Probing the Nature of Dark Matter with the First Galaxies (Reionization, 21-cm signal)

Transcription

1 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

2 Outline The early Universe (brief overview) Effect of various DM models on: 1. Number Counts 2. Thermal history and Reionization cm signal 4. Properties of first stars

3 Cosmic History CMB Dark Ages First Stars and Galaxies Reionization

4 First Stars and Galaxies Form in metal free environment H 2 cooling ~10 5 M sun halos H cooling in ~10 7 M sun 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 v bc ) (e.g., Barkana & Loeb 2004; Tselikhovich & Hirata 2010)

5 Formation of First Stars is Biased 1. Relative supersonic motion between gas and dark mater affects M sun halos Suppresses halo abundance Suppresses gas fraction Delays star formation First star is delayed by Δz ~ 5 O Leary & McQuinn (2012) 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 Fialkov, Barkana, Tseliakhovich, Hirata (2012)

6 Visbal, Barkana, Fialkov, Tseliakhovich, Hirata 2012

7 Formation of First Stars is Biased 2. Radiative feedbacks LW photons destroy H 2, suppress star formation in ~10 6 M sun halos H 2 + γ H 2 * H + H Electrons catalyze H 2 formation H + e - H - + γ H + H - H 2 + e - X-rays catalyze H 2 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.

8 Log(T K ) 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) T K z ~ 200 T CMB Heating mechanisms: X-ray binaries Thermal emission Quasars, mini quasars Dark matter annihilation Etc. Log(1+z)

9 21-cm Signal n = 1 n 1 n 0 3-D map of HI Tool to Probes: Dark Ages, Cosmic Dawn and Reionization

10 Global 21-cm Signal in ΛCDM Sensitive to: Initial conditions δ, v bc (cosmology) Gas Temperature (heating mechanisms) Ly-a, LW, Ionization fraction (properties of sources) Expected Signal Anastasia Fialkov Pritchard and Loeb May, 2014

11 Primordial Landscape with Various DM Models

12 Dark Matter m X ~ kev, thermal relics m X ~ GeV TeV Structure formation at small scales is suppressed by Particle free streaming Heating and ionization at high z (Bode P., Ostriker J. P., Turok N., 2001) Residual velocity dispersion of the particles (Barkana R., Haiman Z., Ostriker J. P., 2001)

13 1. Effect on Abundance of Dark Matter Halos Suppression scale M J ~ m X 4 Cutoff at O(10-10 ) O(10) M sun (+Sommerfeld enhancement) van den Aarssen, Bringmann, Goedecke (2012) Atomic cooling halos m X = 2, 3, 4 kev, CDM Sensitive to m X ~2-3 kev Sitwell, Mesinger, Ma, Sigurdson 2014 Pacucci, Mesinger, Haiman 2013

14 Collapsed Fraction at z = 10 Anastasia Fialkov Fialkov, Preliminary results 20 May, 2014

15 1. Effect on Abundance of Dark Matter Halos. Astrophysical Uncertainties Star formation in M sun halos: Interplay between WDM (~ 10 kev) and v bc. Fialkov et al M J ~ m X 4 M h ~ M 0,vbc (1+aJ LW 0.47 ) Fialkov et al Sitwell, Mesinger, Ma, Sigurdson 2014

16 Log(T K ) 2. Thermal History and Reionization Low-z effect Suppressed structure formation Stars form later Delay in heating and reionization No sinks for ionized gas (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 ) High-z effect on IGM Heating and ionization at high redshifts. Cannot reionize the Universe alone Additional free electrons could catalyze the formation of H 2, thus form the first stars and begin reionization early (Araya, Padilla 2013, Biermann & Kusenko 2006; Kusenko 2007; Stasielak et al. 2007, Valdes et al. 2013, Galli et al. 2009, 2011 ) Log(1+z)

17 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 v bc : Δz < 1 Radiative feedbacks: Δz ~ 2.5 No fbk, no vbc No fbk, vbc Weak fbk Strong fbk Saturated fbk Sitwell, Mesinger, Ma, Sigurdson (2014) WDM: 3 kev, f* = 10% CDM, f* = 10% CDM, f = 1% CMB Fialkov et al. (2013)

18 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.

19 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)

20 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

21 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, v bc 2 kev, 3 kev, 4 kev, CDM f*= 0.3%, 1%, 5%, 10% Anastasia Fialkov Sitwell, Mesinger, Ma, Sigurdson (2014) 20 May, 2014

22 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 (T gas T CMB 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

23 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)

24 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

25 4. Effect on First Stars Annihilating DM Enhanced H 2 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) Stacy, Pawlik, Bromm, Loeb (2014)

26 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): v bc, 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

27 Primordial Magnetic Fields Primordial magnetic fields can heat the gas early - Ambipolar diffusion - Decay of turbulences 0.5 ng Schleicher, Banerjee, Klessen (2009)

28 Global 21-cm Signal in ΛCDM Sensitive to: Initial conditions Heating Ly-a, LW Ionization fraction

29 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 Reionization by z~6, supermassive black holes -> mx > 0.75 kev (Barkana et al 2001) Ly-a forest (m_x>3.3 2σ, thermal relic) Viel et al 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 > kev) de Souza et al 2013 A set of noiseless Ly-a forest spectra for a quasar at z = 4.6z Viel et al. (2013)