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Seeing the universe through redshifted 21-cm radiation

Somnath Bharadwaj Physics & CTS IIT Kharagpur. Seeing the universe through redshifted 21-cm radiation. Tarun D Saini. Biswajit Pandey. Collaborators. Sanjay Pandey. IISc. RRI. Biman Nath. LBSC,Gonda. BITS,Pilani. RRI. Jayaram Chengalur. Tapomoy Guha Sarkar. Shiv K Sethi.

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Seeing the universe through redshifted 21-cm radiation

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  1. SomnathBharadwaj Physics & CTS IIT Kharagpur Seeing the universe through redshifted 21-cm radiation

  2. Tarun D Saini Biswajit Pandey Collaborators Sanjay Pandey IISc RRI Biman Nath LBSC,Gonda BITS,Pilani RRI Jayaram Chengalur Tapomoy Guha Sarkar Shiv K Sethi T Roy Choudhury NCRA,TIFR Suman Majumdar Saiyad Ali NCRA,TIFR IUCAA JU Stockholm Abhik Ghosh Kanan Datta Jayanti Prasad

  3. The Expanding Universe

  4. Redshift – distance - time z2 z1 Observer z3

  5. 21 cm radiation Neutral Hydrogen - HI Ground state

  6. Constituents of the Universe Baryons 75 % Hydrogen 25% Helium

  7. Cosmic Microwave Background Radiation (CMBR) Observer T=2.725 K

  8. HI Evolution

  9. z > 1000 T =2.725 K (1+z) Hydrogen is ionized at z>1,000 Recombination – HI formed for first time at z=1,000

  10. CMBR anisotropies Universe ionized and opaque at z >1000 WMAP NASA Z=1000 T=2.725 K Nearly isotropic T ~ 10 micro K

  11. HI Evolution Dark Age HI seen in absorption against CMBR

  12. HI Evolution Epoch of Reionization HI seen in emission

  13. HI Evolution Post-Reionization HI seen in emision

  14. Evolution of the Universe

  15. Structure Formation Z=0 Z=1000

  16. Rionization Photoionization First Luminous Objects z~30 15 >z > 6

  17. Simulation Majumdar, Bharadwaj& Roy Choudhury 2012,MNRAS, Submitted

  18. What do we observe? Fluctuations in 21-cm radiation with frequency ad angle on sky

  19. The Dark Matter Power Spectrum

  20. Mini-Summary • Redshifted 21-cm radiation fluctuates with frequency and angle on sky • Observations can be used to study: • Universe at z ~ 50 (Dark Age) – only possible probe • Formation of the first luinous objects • Reionization • Structure formation after reionization

  21. Our Efforts Started With

  22. GMRT Giant Meter-wave Radio Telescope

  23. Radio Interferometric Array GMRT 30 antennas 45 diameter 32 MHz bands with 128 separate channels

  24. Have we observed the cosmological 21-cm radiation? No!

  25. Predicted Signal z=10, x=0.5 mK 10 arc-minutes Datta, Roy Choudhury & Bharadwaj 2007, 387,767

  26. Haslam Map - 408 MHz All-Sky Survey) Synchrotron Radiation 180K – 70,000K at 150 MHz ≈ 40 Angular scales (off-galactic)

  27. GMRT Observations FIELD I Ghosh, Prasad, Bharadwaj, Ali & Chengalur 2012, MNRAS, In Press

  28. 14 hrs GMRT Observations RA 01 36 46 DEC 41 24 23 FIELD IV Ali, Bharadwaj & Chengalur 2008,MNRAS,385,2166

  29. Measured Cℓ Expected 21-cm SignalCℓ ~ 10 -3 – 10-4 mK2 Ghosh, Prasad, Bharadwaj, Ali & Chengalur 2012, MNRAS, In Press

  30. Foregrounds Point Sources Diffuse Removal is Biggest Challenge

  31. GMRT Observations FIELD I Point Source Dominated Ghosh, Prasad, Bharadwaj, Ali & Chengalur 2012, MNRAS, In Press

  32. The brightest structures in this map are at 5σ level compared to the local rms value ~ 23.5 mJy/Beam. Low resolution Residual Map. Taper @ |U|=170 Diffuse Structure Appearing On the Map on Scales > 10 arcmin

  33. The brightest structures in this map are at 10σ level compared to the local rms value ~ 35 mJy/Beam. Taper @ |U|=100

  34. Angular Power spectrum : • The power spectrum of the Diffuse emission was fitted by a power-law down to ℓ = 800 ( θ ≈ 10'):

  35. Currently working on • Theoretical Predictions of Expected 21-cm Signal • Detection Strategies • Quantify and Remove Foregrounds

  36. Thank You

  37. Concluding Remarks • Probe Dark Ages, First Luminous Objects, reionization, post-reionization • Potential Probe of Dark Energy • Challenge Foregrounds, RFI

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