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Understanding the Epoch of Reionization: Cosmic Evolution and Structure Formation Insights

This study investigates the Epoch of Reionization (EoR), a pivotal phase in cosmic evolution that marks the end of the dark ages and the onset of the first luminous structures in the universe. It explores key phenomena like the Gunn-Peterson effect and measurements of neutral hydrogen (HI) at high redshifts, offering insights into the transition from opaque to transparent universe. The effects of cosmic microwave background polarization and the implications for dark ages are discussed, along with challenges in current observations and the potential contribution of advanced radio astronomical probes like the Square Kilometer Array.

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Understanding the Epoch of Reionization: Cosmic Evolution and Structure Formation Insights

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  1. History of IGM F(HI) = 0 C.Carilli (NRAO) Heidelberg 05 F(HI) = 1 Epoch of Reionization (EoR) • last phase of cosmic evolution to be tested • bench-mark in cosmic structure formation indicating the first luminous structures F(HI) = 1e-5

  2. z=5.80 z=5.82 z=5.99 z=6.28 The Gunn Peterson Effect End of reionization f(HI) > 0.001 at z = 6.3 => opaque at l_obs<0.9mm Fan et al 2003

  3. Near-edge of reionization: GP Effect Fairly Fast: • f(HI) > 1e-3 at z >= 6.3 (0.87Gyr) • f(HI) < 1e-4 at z <= 5.7 (1.0 Gyr) Although cf. Songaila, Oh, Stern, Malhotra… Fan + 2005; White + 2005

  4. Neutral IGM evolution (Gnedin 2004): ‘Cosmic Phase transition’ at z=6 to 7 8 Mpc (comoving) Normalization: GP absorption, LCDM + z=4 LBGs, T_IGM

  5. WMAP Large scale polarization of CMB (Kogut et al.) CMB Temperature fluctuations imprinted by primordial density fluctuations at last scattering (z=1000) Large scale polarization: Thompson scattering at EoR t_e = 0.17 => F(HI) < 0.5 at z=17 20deg

  6. GP + CMB => ‘complex’ reionization extending from z=20 to 6? • Limitations of current measurements: • CMB polarization: -- t_e= Ln_es_e = integral measure through universe=> allows many reionization scenarios • Gunn-Peterson effect: --t_Lya >>1 for f(HI)>0.001-- High z universe is opaque at (observed) optical wavelengths  Reionization occurs in ‘twilight zone’, observable at near-IR through radio wavelengths

  7. Radio astronomical probes of the Epoch of Reionization and the 1st luminous objects CMB: large scale polarization + secondary anisotropies Objects within EoR – Molecular gas, dust, star formation, process of reionization Neutral IGM – HI 21cm emission and absorption Collaborators USA – Carilli, Walter, Fan, Strauss, Owen, Gnedin, Lo Euro – Bertoldi, Cox, Menten, Omont, Beelen SKA Key Program science team– Briggs, Carilli, Furlanetto, Rawlings Science with the Square Kilometer Array (NAR, Carilli & Rawlings) http://www.skatelescope.org/pages/page_astronom.htm

  8. IRAM 30m + MAMBO: sub-mJy sens at 250 GHz + wide fields  dust • IRAM PdBI: sub-mJy sens at 90 and 230 GHz + arcsec resol. mol. gas • VLA: uJy sens at 1.4 GHz  star formation • VLA: < 0.1 mJy sens at 20-50 GHz + 0.2” resol.  mol. gas (low order)

  9. FIR = 1.6e12 L_sun Magic of (sub)mm: distance independent method of studying objects in universe for z=0.8 to 8 L_FIR = 4e12 x S_250(mJy) L_sun SFR = 1e3 x S_250 M_sun/yr Radio-FIR (Yun+ 02)

