Getting bored with CDM?
— structure formation& dark matter
Ken Nagamine
Osaka U. / UNLVContents• Successful ΛCDM model on large-scales• What about ≲10 kpc? —“small scale problem”• Alternative models: e.g., WDM, SIDM, FDM, …
• Complication of baryonic physics — do we reallyneed alternative DM ?

Evidence of Dark Matterand its success on large scales•

Galaxy clusters — ~80% of mass is dark (Zwicky ’33)•

Galaxy rotation curves (Rubin & Ford ‘70)

•CMB (angular power spectrum)•Structure formation — P(k), galaxy clustering, Ly-α forest•

Gravitational lensing (strong & weak)•Bullet Cluster (Markevich+’02; Clowe+’06)•……

WMAP & Planck CMB results

WMAP9; Hinshaw+ ’13(ESA March 2013)

T ~ 2.73K black body with ~10-5 fluctuations

Cosmic Energy Budget

ESA March 2013

wer spectrum measureind when interpreting
ements are those fromluminosity dependent
M survey (Efstathiou
e from Tegmark et al.
< r ∗ < 22 — see also
f this eﬀect, but rep-Fig. 36.— Same as Figure 35, but restricted to a comparisonof decorrelated power spectra, those for SDSS, 2dFGRS and PSCz.
The similarity in the bumps and wiggles between the three power
spectra is intriguing.

Matter Power SpectrumTegmark 2004
Fig. 37.— Comparison of our results with other P (k) constraints.
The location of CMB, cluster, lensing and Lyα forest points in thisplane depends on the cosmic matter budget (and, for the CMB,

wer spectrum measureind when interpreting
ements are those fromluminosity dependent
M survey (Efstathiou
e from Tegmark et al.
< r ∗ < 22 — see also
f this eﬀect, but rep-Fig. 36.— Same as Figure 35, but restricted to a comparisonof decorrelated power spectra, those for SDSS, 2dFGRS and PSCz.
The similarity in the bumps and wiggles between the three power
spectra is intriguing.

Matter Power Spectrum

small scale P(k)?

Tegmark 2004
Fig. 37.— Comparison of our results with other P (k) constraints.
The location of CMB, cluster, lensing and Lyα forest points in thisplane depends on the cosmic matter budget (and, for the CMB,

MovieMovieCurrent simple picture of DM halo & galaxy~100 kpc~20 kpc

Galaxy Correlation Function & BiasDavis+’85
only 323 ptcl !!
(N-body)

CDM simulation can explain galaxy clustering
w/ the idea of “bias”

(Some possible)

small-scale problems of ΛCDM•

Cusp-Core problem: simulations predicting too steep innerhalo profile•

Missing satellites problem: too much substructure?

•Too-big-to-fail problem: over-abundance of massive
substructures that could host gals after reionization (but notobserved in MW-satellites)•Void phenomenon: gals in voids are too normal?

•Satellites plane problem: satellites aligned in a plane forboth MW and Andromeda•….

Dark matter halo cusp
Navarro-Frenk-White (NFW) profile(NFW ’96)a≃0.1 (Bullock+’01)

Bullock & Boylan-Kolchin ‘17

But observed dwarf gals tend to have flat cores.

Cuspy profile not universal?

Fukushige+’14
list by Boylan-Kolchin & Ma

Supernova-driven gas outflows can remove
DM cusps and create kpc-size cores(Results of zoom-in hydro sim.)

So, is CDM just fine?

Madau+’14Substructure problem?

Movie

Original Substructure Problem

Klypin+’99; Moore+’99

Illustris2015

Substructure Problem Solved?

Garrison-Kimmel+’17
Bullock & Boylan-Kolchin ‘17

No Missing Satellite Problem?
arXiv:1711.06267

Various Dark Matter
Thermal relice.g. WIMP (weakly interacting massive ptcl)

becomes non-relativistic earlier, suppress
perturbation at galactic or smaller scales.
(gravitino, steril neutrino,…)remains relativistic until late time, anderase structures at super-galactic scales.

+FDM (axion-like)So, how about WDM?
e.g., gravitino (Kawasaki+’97)

sterile neutrino ~ keV (Boyarski+’09)

Thermal relic;Streaming velocity vs/c ~ Tx/mx
m~1.5 keV => Rs~0.3 Mpc/hBode+’01

Viel+’12

half-mode mass

Schneider+’12

Colin+’00; Bode+’01; Viel+’05; Colin+’08; Colombi+’09; Viel+’12; Menci+’17Suppression of P(k) @ small scales

Maio & Viel ‘15

z=0

m=1 keV

z=2Viel+’12

Quasars (QSOs) and Ly-α forest

Springel+’05(cf. Cen+’94)

Lukic+16

Ly-𝛼 forest constraint

1D flux
power spec

marginalize over6 cosmo param& T0, γusing COSMOMC
against real obs dataViel+’13

WDM conclusions• WDM models w/ ≲ 3keV have been explored —strong alternative candidate to CDM• mdm ≳ a few keV seems more likely than < 1keV.
• Viel+13, Ly-a forest: m>3.3 keV (2-σ), Mh,min~2e8 M⦿
• Further study is needed with high-resolution and realistic

SF & feedback models — e.g. impact of AGN feedbackon small-scale power (van Daahlen+’11; Semboloni+’11)

-WDM reduces the substructure, but keeps the cusp.
SIDM doesn’t reduce the abundance of substructure, butproduces large const-density core
Rocha+’13; Bullock & Boylan-Kolchin ‘17

SIDM(self-interacting DM)— as a generic consequence of hidden
sector extensions to Standard Model-no couplings to SM particles
possibly strong self-interaction via dark gauge bosons(Feng ‘10; Peter '12 for reviews)
Spergel & Steinhart ‘00
Rocha+’13

can produce results consistent w/ current obs.

LSS & sub halos unchanged.

Fuzzy Dark Matter (FDM)
Ultra Light Bosons, Wave-like, Axion-like••

non-thermal boson field (particularly scalar), non-rela, lowmomentum state as a cold BEC
7-22<10m~10 eV, λde Broglie~1kpc,

⇣m
10

⇣

22 eVm⌘ 3/2M

⌘ 4/3

•

10
<10suppresses halo formation @•halo abundance reduced at•forms a central core as a “soliton” (Schrödinger-Poisson eq.)•on large-scales, ≈ CDM

10 22 eV…, Baldeschi+83; Kim ’87; Sin+94; Hu+00;
Marsh+14; Schive+14; Hui+17; Mocz+17; ….

FDM≈ CDM (more like WDM)

Uncertainty principle counteracts gravity
below Jeans scale

Schive+14- adds new form of quantum pressure from uncertainty- comoving Jeans length:

Solitonic Core of FDM simulation
Schive+14

gravitationally boundsolitonic coree.g.
for Fornax dSph gal.

for MW core

Desjacques+’17

arXiv:1709.07946- constraints from Ly𝛼 P(k):cf. Irsic+17; Armengaud+17; but Zhang+17- But, attractive force due to self-interaction btw ULA- semi-analytic linear stability analysis- cosmic web can be influenced.
- needs further numerical simulation studiesreconsider Schive+14; Calabrese+16; Zhang+16; Mocz+17; ….

f: decay const (symmetry-breaking scale)extremely tiny quartic coupling:Various Dark Matter& Astrophysics
Thermal relice.g. WIMP (weakly interacting massive ptcl)

becomes non-relativistic earlier, suppress
perturbation at galactic or smaller scales.
(gravitino, steril neutrino,…)remains relativistic until late time, anderase structures at super-galactic scales.

+FDM (axion-like)