Corentin Cadiou
CNRS Researcher

Journées Galaxies ATCG | 2026

What flows from the cosmic web into galaxies?

Left: Leclercq+17
Right: Galárraga-Espinosa+23
Bottom left: Ramsøy+21

Cosmic web: a multiscale structure
 

Mpc to galactic scales

Right: Peng+10
Left: Zooniverse

“Environmental” quenching
 

Higher density | high mass \(\rightarrow\) redder galaxies


⚠️ cannot explain morphology/orientations!

Cluster-like

Void-like

Right: Peng+10
Left: Romanowsky&Fall 12

“Environmental” quenching
 

Higher density | high mass \(\rightarrow\) redder galaxies


⚠️ cannot explain angular momentum!

Cluster-like

Void-like

Cosmic web: effects on scalar galaxy properties

Distance to filament changes

  • color & sSFR
  • rotation-support (\(v/\sigma\))

Left: Kraljic,...CC+18 (GAMA)
Right: Laigle+18 (COSMOS)

See also Kuutma+17, Malavasi+17, Alpaslan+16 or O'Kane+24

Triple effect:

  • Bias halo assembly
  • 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 \(<1\,\mathrm{Mpc}\): 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\(\alpha\) is great, but hard to interpret
Other lines are great… but are we getting the right predictions?

Movies: from CC+26
Left: Mitchell, ... CC+20

Ly\(\alpha\)

H\(\alpha\)

CIII] 1906Å

[CIV] 1548Å

HeII 1640Å

The CGM cosmic web \(\lessapprox 100\,\mathrm{kpc}\): theory


Ly\(\alpha\) is great, but hard to interpret
Other lines are great… but are we getting the right predictions?

Movies: from CC+26
Left: Mitchell, ... CC+20

H\(\alpha\)

HeII 1640Å

Ly\(\alpha\)

🚧 Temporary conclusion 🚧

Predictions/interpretation of CGM obs.
may not be mature

[CIV] 1548Å

CIII] 1906Å

Connecting the cosmic web through the CGM

 

Effect of \(>\mathrm{Mpc}\) scale CW on galaxy well-established...
but likely massively underestimated

 

 

 

 

 

 

 

 

 

 

 

 

 

Corentin Cadiou — cadiou@iap.fr

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)