Galaxy alignment and the physical origin Kang Xi PMO, China) - - PowerPoint PPT Presentation

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Galaxy alignment and the physical origin Kang Xi PMO, China) In collaboration with Wang Peng PhD Student), Lin Weipeng, Yang Xiaohu, Dong X, Wang Y (SHAO) Quy Nhon, Vietnam, July 4 2016 How to describe galaxy

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SLIDE 1

Galaxy alignment and the physical origin

Kang Xi （PMO, China)

  • In collaboration with
  • Wang Peng （PhD Student),

Lin Weipeng, Yang Xiaohu, Dong X, Wang Y (SHAO)

Quy Nhon, Vietnam, July 4 2016

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SLIDE 2

How to describe galaxy distribution in space? in 1980,great wall 2PCF widely used for 2dFGRS/SDSS

  • Correlation function: 2-points, 3-points

etc (1980, Peebles)

  • 2PCF describes how galaxies are

biased with dark matter distribution

  • 2PCF etc can well constrain the

cosmological parameters

?

Two-point correlation

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SLIDE 3

Galaxy alignment

  • satellite-satellite
  • satellite-central
  • central-central
  • central-LSS

Several types of galaxy alignment

Small scales

One halo term Two halo term

Galaxy alignment is seen on different scales

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SLIDE 4

In addition to galaxy clustering, Why do we care galaxy alignment?

On small scale (one-halo term)

  • Infer dark matter halo shape from galaxy alignment
  • alignment to infer galaxy formation?
  • primordial anisotropic accretion or evolution

(Nature vs Nurture?) On large scales (two-halo term)

  • Interaction of halo shape to cosmic tidal field
  • intrinsic alignment of galaxies (crucial to weak lensing)
  • formation of cosmic web?
  • dependence on DM/DE properties?
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SLIDE 5

1,satellite-satellite: The great circle （co-rotated plane)

Satellite galaxy in the Milky Way

  • 2005:Milky Way satellites are in a

thin disc

  • 2007:The same is true in M31, but

weaker

  • 2013: Satellites in the disc are co-

rotated !

Kroupa 2005

MW and M31 are special? need large galaxy sample

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SLIDE 6

3, Central-Central alignment

10-4 10-3 10-2 10-1 101 102 c11(r) Angular scale at z=1 (arcmins)

  • 0.01

0.01 10 100 c22(r) r (h-1Mpc)

Jing+ 2009 Li+ 2015 Galaxy(Halo) intrinsic alignment is crucial for Weak Lensing cosmology

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SLIDE 7

2,satellite-central alignment

From 2dFGRS and SDSS

  • satellite galaxies are aligned with the major axis of

central galaxy

  • stronger alignment for red centrals
  • strong alignment for red satellites

Brainerd 05, Yang+06 group galaxy

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SLIDE 8

Modeling the satellite-central alignment Halo is triaxial Kang et al. 07 using SAM

results

  • if central galaxy follow major axis of DM halo

(inside virial radius): signal too strong

  • need some mis-alignment (inner DM halo, or

spin) signal is OK, but no color dependence

N-body study is limited as its difficult to properly determine the shape of central galaxy

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SLIDE 9

Modeling the satellite-central alignment

0.8 0.9 1.0 1.1 1.2 1.3 p(θ) < θ >model= 42.1±0.1 < θ >obs= 42.2±0.2 All Sample < θ >model= 42.4±0.3 < θ >obs= 43.3±0.3 Blue SGs < θ >model= 42.1±0.1 < θ >obs= 41.5±0.3 Red SGs 0 10 20 30 40 50 60 70 80 θ 0.8 0.9 1.0 1.1 1.2 1.3 p(θ) < θ >model= 42.0±0.1 < θ >obs= 44.5±0.5 Blue CGs 0 10 20 30 40 50 60 70 80 θ < θ >model= 43.2±0.2 < θ >obs= 41.5±0.2 Red CGs 0 10 20 30 40 50 60 70 80 θ CGs Defined By Halo Mass

Mh < 2∗1011M Mh < 1012M Mh > 2∗1011M Mh > 1012M

Using hydro-dynamical simulation: star formation, SN feedback (no AGN feedback)

0.0 0.2 0.4 0.6 0.8 1.0 r/r200 0.6 0.8 1.0 1.2 1.4 1.6 P(r/r200) 2D :

Red Satellites Blue Satellites Metal Rich Satellites Metal poor Satellites

0.0 0.2 0.4 0.6 0.8 1.0 r/r200 39 40 41 42 43 44 < θ > 2D : All Sample 1012 1013 1014 1015 MHalo [M] 10 20 30 40 50 < θCG,Halo > 3D: 0.1R :< θ >= 20.2 ± 0.6 3D:

0.3R :< θ >= 28.6 ± 0.6

3D:

1.0R :< θ >= 39.7 ± 0.7

r < 0.1R r < 0.3R r < 1.0R

nel: radial distribution of red and blue, metal-rich (top 30% by order ranking), and metal poor (bottom 30% by order ranki

alignment: dependence on color

alignment with radius

Dong X, Kang X et al. 2014

Result

★There is mis-alignment between shape of central galaxy and DM halo ★Their misalignment is a function of halo mass (color dependence of central) ★misalignment is a function of radial distance (red satellites in inner halo,blues at

  • uter region )
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SLIDE 10

Zel’dovich approximation for formation of cosmic web

x(t) = q + D(t) rψ(q) ,

ρ(x) = ¯ ρ [1 D λ1(q)] [1 D λ2(q)] [1 D λ3(q)]

