Arnaud de Mattia
CEA Saclay
CPPM
November 2024
Thanks to our sponsors and
72 Participating Institutions!
Physics program
- Galaxy and quasar clustering
- Lyman-alpha forest
- Clusters and cross-correlations
- Galaxy and quasar physics
- Milky Way Survey
- Transients and low-z
Physics program
- Galaxy and quasar clustering
- Lyman-alpha forest
- Clusters and cross-correlations
- Galaxy and quasar physics
- Milky Way Survey
- Transients and low-z
10 years = \(10 \times \)
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 \(\sim 40\)M galaxy redshifts!
\(z = 0.4\)
\(z = 0.8\)
\(z = 0\)
\(z = 1.6\)
\(z = 2.0\)
\(z = 3.0\)
imaging surveys (2014 - 2019) + WISE (IR)
target selection
spectroscopic observations
spectra and redshift measurements
focal plane 5000 fibers
wide-field corrector
6 lenses, FoV \(\sim 8~\mathrm{deg}^{2}\)
Kitt Peak, AZ
4 m mirror
focal plane 5000 fibers
fiber view camera
ten 3-channel spectrographs
49 m, 10-cable fiber run
Kitt Peak, AZ
Exposure time (dark): 1000 s
Configuration of the focal plane
CCD readout
Go to next pointing
140 s
0.1 mm
wavelength
fiber number
\(z = 2.1\) QSO
\(z = 0.9\) ELG
Ly\(\alpha\)
CIV
CIII
[OII] doublet at \(2727 \AA\) up to \(z = 1.6\)
[OII]
Ly\(\alpha\) at \(1216 \AA\) down to \(z = 2.0\)
Observations from May 14th 2021 to June 12th 2022
Final survey
- dark time (LRG, ELG, QSO): 7 layers
- bright time (BGS): 5 layers
- 14,000 \(\mathrm{deg}^2\)
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
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
galaxy catalog
galaxy power spectrum (or correlation function)
cosmological constraints
compression = "we measure specific features"
"variance of the density field as a function of scale"
Full Shape (baseline)
BAO
ShapeFit (alternative Full Shape)
Sound waves in primordial plasma
At recombination (\(z \sim 1100\))
spherical shell in the distribution of galaxies, of radius the distance that sound waves travelled
= sound horizon scale at the drag epoch \( r_\mathrm{d} \sim 150 \; \mathrm{Mpc} \sim 100 \; \mathrm{Mpc}/h \)
standard ruler
transverse comoving distance
sound horizon \(r_d\)
Hubble distance
sound horizon \(r_d\)
At multiple redshifts \(z\)
Probes the expansion history, hence the energy content
Absolute size at \(z = 0\): \(H_0 r_d\)
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
BAO peak
Excess probability to find 2 galaxies separated by a distance s
BAO wiggles
Fourier transform of the correlation function
isotropic measurement
anisotropic measurement
Non-linear structure growth and peculiar velocities blur and shrink (slightly) the ruler
Reconstruction: estimate Zeldovich displacements from observed field and moves galaxies back \(\rightarrow\) refurbishes the ruler (improves precision and accuracy)
reconstruction
5.7 million unique redshifts
Effective volume \(V_\mathrm{eff} = 18 \; \mathrm{Gpc}^{3}\)
\(3 \times \) bigger than SDSS!
Considered many possible sources of systematic errors using simulations and data:
no systematics detected
systematics << statistics
Maximum effect: \(\sigma_\mathrm{stat. + syst.} < 1.05 \sigma_\mathrm{stat.}\)
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
Absorption in QSO spectra by neutral hydrogen in the intergalactic medium: \(\lambda_\mathrm{abs} = (1 + z_\mathrm{HI}) \times 1215.17 \; \AA \)
Transmitted flux fraction \(F = e^{-\tau}\) probes the fluctuation in neutral hydrogen density, \(\tau \propto n_\mathrm{HI} \)
credit: Andrew Pontzen
Ly\(\alpha\) - Ly\(\alpha\)
Ly\(\alpha\) - QSO
QSO
QSO
HI cloud
HI cloud
HI cloud
QSO
>420,000 Ly\(\alpha\) QSO at z > 2.1
\(2 \times \) more than SDSS!
