Corentin Cadiou
CNRS Researcher
Journées Galaxies ATCG | 2026
What flows from the cosmic web into galaxies?
And how would we know?
Left: Leclercq+17
Right: Galárraga-Espinosa+23
Bottom left: Ramsøy+21
Cosmic web: a multiscale structure
From Mpc scales
all the way to galactic scales
Cosmic web: effects on scalar halo properties
Biasing formation histories:
- Late formation & high accretion rate (for high-mass halos)
- Early formation & low accretion rate (for low-mass halos)
in filament compared to field
Left: Musso, CC+18
Right: Kraljic, ..., CC+18
See also Gao+05, Hahn+09, Borzyszkowski+17, Tojeiro+17, ...
High mass Low mass
Late form. Early form
High-mass scenario
Cosmic web: effects on scalar galaxy properties
Close to cosmic web:
- redder & lower sSFR
- less rotation-supported (smaller \(v/\sigma\))
Left: Kraljic,...CC+18 (GAMA)
Right: Laigle+18 (COSMOS)
See also Kuutma+17, Malavasi+17, Alpaslan+16 or O'Kane+24
Halo assembly
& baryon-specific effects
- feedback
- accretion
Cosmic web: effects on halo vector properties
Small \(\perp\) alignment of halo spin/shape with filament axis
Left: Codis+18
Right: Ganeshaiah Veena+18
See e.g. Tempel+13 for measurement in observation
\(\perp\) filament
// filament
🚧 ¼ temporary conclusion 🚧
CW drives 1%-level effects?
Cosmic web: effects on halo vector properties
How can we study this?
Sample \(M\) at fixed cosmic web
or sample cosmic web at fixed \(M\)
Storck, CC+25 / Bot. right: Aragon-Calvo 15
\( \pm 20\% \)!
🚧 ½ temporary conclusion 🚧
Local CW drives 20%-level effects!*
*for DM halos
Cosmic web: effects on galactic vector properties
Small \(\perp\) alignment of halo spin with filament
Genetically modified simulations: CC+22
comical to present at “Journées ATCG”
Environment perturbed on \(>\mathrm{Mpc}\) scales
Cosmic-web-scale information trickles to galactic scale \(\Rightarrow\) what's the messenger?
🚧 ¾ temporary conclusion 🚧
Local CW drives 20%-level effects!*
*for galaxies
So… effects of the CW on galaxy formation. Is it \(\ll 1\%\) or \(\gg 20\%\)?
So… effects of the CW on galaxy formation. Is it \(\ll 1\%\) or \(\gg 20\%\)?
Talk to Sabri Errachdi for more information!
The local cosmic web \(<1\,\mathrm{Mpc}\): observations
First (?) measurement of the local cosmic web in observations
\(M_\star=10^{9}-10^{12}M_\odot\); miniJPAS and DESI: Galárraga-Espinosa+25
\(3\,\mathrm{Mpc}\)
\(\sim1/3\,R_\mathrm{vir}\)
The local cosmic web \(<1\,\mathrm{Mpc}\): theory
2-3 “Cold flows” embedded in local cosmic web pancakes, feeding the galaxy
\(z=2.5, M_\star = 10^{12}\,M_\odot\); Danovich+12
The CGM cosmic web \(\lessapprox 100\,\mathrm{kpc}\): observations
Hints of detection of anisotropic extended cold emission
Excess of Ly\(\alpha\) in stacked images
\(3< z< 4\); Gallego+18
Ly\(\alpha\) radiation between quasar pairs; \( z\sim 3\); Herwig+24
Ly\(\alpha\), CIV and HeII emissions; Vayner+23
The CGM cosmic web \(\lessapprox 100\,\mathrm{kpc}\): theory
Ly\(\alpha\), OIII] \(\lambda\lambda 1663\mathrm{Å}\), HeII \(\mathrm{\lambda} \mathrm{1640Å}\), ...: tracers of the CGM-cosmic web connection?
Simulated \(n_\mathrm{OIII}\), Megatron; \(z=4\); CC+26
Mitchell, ... CC+20
The CGM cosmic web \(\lessapprox100\,\mathrm{kpc}\): theory
Survival and observability of cold flows
Aung+24, see also Mandelker+16,19; Padnos+18; Cornuault+18
Connecting the cosmic web through the CGM
Effect of \(>\mathrm{Mpc}\) scale CW on galaxy well-established...
but likely massively underestimated
How this manifest much less so. Theoretical uncertainties
remain on small-scale:
- Effect of feedback/AGNs on CW?
- Survival of cold flows?
- Observational predictions?
- Deblend from outflows?
Prospects of observation of cosmic web/CGM interface:
- VLT/BlueMUSE: \(z\sim 2-4\) (Ly\(\alpha\), CIV)
- ELT/Harmoni: \(z>3\) (Lyα, CIV, HeII, Hβ)
- ALMA: \(z\sim 2-4\) ([CII]158µm)
Corentin Cadiou — cadiou@iap.fr
What flows from the CW into galaxies @ ATCG
By Corentin Cadiou