  10. High Redshift QSOs: SDSS, DPSS (Fan 2005) • z>4: 950 known • z>5: 52 • z>6: 8 • 30 at z~6 expected in the whole survey M_B < -26 => L_bol > 1e14 L_sun M_BH > 1e9 M_sun

  11. QSO host galaxies – M_BH – s relation • Most (all?) low z spheroidal galaxies have SMBH: M_BH=0.002M_bulge • ‘Causal connection between SMBH and spheroidal galaxy formation’ (Gebhardt et al. 2002)? • Luminous high z QSOs have massive host galaxies (1e12 M_sun)

  12. MAMBO surveys of z>2 DPSS+SDSS QSOs 1148+52 z=6.4 1e13L_sun 1048+46 z=6.2 Arp220 • 30% of luminous QSOs have S_250 > 2 mJy, independent of redshift from z=1.5 to 6.4 • L_FIR =1e13 L_sun = 0.1 x L_bol: Dust heating by starburst or AGN?

  13. L_FIR vs L’(CO) High-z sources 1e3 M_sun/yr Index=1 1e11 M_sun Index=1.7 • M(H_2) = X * L’(CO), X=4 (Milkyway), X=0.8 (ULIRGs) • Telescope time: t(dust) = 1hr, t(CO) = 10hr

  14. VLA detections of HCN 1-0 emission n(H_2) > 1e5 cm^-3 (vs. CO: n(H_2) > 1e3 cm^-3) index=1 Solomon et al z=2.58 70 uJy

  15. Objects within EoR: QSO 1148+52 at z=6.4 • highest redshift quasar known • L_bol = 1e14 L_sun • central black hole: 1-5 x 109 Msun(Willotetal.) • clear Gunn Peterson trough (Fan etal.)

  16. Cosmic (proper) time 1/16 T_univ = 0.87Gyr

  17. 1148+52 z=6.42: Dust and Gas detection 46.6149 GHz CO 3-2 Off channels Rms=60uJy M(H_2) = 2e10 M_sun L_FIR = 1.2e13 L_sun, M_dust =7e8M_sun S_250 = 5.0 +/- 0.6 mJy • Dust formation: 1.4e9yr (AGB winds) > t_univ (8.7e8yr) => dust formed in high mass stars? => silicate grains? • C, O production (3e7 M_sun): few e8 yr => Star formation started early (z = 10)?

  18. IRAM Plateau de Bure n2 (6-5) (7-6) (3-2) • Tkin=100K, nH2=105cm-3 • FWHM = 305 km/s • z = 6.419 +/- 0.001  Typical of starburst nuclei (eg. NGC253, Arp220)

  19. VLA imaging of CO3-2 at 0.4” and 0.15” resolution rms=50uJy at 47GHz • Separation = 0.3” = 1.7 kpc • T_B = 20K  Typical of starburst nuclei • Merging galaxies? • CO extended to NW by 1” (=5.5 kpc) tidal(?) feature

  20. 1148+5251: radio-FIR SED Beelen et al. S_1.4= 55 +/- 12 uJy 1048+46 T_D = 50 K • Star forming galaxy characteristics: radio-FIR SED, Gas/Dust, CO excitation and T_B => Coeval starburst/AGN? SFR = 1e3 M_sun/yr • Stellar spheroid formation in few e7 yrs = e-folding time for SMBH • => Coeval formation of galaxy/SMBH at z = 6.4 ?

  21. 1148+52: Masses • M(dust) = 7e8 M_sun • M(H_2) = 2e10 M_sun • M_dyn (r=2.5kpc) = 5e10 M_sun • M_BH = 3e9 M_sun => M_bulge = 1.5e12 M_sun • Gas/dust = 30, typical of starburst • Dynamical vs. gas mass => baryon dominated? • Dynamical vs. ‘bulge’ mass => M – s breaks-down at high z? [SMBH forms first?]

