DESI 2024: Survey overview and cosmological constraints from DR1 BAO and Full Shape measurements
Arnaud de Mattia
CEA Saclay
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CPPM
November 2024
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Thanks to our sponsors and
72 Participating Institutions!
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DESI 3D Map
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Physics program
- Galaxy and quasar clustering
- Lyman-alpha forest
- Clusters and cross-correlations
- Galaxy and quasar physics
- Milky Way Survey
- Transients and low-z
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DESI 3D Map
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Physics program
- Galaxy and quasar clustering
- Lyman-alpha forest
- Clusters and cross-correlations
- Galaxy and quasar physics
- Milky Way Survey
- Transients and low-z
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DESI: a stage IV survey
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10 years = 10×
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DESI Y5 galaxy samples
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Bright Galaxies: 14M (SDSS: 600k)
0 < z < 0.4
LRG: 8M (SDSS: 1M)
0.4 < z < 0.8
ELG: 16M (SDSS: 200k)
0.6 < z < 1.6
QSO: 3M (SDSS: 500k)
Lya 1.8<z
Tracers 0.8<z<2.1
Y5 ∼40M galaxy redshifts!
z=0.4
z=0.8
z=0
z=1.6
z=2.0
z=3.0
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From images to redshifts
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imaging surveys (2014 - 2019) + WISE (IR)
target selection
spectroscopic observations
spectra and redshift measurements
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Mayall Telescope
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focal plane 5000 fibers
wide-field corrector
6 lenses, FoV ∼8 deg2
Kitt Peak, AZ
4 m mirror
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Mayall Telescope
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focal plane 5000 fibers
fiber view camera
ten 3-channel spectrographs
49 m, 10-cable fiber run
Kitt Peak, AZ
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Focal plane: 5000 robotic positioners
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Focal plane: 5000 robotic positioners
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Exposure time (dark): 1000 s
Configuration of the focal plane
CCD readout
Go to next pointing
140 s
0.1 mm
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Spectroscopic pipeline
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wavelength
fiber number
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z=2.1 QSO
z=0.9 ELG
Lyα
CIV
CIII
[OII] doublet at 2727A˚ up to z=1.6
[OII]
Lyα at 1216A˚ down to z=2.0
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DESI data release 1 (DR1)
Observations from May 14th 2021 to June 12th 2022
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Final survey
- dark time (LRG, ELG, QSO): 7 layers
- bright time (BGS): 5 layers
- 14,000 deg2
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Release of DESI DR1 (BAO) results
April 4th 2024
First batch of DESI DR1 cosmological analyses
https://data.desi.lbl.gov/doc/papers/
• DESI 2024 I: First year data release
• DESI 2024 II: Sample definitions and two-point clustering statistics
• DESI 2024 III: BAO from Galaxies and Quasars
• DESI 2024 IV: BAO from the Lyman-Forest
• DESI 2024 V: Full Shape measurements from Galaxies and Quasars
• DESI 2024 VI: Cosmological constraints from BAO measurements
• DESI 2024 VII: Constraints from the Full Shape measurements
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Release of DESI DR1 (FS) results
November 17th 2024
Second batch of DESI DR1 cosmological analyses
https://data.desi.lbl.gov/doc/papers/
• DESI 2024 I: First year data release
• DESI 2024 II: Sample definitions and two-point clustering statistics
• DESI 2024 III: BAO from Galaxies and Quasars
• DESI 2024 IV: BAO from the Lyman-Forest
• DESI 2024 V: Full Shape measurements from Galaxies and Quasars
• DESI 2024 VI: Cosmological constraints from BAO measurements
• DESI 2024 VII: Constraints from the Full Shape measurements
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Clustering analysis
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galaxy catalog
galaxy power spectrum (or correlation function)
cosmological constraints
compression = "we measure specific features"
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"variance of the density field as a function of scale"
Full Shape (baseline)
BAO
ShapeFit (alternative Full Shape)
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Baryon acoustic oscillations
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Sound waves in primordial plasma
At recombination (z∼1100)
- plasma changes to optically thin
- baryons decouple from photons
- sound wave stalls
spherical shell in the distribution of galaxies, of radius the distance that sound waves travelled
