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IntroductionBAO measurement
RSD issues
BAO analysis from the DR14 QSO sample
Héctor Gil-Maŕın (on behalf of the eBOSS QC WG)
Laboratoire de Physique Nucleaire et de Hautes Energies (LPNHE)Institut Lagrange de Paris (ILP)
Understanding Cosmological Observations @ Benasque1st Aug 2017
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Public DR14 data (yesterday!) arXiv:1707.09322
We’re very happy to report that the fourteenth data release ofSDSS is now live!!! Go have a look at www.sdss.org/dr14, and tellall your friends and colleagues that this awesome data set is now
available for them to play with!
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issuesThe eBOSS survey
Introduction: the eBOSS survey
Apache Point Observatory (APO) 2.5-m telescope.SDSS-III project. 2009-2014 BOSS: Baryon OscillationSpectroscopic SurveySDSS-IV project. 2014-2019 eBOSS: extended BaryonOscillation Spectroscopic Survey3 galaxy clustering programs (ELG, LRG, quasars) + Ly-α
new selection algorithms to identifyredshift of galaxies
BOSS had 99% success rateidentifying redshifts of LRGs
first eBOSS tests showed 70% ofsuccess rate on LRGs using sameBOSS algorithms!
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issuesThe eBOSS survey
Introduction: the eBOSS survey
eBOSS survey: ELG, LRG and QSO samples
LRG 0.6 < z < 1.0; zeff = 0.71.
ELG 0.6 < z < 1.1; zeff = 0.85.
QSO 0.8 < z < 2.2; zeff = 1.5.
Ly-α zeff = 2.33
[Credit : Anand Raichoor]
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issuesThe eBOSS survey
Introduction: the eBOSS survey
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issuesThe eBOSS survey
Introduction: the eBOSS survey
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
z
0.2
0.3
0.4
0.5
0.6
0.7fσ
8(z
)assuming Planck ΛCDM cosmology
eBOSS year 6Planck ΛCDM
BOSS DR126dFGSSDSS MGS
GAMAWiggleZVipers
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issuesThe eBOSS survey
Low Density of Quasars!
Shot noise dominated covariance matrices(traditional) Reconstruction algorithms do not provide muchsignal gain
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issuesThe eBOSS survey
Introduction: the eBOSS survey
QSO DR14 area 2044 deg2.
quasar range: 0.8 < z < 2.2(zeff ' 1.5)Number quasars: 147,000
Low density: 2× 10−5 [Mpc/h]33 disconnected areas: 2 SGC &NGC.
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issuesThe eBOSS survey
Introduction: the eBOSS survey
Alphabetical paper Ata et al. 2017submitted to the JournalarXiv:1705.06373
First BAO measurement in0.8 ≤ z ≤ 2.2DV = 3855± 170 rd/rd ,fid Mpc atz=1.52 (4.4% precision)
∼ 2.5σ BAO significanceDR14 Area: 2044→4.4% precisionDR16 Area: 5300→ 2.7% precisioneBOSS is working!
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Alcock-Paczynski effectMethodologyMeasurementSystematic Tests
Alcock-Paczynski effect
By assuming a wrong cosmological model (Ωm) we change theline-of-sight clustering respect to the angular clustering, creating ameasurable anisotropy: constrains H(z) and DA(z) (or acombination of both).
dcomov(z) =
∫ z0
cdz ′
H(z ′; Ωm)
The BAO scale is determined by the comoving sound horizon atreconvination scale (standard ruler)
rs =1
H0Ω1/2m
∫ a∗0
dacs
(a + aeq)1/2
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Alcock-Paczynski effectMethodologyMeasurementSystematic Tests
Baryonic Acoustic Oscillations
k‖ → α‖k‖ k⊥ → α⊥k⊥
α‖ =Hfid(z)
H(z)α⊥ =
DA(z)
DfidA (z)
[Anderson et al. 2014,BOSS DR11]
Surveys measure angles andredshifts, and these are affectedby the assumed fiducial model.
