21 cm Reionization Forecast and Search at GMRT

Ue-Li Pen 彭威礼Tzu-Ching Chang 張慈錦

Julia Odegova

Jeff Peterson, CMU

Chris Hirata, Kris Sigurdson, Yashwant Gupta, Jayanta Roy

Radiative Xfer simulation by Iliev, Mellema, Shapiro, Pen, et al

τ=0.09+/-0.03, zr=11

WMAP 3yr

Universe at recombination

Universe at reionization

Reionization

• First objects: • 21cm @ z=6-15• 90-200 Mhz• ΔT ~ 20 mK, • ~μJy- mJy (up to 1016

Mּס of HI)• Angular scale

5’<Θ<30’, freq res 500 khz

• Challenging theory

Iliev, Mellema, Pen, Shapiro 2006. 100/h Mpc, 1o FOV

Cosmic Reionization

(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

log10 T (mK)

Iliev et al, astro-ph/0702099

Iliev et al, Astro-ph/0702099

Foreground: Galactic Synchrotron

Haslam 408 MHz Much brighter than signal, but no spectral structure

Indian Giant Meterwave Radio Telescope

30 dishes @45m 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)

GMRT EoR Search• Operating telescope, 50,000m2 (geometric), up to

32 MHz BW, fully polarized, lowest band 100-200 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.

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

Power Line Noise

Time-lag: Folded 70ms data on short baseline

Step 2: Phase calibration

Real time pulsar gated imaging calibration

Pen et al 2007, GMRT internal report

Antenna based phase solutions

Fourier (u-v) map (Im)

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.

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.