= sound horizon scale at the drag epoch rd∼150Mpc∼100Mpc/h
standard ruler
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BAO measurements
- transverse to the line-of-sight: DM(z)/rd
- along the line-of-sight: DH(z)/rd=c/(H(z)rd)
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transverse comoving distance
sound horizon rd
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BAO measurements
- transverse to the line-of-sight: DM(z)/rd
- along the line-of-sight: DH(z)/rd=c/(H(z)rd)
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Hubble distance
sound horizon rd
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- transverse to the line-of-sight: DM(z)/rd
- along the line-of-sight: DH(z)/rd=c/(H(z)rd)
At multiple redshifts z
BAO measurements
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Probes the expansion history, hence the energy content
Absolute size at z=0: H0rd
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Release of DESI DR1 (BAO) results
April 4th 2024
First batch of DESI DR1 cosmological analyses
https://data.desi.lbl.gov/doc/papers/
• DESI 2024 I: First year data release
• DESI 2024 II: Sample definitions and two-point clustering statistics
• DESI 2024 III: BAO from Galaxies and Quasars
• DESI 2024 IV: BAO from the Lyman-Forest
• DESI 2024 V: Full Shape measurements from Galaxies and Quasars
• DESI 2024 VI: Cosmological constraints from BAO measurements
• DESI 2024 VII: Constraints from the Full Shape measurements
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Correlation functions
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BAO peak
Excess probability to find 2 galaxies separated by a distance s
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Power spectra
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BAO wiggles
Fourier transform of the correlation function
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Some fits: correlation function
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isotropic measurement
anisotropic measurement
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Density field reconstruction
Non-linear structure growth and peculiar velocities blur and shrink (slightly) the ruler
Reconstruction: estimate Zeldovich displacements from observed field and moves galaxies back → refurbishes the ruler (improves precision and accuracy)
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reconstruction
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Density field reconstruction
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DR1 BAO analysis: what's new?
- Biggest ever spectroscopic BAO dataset (Ntracer and V)
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5.7 million unique redshifts
Effective volume Veff=18Gpc3
3× bigger than SDSS!
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- Biggest ever spectroscopic BAO dataset (Ntracer and V)
- Blind analysis to mitigate observer / confirmation biases (catalog-level blinding)
- Theory developments in BAO fitting code
- New and improved reconstruction methods
- New combined tracer method used for overlapping galaxy samples (LRG and ELG in 0.8<z<1.1)
- Unified BAO pipeline applied to all (discrete) tracer / redshift bins consistently
DR1 BAO analysis: what's new?
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Tests of systematic errors
Considered many possible sources of systematic errors using simulations and data:
- observational effects (imaging systematics, fiber collisions)
- BAO reconstruction (2 algorithms compared)
- covariance matrix construction
- incomplete theory modelling
- choice of fiducial cosmology
- galaxy-halo (HOD) model uncertainties
no systematics detected
systematics << statistics
Maximum effect: σstat.+syst.<1.05σstat.
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Release of DESI DR1 (BAO) results
April 4th 2024
First batch of DESI DR1 cosmological analyses
https://data.desi.lbl.gov/doc/papers/
• DESI 2024 I: First year data release
• DESI 2024 II: Sample definitions and two-point clustering statistics
• DESI 2024 III: BAO from Galaxies and Quasars
• DESI 2024 IV: BAO from the Lyman-Forest
• DESI 2024 V: Full Shape measurements from Galaxies and Quasars
• DESI 2024 VI: Cosmological constraints from BAO measurements
• DESI 2024 VII: Constraints from the Full Shape measurements
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Lyα forest
Absorption in QSO spectra by neutral hydrogen in the intergalactic medium: λabs=(1+zHI)×1215.17A˚
Transmitted flux fraction F=e−τ probes the fluctuation in neutral hydrogen density, τ∝nHI
credit: Andrew Pontzen
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Lyα correlation functions in DESI DR1
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Lyα - Lyα
Lyα - QSO
QSO
QSO
HI cloud
HI cloud
HI cloud
QSO
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DR1 Lyα BAO analysis: what's new?
- Biggest ever Lyα dataset (Ntracer)
>420,000 Lyα QSO at z > 2.1
2× more than SDSS!