  22. Cosmic Stromgren Sphere • Accurate redshiftfrom CO: z=6.419+/0.001 Ly a, high ioniz Lines: inaccurate redshifts (Dz > 0.03) • Proximity effect:photons leaking from 6.32<z<6.419 White et al. 2003 z=6.32 • ‘time bounded’ Stromgren sphere: R = 4.7 Mpc t_qso= 1e5 R^3 f(HI)= 1e7yrs

  23. Loeb & Rybicki 2000

  24. z>6 QSOs with MgII and/or CO redshifts (Wyithe et al. 05) <Dz> = 0.08 => <R> = 4.4 Mpc

  25. Constraints on neutral fraction at z=6.4 ? • GP => f(HI) > 0.001 • If f(HI) = 0.001, then t_qso = 1e4 yrs – implausibly short given QSO fiducial lifetimes (1e7 years)? • Probability arguments suggest: f(HI) > 0.1 P(>x_HI) 10% Wyithe et al. 2005 90% probability x(HI) > curve t_qso/1e7 yrs

  26. Near-edge of reionization: GP + Cosmic Stromgren Spheres Very Fast? • f(HI) > 1e-1 at z > 6.4 (0.87Gyr) • f(HI) < 1e-4 at z < 5.7 (1.0 Gyr) See also Cosmic Stromgren Surfaces (Mesinger & Haiman 2004 but cf. Oh & Furnaletto 2005)

  27. Molecular Gas and dust during the EoR • FIR luminous galaxy at z=6.42: 1e13 Lsun observe dust, gas, star formation, AGN • Sub-kpc imaging: Merging galaxy: M_gas= 2x1010 M_sun, M_dyn=6e10 M_sun • Early enrichment of heavy elements and dust produced => star formation 0.4 Gyr after the big bang • High z: Coeval formation of SMBH + stars and break-down of M-s at high z? • Cosmic Stromgren sphere = 4.7 Mpc => ‘witnessing process of reionization’ t_qso = 1e7 * f(HI) yrs ‘fast’ reionization: f(HI)>0.1 at z=6.4?

  28. Continuum sensitivity of future arrays: Arp 220 vs z (FIR = 1.6e12 L_sun) cm: Star formation, AGN (sub)mm: Dust, molecular gas Near-IR: Stars, ionized gas, AGN

  29. Studying the pristine IGM beyond the EOR: redshifted HI 21cm observations (100 – 200 MHz) with the Square Kilometer Array.‘Pathfinders’: LOFAR, MWA, PAST, VLA-VHF,… Large scale structure: density, f(HI), T_spin SKA goal: mJy at 200 MHz

  30. Low frequency background – hot, confused sky Eberg 408 MHz Image (Haslam + 1982) Coldest regions: T = 100 (n/200 MHz)^-2.6 K Highly ‘confused’: 3 sources/arcmin^2 with S_0.2 > 0.1 mJy

  31. Interference 100 MHz z=13 200 MHz z=6 • Ionospheric phase errors • TIDs – ‘fuzz-out’ sources • ‘Isoplanatic patch’ = few deg = few km • Phase variation proportional to wavelength^2 74MHz Lane 03

  32. Global reionization signature in low frequency HI spectra (Gnedin & Shaver 2003) fast 21cm ‘deviations’ at 1e-4 wrt foreground double Spectral index deviations of 0.001

  33. HI 21cm Tomography of IGM Zaldarriaga + 2003 z=12 9 7.6 • DT_B(2’) = 10’s mK • SKA rms(100hr) = 4mK • LOFAR rms (1000hr) = 80mK

  34. Power spectrum analysis Zaldarriaga + 2003 Z=10 129 MHz LOFAR SKA 1arcmin 2deg

  35. Cosmic Webafter reionization = Ly alpha forest (d <= 10) 1422+23 z=3.62 Womble 1996 N(HI) = 1e13 -- 1e15 cm^-2, f(HI/HII) = 1e-5 -- 1e-6 => Before reionization N(HI) =1e18 – 1e21 cm^-2 Cosmic web before reionization: HI 21Forest • radio G-P (t=1%) • 21 Forest (10%) • mini-halos (10%) • primordial disks (100%) • expect 0.05 to 0.5 deg^-2 at z> 6 with S_151 > 6 mJy (Carlli,Jarvis,Haiman) z=12 z=8 20mJy 130MHz

