21 cm reionization forecast and search at gmrt
Post on 09-Jan-2016
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21 cm Reionization Forecast and Search at GMRTUe-Li Pen Tzu-Ching Chang Julia OdegovaJeff Peterson, CMUChris Hirata, Kris Sigurdson, Yashwant Gupta, Jayanta RoyRadiative Xfer simulation by Iliev, Mellema, Shapiro, Pen, et al
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=0.09+/-0.03, zr=11WMAP 3yrUniverse at recombinationUniverse at reionization
- ReionizationFirst objects: 21cm @ z=6-1590-200 MhzT ~ 20 mK, ~Jy- mJy (up to 1016 M of HI)Angular scale 5
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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, etclog10 T (mK)
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Iliev et al, astro-ph/0702099
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Iliev et al, Astro-ph/0702099
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Foreground: Galactic SynchrotronHaslam 408 MHzMuch brighter than signal, but no spectral structure
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Indian Giant Meterwave Radio Telescope30 dishes @45m ea.Operates in 2m bandCollaborators: Y. Gupta (chief scientist), Rajaram Nityananda (director), J. Roy, J. Peterson (CMU), C. Hirata (IAS), T. Chang (CITA), J. Odegova (Toronto), K. Sigurdson (UBC)
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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.
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Step 1: new software correlator:imaging the full sky+horizon
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Power Line NoiseTime-lag: Folded 70ms data on short baseline
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Step 2: Phase calibrationReal time pulsar gated imaging calibrationPen et al 2007, GMRT internal report
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Antenna based phase solutions
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Fourier (u-v) map (Im)
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Current StatusSensitivity forecasts for GMRT promisingRFI 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.
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OutlookExisting constraints: optical depth from WMAP (Poln), SDSS QSOs.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.
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