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- Biggest ever Lyα dataset (Ntracer)
- First blind analysis to mitigate observer / confirmation biases (correlation function-level blinding)
DR1 Lyα BAO analysis: what's new?
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- Biggest ever Lyα dataset (Ntracer)
- First blind analysis to mitigate observer / confirmation biases (correlation function-level blinding)
- Modelling of the correlation function: cosmological signal, and many contaminants!
- Very stable results, systematic uncertainty neglected
DR1 Lyα BAO analysis: what's new?
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- transverse to the line-of-sight: DM(z)/rd
- along the line-of-sight: DH(z)/rd=c/(H(z)rd)
- low S/N, isotropic average: DV(z)/rd=(zDM2(z)DH(z))1/3/rd
BAO measurements
Let's factor out the h terms:
- [DM(z)h](Ωm,fDE,ΩK,...)/[rd(Ωmh2,Ωbh2)h]
- [DH(z)h](Ωm,fDE,ΩK,...)/[rd(Ωmh2,Ωbh2)h]
BAO measurements at different z constrain:
- energy content (Ωm,fDE,...)
- constant-over-z product rdh i.e. H0rd
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DESI DR1 BAO
DESI DR1 BAO measurements
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DESI DR1 BAO
DESI DR1 BAO measurements
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DESI DR1 BAO
DESI DR1 BAO measurements
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DESI DR1 BAO
DESI DR1 BAO measurements
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DESI DR1 BAO
DESI DR1 BAO measurements
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DESI DR1 BAO
DESI DR1 BAO measurements
Consistent with each other,
and complementary
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DESI DR1 BAO
DESI DR1 BAO measurements
Consistency with other probes
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DESI DR1 BAO consistent with:
Consistency with other probes
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DESI DR1 BAO consistent with:
Consistency with other probes
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DESI DR1 BAO consistent with:
- SDSS eBOSS Collaboration, 2020
- primary CMB: Planck Collaboration, 2018 and CMB lensing: Planck PR4 + ACT DR6 lensing ACT Collaboration, 2023, Carron, Mirmelstein, Lewis, 2022
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- BAO constrains rd(Ωmh2,Ωbh2)h
- Ωm constrained by BAO at different z
- Ωbh2 can be constrained by light element abundance from Big Bang Nucleosynthesis (BBN): Schöneberg 2024
⟹ constraints on h i.e. H0=100hkm/s/Mpc
Hubble constant
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Hubble constant
θ∗ CMB angular acoustic scale
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- Consistency with SDSS
Hubble constant
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- Consistency with SDSS
- In agreement with CMB
- In 3.7σ tension with SH0ES
Hubble constant
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Release of DESI DR1 (FS) results
November 17th 2024
Second batch of DESI DR1 cosmological analyses
https://data.desi.lbl.gov/doc/papers/
• DESI 2024 I: First year data release
• DESI 2024 II: Sample definitions and two-point clustering statistics
• DESI 2024 III: BAO from Galaxies and Quasars
• DESI 2024 IV: BAO from the Lyman-Forest
• DESI 2024 V: Full Shape measurements from Galaxies and Quasars
• DESI 2024 VI: Cosmological constraints from BAO measurements
• DESI 2024 VII: Constraints from the Full Shape measurements
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Full Shape measurements
clustering
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We fit the "full shape" (FS) of the galaxy power spectrum multipoles
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Full Shape measurements
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RSD
observed redshift = Hubble flow and peculiar velocities (RSD = "redshift space distortions")
We fit the "full shape" (FS) of the galaxy power spectrum multipoles
shape
(Ωcdmh2,Ωbh2,ns,∑mν)
growth of structure fσ8 sensitive to the theory of gravity and dark energy
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Full Shape models
Three power spectrum Effective Field Theory models considered:
- velocileptors Maus et al. 2024
- folps Noriega et al. 2024
- pybird Lai et al. 2024
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credit: Mark Maus, Hernan Noriega, Yan Lai
Comparison paper:
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Full Shape models
perturbation theory term
linear and quasi-linear physics
counter-terms contribution
truncation of perturbative series
stochastic-terms contribution
small-scale galaxy physics
The Effective Field Theory in a nutshell
- perturbation theory model + counter-terms and stochastic terms
- dependence on cosmology into Plin, f and Alcock-Paczynski parameters (R.A.,Dec.,z⇒distance)
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- Biggest ever spectroscopic dataset (Ntracer and V)
- Blind analysis to mitigate observer / confirmation biases (catalog-level blinding)
- Effective Field Theory models
- Full-Modelling (Ωcosmo) and updated compression approach (ShapeFit)
- Improvements in the treatment of observational systematics (e.g. fiber assignment)
- Unified Full Shape pipeline applied to all (discrete) tracer / redshift bins consistently
DR1 Full Shape analysis: what's new?
