Cosmology session overview

Journée de Rencontre Jeunes Chercheur.se.s 2024

 

Corentin Ravoux

LPCA, CNRS/IN2P3, Clermont-Ferrand

 

ACCEL² simulation

Cosmological context

How did the Universe evolve to its current state?
What are the fundamental constituents of our Universe?
How is matter distributed in the Universe?

The Story of Our Universe - NASA

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JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

Global Universe description

Structures in the Universe

\mathrm{flat}\ \Lambda\mathrm{CDM}

Chabanier et al. 2019

Walther et al. 2021

Planck 2018

Adapted from Dijkstra 2017

Cosmic Krampouz

Galette dark matter model ?

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

Global Universe description

\mathrm{flat}\ \Lambda\mathrm{CDM} = \left\{\Omega_{\mathrm{b}} ; \Omega_{\mathrm{cdm}} ; H_0 ; \tau ; A_{\mathrm{s}} ; n_{\mathrm{s}}\right\}
G_{\mu \nu}+\Lambda g_{\mu \nu} = 8 \pi G_{\mathrm{N}} T_{\mu \nu}

Einstein equation

Flat FLRW metric

Cosmological constant

Energy-momentum tensor

Components of the Universe (dark energy, dark matter, baryons, neutrinos, photons) modify the Universe expansion (Only 5% known)

Adapted from Dijkstra 2017

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

Global Universe description

Structures in the Universe

\mathrm{flat}\ \Lambda\mathrm{CDM} = \left\{\Omega_{\mathrm{b}} ; \Omega_{\mathrm{cdm}} ; H_0 ; \tau ; A_{\mathrm{s}} ; n_{\mathrm{s}}\right\}
G_{\mu \nu}+\Lambda g_{\mu \nu} = 8 \pi G_{\mathrm{N}} T_{\mu \nu}

Einstein equation

Flat FLRW metric

Cosmological constant

Energy-momentum tensor

Friedmann equation

H^2=\frac{8\pi G \rho}{3}+\frac{\Lambda}{3}

Hubble constant

Adapted from Dijkstra 2017

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

Structures in the Universe

\mathrm{flat}\ \Lambda\mathrm{CDM} = \left\{\Omega_{\mathrm{b}} ; \Omega_{\mathrm{cdm}} ; H_0 ; \tau ; A_{\mathrm{s}} ; n_{\mathrm{s}}\right\}

Planck 2018

Cosmic Microwave Background = First light after recombination (e⁻,p)

  • Initial density perturbations in the primordial Universe seen on CMB
  • Measuring CMB provides information on the opacity of the Universe = optical depth to reionisation

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

Structures in the Universe

\mathrm{flat}\ \Lambda\mathrm{CDM} = \left\{\Omega_{\mathrm{b}} ; \Omega_{\mathrm{cdm}} ; H_0 ; \tau ; A_{\mathrm{s}} ; n_{\mathrm{s}}\right\}

Chabanier et al. 2019

Walther et al. 2021

  • Perturbations grows to form the cosmic web: Nodes, filaments, walls and voids
  • Large-scale distribution of matter characterized by the linear power spectrum amplitude and slope
\delta G_{\mu \nu}=\kappa \delta T_{\mu \nu}

Perturbed Einstein equation

... or full simulation

Only the simplest model !

ACCEL² simulation

Current questions in Cosmology

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

  • Dark energy: Nature (cosmological constant? particle? field? fifth force?) and Behavior (evolution? interaction?)
  • Dark matter: Nature (particle? field?) and Behavior (cold? warm? interaction?)
  • Testing general relativity: modified gravity at large scale could explain unknowns?
  • Neutrinos: Impact on cosmology can constrain neutrino mass
  • Inflation: Indirect detection, constraining theories
  • Hubble tension: mismatch between early and late-time probe (up to 5σ)

ACCEL² simulation

Cosmological experiments

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

ACCEL² simulation

Types of telescope

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

Source

Cosmic web

Telescope

Atmosphere

Milky Way

Electromagnetic radiation observations (from gamma to radio)

CMB, Supernova, galaxy...

ground/space

CMB experiments

The Story of Our Universe - NASA

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JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

Cosmic Microwave Background (CMB)

