@let@token BOSS DETECTS BAOs IN THE LY-...
Transcript of @let@token BOSS DETECTS BAOs IN THE LY-...
BOSS DETECTS BAOsIN THE LY-α FOREST
Graziano Rossi
CEA, Centre de Saclay, Irfu/SPP
on behalf of the BOSS team (FPG)
Rencontres du Vietnam
August 2, 2013
G. Rossi
MAIN MESSAGES
1. FIRST detection of the BAO peak at z = 2.3 in the 3D correlationfunction of the Ly-α forest with SDSS-III BOSS data
2. FIRST confirmation of the deceleration of the Universe in thematter-domination era → direct proof of Dark Energy
3. Ongoing related science → 1D LyA PS, neutrinos, QSOs-LyA CC
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DataModel w. peakModel w/o peak
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)/(1
+z)
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)
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G. Rossi
OUTLINE
1. Introduction: BAO, Ly-α, and BOSS
2. BAOs in the Ly-α Forest
3. BOSS-related projects
4. Ly-α 1D power spectrum and massive neutrinos
5. Summary and ongoing work
MAINLY BASED ON
N. Busca, T. Delubac, J. Rich, et al (2013), A&A, 552, A96
N. Palanque-Delabrouille et al. (2013), arXiv:1306.5896
SELECTED REFERENCES
K. S. Dawson, D. J. Schlegel, C. P. Ahn, et al. 2013, AJ, 145, 10
K.-G. Lee, S. Bailey, L. E. Bartsch, et al. 2013, AJ, 145, 69
J. Lesgourgues, S. Pastor (2012), Special Issue on Neutrino PhysicsG. Rossi
INTRODUCTION: BAO, Ly- α, and BOSS
COSMOLOGY TODAY ... NEW WINDOWS ...
Credit: B. Bassett
G. Rossi
INTRODUCTION: BAO, Ly- α, and BOSS
NEW FUNDAMENTAL PHYSICS?
Grand Unified Model of DarkEnergy →
MYSTERY SCIENCE...Dark Energy: a cosmological constant?
Dark Energy: isotropic - homogeneous?
Acceleration caused by modified gravity?
Dark matter?
Non-Gaussianity? Massive neutrinos?
Credit: D. Weinberg
Call for physics beyond standard model? → THEORY CHALLENGES
Call for breakthrough facilities? → OBSERVATIONAL CHALLENGES
G. Rossi
INTRODUCTION: BAO, Ly- α, and BOSS
PROBING DARK ENERGY
Dark energy affects the expansion of the Universe → H2(z) = 8πG3
∑i ρi(z)
CLASSICAL METHODS
Standard candles
Standard rulers
Growth of fluctuations
PROPERTIES OF THE RULER
Accurate calibration of the ruler
Measurement of the ruler in avolume as large as possible
Ultra-precise measurements ofthe ruler
Object of known length ∆χ as a functionof cosmic epoch
Measure angle ∆θ subtended by ruleras a function of z → map DA
∆θ = ∆χ/DA(z), DA(z) ∝∫ z
0 dz′/H(z′)
Measure redshift interval ∆z associatedwith distance → map H(z)
c∆z = H(z)∆χ
G. Rossi
INTRODUCTION: BAO, Ly- α, and BOSS
BAOS IN A NUTSHELL
BAOS: BASICS
Acoustic waves in the early Universe → thecosmic sound
Bump in the CF at a comoving separation equalto the sound horizon at recombination
Standard ruler for length scale in cosmology
BAOS: IMPORTANCE
Measuring stick to better understand the natureof acceleration
Help understanding nature of DE by constrainingcosmological parameters
Cole et al. (2005)