Let's factor out the \(h\) terms:
BAO measurements at different \(z\) constrain:
DESI DR1 BAO measurements
DESI DR1 BAO measurements
DESI DR1 BAO measurements
DESI DR1 BAO measurements
DESI DR1 BAO measurements
DESI DR1 BAO measurements
Consistent with each other,
and complementary
DESI DR1 BAO measurements
DESI DR1 BAO consistent with:
DESI DR1 BAO consistent with:
DESI DR1 BAO consistent with:
\(\implies\) constraints on \(h\) i.e. \(H_0 = 100 h \; \mathrm{km} / \mathrm{s} / \mathrm{Mpc}\)
\(\theta_\ast\) CMB angular acoustic scale
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
clustering
We fit the "full shape" (FS) of the galaxy power spectrum multipoles
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
(\( \Omega_\mathrm{cdm} h^2, \Omega_\mathrm{b} h^2, n_\mathrm{s}, \sum m_\nu \))
growth of structure \(f\sigma_8\) sensitive to the theory of gravity and dark energy
Three power spectrum Effective Field Theory models considered:
- velocileptors Maus et al. 2024
- folps Noriega et al. 2024
- pybird Lai et al. 2024
credit: Mark Maus, Hernan Noriega, Yan Lai
Comparison paper:
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
Groups of galaxies too close to each other cannot all receive a fiber
\(0.05^\circ \simeq\) positioner patrol diameter
Impacts power spectrum measurements (altMTL vs complete)
Impacts power spectrum measurements (altMTL vs complete)
Solution: \(\theta\)-cut = remove all pairs \(< 0.05^\circ\)
New window matrix \(W^\mathrm{cut}\); \(\langle P_o(k) \rangle = W^\mathrm{cut}(k, k^\prime) P_t(k^\prime)\)
New window matrix \(W^\mathrm{cut}\); \(\langle P_o(k) \rangle = W^\mathrm{cut}(k, k^\prime) P_t(k^\prime)\)
Very non diagonal: let's "rotate" it
Theoretical modelling (Maus et al. 2024ab, Lai et al. 2024, Noriega et al. 2024, Ramirez et al. 2024)
Galaxy-halo connection (Findlay et al. 2024)
Fiducial cosmology (Gsponer et al. 2024)
Fibre assignment (Pinon et al. 2024)
Inhomogeneities in the target selection (Zhao et al. 2024)
Spectroscopic redshift failures/uncertainties (Yu et al. 2024, Krowleski et al. 2024)
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
Observable: power spectrum monopole and quadrupole, post-reconstruction BAO
Model: Effective Field Theory
Covariance: mock-based
Systematic error: at the data vector level
Fitting range: \(0.02 < k\, [h/\mathrm{Mpc}] < 0.2\)
Fitting parameters:
7 nuisance parameters
5 \(\Lambda\)CDM parameters
External information
\(\Omega_\mathrm{b} h^2\): BBN from Schöneberg 2024
\(n_\mathrm{s} \sim \mathcal{G}(0.9649, 0.042^2)\): "\(n_{\mathrm{s}10}\)" \(10\times\) wider than Planck posterior
\(\omega_\mathrm{b}\): BBN, \(n_\mathrm{s} \sim \mathcal{G}(0.9649, 0.042^2)\)
\(\omega_\mathrm{b}\): BBN, \(n_\mathrm{s} \sim \mathcal{G}(0.9649, 0.042^2)\)
\(\omega_\mathrm{b}\): BBN, \(n_\mathrm{s} \sim \mathcal{G}(0.9649, 0.042^2)\)
\(\omega_\mathrm{b}\): BBN, \(n_\mathrm{s} \sim \mathcal{G}(0.9649, 0.042^2)\)
\(\omega_\mathrm{b}\): BBN, \(n_\mathrm{s} \sim \mathcal{G}(0.9649, 0.042^2)\)
\(\omega_\mathrm{b}\): BBN, \(n_\mathrm{s} \sim \mathcal{G}(0.9649, 0.042^2)\)
\(\omega_\mathrm{b}\): BBN, \(n_\mathrm{s} \sim \mathcal{G}(0.9649, 0.042^2)\)
\(S_8 = \sigma_8 (\Omega_\mathrm{m} / 0.3)^{0.5}\) best constrained by weak lensing surveys
\(S_8 = \sigma_8 (\Omega_\mathrm{m} / 0.3)^{0.5}\) best constrained by weak lensing surveys
\(S_8 = \sigma_8 (\Omega_\mathrm{m} / 0.3)^{0.5}\) best constrained by weak lensing surveys