This changes theapparent/observed position ofthe BAO peak in the powerspectrum differently in theradial and angular direction
Isotropic Correlation Function /Power Spectrum sensitive to
DV (z) =
[(1 + z)2D2A(z)
cz
H(z)
]1/3Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Alcock-Paczynski effectMethodologyMeasurementSystematic Tests
Methodology
We perform two complementary and independent analyses onthe same dataset using the i) Power Spectrum and ii)Correlation Function.
Both observables should contain the same amount ofinformation, but in practice are affected differently by noiseand systematic effects.
We use mocks (1000 EZ mocks) and (400 QPM mocks) toestimate the covariance matrices and perform systematic tests.
We model the broadband shape of the PS/CFphenomenologically and the BAO as linear+damping (Σnl)
P(k , α) = Psm(k){
1 + [Olin(k/α)− 1] e−12
Σ2nlk2}
smooth PS: Psm(k) ≡ B2P linnw(k) + A1k + A2 + A3/kUnderstanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Alcock-Paczynski effectMethodologyMeasurementSystematic Tests
Measurement
DR14 QSO isotropic Power spectrum and Correlation function
0.05 0.10 0.15 0.20 0.25 0.30k (hMpc−1)
200
400
600
800
1000
1200
kP
0(k
)(h−
2M
pc2
)
SGC, χ2/dof =22.1/27NGC, χ2/dof =33.2/27
25 50 75 100 125 150 175 200s (h−1Mpc)
−80
−60
−40
−20
0
20
40
60
80
100
s2ξ 0
(s)
(h−
2M
pc2
)
SGC, χ2/dof =28.3/24NGC, χ2/dof =21.0/24
Actual data + diagonal errors from EZ mocks.Dashed lines mean of the EZ-mocks
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Alcock-Paczynski effectMethodologyMeasurementSystematic Tests
Measurement
DR14 QSO isotropic Power spectrum and Correlation function
0.05 0.10 0.15 0.20
k(hMpc−1)
−1.5
−1.0
−0.5
0.0
0.5
1.0
1.5
10(P−P
smoot
h)/P
smoot
h
25 50 75 100 125 150 175
s (h−1Mpc)
−4
−2
0
2
4
103(ξ
[s]−
ξ sm
oot
h)
Actual data + diagonal errors from EZ mocks.Solid lines best-fit model
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Alcock-Paczynski effectMethodologyMeasurementSystematic Tests
Tests on Mocks
0.85 0.90 0.95 1.00 1.05 1.10 1.15
Correlation Function α
0.85
0.90
0.95
1.00
1.05
1.10
1.15
Pow
erS
pec
tru
mα
DR14
Mocks
0.02 0.03 0.04 0.05 0.06 0.07 0.08
Correlation Function σ(α)
0.02
0.03
0.04
0.05
0.06
0.07
0.08
Pow
erS
pec
tru
mσ
(α)
Correlation coefficient between PS and CF ρ = 0.97.Data is a very typical case of mocks (both in measurement and
error).
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Alcock-Paczynski effectMethodologyMeasurementSystematic Tests
Tests on Mocks
NL effects shift the BAO peak to higher α.∼ 0.1% effect on measured α. Negligible on data!
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Alcock-Paczynski effectMethodologyMeasurementSystematic Tests
Tests on data
Both P(k) and ξ(s) measurementsare very consistent!
0.8 0.9 1.0 1.1 1.2αBAO
0
2
4
6
8
10
12
14
16
∆χ
2
1σ
2σ
3σ
ξ(s)P (k)P (k) + ξ(s)
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Alcock-Paczynski effectMethodologyMeasurementSystematic Tests
Cosmology
Fully consistent with LCDM + Planck.
Ly-α 2.5 measurement dominates at high z .
Further analyses will focus on redshift weighting schemes.