Eisenstein et al. (2005), Seo et al. (2006), James et al.(2009), Percival et al. (2010), Kazin et al. (2010),Padmanabhan et al. (2012), Xu et al. (2012), Andersonet al. (2013) ... and many more
G. Rossi
INTRODUCTION: BAO, Ly- α, and BOSS
LY-α FOREST: A NEW FRONTIER
LY-α: BASICS
Sum of absorption lines arising from Ly-αtransition of neutral H in spectra of distantQSOs/galaxies
Forest due to Hubble redshift of photons fromQSOs/galaxies
LY-α: IMPORTANCE
Probes the intergalactic medium at high-z
Maps the primordial density fluctuations
Synergy with other LSS probes
G. Rossi
INTRODUCTION: BAO, Ly- α, and BOSS
SDSS-III → BOSS SURVEY
BARYON OSCILLATION SPECTROSCOPICSURVEY
Dark Energy and the Geometry of Space
Will map LRG and quasars
Use the acoustic scale as a ruler
Measure H(z) with 1 − 2% precision at different z
BOSSAT A GLANCE
Fall 2009 – Spring 2014
1,000 fiber spectrograph, resolution R ∼ 2000
10,000 square degrees
1.5 milion LRG at z = 0.7
Lyman-α forest spectra of 160,000 QSO at 2.2 < z < 3
Wavelenghts 360 − 1000 nm
G. Rossi
BAOs IN THE Ly- α FOREST
THE GREAT SPACE COASTER
G. Rossi
BAOs IN THE Ly- α FOREST
THEORETICAL BACKGROUND
BAO effects first seen in CMB peaks of angular PS (de Bernardis et al.2000)
BAO at z ≃ 0.3 seen as a peak in galaxy-galaxy CF (Eisenstein et al.2005; Cole et al. 2005)
BAO peak in CF at z appears at ∆θ = rs/[(1 + z)DA(z)],∆z = (rs/c)H(z)
Peak position at any z → constrains combinations of cosmologicalparameters that determine rsH and rs/DA
Most measurements assume isotropy →
Dv = [c z (1 + z)2D2A/H]1/3 = rs[z/(∆z ∆θ2)]1/3
∝ D2/3A /H1/3
BAO-Hubble diagram → Dv/rs versus z
G. Rossi
BAOs IN THE Ly- α FOREST
LY-α VERSUSGC BAOS
Galaxy surveys → positions in z-space, high overdensities
Forest → maps of absorption over 400 Mpc/h comoving range
Overdensities in the forest of the order of ≃ 1 ÷ 10 → filaments
On large scales Ly-α absorption is linear tracer of mass overdensity
Forest z-range inaccessible to current LSS surveys
Less influence of nonlinear effects
LY-α COMPLICATIONS
Photoionization equilibrium & UV background
H can be self-shielded to ionizing photons
Metal contaminations in the IGM
Continuum estimation uncertainties
BAO reconstruction technique not feasible for Ly-α → BAO directly measuredin the CF of the transmitted flux fraction , with two independent methods
G. Rossi
BAOs IN THE Ly- α FOREST
DATA SAMPLE
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30
60
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BOSS QSO DATA SAMPLE
CORE + BONUS samples DR9
Mean density 15 ÷ 20/deg2
3000 deg2, 1/3 of final BOSS footprint
Visual inspection of spectra
Discard BALs and DLAs
48,640 QSOs total, 2.1 < z < 3.5
Busca et al. (2013)
2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4redshift of absorbers
0
1
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3360 400 440 480 520
wavelength (nm)
<z> = 2.31
Analysis pixels → flux average over 3 adjacentpipeline pixels
15 sets of mock spectra for qualitativeunderstanding
G. Rossi
BAOs IN THE Ly- α FOREST
CORRELATION FUNCTION MEASUREMENTS
(1) CONSTRUCTδ-FIELD