Dark Energy fluid, pressure \(p\), density \(\rho\)
Equation of State parameter \(w = p / \rho\)
Linked to the evolution of Dark Energy \(w(z) = -1 + \frac{1}{3}\frac{d \ln f_\mathrm{DE}(z)}{d \ln (1 + z)}\)
Let's assume the CPL parameterization
\(\Lambda\)CDM: \((w_0, w_a) = (-1, 0)\)
DESI + CMB + SN (uncalibrated):
\(\Lambda\)CDM
\(2.5\sigma\)
\(3.4\sigma\)
\(3.8\sigma\)
Massive neutrinos impact:
i) the expansion history
ii) the growth of structure: \( \Delta P(k)/P(k) \propto -\sum m_\nu / \omega_\mathrm{m} \)
the \(k\)-fitting range
Massive neutrinos impact:
i) the expansion history
ii) the growth of structure: \( \Delta P(k)/P(k) \propto -\sum m_\nu / \omega_\mathrm{m} \)
Taking \(n_\mathrm{s}\) prior from Planck:
Internal CMB degeneracies limiting precision on the sum of neutrino masses
Broken by DESI, especially through \(H_{0}\)
Internal CMB degeneracies limiting precision on the sum of neutrino masses
Broken by DESI, especially through \(H_{0}\)
Low preferred value of \(H_{0}\) yields
\(\sum m_\nu < 0.071 \, \mathrm{eV} \; (95\%, \color{green}{\text{DESI + CMB})}\)
(\(15\%\) better than BAO-only: \(0.082 \, \mathrm{eV} \))
\(\sum m_\nu < 0.081 \, \mathrm{eV} \; (95\%, \color{green}{\text{DESI + CMB[hillipop]})}\)
In \(w_0w_a\mathrm{CDM}\), with DES-SN5YR: \(\sim 0.2\, \mathrm{eV} \; (95\%)\)
In general relativity, \(\green{\mu(a, k)} = \green{\Sigma(a, k)} = 1\)
To test GR, introduce \(\green{\mu_0, \Sigma_0}\)
Perturbed FLRW metric
\(ds^2=a(\tau)^2[-(1+2\orange{\Psi})d\tau^2+(1-2\orange{\Phi})\delta_{ij}dx^i dx^j]\)
At late times:
(mass) \(k^2\orange{\Psi} = -4\pi G a^2 \green{\mu(a,k)} \blue{\sum_i\rho_i\Delta_i}\)
(light) \(k^2(\orange{\Phi} + \orange{\Psi})=-8\pi G a^2 \green{\Sigma(a,k)} \blue{\sum_i\rho_i\Delta_i}\)
gravitational potentials
density perturbations
DESI constrains
GR
\(\Sigma_0\) constrained by
- CMB (ISW and lensing)
- galaxy lensing
DESI constrains
\(\Sigma_0\) constrained by
- CMB (ISW and lensing)
- galaxy lensing
compared to CMB-nl + DESY3 (3x2pt) only: \(\sigma(\mu_0) / 2.5\), \(\sigma(\Sigma_0) / 2\)
DESI constrains
BAO
- compared to Planck: low \(\Omega_\mathrm{m}\), high \(H_{0}\)
- hint of dynamical dark energy (depending on SN dataset)
Adding Full Shape
- \(\sigma_8, S_8\) consistent with Planck
- modified gravity \(\mu_0\) parameter consistent with GR
- small improvements in \(w_0, w_a\) and \(\sum m_\nu\) constraints
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
Chaussidon et al. 2024, in prep
DR1: \(\sigma(f_\mathrm{NL}^\mathrm{loc}) \sim 10\)
SDSS: \(\sigma(f_\mathrm{NL}^\mathrm{loc}) \sim 20\)
LRG
QSO
Successfully removes the \( > 1 \sigma\) bias
credit: Ruiyang Zhao
*DES and SPT collaborations 2022
6x2pt = galaxy-galaxy, galaxy-shear, shear-shear, galaxy-CMB lensing, shear-CMB lensing, CMB lensing-CMB lensing
(\(\Omega_\mathrm{m}, \sigma_{8})\) constraints remain stable when opening up to \(w_0w_a\text{CDM}\)
(\(\Omega_\mathrm{m}, \sigma_{8})\) constraints remain stable when opening up to \(w_0w_a\text{CDM}\)
SN (uncalibrated):
DESI + CMB measurements favor a flat Universe
Constant EoS parameter \(w = p / \rho\)
Constant EoS parameter \(w = p / \rho\)
SNe (uncalibrated):
Constant EoS parameter \(w = p / \rho\)
SNe (uncalibrated):
Constant EoS parameter \(w = p / \rho\)
SNe (uncalibrated):
Constant EoS parameter \(w = p / \rho\)
Assuming a constant EoS, DESI BAO fully compatible with a cosmological constant...
