1 / 29

HI 21cm Signal from Cosmic Reionization IAU 2006, Long Wavelength Astrophysics

HI 21cm Signal from Cosmic Reionization IAU 2006, Long Wavelength Astrophysics Chris Carilli (NRAO). Ionized. Neutral. Reionized. Chris Carilli (NRAO) Berlin June 29, 2005. WMAP – structure from the big bang. Hubble Space Telescope Realm of the Galaxies. Dark Ages. Epoch of Reionization.

brielle-brock
Download Presentation

HI 21cm Signal from Cosmic Reionization IAU 2006, Long Wavelength Astrophysics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. HI 21cm Signal from Cosmic Reionization IAU 2006, Long Wavelength Astrophysics Chris Carilli (NRAO) Ionized Neutral Reionized

  2. Chris Carilli (NRAO) Berlin June 29, 2005 WMAP – structure from the big bang

  3. Hubble Space Telescope Realm of the Galaxies

  4. Dark Ages Epoch of Reionization Age of Enlightenment • last phase of cosmic evolution to be tested • bench-mark in cosmic structure formation indicating the first luminous structures

  5. HI 21cm observations of Cosmic Reionization, and beyond • Most direct probe of epoch and process of reionization • Rich in physical diagnostics • Only probe of cosmic evolution during ‘dark ages’ • TALK: • Current observational constraints on reionization (Fan et al. ARAA 2006) • Predicted HI 21cm signals • Telescopes and Challenges

  6. Reionization: the movie 8Mpc comoving Gnedin 03

  7. Constraint I: Gunn-Peterson Effect End of reionization? f(HI) > 1e-3 at z = 6.3 vs. <1e-4 at z= 5.7 Fan et al 2006

  8. Constraint II: CMB large scale polarization: Thompson scattering during reionization • Scattered CMBquad. => polarized • Horizon scale => 10’s deg • t = 0.09+/-0.03 => z_reion= 11+/3 TT TE EE Fan et al 2003 Page + 06

  9. Current observations => z_reion = 6 to 11? • Not ‘event’ but complex process, large variance time/space • GP => occurs in ‘twilight zone’, opaque l_obs< 0.9 mm

  10. Limitations of current measurements:CMB polarization • t_e = integral measure through universe=> allows many reionization scenarios • Still a 3s result (now in EE vs. TE before)Gunn-Peterson effect • t_Lya >>1 for f(HI)>0.001 => low f(HI) diagnostic • t to f(HI) conversion requires ‘clumping factor’ (cf. Becker, Rauch, Sargent 2006)

  11. Studying the pristine IGM into the EOR using redshifted HI 21cm observations (100 – 200 MHz) • Large scale structure: • cosmic density, d • neutral fraction, f(HI) • Temp: T_K, T_CMB, T_spin • Heating: Lya, Xrays, shocks

  12. Signal I: Global (‘all sky’) reionization signature in low frequency HI spectra IGM heating: T_spin=T_K > T_CMB Lya coupling: T_spin=T_K < T_CMB Gnedin & Shaver 03 21cm ‘deviations’ < 1e-4 wrt foreground

  13. Signal II: 3D Power spectrum analysis d only LOFAR d + f(HI) SKA McQuinn + 06

  14. Signal III: 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

  15. Cosmic Webafter reionization Ly alpha forest at z=3.6 (d < 10) Womble 96 N(HI) = 1e13 – 1e15 cm^-2, f(HI/HII) = 1e-5 -- 1e-6 => Before reionization N(HI) =1e18 – 1e21 cm^-2

  16. Signal IV: Cosmic web before reionization: HI 21Forest 19mJy z=12 z=8 130MHz • 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

  17. Signal V: Cosmic Stromgren spheres around z > 6 QSOs • LOFAR ‘observation’: • 20xf(HI)mK, 15’,1000km/s • => 0.5 x f(HI) mJy • Pathfinders: Set first hard limits on f(HI) at end of cosmic reionization • Easily rule-out cold IGM (T_s < T_cmb): signal = 360 mK 5Mpc 0.5 mJy Wyithe et al. 2006

  18. Signal VI: pre-reionization HI signal eg. Baryon Oscillations (Barkana & Loeb) • Very difficult to detect ! • z=50 => n = 30 MHz • Signal: 30 arcmin, 50 mk =>S_30MHz= 0.1 mJy • SKA sens in 1000hrs: • T_fg = 20000K => • rms = 0.2 mJy z=50 z=150

  19. ‘Pathfinders’: PAST, LOFAR, MWA, PAPER, … MWA (MIT/ANU) LOFAR (NL) PAST (CMU/China) PAPER Berk/NRAO

  20. Challenge I: Low frequency foreground – hot, confused sky Eberg 408 MHz Image (Haslam + 1982) Coldest regions: T = 100 (n/200 MHz)^-2.6 K Highly ‘confused’: 1 source/deg^2 with S_0.14 > 1 Jy

  21. Solution: spectral decomposition (eg. Morales, Gnedin…) 10’ FoV; SKA 1000hrs All sky: SI deviations = 0.001 Freq Signal Foreground Power spectral analysis: Fourier analysis in 3D – different symmetries in freq space (ie. Different spectral chan-chan correlation)

  22. Challenge II: Ionospheric phase errors – varying e- content • TIDs – ‘fuzz-out’ sources • ‘Isoplanatic patch’ = few deg = few km • Phase variation proportional to l^2 • Solution: • Wide field ‘rubber screen’ phase self-calibration Virgo A VLA 74 MHz Lane + 02

  23. Challenge III: Interference 100 MHz z=13 200 MHz z=6 • Solutions: RFI Mitigation • Digital filtering • Beam nulling • Real-time ‘reference beam’ KNMD Ch 9 Digital TV

  24. Solution – RFI mitigation: location, location location… 100 people km^-2 1 km^-2 0.01 km^-2

  25. Destination: Moon!

  26. GMRT 230 MHz – HI 21cm abs toward highest z radio galaxy, 0924-220 z=5.2 RFI = 20 kiloJy ! 8GHz 1” 230Mhz0.5 Jy Van Breugel et al. rms(20km/s) = 5 mJy CO Klamer + z(CO)

  27. Radio astronomy – Probing Cosmic Reionization • ‘Twilight zone’: study of first light limited to near-IR to radio l’s • First constraints: GP, CMBpol => reionization is complex and extended: z_reion = 6 to 11 • HI 21cm: most direct probe of reionization • Low freq pathfinders: All-sky, PS, CSS • SKA: imaging of IGM

  28. Constraint III: Cosmic Stromgren Spheres • 1148+5251: Accurate z_hostfrom CO: z=6.419+/0.001 • Proximity effect:photons leaking from 6.32<z<6.419 White et al. 2003 • ‘time bounded’ Stromgren sphere: R = 4.7 Mpc • f(HI) = 1e-5 R^-3 (t_qso/1e7) yrs • <f(HI)> ~ 0.1 for sample 19 QSOs at z>5.7 (Fan et al. 06; Wyithe et al. 04)

More Related