δq(λ) =fq(λ)
Cq(λ)F (z)− 1
(2) COMPUTE CORRELATION FUNCTION
ξA =
∑i,jǫA wi,jδiδj∑
i,jǫA wi,j
Cq (λ)F(z) = mean expected flux
A = region in space separated by ri − rj
r = |ri − rj |, µ = (ri − rj )‖/r
(ra, dec, z) → (r , µ) with fiducial cosmology
Busca et al. (2013)
440 460 480 500 520 540λ (nm)
−5
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17 e
rg s−
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−1 ]
Method 1Method 2
METHOD 1
Cq F = a + q[λ/〈λ〉]bq f(λrf , z)
METHOD 2
Maximize L(Cq) =∏
i pi [fi , Cq (λi )]
F (z) from data
G. Rossi
BAOs IN THE Ly- α FOREST
LY-α BAO: RESULTS
ξ(r , µ) in r -bins of 4 Mpc/h width &µ-bins of 0.02 width
50 × 50 r − µ bins
ξ(r , µ) averaged over bins in µ
Peak at rs = 105 Mpc/h in bin0.8 < µ < 1.0, 37o LOS separations
Data divided in various sub-samplesto test for systematics
0.8 < µ < 1.0
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G. Rossi
BAOs IN THE Ly- α FOREST
LY-α MONOPOLE& QUADRUPOLE
STANDARD MULTIPLE DECOMPOSITION
ξ(r , µ) =∑
ℓ=0,2
ξℓ(r)Pℓ(µ)
= [ξ0(r)− ξ2(r)/2] + [3ξ2(r)/2]/µ2
COVARIANCES
30% smaller errorbars if ignoring correlations
Covariances for ξ0 and ξ2 by dividing data intosub-samples
BAO PEAK SIGNIFICANCE
ξℓ(r) = BℓξBBℓ (r) + Cℓξ
peakℓ (r) + Aℓξ
distℓ (r)
Busca et al. (2013)
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Method 1Method 2
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G. Rossi
BAOs IN THE Ly- α FOREST
COSMOLOGY WITH THE BAO PEAK
Model: Open ΛCDM
0.2 0.4 0.6 0.8 1.0Ωm
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ΩΛ
Ly-α + H0
CMASS + H0
LRG + H0
6df + H0
Model: Open ΛCDM
0.2 0.4 0.6 0.8 1.0Ωm
0.0
0.5
1.0
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2.0
ΩΛ
Model: Flat wCDM
0.2 0.4 0.6 0.8 1.0Ωm
-2.0
-1.5
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-0.5
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Model: Flat wCDM
0.2 0.4 0.6 0.8 1.0Ωm
-2.0
-1.5
-1.0
-0.5
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w
Ly-α + H0
CMASS + H0
LRG + H0
6df + H0
Busca et al. (2013)
H(z
)/(1
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/Mpc
)0 1 2
z
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H(z = 2.3)
1 + z= (67.8±2.4)kms−1Mpc−1
( 152.76Mpc
rs
)
G. Rossi
BOSS-RELATED PROJECTS
KIRKBY ET AL . (2013)
Fitting Methods for BAOs in the Ly- α Forest Fluctuations in BOSS DR9D. Kirkby, D. Margala, A. Slosar, et al. (2013), JCAP, 3, 24
MAIN POINTS
• Fitting methods to analyzefluctuations in the Ly-α forest
• Measure the parameters ofBAOs
• Applications to BOSS DR9
• Independent scale factors alongand across LOS
• Fitting software publiclyavailable
G. Rossi
BOSS-RELATED PROJECTS
LEE ET AL. (2013)
The BOSS Ly- α forest sample from SDSS DR9K.G. Lee, S. Bailey, L. E. Bartsch, et al., (2013), AJ, 145, 69
MAIN POINTS
• BOSS Ly-α forest samplefrom DR9
• 54,468 quasar spectrawith zqso > 2.15
• IGM probe with2.0 < zα < 5.7 over3275 deg2
• Comoving volume of20h−3Gpc3
• Several ancillary products(sky masks, noisecorrections, pipelinecorrections, ...)
