

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WFMOS Surveys

• Parkinson et al. (2007)
• Emission-line galaxies
• 5600 deg2 at z1.1 (dz 0.3)
• gt 5 million galaxies
• 150 deg2 at z3.15 (dz 0.2)
• FoM an order of magnitude larger than SDSS (dw
  4, dw/dz 15)
• Optimum is broadly peaked and insensitive to
  other surveys
• Now investigating curvature and other w(z) models
  (Clarkson et al. 2007)

Optimize instrument parameters
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Conclusion

• With WiggleZ, FastSound, WFMOS can deliver tight
  constraints on dw/dz (testing DE beyond
  wconstant modified gravity)
• WFMOS is alive and kicking Concept Design
  teams eager to begin hard work of finalizing the
  design of science and instrument
• Challenges ahead include
• What targets? ImagingWFMOS looks attractive
  (SDSS at z1)