Status of LOFAR Beam-Formed Observations

Jason Hessels
LOFAR Transients Key Project Meeting, Meudon, December 2011

Transcript

1. Jason Hessels (ASTRON / UvA) The Latest on Beam-Formed Data with LOFAR +LOFAR Pulsar Working Group TKP - Meudon - December 15th, 2011
2. Roughly speaking, beam-formed modes trade spatial resolution for time resolution. Station Beam Element Beam Tied-array Beams Beam-formed: adding, us-ms, many telescopes Imaging: multiplying, >1 sec, ~1 telescope TKP - Meudon - December 15th, 2011
3. Simultaneous Imaging + Pulsar Observations Obs. L2010_06928 PSR B0329+54 Thanks George Heald! TKP - Meudon - December 15th, 2011
4. Credit: Hessels & Greissmeier Full core on single clock = 4x the raw sensitivity TKP - Meudon - December 15th, 2011
5. See Mol & Romein 2011 for multi-beam tied-array benchmarking results Credit: Hessels, Stappers & Scaife TKP - Meudon - December 15th, 2011
6. http://www.astron.nl/~heald/lofarStatusMap.html TKP - Meudon - December 15th, 2011
7. TKP - Meudon - December 15th, 2011
8. Element beam Stations beam(s) Tied-array beam(s) Flexible Beam-forming (sparse aperture array) This is driving the development of beam-formed modes, of which tens of different sub-modes are possible Credit: van Leeuwen TKP - Meudon - December 15th, 2011
9. 0.5 degree Multiple Station Beams Credit: Hessels TKP - Meudon - December 15th, 2011
10. Multiple, widely separated FoVs Credit: Hassall & Hessels @ 24MHz TKP - Meudon - December 15th, 2011
11. Beam-formed modes ...there are many possible. Mode Description Data Rate FoV (sq. deg.) Res. (deg.) Sens. (norm.) Incoherent (par. imaging) Stations added without proper phase correction. 2-250 GB/hr 12,5 2 6,0 Tied-array Stations added properly in phase. Up to 23TB/hr 0,2 0,03 36,0 Single Station For projects with high time, but lower sensitivity requirements. 2-250 GB/hr 12,5 2 1,0 Superstation Interesting balance of sensitivity and FoV. Up to 23TB/hr 9,0 0,2 12,0 Fly’s Eye Maximize total FoV for bright transient survey. Up to 8TB/hr 450 2 1,0 Flexible to match different science goals! TKP - Meudon - December 15th, 2011
12. LOFAR v1.0: Beam-Formed Modes Coherent Stokes Incoherent Stokes Beam-Formed Observation I IQUV XXYY I IQUV (+ imaging) Online coherent dedispersion 1, 16, 32, 64, 128, 256 channels per subband 5us - 10ms (or more) time res. 1-300 TABs 1-8 SAPs 1-8 SAPs All written to HDF5 with metadata (+) TKP - Meudon - December 15th, 2011
13. Some recent highlights PBW #15 was just last week... TKP - Meudon - December 15th, 2011
14. LOFAR Pilot Pulsar Survey (LPPS) • Incoherent beams - all avail. (~20) stations • 7 beams of 7 MHz each and 0.65ms samp. • 57 minutes per pointing (82GB) • ~167 sq. deg. total FoV per pointing • ~250 pointings taken during Christmas 2010 • Data being processed on “Hydra” at the University of Manchester. TKP - Meudon - December 15th, 2011
15. Only ~400 7-beam pointings > -35 deg DEC LOFAR Pilot Pulsar Survey (LPPS) TKP - Meudon - December 15th, 2011
16. high resolution images; while in beam) formed mode the data is stored at high time resolution( but with limited spatial information' probes the interstellar material and magnetic fields( and can be used to map the Galactic free)electron distribution' Neutron stars provide constraints on stellar evolution models and supernovae' radio pulsar population( out to % kpc *#+' LOFAR will also elucidate the unknown low frequency end of the pulsar spectrum' For more information see *%+' This work: LPPS We are currently performing a first shallow survey of the northern sky: the LOFAR Pilot Pulsar Survey !LPPS"' All available LOFAR stations are used and Transients !RRAT"( and single dispersed bursts from general fast radio transients' The LPPS survey is currently underway interference can be identified by its absence of dispersion measure !i'e' no free electrons along the line of sight"( unnatural brightness( occurrence in RFI !DM " # cm$% pc& Re$detection J'())*')+) Re$detection J'(,%*#++# Re$detection J'()'*#-', Beam $ LPPS pointings contains . beams Beam # Beam % Beam / Beam & Beam . Beam - Courtesy: Thijs Coenen LOFAR Pilot Pulsar Survey (LPPS) TKP - Meudon - December 15th, 2011
