1. 21 cm Reionization Forecast and Search at GMRT
Ue-Li Pen 彭威礼
Tzu-Ching Chang 張慈錦
Julia Odegova
Radiative Xfer simulation by Iliev, Mellema, Shapiro, Pen, et al
Jeff Peterson, CMU
Chris Hirata, Kris Sigurdson, Yashwant Gupta, Jayanta Roy

2. WMAP 3yr Universe at reionization Universe at recombination
τ=0.09+/-0.03, zr=11
Universe at recombination

3. Reionization First objects: 21cm @ z=6-15 90-200 Mhz ΔT ~ 20 mK,
~μJy- mJy (up to 1016 Mסּ of HI)
Angular scale 5’<Θ<30’, freq res 500 khz
Challenging theory
Iliev, Mellema, Pen, Shapiro /h Mpc, 1o FOV

4. Cosmic Reionization (Iliev, Mellema, Pen, Shapiro 2006)
log10 T (mK)
(Iliev, Mellema, Pen, Shapiro 2006)
Largest radiative transfer cosmological reionization simulations: 1 degree FOV.
Detection in 21cm hyperfine transition with radio telescopes. Structure on large scales (>20’).
See also Furlanetto, Oh, Zaldarriaga, Zahn, Morales, Mesinger, Croft, Ciardi, etc

5. Iliev et al, astro-ph/

6. Iliev et al, Astro-ph/

7. Foreground: Galactic Synchrotron
Haslam 408 MHz
Much brighter than signal, but no spectral structure

8. Indian Giant Meterwave Radio Telescope
30 ea.
Operates in 2m band
Collaborators: Y. Gupta (chief scientist), Rajaram Nityananda (director), J. Roy, J. Peterson (CMU), C. Hirata (IAS), T. Chang (CITA), J. Odegova (Toronto), K. Sigurdson (UBC)

9. GMRT EoR Search
Operating telescope, 50,000m2 (geometric), up to 32 MHz BW, fully polarized, lowest band MHz, sky limited. Currently biggest collecting area in this band.
Half in central 1km core (relevant for EoR), rest in 20 km Y (useful for calibration).
Previously reached RFI limit at 150 MHz after a few minutes of integration: power lines, TV stations, HAM amateurs, faulty home electronics.
Software correlator: success of new RFI mitigation schemes, nearfield clean.
Current effort invests 100 hours observing time per semester.

11. Step 1: new software correlator: imaging the full sky+horizon

14. Power Line Noise
Time-lag: Folded 70ms data on short baseline

20. Step 2: Phase calibration
Real time pulsar gated imaging calibration
Pen et al 2007, GMRT internal report

21. Antenna based phase solutions

23. Fourier (u-v) map (Im)

24. Current Status Sensitivity forecasts for GMRT promising
RFI mitigation successful, physical elimination under investigation.
Pulsar phase referencing successful.
Polarization calibration and imaging achieved – no non-pulsar sources found.
Foreground subtraction under way. Frequency dependent primary beam: holographic pulsar beam mapping.

25. Outlook
Existing constraints: optical depth from WMAP (Pol’n), SDSS QSO’s.
Theoretical progress: direct simulations indicate power on larger scales (>20’), making detections more tractable.
current: large data sets from GMRT, data analysis in progress. RFI problems solved: separate imaging of sky and RFI. Foreground subtraction main challenge.
Bright outlook: several experiments underway to tap the next cosmic horizon: GMRT, LOFAR, MWA, Past/21CMA, Paper …
Exciting new window on universe for precision cosmology. Open field for theory and experiment.