ACCEL² simulation

Cosmic Microwave Background

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

Planck 2018 temperature map

  • CMB = quasi-perfect black body at 2.73 K
  • Telescopes generally use bolometers to measure frequency maps (microwave range)
  • Variation in the temperature map used to constrain primordial Universe:
    • Spatial variations (T)
    • Polarization (E, B)

Planck 2015 frequency maps

ACCEL² simulation

Current and future CMB experiments

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

  • COBE, WMAP, Planck: Space telescopes that gave precise temperature maps and stringent CMB constraints.
  • Current: Atacama Cosmology Telescope, Simons Observatory, BICEP
  • Future: CMB-S4 (2032)
  • Science cases:
    • Inflation constraints (T, E, B maps)
    • ΛCDM constraints (Neff, τ)
    • CMB lensing
    • Cluster detection

Planck 2018

TT power spectrum

ACCEL² simulation

Signature from inflation

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

  • Most of inflation theories predict primordial gravitational waves, which create B-type polarization on CMB maps
  • CMB measurement put constraints on the scalar-to-tensor ratio

 

  • A lot of contaminants: lensing, dust, atmosphere, galactic synchrotron, systematics, noise...

See talk from Leonora Kardum

r = A_{\mathrm{t}} / A_{\mathrm{s}}

Galaxy experiments

The Story of Our Universe - NASA

You are here

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

Galaxy surveys

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

Photometric surveys

Source: DESI communication figures

  • Measure the spectra of objects (selected or not)
  • Examples: SDSS, 6dFGS, DESI, 4MOST, Euclid NISP (spectro)
  • Measure the object flux through a filter
  • Examples: DES, ZTF, CFHT, LSST, Euclid VIS, Euclid NISP (photo)

Spectroscopic surveys

ACCEL² simulation

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

Zwicky Transient Facility (ZTF)

  • ZTF = high-cadence photometric telescop in the Palomar observatory
  • Very large field of view (47 deg²)
  • Observing 3/4 of the sky every nights with 3 filters (g, r, i)

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

Zwicky Transient Facility (ZTF)

  • Transient sky: Supernovae, gamma ray burst, tidal distruptive events, comets, asteroids

  • Dedicated spectroscopic telescope measuring transient spectra

  • Latest release: More than 3000 classified supernovae of type Ia

ACCEL² simulation

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

ZTF - supernovae of type Ia

See talk from Constance Ganot

  • SNIa: White dwarf in a binary system reaches Chandrasekhar mass
  • Standardizable candle: can be used to measure distance
  • Science cases:
    • Hubble constant measurement
    • Dark energy constraints (with high-z)
    • Modified gravity constraints

Betoule et al. 2014

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

Rubin - LSST

30 m diameter dome

Telescope mount assembly

AuxTel: 1.2m atmospheric telescop

Cerro Pachon

Service and maintenance facility

Control room

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

Rubin - LSST: instrument

  • Largest numerical camera in the world: 3.2 Gpixels with 2s readout time
  • 8.4 m primary mirror and 9.6 deg² field of view
  • 6 filters: (u, g, r, i, z, y)
  • 10-year photometric survey of half of the sky (~ 20 000 deg²)
  • Complete coverage every 4 nights (static and transient survey)
  • In commissioning, expected start in september 2025

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

LSST survey: science

Dark matter & Dark energy

       - Strong & Weak lensing

       - BAO (angular and photo-z)

       - Clusters, Supernovae cosmology

Mapping the Milky Way

       - Structure and evolution

       - Stellar properties

Solar System science

       - Comets & asteroids

       - Small body census

Transient sky

       - Supernovae, variable stars

       - Rare events (kilonovae, TDE)

       - New classes of transients

JRJC 2024 - Cosmology session                                                                                                                                                                  25 november 2024

LSST survey: clusters

See talk from Nathan Amouroux

  • Cluster = group of galaxies bounded by gravity
  • Cluster science:
    • Abundance = Number as a function of redshift and mass (ΛCDM constraints)
    • Cluster structure and history (DM constraints)
    • Cluster clustering
  • Bright object saturates on LSST camera and masking them can impact cluster science

ACCEL² simulation

Conclusion

  • Still a lot of questioning concerning the "not-so-standard" model of Cosmology
  • Current cosmological experiments (CMB, SNIa, galaxy surveys...) help tightening constraints and provide feedback to theory
  • Improvement of analysis methods is necessary as we are getting more and more data (see next talks)