0.0 0.5 1.0 1.5 2.0 2.5
Redshift
0.95
1.00
1.05
Dis
tan
ce/D
ista
nce
(Pla
nck
ΛC
DM
)
6dFGSBOSS DR12
SDSS MGS
WiggleZDR14 quasars
BOSS Lyα
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Alcock-Paczynski effectMethodologyMeasurementSystematic Tests
BAO Summary
Summary,
We have a robust BAO isotropic measurement at z ' 1.5.with 4.4% precision: DV (1.52) = 3855± 170 rd/rd ,fid Mpc.Very consistent with mocks and between P and ξ observables.
Fully consistent with LCDM+Planck
First BAO science result from WG, but not last one. Morecomplex BAO analyses will be done in the forthcomingmonths (weighting z evolution).
Future quasar releases (DR16) will focus on the anisotropicquasar BAO → Constrain DA and H.Further information on DV can be extracted from RSDanalysis (several papers to be released this Fall)
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Alcock-Paczynski effectMethodologyMeasurementSystematic Tests
BAO Summary
Summary,
We have a robust BAO isotropic measurement at z ' 1.5.with 4.4% precision: DV (1.52) = 3855± 170 rd/rd ,fid Mpc.Very consistent with mocks and between P and ξ observables.
Fully consistent with LCDM+Planck
First BAO science result from WG, but not last one. Morecomplex BAO analyses will be done in the forthcomingmonths (weighting z evolution).
Future quasar releases (DR16) will focus on the anisotropicquasar BAO → Constrain DA and H.Further information on DV can be extracted from RSDanalysis (several papers to be released this Fall)
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
The main difficulty when performing RSD analyses is controllingthe observational systematic effects.Such effects have minor effect on the position of the BAO (giventhe current errorbars), but they turn to be more important for RSDanalyses,
Failure rate as a function of the plate position.
Spectroscopic errors.
Estimate of the quasar redshift using different algorithms.
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Failure rate in NGC
0 5 10 15 20 25 30 35 40 45
0
5
10
15
20
25
30
35
40
45
0.75
0.8
0.85
0.9
0.95
1
∼ 10% failure rate
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Failure rate in NGC
0 5 10 15 20 25 30 35 40 45
0
5
10
15
20
25
30
35
40
45
0.86
0.88
0.9
0.92
0.94
0.96
0.98
1
∼ 3.5% failure rate
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Why do the quasars always fail at the same plate positions?
[Credit: P. Zarrouk]
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Even with ∼ 3.5% failure rate, applying the nearest angularneighbour reduces the amplitude of the monopole and enhancesthe quadrupole signal significantly.As a consequence, f σ8 is affected by ∼ 0.7σ.BAO not affected
∆αiso Sα ∆f σ8 Sf σ8 NdetEZ 〈x〉i −1.64± 0.13 - −1.43± 0.16 - -EZ 〈xi 〉 −1.6± 4.4 4.8 −1.4± 4.9 5.5 979
EZ 〈x〉i wcol −1.90± 0.13 - 2.24± 0.17 - -EZ 〈xi 〉 wcol −1.7± 4.4 4.6 2.4± 5.4 5.4 959
(units of the table in 10−2).Better correction than just up-weight the nearest neighbour isneeded!
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Quasar Clustering Working Group ReportCurrent RSD & BAO projects DR14 QSO sample
Gil-Marin et al. Fourier Space Multipoles RSD
Hou et al. Configuration Space Wedges RSD
Ruggeri et al. Fourier Space Multipoles with z-weights RSD
Wang et al. Fourier Space Multipoles with z-weights BAO
Zarrouk et al. Configuration Space Multipoles RSD
Zhao et al. Fourier Space Multipoles with z-weights RSD
Zhu et al. Configuration Space Multipoles with z-weightsBAO
WG is currently focused on
Producing reliable mocks for covariance matrix
Building appropriate weighting scheme for correcting redshiftfailures and close pairs.
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionBAO measurement
RSD issues
Thank you!
Understanding Cosmological Observations @ Benasque, 1st Aug 2017BAO from the DR14 QSO sample
IntroductionThe eBOSS survey
BAO measurementAlcock-Paczynski effectMethodologyMeasurementSystematic Tests
RSD issues