17. Independent Discovery of PSR J2317+68! Credit: Green, Hassall & Stappers TKP - Meudon - December 15th, 2011
18. LOFAR Tied-Array Survey (LOTAS) • Tied-array (coherent) beams (Superterp) • 19 beams with full 48MHz and 1.3ms samp. • 17 minutes per pointing (246GB) • ~3.7 sq. deg. FoV per pointing • ~200 pointings taken from May 11-15th • Increase in sensitivity ~10 x LPPS • Less affected by RFI? TKP - Meudon - December 15th, 2011
19. See Mol & Romein 2011 for multi-beam tied-array benchmarking results Credit: Hessels, Stappers & Scaife TKP - Meudon - December 15th, 2011
20. Pulsar is 10x brighter in the correct beam (beam 7)! Shifted 1 deg south Credit: Alexov & Hessels LOFAR 127-beam Tied-Array!! TKP - Meudon - December 15th, 2011
21. LOFAR 127-beam Tied-Array!! Credit: Hessels & Alexov S/N in each beam Linear Scaling Log Scaling Full core requires 4500 TABs TKP - Meudon - December 15th, 2011
22. Andromeda TKP - Meudon - December 15th, 2011
23. Virgo Cluster TKP - Meudon - December 15th, 2011
24. Timing Observations Credit: Verbiest From 20 3-min observations of B0834+06, each spaced by 10 minutes TKP - Meudon - December 15th, 2011
25. Measuring Earth’s Ionosphere Credit: Sobey Plan to do for multiple pulsars simultaneously PSR B0834+06 TKP - Meudon - December 15th, 2011
26. Measuring Earth’s Ionosphere Credit: Sobey Plan to do for multiple pulsars simultaneously 35 40 45 Altitude [deg] 140 160 180 200 Azimuth [deg] SOUTH 04:00 05:00 06:00 07:00 UT [hh:mm] -29 -28 -27 -26 RM [rad m-2] SR SR TC TC TN TN TA TA d azimuth of B0834+06 (red circles), as well as the RM as a function of time, before and after ’zapping’ (blue circles and gree onomical,Nautical,Civil], SR = Sunrise. The RM before and after sunset differs by >3 rad m−2. PSR B0834+06 TKP - Meudon - December 15th, 2011
27. Measuring Earth’s Ionosphere Credit: U. Bern Plan to do for multiple pulsars simultaneously and for 24hrs Table 2: Ionospheric TEC measurements for the globe on 20th October 2011. Credit: Universit¨ at Bern. 04:00 UT 06:00 UT 08:00 UT 3 Oct. 20th, 2011 TKP - Meudon - December 15th, 2011
28. Low-Frequency Polarimetry Credit: Sobey Close to the only pulsar polarimetry at < 100MHz PSR HBA profile LBA profile FDFHBA FDFLBA B0950+08: DMpc = 2.958 RMpc = -0.66 DM = 2.958 DM = 2.987 RM = -3.35 RM = -2.386 33+16: DMpc = 4.864 RMpc = 1.1 TKP - Meudon - December 15th, 2011
29. Polarization Calibration ! ! "#$%&'(!)*+,!-./0)12- !34/*5!6789:;2+*65!)*+,!<=>"4?!@ABC>#?!D9)!E6598!A2+:*F G20C4'"AHGI JKLMNOLPQRG20LPQSOTUVW Credit: Kuniyoshi TKP - Meudon - December 15th, 2011
30. PSR B0809+74 detected all the way down to 16MHz! 15 - 63 MHz Observing Frequency 20m Superterp stations in sync to ~1ns (single clock for the entire core is on the way) TKP - Meudon - December 15th, 2011
31. Fitting Pulse Profile Evolution • Two Gaussians with frequency dependent amplitudes, widths, and separation. B0809+74 • Simultaneous, so no DM variation. LOFAR bands • Nice demonstration of sub- arraying and single-station use. Hassall et al., submitted TKP - Meudon - December 15th, 2011
32. 100+ Pulsars Detected with LOFAR Credit: Hessels TKP - Meudon - December 15th, 2011
33. Recent LBA Pulsar Observations Large, intrinsic (and extrinsic) profile evolution across band 30-36 MHz 36-42 MHz 42-48 MHz 48-54 MHz 54-60 MHz 60-66 MHz 66-72 MHz 72-78 MHz (post station calibration) Credit: Stappers & Hassall TKP - Meudon - December 15th, 2011
34. Low-Frequency Pulse Profiles Credit: Hessels & Pilia TKP - Meudon - December 15th, 2011
35. LOFAR + XMM Credit: van Leeuwen TKP - Meudon - December 15th, 2011
36. LOFARv1.1 • Simultaneous Obs. • Direct link between data and dspsr (offline tool) • True Fly’s Eye mode • Online RFI excision TKP - Meudon - December 15th, 2011