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Groups of galaxies too close to each other cannot all receive a fiber
0.05∘≃ positioner patrol diameter
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Fiber assignment
Fiber assignment
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Impacts power spectrum measurements (altMTL vs complete)
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Impacts power spectrum measurements (altMTL vs complete)
Solution: θ-cut = remove all pairs <0.05∘
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Fiber assignment
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New window matrix Wcut; ⟨Po(k)⟩=Wcut(k,k′)Pt(k′)
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Fiber collisions
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New window matrix Wcut; ⟨Po(k)⟩=Wcut(k,k′)Pt(k′)
Very non diagonal: let's "rotate" it
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Fiber collisions
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Systematic effects
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Theoretical modelling (Maus et al. 2024ab, Lai et al. 2024, Noriega et al. 2024, Ramirez et al. 2024)
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Galaxy-halo connection (Findlay et al. 2024)
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Fiducial cosmology (Gsponer et al. 2024)
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Fibre assignment (Pinon et al. 2024)
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Inhomogeneities in the target selection (Zhao et al. 2024)
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Spectroscopic redshift failures/uncertainties (Yu et al. 2024, Krowleski et al. 2024)
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Covariance matrix: mock-based vs analytic (Forero-Sanchez et al. 2024, Alves et al. 2024, Rashkovetskyi et al. 2024)
Total systematic error = ⅖ of DR1 statistical uncertainty
no systematics detected
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Full Shape (+ BAO) measurements
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Observable: power spectrum monopole and quadrupole, post-reconstruction BAO
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Model: Effective Field Theory
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Covariance: mock-based
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Systematic error: at the data vector level
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Fitting range: 0.02<k[h/Mpc]<0.2
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Fitting parameters:
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7 nuisance parameters
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5 ΛCDM parameters
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External information
Ωbh2: BBN from Schöneberg 2024
ns∼G(0.9649,0.0422): "ns10" 10× wider than Planck posterior
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Full Shape + BAO measurements
ωb: BBN, ns∼G(0.9649,0.0422)
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Full Shape + BAO measurements
ωb: BBN, ns∼G(0.9649,0.0422)
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Full Shape + BAO measurements
ωb: BBN, ns∼G(0.9649,0.0422)
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Full Shape + BAO measurements
ωb: BBN, ns∼G(0.9649,0.0422)
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Full Shape + BAO measurements
ωb: BBN, ns∼G(0.9649,0.0422)
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Full Shape + BAO measurements
ωb: BBN, ns∼G(0.9649,0.0422)
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Full Shape + BAO measurements
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ωb: BBN, ns∼G(0.9649,0.0422)
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S8 constraints
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S8=σ8(Ωm/0.3)0.5 best constrained by weak lensing surveys
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S8 constraints
- Consistency with SDSS
- In agreement with CMB
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S8=σ8(Ωm/0.3)0.5 best constrained by weak lensing surveys
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S8 constraints
- Consistency with SDSS
- In agreement with CMB
- Weak lensing prefers lower S8, but still consistent
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S8=σ8(Ωm/0.3)0.5 best constrained by weak lensing surveys
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Dark Energy fluid, pressure p, density ρ
Equation of State parameter w=p/ρ
Linked to the evolution of Dark Energy w(z)=−1+31dln(1+z)dlnfDE(z)
Let's assume the CPL parameterization
Dynamical Dark Energy - (w0,wa)
ΛCDM: (w0,wa)=(−1,0)
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Dynamical Dark Energy - (w0,wa)
DESI + CMB + SN (uncalibrated):
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ΛCDM
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Dynamical Dark Energy - (w0,wa)
- same preference for w0>−1,wa<0
