n
LWDM cosmologies, “spiced” with a pinch of strongly coupled CDM, meet all data LCDM fits, as well as data LCDM fails to fit sterile n mass predicted?
Silvio Bonometto
Physics Dep., Trieste Univ. &
INAF, Trieste Observatory
Conca Specchiulla, sep 10, 2014
Paper in collaboration with 3M’s
R.Mainini, A. Macciò, I.Musco

LCDM cosmologies meet cosmological data down to galactic scale
Problems below galactic scale:
•Milky Way satellite abundance
LCDM N-body simulations yield 20 times more satellites than observed, for a galaxy of the MW size hydro sim.
Klypin et al ApJ 522 (1999) 82, Moore et al. ApJ 524 (1999) L19 physics reduce
•Dwarf galaxies exhibit a core discrepancy radial density not NFW in the central region to factor 2-3
Moore, Nature 370 (1994) 629, Flores & Primack, ApJ 427 (1994) L1,
Diemand et al MNRAS 364 (2005) 665, Macciò et al MNRAS 378 (2007) 55,
Springel et al., MNRAS 391 (2008) 1685, de Block et al., ApJ 552(2001) L23,
Oh et al., AJ 141 (2011) 193
•Dwarf galaxy abundance in large voids …. bigger galaxies also found to have core more controversial
M-ind’nt size
500-1000 pc

LWDM cosmologies halos with core e.g. Macciò et al., MNRAS 428 (2013)
Core radius related to
DM particle mass:
To have a core around 500-1000 pc need m n
= 80-110 eV
STERILE NEUTRINO with m \sim 90eV ?

As previous plot in terms of power spectrum
P(k)

•
•
Background
A dual component in a stationary primeval Universe
Connecting DE with inflation
• Stationarity break and rise of present cosmic environment
Inhomogenities
• Linear theory
• Simulations: satellites and profiles preliminary
Problems
• Early non linearity , DE-CDM decoupling
Bonometto S.A., La Vacca G., Sassi G., JCAP08 (2012) 015
Bonometto S.A. & Mainini R., JCAP03 (2013) 038
Macciò A.V., Bonometto S.A., Mainini R., Musco I. (in preparation)
Strong CDM-DE coupling allows fluctuations to persist also on dwarf galaxy and MW substructure scales

Background metric
Quintessential DE covariant form
Cou.DE :
J.Ellis et al., PL 228B (1989) 264
C.Wetterich, A&A 301 (1995) 321
L.Amendola, PRD 69 (1999) 043501
L.A. & Tocchi-Valentini D., PRD 66
(2002)043528
…. and many many others
In FRW space  data (hopefully) to yield w(a) [sooner than V(F)] coupling allows DE to keep signif.
density also at high z

We shall forget the potential shape, just assuming w  +1 at large z, w  -1 at small z, transition at zd w=+1 at large z is a generic feature for any choice of self-inter. potential results mildly dep. on z d scarse dep.
on e classical approaches assume cou.CDM to be only DM, then b
<< 1 here CDM is a tiny component main DM is uncoupled this allows quite large b results mildly dependent on a d
& e

F
= (m p
/b) ln( t
) density parameters during radiative expansion f=exp[-ln( t )]=1/
L = ( m/t ) yy t
“…. mass redshifting”
Kinetic field would dilute as a
CDM would dilute as a --
3
-6
Energy flow from CDM to DE makes both component to dilute as a --4

The solution found is an

Coupling persists down to z=0 Coupling fades after invariance break b =10
At high z all components share similar densities (reminding similar decoupling redshifts) in a fully stationary expansion
Eve of the present epoch: T approaches m w apologies for different color choice

slow

” Cou.CDM : NO meszaros’ effect fluc’ns in CDM continue to grow after entering the horizon, over any scale
Creating deep “potential wells”
WDM fluc.’ns restarted & baryon fluc.’ns enhanced by large ampl. cou-CDM fluc.’ns