• Starting point to analyzeclustering in BOSS Ly-αforest data
G. Rossi
BOSS-RELATED PROJECTS
OTHER PROJECTS
QSOs-LyA Forest cross-correlation from BOSS-DR11: BAOsA. Font Ribeira et al. (2013)
BAO in LyA Forest–QSO cross-correlationR. O’Connell et al. (2013)
Detection of Ly- β auto-correlations and Ly- α-Ly-β cross-correlations inBOSS Data Release 9
Iršic, V., Slosar, A., Bailey, S., et al. 2013, arXiv:1307.3403
G. Rossi
LY-α 1D POWER SPECTRUM AND MASSIVE NEUTRINOS
COSMIC NEUTRINO BACKGROUND (CNB)
PREDICTIONS AND EVIDENCE
• CNB → generic feature of standard hot Big Bang model
• Neutrino experiments → neutrino flavor oscillations
NEUTRINO MASSES: COSMOLOGICAL EFFECTS
• Fix expansion rate at BBN
• Change background evolution → PS effects
• Slow down growth of structures
OBSERVABLES AND TECHNIQUES
• CMB anisotropies → PS, lensing
• LSS probes
– Galaxy PS– Cluster mass function– Galaxy weak lensing– Ly-α forest– 21-cm surveys
Viel et al. (2010), JCAP, 6, 15
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10
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y [
h-1 M
pc ]
z=3, DM (blue) + GAS (red) z=3, DM (blue) + GAS (red) + ν (green)
20 40 60 80 1001+δGAS
20 40 60 80 1001+δDM
0.90 0.95 1.00 1.05 1.101+δν
G. Rossi
LY-α 1D POWER SPECTRUM AND MASSIVE NEUTRINOS
EFFECTS OF NEUTRINO MASSES ON COSMOLOGY
NEUTRINO FREE-STREAMING
• After thermal decoupling → ν as a collisionless fluid
• Individual particles free-stream with thermal velocity vth
• When neutrinos are relativistic → λFS ≡ Hubble radius
• When neutrinos are non-relativistic
vth ≃ 158(1 + z)( 1eV
m
)
km/s
• Minimum free-steaming wavenumber for ν
knr ≃ 0.018Ω1/2m
( m
1eV
)
h/Mpc
IMPACT ON MATTER PS (k > knr )
1 Massive neutrinos do not cluster
2 zeq or baryon-to-CDM ratio affected
3 Growth rate of CDM perturbations reduced
Lesgourgues & Pastor (2012)
Ratio of the matter PS including 3 degeneratemassive neutrinos (wm,ΩΛ fixed)
G. Rossi
LY-α 1D POWER SPECTRUM AND MASSIVE NEUTRINOS
BOUNDS ON NEUTRINO MASSES
LABORATORY EXPERIMENTS
• Solar, atmospheric, reactors, accelerators →
Mν > 0.05 eV
• β-decay → Mν < 2.2 eV
• Wolf & KATRIN (future) → Mν < 0.2 eV
COSMOLOGY: NOW (EXAMPLES, 95% CL)
• LyA → Mν < 0.9 eV
• WMAP9 → Mν < 0.44 eV
• WMAP7+LRG+H0 → Mν < 0.44 eV
• WMAP7+ACT+BAO+H0 → Mν < 0.39 eV
• WMAP7+WiggleZ+BAO+H0 → Mν < 0.29 eV
• WMAP7+MegaZ+BAO+SNIa+H0 → Mν < 0.281 eV
• Planck+WP+highL+BAO → Mν < 0.23 eV
• Planck+WiggleZ+BAO → Mν < 0.15 eV ?
COSMOLOGY: NEAR FUTURE
• BOSS LyA + other probes → Mν ∼ 0.1 eV
• ACTPol + Planck → Mν ∼ 0.07 eV
• Planck + BOSS, LSST, DES → Mν ∼ 0.06 eV
• Surveys in 2020 → Mν ∼ 0.03 eV
WARNING
Systematic offset between estimates of the matter PSobtained with different methods!
G. Rossi
LY-α 1D POWER SPECTRUM AND MASSIVE NEUTRINOS
WHY THE LYA FOREST?
