1. 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

2. Introducing the EVLA

3. Overall EVLA Performance Goals
Parameter
VLA
EVLA
Factor
Point Source Sensitivity (1-s, 12 hr.)
10 mJy
1 mJy 10
Maximum BW in each polarization
0.1 GHz
8 GHz 80
# of frequency channels at max. BW 16
16,384
1024
Maximum number of freq. channels
512
4,194,304
8192
Coarsest frequency resolution
50 MHz
2 MHz 25
Finest frequency resolution
381 Hz
0.12 Hz
3180
# of independent sub-correlators 2 64 32
(Log) Frequency Coverage (1 – 50 GHz)
22%
100% 5

4. MicroJy Sensitivity in 12 hours
Green shows
deepest image ever made (as of 1999) 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 GHz Frequency Coverage
Additional EVLA
Coverage
Blue areas show existing coverage
Green areas show new 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 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’nBW
Dnu Dv
Nch
(GHz)
(kHz)
(km/sec)
1-2
1.024 31 6
131,076
2-4
2.048
125 12
65,536
4-8
4.096
500 25
32,768
8-12
16.5
12-18
6.144
2000/500
37/12
24,576
8.192
2000 27
16,384 13
40-50

8. 64 different lines: 1 km/s, full polarization
Band BW
Nch
Dnu Dv
Vel.Cov.
Total
(GHz)
(MHz)
(kHz)
(km/s)
(km/sec)
Nchan
1-2 4
2048
2.0
0.39
800
524,288
2-4 8
1024
7.8
0.78
320
262,144
4-8
400
8-12 16
512 31
0.94
480
131,072
12-18
0.63
0.41
210 32
256
125
1.1
282
65,536
40-50
0.83
213

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 Rotation measures Spectral curvature
(& absorption)
Spectral curvature
(& Faraday rotation)
Neutral hydrogen
for free!

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 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. 1.5 GHz
MHz
8192 x 62.5 kHz (13 km/s for local HI)
512 MHz

19. 1.5 GHz
MHz
8192 x 62.5 kHz (13 km/s for local HI) HI
ABQ
radars
VLA
polarizer
satellites
512 MHz

20. 1.5 GHz
MHz
8192 x 62.5 kHz (13 km/s for local HI) HI
ABQ
radars
VLA
polarizer
satellites
Current VLA: kHz
512 MHz

21. 1.5 GHz
MHz
8192 x 62.5 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: 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 Zoomed in here!
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
MHz
MHz
Tau~0.003
430 km/s
MHz

24. 3C84 @ 1.5 GHz 8 x 8 MHz subbands 8 x 4096 channels Zoomed in here!
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
MHz
MHz
Tau~0.003
430 km/s
MHz

25. 22 GHz
MHz
8192 x 125 kHz (1.7 km/s)
1 GHz

26. 3C84 @ 22 GHz 1 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 1.4% shown here
31.25 kHz/channel (0.4 km/s)
1.4% shown here

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

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

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

31. Schedule

32. EVLA and You Now 2009 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
Sub-band
BW (MHz)
Number of
poln. products
channels/poln product
Channel
width (kHz)
Channel width
(kms-1 at 1 GHz)
Total velocity coverage
128 4 64
2000
600/n(GHz)
38,400/n(GHz)
1000
300
19,200 32
500
150
9,600 16
250 75
4,800 8
125
37.5
2,400
62.5 19
1,200 2
31.25
9.4
600 1
15.625
4.7
0.5
7.813
2.3
0.25
3.906
1.2
0.125
1.953
0.59
0.0625
0.977
0.29
18.75
0.488
0.15
9.375

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
Sub-band
BW (MHz)
Number of
poln. products
channels/poln product
Channel
width (kHz)
Channel width
(kms-1 at 1 GHz)
Total velocity coverage
128 2
256
500
150/n(GHz)
38,400/n(GHz) 64
250 75
19,200 32
125
37.5
9,600 16
62.5 19
4,800 8
31.25
9.4
2,400 4
15.625
4.7
1,200
7.813
2.3
600 1
3.906
1.2
300
0.5
1.953
0.59
150
0.25
0.977
0.29
0.125
0.488
0.15
0.0625
0.244
0.073
18.75
0.122
0.037
9.375

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 to or
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, MHz, full pol’n) ideas also welcome