@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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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


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


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


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


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


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


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


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


DATA SAMPLE

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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

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2

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


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)

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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


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


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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G. Rossi


COSMOLOGY WITH THE BAO PEAK

Model: Open ΛCDM

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CMASS + H0

LRG + H0

6df + H0

Model: Open ΛCDM

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Model: Flat wCDM

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Model: Flat wCDM

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Ly-α + H0

CMASS + H0

LRG + H0

6df + H0

Busca et al. (2013)

H(z

)/(1

+z)

(km

/sec

/Mpc

)0 1 2

z

90

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60

50

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


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


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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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


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


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


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


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


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


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


VISUALIZATIONS : GAS PROPERTIES

G. Rossi et al. (2013), in prep.

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Internal Energy

G. Rossi


VISUALIZATIONS : COMPARISONS(PROJECTION)

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Gas Dark Matter Neutrinos

G. Rossi


VISUALIZATIONS : COMPARISONS(SLICES)

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Gas Dark Matter Neutrinos

G. Rossi


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


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


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/

-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

G. Rossi


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

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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

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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

@let@token BOSS DETECTS BAOs IN THE LY-...

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