- similar significance for w0waCDM vs ΛCDM
- 20% better constraints in (w0,wa) than without FS
2.5σ
3.4σ
3.8σ
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Sum of neutrino masses
Massive neutrinos impact:
i) the expansion history
ii) the growth of structure: ΔP(k)/P(k)∝−∑mν/ωm
the k-fitting range
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Sum of neutrino masses
Massive neutrinos impact:
i) the expansion history
ii) the growth of structure: ΔP(k)/P(k)∝−∑mν/ωm
Taking ns prior from Planck:
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Sum of neutrino masses
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Internal CMB degeneracies limiting precision on the sum of neutrino masses
Broken by DESI, especially through H0
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Sum of neutrino masses
Internal CMB degeneracies limiting precision on the sum of neutrino masses
Broken by DESI, especially through H0
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Low preferred value of H0 yields
∑mν<0.071eV(95%,DESI + CMB)
(15% better than BAO-only: 0.082eV)
∑mν<0.081eV(95%,DESI + CMB[hillipop])
In w0waCDM, with DES-SN5YR: ∼0.2eV(95%)
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Modified gravity constraints
In general relativity, μ(a,k)=Σ(a,k)=1
To test GR, introduce μ0,Σ0
Perturbed FLRW metric
ds2=a(τ)2[−(1+2Ψ)dτ2+(1−2Φ)δijdxidxj]
At late times:
(mass) k2Ψ=−4πGa2μ(a,k)∑iρiΔi
(light) k2(Φ+Ψ)=−8πGa2Σ(a,k)∑iρiΔi
gravitational potentials
density perturbations
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Modified gravity constraints
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DESI constrains
GR
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Modified gravity constraints
Σ0 constrained by
- CMB (ISW and lensing)
- galaxy lensing
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DESI constrains
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Modified gravity constraints
Σ0 constrained by
- CMB (ISW and lensing)
- galaxy lensing
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compared to CMB-nl + DESY3 (3x2pt) only: σ(μ0)/2.5, σ(Σ0)/2
DESI constrains
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Conclusions
BAO
- compared to Planck: low Ωm, high H0
- hint of dynamical dark energy (depending on SN dataset)
Adding Full Shape
- σ8,S8 consistent with Planck
- modified gravity μ0 parameter consistent with GR
- small improvements in w0,wa and ∑mν constraints
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What to do next?
DR2 data (Y3 > Y1) on disk, DR2 BAO analysis on-going... stay tuned!
DR2 analyses will include joint 2-pt, 3-pt measurements: new challenges!
Possible improvements to the current analyses:
- more / improved mocks
- faster cosmological inference with emulators / JAX
- simplify P(k) and associated window measurements
fNLloc - mock constraints
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Chaussidon et al. 2024, in prep
DR1: σ(fNLloc)∼10
SDSS: σ(fNLloc)∼20
LRG
QSO
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Successfully removes the >1σ bias
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credit: Ruiyang Zhao
Fiber collisions
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Combined constraints
*DES and SPT collaborations 2022
6x2pt = galaxy-galaxy, galaxy-shear, shear-shear, galaxy-CMB lensing, shear-CMB lensing, CMB lensing-CMB lensing
- Adding DESI to DESY3 6x2pt improves σ8 and Ωm precision by ×2 (S8 by 20%)
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Combined constraints
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- Adding DESI to DESY3 6x2pt improves σ8 and Ωm precision by ×2 (S8 by 20%)
- Adding DESI to CMB improves Ωm, H0 and S8 precision by 30%
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Combined constraints
- Adding DESI to DESY3 6x2pt improves σ8 and Ωm precision by ×2 (S8 by 20%)
- Adding DESI to CMB improves Ωm, H0 and S8 precision by 30%
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Dynamical Dark Energy - (Ωm,σ8)
(Ωm,σ8) constraints remain stable when opening up to w0waCDM
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Dynamical Dark Energy - (Ωm,σ8)
(Ωm,σ8) constraints remain stable when opening up to w0waCDM
SN (uncalibrated):
- Pantheon+ Brout, Scolnic, Popovic et al., 2022
- Union3 Rubin, Aldering, Betoule et al. 2023
- DES-SN5YR DES Collaboration et al. 2024
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Other datasets
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- SDSS (for comparisons only): eBOSS Collaboration, 2020
- Primary CMB: Planck Collaboration, 2018
- CMB lensing: Planck PR4 + ACT DR6 lensing ACT Collaboration, 2023, Carron, Mirmelstein, Lewis, 2022
- BBN: Schöneberg 2024
- SN: Pantheon+ Brout, Scolnic, Popovic et al. 2022, Union3 Rubin, Aldering, Betoule et al. 2023, DES-SN5YR DES Collaboration
- DESY3 3x2pt DES collaboration 2021, 6x2pt DES and SPT collaborations 2022
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DESI + CMB measurements favor a flat Universe
