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