Sheet—>Filament—>Node

100 h-1 Mpc ΛCDM, z=0

4: Alignment with LSS:

  • I. define the LSS environment

ƛ ~ eig of (∂i∂j ɸ)

Following Zeldovich, Hahn+2007. define the LSS environment:

  • smooth the density field
  • compute the potential
  • compute eigenvector of tidal field

Tij(x) = ∂2φ ∂xi∂xj ,

  • number of +- eigenvalue determine: voids, sheet, filament, nodes

1 8 h

  • 1

M p c

Hahn, Porciani, Carollo, Dekel (2007a), MNRAS 375, 489

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SLIDE 11
  • I. Halo-LSS alignment from simulation

Halo major axis-LSS Halo spin -LSS Hahn+ 2007,Codis+12

These correlation are widely confirmed by many others using simulations (Aragon-Calvo+08, Codis+12, Libeskind+14， Kang & Wang 15 …..) M_flip~1012Msun*(1+z)-2.5

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SLIDE 12

Space configuration of Halo shape & Spin Major axis of halo: align with the least collapsed direction

  • Minor axis of halo:

align with the most collapsed direction

  • Spin of halo : normal

to the mass accretion direction

Why there is a mass dependence?

Spin

Major axis

M<M* M>M* Filament Wall

Spin

Major axis

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SLIDE 13
  • II. Galaxy-LSS alignment from observation

Figure 4. Same as Figure 2, but for different sub-samples (“red” and “blue“) of

Galaxy Major axis-Filament

P(|cos θ|) |cos(θ)| e3-vector (filament axis) <cos(θ)> = 0.513 <σ> = 1.62 pKS = 2.8⋅10-3 Spiral galaxies 0.8 1 1.2 0.2 0.4 0.6 0.8 1 P(|cos θ|) |cos(θ)| e3-vector (filament axis) <cos(θ)> = 0.479 <σ> = 3.38 pKS = 7.7⋅10-9 Elliptical galaxies 0.8 1 1.2 0.2 0.4 0.6 0.8 1

Spin - Filament Zhang Y+2013 Tempel & Libeskind 2014 Observations agree well with Theory ! Signal is weaker (galaxy-halo misalignment)

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SLIDE 14

A common scenario for mass flow in cosmic web

Codis+12, Cautun+14

  • mass flow from Voids —> Wall —

>Filament —>Nodes

  • environment of halo changes as

Wall—>Filament-Nodes

  • the velocity field around cosmic

web determines the spin-LSS correlation!

  • riginal idea from Bond+96,

van de Weygaert 96

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SLIDE 15
  • in Wall, spin is parallel to wall.
  • In Filament, spin is perpendicular to filament

This scenario is basically right but details to be declared From this cosmic mass flow, we expect But, simulations have found In Filament, there is still a mass dependence (spin flip) Any dependence on halo migrating time ? (from wall to filament) can we see the spin flip during the history of a massive halo?

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SLIDE 16

1) accretion along Halo major axis (λ1):

2) accretion along e3 of LSS (λ3): The least compressed

direction

N-body simulation

  • WMAP7 cosmology, LCDM
  • box: 200Mpc/h, 1024^3 particles
  • Full merger trees are constructed for every

halo from z=10 to z=0

Increasing time

tracing the evolution of halo mass accretion and spin

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SLIDE 17

subhalos accretion along halo major axis and e3 of LSS dependence on host halo mass (selected at z=0)

black: along halo major axis red: along e3 of LSS

Kang & Wang, 2015 ApJ

we find: Accretion along halo major axis: universal Accretion along e3 of LSS: not universal

  • Libeskind+14, Universal along e3 of LSS

(their mass bin is too wide)

halo mass dependence

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SLIDE 18

The evolution of spin-LSS and mass accretion spin-e3 correlation

mass accretion-e3 correlation

There are evolution effects, at earlier times

  • mass accretion is perpendicular to Filament
  • Spin is parallel to Filament

Wang & Kang, 2016 in prep

black line: low-mass halo, red lines: massive halo

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SLIDE 19

An useful parameter for anisotropic collapse

FA = 1 √ 3

  • (λ1 − λ3)2 + (λ2 − λ3)2 + (λ1 − λ2)2

λ2

1 + λ2 2 + λ2 3

,

Large FA: highly anisotropy Lower FA: collapse happen

  • n all directions

ƛ ~ eig of (∂i∂j ɸ)

Wang & Kang, 2016 in prep

Nodes: spin is normal to e3 Filament: mass dependence

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SLIDE 20

Dependence on time of formation and entering in Filament

Spin-LSS: dependence on Z_formation and Z_filament

  • Later formed halo is more perpendicular to filament
  • Massive haloes: entering filament first, and then formed later

(spin is build by mass accretion along filament)

  • Low-mass halo: forms early, but entering filament later (spin is

build when they were in wall)

Wang & Kang, 2016 in prep

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SLIDE 21
  • satellite-central alignment can be

ascribed to primordial anisotropy at accretion or the triaxial nature of DM halo

  • central galaxy is better aligned with

inner halo shape, and alignment increases with halo mass

  • subhalo accretion along halo major

axis is universal, being strong in massive haloes

  • Halo spin-LSS is not universal

(subhalo accretion along LSS is not universal)

  • Low-mass halo forms early, but

enter filament later (spin is formed in wall, so parallel to filament)

  • High-mass halo enter filament

early, but form later (spin is formed in filament by mass accretion along it)

Summary

  • Galaxies are distributed anisotropically on different scales

On small scales On large scales Thank you !