Constant EoS parameter \(w = p / \rho\)
Varying EoS
Varying EoS
Varying EoS
Varying EoS
Varying EoS
Combining all DESI + CMB + SN
Combining all DESI + CMB + SN
Combining all DESI + CMB + SN
Combining all DESI + CMB + SN
\(w_{0} > -1, w_{a} < 0\) favored, level varying on the SN dataset
Internal CMB degeneracies limiting precision on the sum of neutrino masses
Internal CMB degeneracies limiting precision on the sum of neutrino masses
Broken by BAO, especially through \(H_{0}\)
Low preferred value of \(H_{0}\) yields
\(\sum m_\nu < 0.072 \, \mathrm{eV} \; (95\%, \color{green}{\text{DESI + CMB})}\)
Limit relaxed for extensions to \(\Lambda\mathrm{CDM}\)
\(\sum m_\nu < 0.195 \, \mathrm{eV}\) for \(w_0w_a\mathrm{CDM}\)
With \(> 0.059 \, \mathrm{eV}\) prior (NH)
With \(> 0.059 \, \mathrm{eV}\) prior (NH)
With \(> 0.1 \, \mathrm{eV}\) prior (IH)
With \(> 0.059 \, \mathrm{eV}\) prior (NH)
With \(> 0.1 \, \mathrm{eV}\) prior (IH)
Current constraints do not strongly favor normal over inverted hierarchy (\(\simeq 2 \sigma\))
DESI already has the most precise BAO measurements ever
DESI already has the most precise BAO measurements ever
DESI BAO is consistent (at the \(\sim 1.9\sigma\) level) with CMB in flat ΛCDM
DESI already has the most precise BAO measurements ever
DESI BAO is consistent (at the \(\sim 1.9\sigma\) level) with CMB in flat ΛCDM
In flat ΛCDM, DESI prefers "small \(\Omega_\mathrm{m}\), large \(H_0\) (though \(3.7\sigma\) away from SH0ES), small \(\sum m_\nu\)"
DESI already has the most precise BAO measurements ever
DESI BAO is consistent (at the \(\sim 1.9\sigma\) level) with CMB in flat ΛCDM
In flat ΛCDM, DESI prefers "small \(\Omega_\mathrm{m}\), large \(H_0\) (though \(3.7\sigma\) away from SH0ES), small \(\sum m_\nu\)"
Some hint of time-varying Dark Energy equation of state especially when combined with supernovae measurements
5.7 million unique redshifts at z < 2.1 and > 420,000 Ly\(\alpha\) QSO at z > 2.1
Survey Validation (arXiv:2306.06307)
BAO and RSD constraints at the end of the survey (\( \Delta z = 0.1 \))
Ly\(\alpha\)
Survey Validation (arXiv:2306.06307)
BAO and RSD constraints at the end of the survey (\( \Delta z = 0.1 \))
Ly\(\alpha\)
(w/ Planck)
BAO wiggles
linear bias + RSD
hydro-sim
BAO
SiII
physical model fit
+ broadband polynomial
broadband: \(< 0.1\sigma\)
Correlation matrix
smoothed jackknife, validated with mocks
tests with same dataset (not red): shifts \(< \sigma_\mathrm{stat}/3\)
tests with varying datasets (red): shifts consistent with stat.
fiducial cosmology
blinded cosmology (\(\Omega_\mathrm{m}, w_0, w_a\))
(random & unknown)
+ RSD blinding: change reconstructed peculiar velocities
+ \(f_\mathrm{NL}\) blinding: add clustering-dependent signal on large scales with weights
Chen, Howlett et al. 2024
credit: Christophe Yèche
Perfectly consistent!
Using these 2 points alone moves \(\Omega_\mathrm{m}\) by \(< 2 \sigma\)
Not so much in flat \(\Lambda\mathrm{CDM}\)...
(so we do not combine them in this model!)
Consistent in \(w_0w_a\mathrm{CDM}\)!
Appendix B
Preference for \(w_{0} > -1, w_{a} < 0\) persists when curvature is left free
Not that much!
DESI + SDSS swaps DESI measurements with SDSS for \(z < 0.6\)
\(- 0.4 \sigma\) compared to DESI only
Dark energy equation of state:
\(P = w \rho\)