Spatial curvature
Dark Energy Equation of State
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Constant EoS parameter w=p/ρ
Dark Energy Equation of State
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Constant EoS parameter w=p/ρ
Dark Energy Equation of State
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SNe (uncalibrated):
- Pantheon+ Brout, Scolnic, Popovic et al., 2022
Constant EoS parameter w=p/ρ
Dark Energy Equation of State
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SNe (uncalibrated):
- Pantheon+ Brout, Scolnic, Popovic et al., 2022
- Union3 Rubin, Aldering, Betoule et al. 2023
Constant EoS parameter w=p/ρ
Dark Energy Equation of State
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SNe (uncalibrated):
- Pantheon+ Brout, Scolnic, Popovic et al., 2022
- Union3 Rubin, Aldering, Betoule et al. 2023
- DES-SN5YR DES Collaboration et al. 2024
Constant EoS parameter w=p/ρ
Dark Energy Equation of State
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Assuming a constant EoS, DESI BAO fully compatible with a cosmological constant...
Constant EoS parameter w=p/ρ
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Dark Energy Equation of State
Varying EoS
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Dark Energy Equation of State
Varying EoS
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Dark Energy Equation of State
Varying EoS
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Dark Energy Equation of State
Varying EoS
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Dark Energy Equation of State
Varying EoS
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Dark Energy Equation of State
Combining all DESI + CMB + SN
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Dark Energy Equation of State
Combining all DESI + CMB + SN
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Dark Energy Equation of State
Combining all DESI + CMB + SN
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Dark Energy Equation of State
Combining all DESI + CMB + SN
w0>−1,wa<0 favored, level varying on the SN dataset
Sum of neutrino masses
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Internal CMB degeneracies limiting precision on the sum of neutrino masses
Sum of neutrino masses
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Internal CMB degeneracies limiting precision on the sum of neutrino masses
Broken by BAO, especially through H0
Low preferred value of H0 yields
∑mν<0.072eV(95%,DESI + CMB)
Limit relaxed for extensions to ΛCDM
∑mν<0.195eV for w0waCDM
Neutrino mass hierarchies
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With >0.059eV prior (NH)
Neutrino mass hierarchies
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With >0.059eV prior (NH)
With >0.1eV prior (IH)
Neutrino mass hierarchies
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With >0.059eV prior (NH)
With >0.1eV prior (IH)
Current constraints do not strongly favor normal over inverted hierarchy (≃2σ)
Summary
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DESI already has the most precise BAO measurements ever
Summary
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DESI already has the most precise BAO measurements ever
DESI BAO is consistent (at the ∼1.9σ level) with CMB in flat ΛCDM
Summary
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DESI already has the most precise BAO measurements ever
DESI BAO is consistent (at the ∼1.9σ level) with CMB in flat ΛCDM
In flat ΛCDM, DESI prefers "small Ωm, large H0 (though 3.7σ away from SH0ES), small ∑mν"
Summary
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DESI already has the most precise BAO measurements ever
DESI BAO is consistent (at the ∼1.9σ level) with CMB in flat ΛCDM
In flat ΛCDM, DESI prefers "small Ωm, large H0 (though 3.7σ away from SH0ES), small ∑mν"
Some hint of time-varying Dark Energy equation of state especially when combined with supernovae measurements
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DESI data release 1 (DR1)
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5.7 million unique redshifts at z < 2.1 and > 420,000 Lyα QSO at z > 2.1
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DESI Y5 forecasts
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Survey Validation (arXiv:2306.06307)
BAO and RSD constraints at the end of the survey (Δz=0.1)
Lyα
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DESI Y5 forecasts
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Survey Validation (arXiv:2306.06307)
BAO and RSD constraints at the end of the survey (Δz=0.1)
Lyα
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(w/ Planck)
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Power spectra
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Power spectra
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BAO wiggles
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Density field reconstruction
