z ≥ 2: some puzzle(s) of galactic disks

• Alignment at large scales
  → common origin of gal. spins
   
• Spin of DM halo ≠ spin of disk
  → diff. evol. of DM vs baryons
   
• Virial shock → should prevent coherent accretion
• Feedback → disk destruction?

Simulation setup

• suite of zoom-in simulations (~6), RAMSES (Teyssier 2002)
• Δx = 35pc, Mstar = 1.1 10⁴ M☉ Mhalo=10¹² M☉
• Turbulent star formation (Kimm+17, Trebitsch+17)
• Mechanical feedback (Kimm+15)
• AGN formation with spin-regulated efficiency (Dubois+12,+14)
• 30,000,000 tracer particles (~10/cell, 0.5/star, Cadiou+19)

Gas density

Gas tracer density

Filamentary accretion is responsible for most of the mass and angular momentum acquisition (at z>3 ; Kereš+05, Pichon+11, Tillson+12, …)

Filamentary accretion: natural "bridge" between large scale structures (cosmic web) and galaxy formation

Cold gas selection

 

( \( \forall t, T(t)\leq 10⁵\ \mathrm{K} \) and

\( 0.3 R_\mathrm{vir} \leq r(t) \leq 2 R_\mathrm{vir} \))

or

$$ r < 0.3 R_\mathrm{vir} \text{ or } r > 2R_\mathrm{vir} $$

Hot gas selection

 

$$ \exists t, T(t)> 10⁵\ \mathrm{K} \\ 0.3 R_\mathrm{vir} \leq r(t)\leq 2 R_\mathrm{vir} $$

⇒ Defined with Lagrangian history

    + removing accretion from satellites

Kinematics

Kinematics

Cold gas: well aligned down to inner halo

Hot gas: aligned down to inner halo

(Local) dynamics

The (Lagrangian) spAM dynamics is given by

\( \displaystyle \frac{\mathrm{d} \mathbf{l}}{\mathrm{d} t} = \textcolor{darksalmon}{\text{pressure torque}} \)

Mean of ⊥ force magnitude

(Global) dynamics

Compute global torque in shell

Dynamics

Locally: pressure dominated...

esp. in the hot phase

Time-coherence of torques

Compute \(t_\mathrm{decorr.}\) using Lagrangian history such that

$$ \vec{\tau}(t_\mathrm{decorr.}) \perp \vec{\tau}(0) \color{gray}\qquad\text{ (i.e. } \vec{\tau}(t_\mathrm{decorr.}) \cdot \vec{\tau}(0) = 0)$$

A/ Longer coherence in cold phase (esp. pressure)

Slow decorrelation

Fast decorrelation

Spatial-coherence of torques

Compute sum-of-norm vs norm-of-sum

$$ \dfrac{\left\| \sum_\text{neigh}\tau\right\|}{ \sum_\text{neigh}\left\| \tau\right\|} $$

B/ Pressure: \(\lambda_\mathrm{fluct.}\) is small

Spatial-coherence of torques

Compute sum-of-norm vs norm-of-sum

$$ \dfrac{\left\| \sum_\text{neigh}\tau\right\|}{ \sum_\text{neigh}\left\| \tau\right\|} $$

B/ Pressure: \(\lambda_\mathrm{fluct.}\) is small

Conclusions

Conclusions

Kinematics:

• AM transported through CGM
• orientation mostly retained down to outer disk

• pressure locally dominant (esp. in hot)
• gravity globally dominant (esp. in cold)
• torques have spatial & time variations ⇒ need careful treatment

Tracer particles

Eulerian method

Lagrangian method

Tracer particles

Lagrangian method

Density \(\rho\)

\(v\) tracers

MC tracers

Applications

Formation & destruction of filamentary structures in Perseus-like cluster

Tracer: history of each clump

Beckmann+19

Applications

Study of gas in & out — origin of Ly\(\alpha\) emitting gas

Mitchell+20