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Measuring the Gas in Galaxies in the Distant Past

Measuring the Gas in Galaxies in the Distant Past. Philip Lah. Too late. H ere comes the SKA. Who am I ?. I am astronomer with a joint appointment at the: National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, India a nd the

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Measuring the Gas in Galaxies in the Distant Past

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  1. Measuring the Gas in Galaxies in the Distant Past Philip Lah Too late. Here comes the SKA.

  2. Who am I? • I am astronomer with a joint appointment at the: National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, India and the Research School of Astronomy & Astrophysics, Mount Stromlo Observatory, Australian National University • I use both radio and optical telescopes for my research

  3. Atmospheric Transmission optical gamma rays, X-rays & ultraviolet infrared radio 100 % Atmospheric Opacity 50 % 0 % 1nm 1 μm 1 mm 1 m 1 km Wavelength → ← Frequency

  4. Hydrogen Gasin the Universe

  5. Hydrogen Gas in the Universe Hydrogen 76%by mass of the baryons – normal matter (that is not the weird stuff – Dark Matter) Neutral Atomic Hydrogen Gas produces emission at a wavelength of 21 cm

  6. Hydrogen Gas in the Universe Hydrogen 76%by mass of the baryons – normal matter (that is not the weird stuff – Dark Matter) Neutral Atomic Hydrogen Gas (HI) produces emission at a wavelength of 21 cm

  7. Atmospheric Transmission optical gamma rays, X-rays & ultraviolet infrared radio 100 % Atmospheric Opacity 50 % 0 % 1nm 1 μm 1 mm 1 m 1 km Wavelength → ← Frequency 21 cm

  8. HI 21-cm Emission From Galaxies

  9. Galaxy M33: optical

  10. Galaxy M33: HI 21-cm emission

  11. Galaxy M33: optical and HI

  12. Galaxy M33: optical

  13. Why StudyNeutral Atomic Hydrogen Gas?

  14. molecular gas cloud (H2) star formation neutral atomic hydrogen gas cloud (HI) HI Gas and Star Formation

  15. Redshift, Observing the Past

  16. The Expanding Universe

  17. Hubble`s Law redshift velocity related to distance distance related to age (due to light travel time)

  18. Hubble`s Law redshift velocity related to distance distance related to age (due to light travel time)

  19. Atmospheric Transmission optical gamma rays, X-rays & ultraviolet infrared radio 100 % redshifted Atmospheric Opacity 50 % 0 % 1nm 1 μm 1 mm 1 m 1 km Wavelength → ← Frequency 21 cm

  20. The History of Star Formation in the Universe

  21. Star Formation Rate Density

  22. Star Formation Rate Density ~10 times current rate

  23. The Amount of HI Gas in the Universe

  24. HI Gas Density

  25. HI Gas Density ~2 times current density

  26. HI Gas Density

  27. HI Gas Density region where I have been working

  28. Current Observations

  29. Giant Metrewave Radio Telescope

  30. Giant Metrewave Radio Telescope

  31. Coadding HI signals

  32. Coadding HI signals Radio Data Cube Frequency HI redshift DEC RA

  33. Coadding HI signals Radio Data Cube Frequency HI redshift DEC positions of optical galaxies RA

  34. Coadding HI signals flux frequency

  35. Coadding HI signals z2 z1 z3 flux z1, z2 & z3 optical redshifts of galaxies frequency

  36. Coadding HI signals z1 z2 z3 flux z1, z2 & z3 optical redshifts of galaxies velocity

  37. Coadding HI signals z1 z2 z3 Coadded HI signal flux velocity z1, z2 & z3 optical redshifts of galaxies velocity

  38. My Current Best Observation

  39. HI blue outside x-ray gas blue galaxies surrounding the core of a large galaxy cluster galaxies observed as they were 4 billion years ago coadding signal from 94galaxies

  40. HI blue outside x-ray gas blue galaxies surrounding the core of a large galaxy cluster galaxies observed as they were 4 billion years ago coadding signal from 94galaxies

  41. Future Observations

  42. The SKA and Me • SKA`s collecting area 20GMRT`s collecting area • SKA better receivers • SKA larger field of view • SKA better RFI environment

  43. The SKA and Me • my current research looking at galaxies 3 to 4 billion years ago – SKA directly detect HI signal • originally SKA proposed to detect HI gas from 8 billion years ago • stacking with SKA ~12.7 billion years ago, the era of first galaxies SKA fully operational 2024

  44. The SKA pathfinders

  45. MeerKAT • South African SKA pathfinder • 13.5 m diameter dishes • 64 dishes • finished 2014 (2018)

  46. ASKAP • 12 m diameter dishes • 30 dishes • focal plane array • finished 2013

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