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DESI DR1 Lyα BAO analysis
- Biggest ever Lyα dataset (Ntracer)
- First blind analysis to mitigate observer / confirmation biases (correlation function-level blinding)
- Modelling of the correlation function:
- cosmo signal
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linear bias + RSD
hydro-sim
BAO
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DESI DR1 Lyα BAO analysis
- Biggest ever Lyα dataset (Ntracer)
- First blind analysis to mitigate observer / confirmation biases (correlation function-level blinding)
- Modelling of the correlation function:
- cosmo signal
- high-column density
- metal absorbers
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SiII
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DESI DR1 Lyα BAO analysis
- Biggest ever Lyα dataset (Ntracer)
- First blind analysis to mitigate observer / confirmation biases (correlation function-level blinding)
- Modelling of the correlation function:
- cosmo signal
- high-column density
- metal absorbers
- correlated noise (sky subtraction)
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DESI DR1 Lyα BAO analysis
- Biggest ever Lyα dataset (Ntracer)
- First blind analysis to mitigate observer / confirmation biases (correlation function-level blinding)
- Modelling of the correlation function:
- cosmo signal
- high-column density
- metal absorbers
- correlated noise (sky subtraction)
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DESI DR1 Lyα BAO analysis
- Biggest ever Lyα dataset (Ntracer)
- First blind analysis to mitigate observer / confirmation biases (correlation function-level blinding)
- Modelling of the correlation function
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physical model fit
+ broadband polynomial
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broadband: <0.1σ
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DESI DR1 Lyα BAO analysis
- Biggest ever Lyα dataset (Ntracer)
- First blind analysis to mitigate observer / confirmation biases (correlation function-level blinding)
- Modelling of the correlation function
- Covariance matrix
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Correlation matrix
smoothed jackknife, validated with mocks
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Tests of systematic errors
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tests with same dataset (not red): shifts <σstat/3
tests with varying datasets (red): shifts consistent with stat.
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Tests of systematic errors
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DESI DR1 BAO analysis
- Biggest ever spectroscopic BAO dataset (Ntracer and V)
- Blind analysis to mitigate observer / confirmation biases (catalog-level blinding)
fiducial cosmology
blinded cosmology (Ωm,w0,wa)
(random & unknown)
+ RSD blinding: change reconstructed peculiar velocities
+ fNL blinding: add clustering-dependent signal on large scales with weights
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DESI DR1 BAO analysis
- Biggest ever spectroscopic BAO dataset (Ntracer and V)
- Blind analysis to mitigate observer / confirmation biases (catalog-level blinding)
- Theory developments in BAO fitting code
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Chen, Howlett et al. 2024
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Some fits: Fourier space
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∑mν
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credit: Christophe Yèche
w(z)
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DESI - SDSS consistency (Ωm)
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Perfectly consistent!
Using these 2 points alone moves Ωm by <2σ
Are SN Ωm consistent?
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Not so much in flat ΛCDM...
(so we do not combine them in this model!)
Are SN Ωm consistent?
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Consistent in w0waCDM!
plik vs PR4 Planck likelihoods
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Appendix B
w0−wa with ∑mν free
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w0−wa with ΩK
Preference for w0>−1,wa<0 persists when curvature is left free
DE constraints driven by low-z ?
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Not that much!
DESI + SDSS swaps DESI measurements with SDSS for z<0.6
−0.4σ compared to DESI only
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w(z)
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Dark energy equation of state:
P=wρ
- w = constant
BAO measurements: dark energy
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BAO measurements: dark energy
Full tables
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Full tables
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Full tables
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Full tables
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Marseille_November2024
By Arnaud De Mattia
Marseille_November2024
- 138