LYA: ADVANTAGES
• Mildly nonlinear scalesi.e. → k [0.1 – 2] h/Mpc, [0.002 – 0.02] s/km
• High redshift (2 ≤ z ≤ 5)
• Special role in probing free-streaming of neutrinos onmatter PS
• Evolution of ν → signature with z (scale-dependentsuppression)
• Complementary and orthogonal to other probes
LYA: DIFFICULTIES
• Need numerical simulations with full hydro
• Complicated thermodynamical evolution if IGM
• Star formation uncertain
• Non-trivial frequency dependence
• Systematics and other technical issues
LyA information can break degeneracies →cross-correlation signals between transmittedLyA flux and CMB weak lensing convergence
G. Rossi
LY-α 1D POWER SPECTRUM AND MASSIVE NEUTRINOS
PROPOSAL: NEUTRINO PHYSICS IN THE LY-α
Determination of the masses of cosmological neutrinos
with Nathalie Palanque-Delabrouille, Christophe Yeche, James Rich,Jean-Marc LeGoff, Arnaud Borde, Matteo Viel, Julien Lesgourgues
GOALS
• Use signature in Ly-α forest to constrainthe sum of neutrino masses with BOSSdata (at 0.1 eV level)
• Study impact of systematics in 1D PS
• Cosmological interpretation of matterPS + impact of massive neutrinos on SF
• Constrain cosmological parameters andDE EoS
• Link particle physics & cosmology
METHODS
• Analysis of Ly-α BOSS data to derivethe 1D PS with high-precision
• N-body hydrodynamical code withmassive neutrinos
• Additional physics (e.g. cooling/heating,SF rate, AGN feedback, ...) and impacton structure formation
• Post-processing for extracting the 1D PS
• Combine with topological techniques
TIMELINE
• European proposal(7 million CPU scalar hrsrequested on TGCC BULLCurie thin nodes)
• Successful , time grantedin March 2013!
• DR10 & Planck DRs
G. Rossi
LY-α 1D POWER SPECTRUM AND MASSIVE NEUTRINOS
THEORY PART: SIMULATIONS
IMPROVING ON VIEL ET AL . (2010)“Reaching an accuracy below 1% level at scales relevant for the Ly-α forest or weak lensing data will bechallenging, but should be doable and will be an important step in turning the exciting prospect of an actualmeasurement of neutrino masses into reality"
THEORY PART
• Full hydro simulation with massive neutrinos
• Neutrinos are included as a new type of particle,as opposed to grid implementations (i.e. toaccount for their nonlinear evolution)
• Numerical issues + shot noise → several tricks
• Short-range gravitational tree force for neutrinosnot computed
• ICs, convergence and resolution tests
• Post-processing and flux PS extraction
NOVEL FEATURES
• 2LPT ICs + CAMB
• Higher resolution
• Larger box size
• Planck cosmological parameters
• New prescriptions for radiative cooling andheating processes
• Updated reionization history
G. Rossi
LY-α 1D POWER SPECTRUM AND MASSIVE NEUTRINOS
CONSTRUCTINGFULL HYDRO SIMS WITH ν
TARGETEDSIMULATIONS
• Curie thin node architecture
• 5040 B510 bullx nodes
• For each node → 2 eight-core Intel processorsSandy Bridge EP (E5-2680) 2.7 GHz, 64 GB
• 10080 eight-core processors, Intel Xeon NextGeneration, total of 80640 cores
• 7683 particles, 20 ÷ 100 h−1Mpc, 80 khrs
• 0.1 ÷ 0.8 eV
SIMULATIONS SHOWN HERE
• DM+GAS+NEUTRINOS
• 1283 particles per type
• 25h−1Mpc, 0.5 eV
• ICs → 2LPT at z = 30
G. Rossi
LY-α 1D POWER SPECTRUM AND MASSIVE NEUTRINOS
VISUALIZATIONS : GAS PROPERTIES
G. Rossi et al. (2013), in prep.
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Internal Energy
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LY-α 1D POWER SPECTRUM AND MASSIVE NEUTRINOS
VISUALIZATIONS : COMPARISONS(PROJECTION)
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Gas Dark Matter Neutrinos
G. Rossi
LY-α 1D POWER SPECTRUM AND MASSIVE NEUTRINOS
VISUALIZATIONS : COMPARISONS(SLICES)
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Gas Dark Matter Neutrinos
G. Rossi
LY-α 1D POWER SPECTRUM AND MASSIVE NEUTRINOS
POWER SPECTRA AND FLUX STATISTICS
IMPACT ON MATTER PS (k > knr )
