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Surveying Cosmic Time with the WIDAR Correlator

National Radio Astronomy Observatory. Galaxies through Cosmic Time – December 16-18, 2008. Surveying Cosmic Time with the WIDAR Correlator. Michael P. Rupen Project Scientist for WIDAR. Introducing the EVLA. Overall EVLA Performance Goals. MicroJy Sensitivity in 12 hours. Green shows

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Surveying Cosmic Time with the WIDAR Correlator

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  1. National Radio Astronomy Observatory Galaxies through Cosmic Time – December 16-18, 2008 Surveying Cosmic Timewith the WIDAR Correlator Michael P. Rupen Project Scientist for WIDAR

  2. Introducing the EVLA

  3. Overall EVLA Performance Goals

  4. MicroJy Sensitivity in 12 hours Green shows deepest image ever made (as of 1999) -- 1.9 microJy/bm at 8.5 GHz (152 hrs; Richards et al.) -- 3 hours with the EVLA! We are meeting (and exceeding, at high frequencies) almost all of these goals.

  5. Full 1-50 GHzFrequency Coverage Blue areas show existing coverage Green areas show new coverage Additional EVLA Coverage Current Frequency Coverage

  6. WIDAR correlator • 8 GHz, full polarization, in one go • 64 independent subband-pair correlators • Can individually trade bandwidth for channels • 128 MHz to 31.25 kHz • 256 to 4096 channels • Can link subband correlators for even more channels • Independently tunable -- can target up to 64 individual lines (up to 128 in one polarization)

  7. Wideband observations:full pol’n

  8. 64 different lines:1 km/s, full polarization

  9. The EVLA combines power and flexibility to allow you to tune the instrument to your science -- not the reverse.

  10. The EVLA and Evolving Galaxies a few illustrative examples

  11. Survey Speed I • Time to observe 1 square degree to 40 microJy/beam rms • doesn’t include overhead (--> x1.5, from NVSS) • Rms chosen to ensure at least 20s/ptg (NVSS: 30s with 23.3s on-source) • Note uv-coverage issues • Assumes no overlap

  12. Survey Speed II • Square degrees observed per hour as a function of frequency, to an rms of 40 microJy/bm • Assumptions as in last slide

  13. Background sources:12 hour integration Number of background sources in the primary beam in a 12-hour integration 1, 5, 150 sigma

  14. Searching Hi-z Galaxies for CO emission • Arp 220 at z = 8 • VLA search: • Restricted bands • Covers 100 MHz (1000km/s) • 100 MHz (1000 km/s) resolution • EVLA search: • All freqs. available • Covers 8 GHz (80,000 km/s) • 1 MHz (10 km/s) resolution

  15. Nearby Galaxies Neutral hydrogen for free! Spectral curvature (& Faraday rotation) Rotation measures (& absorption)

  16. Prototype Correlator • 4 antennas • 1 GHz @ 8-bits, RCP only • 4-bit requantization • 8 x 128 MHz subbands • 1024 x 125 kHz per subband • Dumptime 0.05-1 sec • up to 7 MB/s • 1 GB/hr with 1sec dumps

  17. Final Correlator • Racks installed & fully cabled up • Begins open observations (VLA emulation modes) Jan 2010

  18. 3C84 @ 1.5 GHz • 1244-1756 MHz • 8192 x62.5 kHz(13 km/s for local HI) 512 MHz

  19. 3C84 @ 1.5 GHz • 1244-1756 MHz • 8192 x62.5 kHz(13 km/s for local HI) HI ABQ radars VLA polarizer satellites 512 MHz

  20. 3C84 @ 1.5 GHz • 1244-1756 MHz • 8192 x62.5 kHz(13 km/s for local HI) HI ABQ radars VLA polarizer satellites Current VLA: 6.25 MHz @ 98 kHz 512 MHz

  21. 3C84 @ 1.5 GHz • 1244-1756 MHz • 8192 x62.5 kHz(13 km/s for local HI) • Final EVLA: • 512 MHz (z=0-0.3) @ 7.8 kHz (1.7 km/s) HI ABQ radars VLA polarizer satellites Current VLA: 6.25 MHz @ 98 kHz 512 MHz

