Slides

Probing the Nature of Dark
Matter with the First Galaxies
(Reionization, 21-cm signal)
Anastasia Fialkov
Ecole Normale Superieure
Debates on the Nature of Dark Matter
20 May 2014
Outline
• The early Universe (brief overview)
• Effect of various DM models on:
1.
2.
3.
4.
Number Counts
Thermal history and Reionization
21-cm signal
Properties of first stars
Anastasia Fialkov
20 May, 2014
Cosmic History
• CMB
• Dark Ages
• First Stars and Galaxies
• Reionization
Anastasia Fialkov
20 May, 2014
First Stars and Galaxies
Form in metal free environment
• H2 cooling ~105 Msun halos
• H cooling in ~107 Msun halos
(e.g., Tegmark et al. 1997, Machacek, Bryan & Abel 2001)
(Stacy et al. 2013)
Fragmentation (rotation, radiative feedback)
(e.g., Stacy, Greif, Klessen, Bromm, Loeb 2013; Stacy, Greif, Bromm 2010)
Start forming at z ~ 65
(Naoz et al. 2006, Fialkov et al. 2012)
Rare at high redshifts (biased by δ and vbc)
(e.g., Barkana & Loeb 2004; Tselikhovich & Hirata 2010)
Anastasia Fialkov
20 May, 2014
Formation of First Stars is Biased
1. Relative supersonic motion between gas and dark mater
affects 104-108 Msun halos
•
•
•
•
Suppresses halo abundance
Suppresses gas fraction
Delays star formation
First star is delayed by Δz ~ 5
Tselikhovich & Hirata 2010; Naoz, Yoshida,
Barkana 2011; Dalal, Pen & Seljak 2010;
Tselikhovich, Barkana & Hirata 2011; Naoz,
Yoshida, Gnedin 2012, 2013; Fialkov, Barkana,
Tselikhovich & Hirata 2012; Maio, Koopmans &
Ciardi 2011; Stacy, Bromm & Loeb 2011; Greif,
White, Klessen & Springel 2011; Naoz, Yoshida &
Gnedin 2011; O’Leary & McQuinn 2012; Bromm
2013; Yoo, Dalal, Seljak 2011 …
Anastasia Fialkov
O’Leary & McQuinn (2012)
Fialkov, Barkana, Tseliakhovich,
Hirata (2012)
20 May, 2014
Anastasia Fialkov
Visbal, Barkana, Fialkov, Tseliakhovich, Hirata 2012
20 May, 2014
Formation of First Stars is Biased
2. Radiative feedbacks
• LW photons destroy H2, suppress star formation in ~106 Msun
halos
H 2 + γ → H 2* → H + H
• Electrons catalyze H2 formation
H + e- → H - + γ
H + H - → H 2 + e-
• X-rays catalyze H2 formation (additional ionization)
• Delay build-up of radiative backgrounds up to Δz ~ 5
Machacek et al. 2001; Wise & Abel 2007; O’Shea & Norman 2008, Fialkov et al.
2013; Visbal et al. 2014; Machacek, Bryan, Abel 2003….
Anastasia Fialkov
20 May, 2014
Thermal History of Cosmic Gas in
ΛCDM
z > ~200: thermal coupling to CMB (Compton scattering),
cooling as (1+z)
~20 < z < ~200: adiabatic cooling as (1+z)2
z < ~20: heating of gas (very model dependent)
Heating mechanisms:
• X-ray binaries
• Thermal emission
• Quasars, mini quasars
• Dark matter annihilation
• Etc.
Log(TK)
TK
z ~ 200
TCMB
Anastasia Fialkov
Log(1+z)
20 May, 2014
21-cm Signal
𝑛=1
𝑛1
𝑛0
• 3-D map of HI
• Tool to Probes: Dark
Ages, Cosmic Dawn
and Reionization
Anastasia Fialkov
20 May, 2014
Global 21-cm Signal in ΛCDM
Sensitive to:
• Initial conditions δ, vbc (cosmology)
• Gas Temperature (heating mechanisms)
• Ly-a, LW, Ionization fraction (properties of sources)
Expected Signal
Anastasia Fialkov
Pritchard and Loeb 2012
20 May, 2014
Primordial Landscape with Various
DM Models
Anastasia Fialkov
20 May, 2014
Dark Matter
mX ~ keV, thermal relics
mX ~ GeV – TeV
Structure formation at small
scales is suppressed by
Heating and ionization at
high z
– Particle free streaming
(Bode P., Ostriker J. P., Turok N.,
2001)
– Residual velocity
dispersion of the particles
(Barkana R., Haiman Z., Ostriker J.