CMB spectra almost identical to standard LCDM even for very high b

Transfer functions (CMBFAST)

A typical spectrum
(m w
=220 eV b = 20)

A possible model pathology: coup’d CDM fluc.ns
may become >>1
Simplest solution: coupling should fade at low z necessarily after conformal inv. break by wdm derelativization this preserves wdm fluc’n restoration delay=Log[a(dec’g)/a(der’l’n)]

delay = 4 decoup’g approximatively when w shifts from +1 to -1 delay = 2 shown in the plot after dec’g sufficient that
CDM+bar fluc’ns are linear however :
W c<<
W b models with non-linear
CDM fluc’s could still be physical just hard to compute structure formation early non-linearity to modify pop III predictions
2

m w
/eV
96.80
48.51
g*/m w
= 0.980

CDM pa.
m w
=95eV (thermal velocities)
Original simul.: L box
=20 Mpc/h, N pa
=300^3 zoom grid: N pa
=7200^3=3.73x10^11  N pa,halo
=13.1x10^6,m pa
=1500 M s
/h
Same halo: 2.07x10^10 M s
/h (within R
200
)
CDM particles (v=0) WDM particles (thermal vel)

Same halo: 2.07x10^10 M s
/h
CDM particles (v=0) 5 WDM part :1 part v=0

Original simul.: L box
= 90 Mpc/h, N pa
=300^3 zoom grid: N pa
=4800^3, N pa,halo
=2.4x10^6, m pa
=4.57x10^5 M s
/h
M_halo = 1.1x10^12 M s
/h
(not a lucky halo choice)
CDM particles WDM particles only
NO small halos

M = 10^10 M s
/h
Density profiles
1kpc/h

MW size halo : almost overlapping profiles (but resolution is different)
1 kpc/h

s
LCDM “MW” sLWDM “MW”

PRELIMINARY CONCLUSIONS FROM SIMULATIONS s-LWDM LCDM 1:6 cold
10^10 profile forming core NFW intermediate
Dwarf closer to NFW
Galaxy satellites almost 0 in excess intermediate just a few
10^12 profile NFW in all cases
Milky fattening blobs
Way satellites massive satellites remain small ones vanish resolution
....
BUT: small halo component proportions
?

Conclusions
• Sub-galactic scale features hard to explain by LCDM
• LWDM can help: critical feature warm particle mass
• LWDM with particle 80-110 eV meets rotation curves, satellites, etc.
• LWDM spectrum for such mass unsuitable
• New tracker solution for cou-DE models (background)
• Primeval conformal invariance
• 2 DM component already widely considered in literature
• here CDM coupled + WDM uncoupled, similar primeval densities
• LWDM models spiced with a pinch of cold dark pepper ….
• tracker solution holding since inflation
• possible connection with inflationary dynamics
• linear fluctuation evolution solved
• Cou-CDM does not feel Meszaros effect
• CMB spectra identical to LCDM
• CDM fluc’ns re-create WDM fluc’ns mostly
• excessive amplitude of CDM fluctuations: a computational problem
• however: once conformal invariance brocken, decoupling harmless
• Simulations based on s-LWDM cosmologies confirm : rotation curves, satellite problems solved
• Pop III physics to be revisited: early seeds

Small values of b to be coherent with observational data r
DE decreases when w close -1, then almost parallel to r
CDM when coupling switched on


11 eq
(cold uncoupled…)

b up to 0.18 consistent with data if neutrino mass O(0.2eV)
La Vacca G. et al. JCAP 0904 (2009) 007
Amendola L. et al arXiv: 1111.1404
(0.18
 0.16)
p
Spectral distorsions due to energy flow from DM to DE compensated by spectral distorsions due to neutrino mass O(1ev)
CDM-DE coupling: a MUST if
“large” n mass detected in particle experiments (e.g.: bb ) early universe:
DE purely kinetic: constantly r d \sim 0.01
r c at z \sim 10 potential term takes over

obtained with 11 eq ad-hoc program
(uncoupled DM is cold)