1 Massive neutrinos do not cluster
2 zeq or baryon-to-CDM ratio affected
3 Growth rate of CDM perturbations reduced
G. Rossi et al. (2013), in prep.
G. Rossi
LY-α 1D POWER SPECTRUM AND MASSIVE NEUTRINOS
DATA PART: BOSS LY-α 1D POWER SPECTRUM
MAIN GOALS
• Measure the 1D PS of the transmitted flux in the Ly-α forest
• 2 independent methods: (1) Fourier transform (2) Maximum likelihood estimator
• Application of the method to 13,821 QSOs spectra from SDSS-III/BOSS DR9
• Preliminary cosmological interpretation → σ8, ns
• 2-3 factor improved precision on previous estimates of cosmological parameters
PHILOSOPHY AND STRATEGY
• Global correction of the mean transmitted flux and continuum (LUT)
• FFT of Ly-α forest region and Likelihood fit
• Correction of noise and resolution
• Power spectrum stacked per redshift slices
• New noise model
G. Rossi
LY-α 1D POWER SPECTRUM AND MASSIVE NEUTRINOS
1D POWER SPECTRUM: METHODS AND FITS
N. Palanque-Delabrouille et al. (2013)
-1k (km/s)0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018
πP
(k)*
k/
-210
-110
z=2.2
z=2.4 z=2.6
z=2.8
z=3.0 z=3.2
z=3.4
z=3.6
z=3.8
z=4.0
z=4.2 z=4.4
Fourier Transform
-1k (km/s)0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
πP
(k)*
k/
-210
-110
z=2.2
z=2.4 z=2.6
z=2.8
z=3.0 z=3.2
z=3.4
z=3.6
z=3.8
z=4.0
z=4.2 z=4.4
Likelihood
-1k (km/s)-210
πP
(k)*
k/
-210
-110
z=2.2
z=2.4 z=2.6
z=2.8
z=3.0 z=3.2
z=3.4
z=3.6
z=3.8
z=4.0
z=4.2
SDSS
BOSS FFT
BOSS Likelihood
-1k (km/s)-210
πP
(k)*
k/
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-110
z=2.2
z=2.4
z=2.6
z=2.8
z=3.0
z=3.2
z=3.4
z=3.6
G. Rossi
LY-α 1D POWER SPECTRUM AND MASSIVE NEUTRINOS
COSMOLOGICAL FITS
N. Palanque-Delabrouille et al. (2013)
8σ0.75 0.8 0.85 0.9 0.95 1
sn
0.86
0.88
0.9
0.92
0.94
0.96
0.98
1
1.02
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0SDSS + H
0BOSS + H
8
σ0.7 0.75 0.8 0.85 0.9 0.95 1
Con
fiden
ce L
evel
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 SDSS + H 0 BOSS + H 8σ
sn0.86 0.88 0.9 0.92 0.94 0.96 0.98 1 1.02
Con
fiden
ce L
evel
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 SDSS + H 0 BOSS + H sn
DETAILS
• BOSS results are 2-3 better in terms of statistical errors
• Frequentist contours of cosmological parameters
• σ8 = 0.83 ± 0.03, ns = 0.97 ± 0.02 in the range 2.1 < z < 3.7
G. Rossi
SUMMARY
MAIN MESSAGES
1. FIRST detection of the BAO peak at z = 2.3 in the 3D correlationfunction of the Ly-α forest with SDSS-III BOSS data
2. FIRST confirmation of the deceleration of the Universe in thematter-domination era → direct proof of Dark Energy
3. Ongoing related science → 1D LyA PS, neutrinos, QSOs-LyA CC
50 100 150 200r [h−1Mpc]
−0.4
−0.2
0.0
0.2
0.4
r2 ξ0(
r)
50 100 150 200r [h−1Mpc]
−0.4
−0.2
0.0
0.2
0.4
r2 ξ0(
r)
DataModel w. peakModel w/o peak
H(z
)/(1
+z)
(km
/sec
/Mpc
)
0 1 2z
90
80
70
60
50
x
y
0 5000 1×104 1.5×104 2×104
5000
1×104
1.5×104
2×104
-5.6
-5.4
-5.2 log
co
lum
n d
ensi
ty
z =2
G. Rossi
G. Rossi