P., 2001)
Anastasia Fialkov
20 May, 2014
1. Effect on Abundance of Dark Matter
Halos
• Suppression scale
3
2
MJ ~ ×
1010 𝑚 −4
𝑋
Atomic cooling halos
mX = 2, 3, 4 keV, CDM
Sitwell, Mesinger, Ma, Sigurdson 2014
Anastasia Fialkov
• Cutoff at O(10-10) – O(10) Msun
(+Sommerfeld enhancement)
van den Aarssen, Bringmann, Goedecke (2012)
Sensitive to
mX ~2-3 keV
Pacucci, Mesinger, Haiman 2013
20 May, 2014
Collapsed Fraction at z = 10
Anastasia Fialkov
Fialkov, Preliminary results
20 May, 2014
1. Effect on Abundance of Dark Matter
Halos. Astrophysical Uncertainties
Star formation in 105-107 Msun halos: Interplay between
WDM (~ 10 keV) and vbc.
Fialkov et al. 2012
Mh ~ M0,vbc(1+aJLW0.47)
Fialkov et al. 2013
Anastasia Fialkov
3
2
MJ ~ × 1010 𝑚𝑋 −4
Sitwell, Mesinger,
Ma, Sigurdson 2014
20 May, 2014
2. Thermal History and Reionization
•
•
•
•
•
• High-z effect on IGM
Low-z effect
Suppressed structure formation • Heating and ionization at high
redshifts.
Stars form later
Delay in heating and reionization • Cannot reionize the Universe
alone
No sinks for ionized gas
• Additional free electrons could
(e.g., Haiman et al. 2001, Benson et al.
catalyze the formation of H2, thus
2001; Barkana & Loeb 2002; Shapiro et al.
form the first stars and begin
2004; Iliev et al. 2004, 2005; Ciardi et al.
2006; Yue et al. 2009; Alvarez & Abel 2010;
reionization early
Yue, Chen 2012…)
Log(TK)
(Araya, Padilla 2013, Biermann &
Kusenko 2006; Kusenko 2007;
Stasielak et al. 2007, Valdes et al. 2013,
Galli et al. 2009, 2011…)
Anastasia Fialkov
Log(1+z)
20 May, 2014
2. Thermal History WDM vs CDM
Later Heating: Delay of Δz ~ 2 (3 keV)
Astrophysical uncertainties (in the redshift of heating transition):
Heating efficiencies Δz ~ few
Star formation scenario Δz ~ 0.8
Sitwell, Mesinger, Ma, Sigurdson (2014)
vbc : Δz < 1
Radiative feedbacks: Δz ~ 2.5
No fbk, no vbc
No fbk, vbc
Weak fbk
Strong fbk
Saturated fbk
WDM: 3 keV, f* = 10%
CDM, f* = 10%
CDM, f = 1%
CMB
Fialkov et al. (2013)
Anastasia Fialkov
20 May, 2014
2. Reionization WDM vs CDM
Fraction of volume in ionized regions
Redshift of reionization
Yue, Chen (2012)
• Delayed: fewer stars at high redshifts
(Mesinger, Ewall-Wice, Hewitt 2014; Yue, Chen 2012).
• Enhanced: less sinks (minihalos), lower recombination rate
(e.g., Haiman et al. 2001, Benson et al. 2001; Barkana & Loeb 2002; Shapiro et al. 2004; Iliev
et al. 2004, 2005; Ciardi et al. 2006; Yue et al. 2009; Alvarez & Abel 2010; Yue, Chen 2012).
• Astrophysics: star formation efficiency; escape fraction.
Anastasia Fialkov
20 May, 2014
2. Thermal History and Reionization
DMA vs no-DMA
DMA: heat and ionize gas (high z).
Gas has less adiabatic cooling
No heating at z ≳ 30 is expected
within standard assumptions!