  22. 3C84 @ 1.5 GHz • 1376-1384 MHz (one 8 MHz subband) • 4096 x 1.95 kHz (0.4 km/s)

  23. 3C84 @ 1.5 GHz • 8 x 8 MHz subbands • 8 x 4096 channels Avg’d x2 (3.9 kHz) or x64 (470 kHz) • Zoomed in here! Tau~0.15 Tau~0.21 32 km/s 17 km/s 1382.95 MHz 1420.35 MHz Tau~0.003 430 km/s 1395.5 MHz

  24. 3C84 @ 1.5 GHz • 8 x 8 MHz subbands • 8 x 4096 channels Avg’d x2 (3.9 kHz) or x64 (470 kHz) • Zoomed in here! • Full EVLA: • 64 independently tunable subband pairs • Different bandwidth & resolution for each subband pair Tau~0.15 Tau~0.21 32 km/s 17 km/s 1382.95 MHz 1420.35 MHz Tau~0.003 430 km/s 1395.5 MHz

  25. 3C84 @ 22 GHz • 21988-23012 MHz • 8192 x 125 kHz (1.7 km/s) 1 GHz

  26. 3C84 @ 22 GHz • 21988-23012 MHz • 8192 x 125 kHz (1.7 km/s) • Full EVLA: • 8 GHz (BWR 1.5:1) • Full pol’n • 8192 x 1 MHz (14 km/s) 1 GHz

  27. Orion water masers • 8 x 64 MHz, 2048 channels • 31.25 kHz/channel (0.4 km/s) • 1.4% shown here

  28. H70a H67a H69a H71a H62a H64a H65a H66a H63a H68a Example: massive star-forming region • Example from Claire Chandler

  29. Example: massive star-forming region • 32 molecular density/temp. tracers @ 0.2 km/s • 8 RRL @ 1 km/s • 3 GHz (24 x 128 MHz) left over for continuum 18-26.5 GHz

  30. Example: massive star-forming region • 32 molecular density/temp. tracers @ 0.2 km/s • 8 RRL @ 1 km/s • 3 GHz (24 x 128 MHz) left over for continuum 22.6-24.6 GHz

  31. Schedule

  32. EVLA and You • Now • Expanded tuning ranges • 3-antenna Prototype Correlator (more anon) • 2009 • Ka band • 10-antenna WIDAR0 • 3-bit samplers

  33. EVLA and You • Jan 2010 • Open Shared Risk Observing • Turn off VLA correlator • WIDAR in “VLA emulation mode” (2 x 128 MHz subband pairs) • Re-cycle configurations: Dvla-Dwidar-C-B-A (data rates!) • Resident Shared Risk Observing ?

  34. Receiver upgrades

  35. OSRO WIDAR modes (1) • Continuum applications and spectro-polarimetry • Two independently-tunable sub-bands (IFs), full polarization, each with bandwidth 128/2n MHz (n=0,..,12), 64 channels

  36. OSRO WIDAR modes (2) • Spectral line applications • One tunable sub-band (IF), dual polarization, with bandwidth 128/2n MHz (n=0,..,12), 256 channels

  37. Having fun with WIDAR

  38. Demonstration Observations • What can we do with the PTC that will get the whole astronomical community fired up?

  39. Demonstration Observations • Prototype correlator • 3 antennas • 1 GHz, 1 pol’n, 8192 channels • 0.1-1 sec dumps (possibly 10msec…) • Short observations -- up to 10 hours • See handout for detailed specifications

  40. Demonstration Observations • Write up a proposal (a few paragraphs) by tomorrow (Wednesday) morning • Put it in the box (appearing soon, just outside the auditorium) • Or e-mail to jvangork@astro.columbia.edu or mrupen@nrao.edu • SOC will review these (with technical advice as needed) and pick one (or more!) to be observed • No guarantees, but we’ll aim at the end of the year • Raw & processed data put up on the conference web site (note VLA archive!) • Correlator tee shirt to the winner, if I get around to designing one • Winner(s) announced by the end of the meeting • WIDAR0 (10 antenna, 256-640 MHz, full pol’n) ideas also welcome

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