Corentin Cadiou — PhD student
In collaboration with Marcello Musso, Yohan Dubois, Christophe Pichon
MPA — 18/12/2018
A very biased view on galaxy formation
Silk&Mamon 12
Press&Schechter 74
"Mass function from first principle"
Works nicely to describe anisotropic features in the Universe
Marginalise position
Galaxies do not form anywhere at anytime
Need to create anisotropic methods → beyond two-point correlation function
Structure in the GAMA survey, Kraljic+18
How to measure position?
What metric modulates galaxy properties?
Galaxy properties & evolution from initial conditions
⇒ Find largest mass that will collapse by z at given location
Theory | Real space |
---|---|
R | M |
z |
Spherical collapse model:
Structure of size R will collapse at z iff
R
Height: determined by (over-)density
Curvature: controlled by (traceless) tidal tensor
Poisson equation
Critical point constrain*
* we work in the free-falling frame
Direction of void
Direction of filament
In filaments, halos are...
... than in voids
(Musso, Cadiou et al 2018)
Excursion set theory + saddle point constrain
The results hold for galaxies (at least simulated ones)!
This is largely WIP
We can try using numerical simulations
*See Cadiou+18
Gas density
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
Tillson+2015
Cadiou+ in prep
The cold flows are
for small enough galaxies/high z
Time →
High sAM →
Innermost regions
Outermost regions
Cadiou+ in prep
Perfect candidates to transport anisotropic information from cosmic web to smale scales.
Tillson+15
Danovich+15
1
2
3
4
Cadiou+ in prep
New Horizon simulation, Dubois+ in prep
PS: I am available for a postdoc!
Bulge
Red or blue?
Disk
All the properties vary with cosmic time…
Do they vary with spatial location?
Halo model: galaxy properties are inherited from their parent halo + local density (~no effect of the cosmic web)
How do galactic and DM halo scales couple to the large scale anisotropies of the cosmic web?
Galaxy properties & evolution from initial conditions
⇒ Find largest mass that will collapse by z at given location
Large mass Small mass
Early collapse
Late collapse
+
``How does the cosmic web biases the excursion and halo properties?´´
Nodes (maxima of density)
Saddle point (center of filament)
1
2
3
Describe the critical points only
The relevant parameter for quantifying the anisotropy is:
Observation (in simu)
v/σ residuals at fixed dens + mass
Theory
The filament constrains
Void Filament Void
Towards a more comprehensive halo model
! WIP !
How did the disk acquire its AM?
Requires the knowledge of the Lagrangian evolution of the gas
⇒ now possible using tracer particles
Let look at the filamentary accretion of cold gas at z≥2
Compute halo properties from first principles (e.g. excursion set theory)
Run "full-featured" simulations of galaxies.
What for?
How?
Study how the large scale assembly variables are coupled to galaxy variables (morphology, spin, …)
Study the effect of LSS on halo assembly variables (mass, accretion rate, formation time, …)