Stars interfere at z ≲ 30
Bino (10 GeV)
Heavy DM (1 TeV) to leptons
Wino (200 GeV)
No DM annihilation
Valdes, Evoli, Mesinger, Ferrara, Yoshida (2013)
Anastasia Fialkov
20 May, 2014
3. DM Fingerprints in the 21-cm Signal
• Delayed stellar evolution
• Deeper absorption trough
• “Accelerated” heating
• Suppressed signal from Dark
Ages
• Suppressed absorption trough
LEDA
SKA
Anastasia Fialkov
20 May, 2014
3. DM Fingerprints in the 21- cm Signal
WDM vs CDM
•
•
•
•
Absorption trough is deeper by ~25 % (3 keV versus CDM)
Shift of the trough Δz ~ 5 (3 keV versus CDM)
Larger derivatives at higher freq. Easier to observe (e.g., LEDA)
Astro: feedback, X-ray heating, vbc …
2 keV, 3 keV, 4 keV, CDM
f*= 0.3%, 1%, 5%, 10%
Anastasia Fialkov
Sitwell, Mesinger, Ma, Sigurdson (2014)
20 May, 2014
3. DM Fingerprints in the 21-cm Signal
DMA vs no-DMA
•
•
•
•
•
For some models - no signature
Suppressed power during dark ages. (Observations from space!)
10 GeV WIMP: factor ~2 weaker signal from dark ages.
Suppressed absorption feature (Tgas →TCMB in average)
Uncertainties: astrophysics at z < 30 (Star formation), magnetic fields at
high redshifts
Bino (10 GeV)
Heavy DM (1 TeV)
Wino (200 GeV)
No DM annihilation
Anastasia Fialkov
Valdes, Evoli, Mesinger, Ferrara, Yoshida (2013)
20 May, 2014
4. Effect on First Stars
WDM
• Collapsed structures form later, less concentrated.
Barkana et al. 2001; Smith & Markovic 2011
• First stars could form in filaments (1.5 keV → SF in
filaments z > 6).
• Detectable: Lyman-limit (LLS) or Damped Lyman - systems
(DLAs); “chain” galaxies at z ~ 10.
• However: “No theory” for star formation in filaments yet.
Gao & Theuns (2007); Gao, Theuns, Springel (2014)
Anastasia Fialkov
20 May, 2014
4. Effect on First Stars
WDM
Example: Star Formation in Filaments for 1.5 keV WDM, atomic cooling
GADGET 3, SPH,
100 Mpc/h
Anastasia Fialkov
Gao, Theuns, Springel (2014)
20 May, 2014
4. Effect on First Stars
Annihilating DM
• Enhanced H2 abundance and
more rapid cooling
• DMA is not very effective in
suppressing gas collapse and
subsequent fragmentation
• However: Heating from DMA
is important in modifying the
thermodynamics of primordial
gas
Smith et al. (2012); Ripamonti et al. (2010);
Iocco et al. (2008); Chuzhoy (2008)
Anastasia Fialkov
Stacy, Pawlik, Bromm, Loeb (2014)
20 May, 2014
Summary
• Mainly manifests itself at low z
• Suppresses fluctuations at small
scales
• Delays stellar evolution
• Delays build-up of radiative
feedbacks
• Affects reionization
• 21-cm signal from z ≲ 20
• Stars could form in filaments
‘Noises’ (e.g. in 21-cm signal):
• vbc, feedbacks, X-ray heating, SF
efficiency, escape fraction,…
• Mainly manifests itself at high z
• Modified thermal history and
ionization at high redshifts z ≳ 30
• Stars could start forming earlier
• Smoking gun (in some models):
Suppressed signal from Dark
Ages
‘Noises’:
• Star formation at z ≲ 30
• Primordial magnetic fields
Primordial Magnetic Fields
Primordial magnetic fields can heat the gas early
- Ambipolar diffusion
- Decay of turbulences
0.5 nG
Schleicher, Banerjee, Klessen (2009)
Global 21-cm Signal in ΛCDM
Sensitive to:
• Initial conditions
• Heating
• Ly-a, LW
• Ionization fraction
Anastasia Fialkov
20 May, 2014
Observational constraints WDM
• Strongly lensed high redshift galaxies number counts Pacucci
et al 2013 (independent of astrophysics) mx > 1 keV
• stellar mass function + TF relation mx > 0.75 keV Kang et al.
2013
• Reionization by z~6, supermassive black holes -> mx > 0.75
keV (Barkana et al 2001)
• Ly-a forest (m_x>3.3 keV @ 2σ, thermal relic) Viel et al 2013
• 21-cm signal (Interplay between WDM, vbc and astrophysical
feedbacks (e.g. LW negative feedback) probes perturbations
up to Jeans scale.
• High redshift gamma-ray bursts (mx > 1.6-1.8 keV) de Souza
et al 2013
A set of noiseless Ly-a forest spectra for a quasar at z = 4.6z
Anastasia Fialkov
Viel et al. (2013)
20 May, 2014

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