  36. ‘Pathfinders’: PAST, LOFAR, MWA, VLA-VHF, … MWA prototype (MIT/ANU) LOFAR (NL) PAST (CMU/China) VLA-VHF (CfA/NRAO)

  37. VLA-VHF: 180 – 200 MHz Prime focus X-dipole Greenhill, Blundell (SAO Rx lab); Carilli, Perley (NRAO) Leverage: existing telescopes, IF, correlator, operations • $110K D+D/construction (CfA) • First light: Feb 16, 05 • Four element interferometry: May 05 • First limits: Dec 05

  38. Main Experiment: Cosmic Stromgren spheres around z=6 to 6.5 SDSS QSOs (Wyithe & Loeb 2004) VLA-VHF 190MHz 250hrs 20 f(HI) mK 15’ • VLA spectral/spatial resolution well matched to expected signal: 7’, 1000 km/s • Set first hard limits on f(HI) at end of cosmic reionization (f(HI) < 0.3) • Easily rule-out cold IGM (T_s < T_cmb): signal = 360 mK 0.50+/-0.12 mJy

  39. Other Experiments: power spectrum analysis, ‘HI 21cm forest’ 2deg

  40. System characteristics • First sidelobe = 14% (goal < 5%) • Efficiency = 28% (goal: 50%) • Xpol = 20% (goal: 5%) • T_sys = 50 (Rx) + 150 (sky) K • FoV = 12 deg^2 • rms/chan= 0.12mJy in 250 hrs (goal) • Correlator: 0.8MHz/chan, 16 chan, 2 pol. 4deg 3C313 --first image

  41. Main hurdle: Interference! Digital TV: 186 to 192MHz, 200 W from ABQ KNMD Ch 9 Digital TV

  42. Radio astronomy – Probing the EoR • ‘Twilight zone’:physics of 1st luminous sources (limited to near-IR to radio wavelengths) • Currently limited to pathological systems (‘HLIRGs’) • EVLA, ALMA 10-100x sensitivity is critical to study normal galaxies • Low freq pathfinders: HI 21cm signatures of neutral IGM • SKA imaging of IGM z=6.4

  43. PKS 2322+1944 z=4.12: [CI] (492 GHz rest freq; Pety et al.) VLA CO2-1 PdBI => Solar Metalicity

  44. GMRT 228 MHz – HI 21cm abs toward highest z radio galaxy, 0924-220 z=5.2 RFI = 20 kiloJy ! 8GHz 1” Van Breugel et al. rms/(40km/s chan) = 5 mJy 230Mhz point source = 0.55 Jy; z(CO)

  45. Richards et al. 2002 SDSS QSOs 1000km/s => Dz = 0.03

  46. J1048+4637: A second FIR-luminous QSO source at z=6.2 S_250 = 3.0 +/- 0.4 mJy=> L_FIR=7.5e12 L_sun VLA CO(3-2) z(MgII) z(opt) GBT/EVLA/ALMA/LMT correlator: 8–32 GHz, 16000 channels

  47. Gunn-Peterson effect Barkana and Loeb 2001

  48. Complex reionization example: Double reionization? (Cen 2002; cf. Furlanetto, Gnedin,…) Pop III stars in ‘mini-halos’ (<1e7 M_sun) ‘normal’ galaxies (>1e8M_sun) • Recombination time < hubble time at z > 8 • Stellar fusion produces 7e6eV/H atom, reionization requires 13.6eV/H atom =>Need to process only 1e-5 of baryons through stars to reionize the universe

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