Pulsar surveys with

1. Pulsar surveys with Present surveys, plans for the near future Paulo C. Freire, NAIC Arecibo, 29th of August 2004

2. In this talk… • Proposed WAPP/ALFA surveys • General considerations • Sky coverage • The ongoing preliminary surveys • Pointing strategy • Processing • Results • Near-term plans • Commensality

3. Proposed WAPP/ALFA surveys • For pulsar surveys, one is interested in using as large a bandwidth as possible. For this reason, the ALFA pulsar consortium suggested the construction of 14 spectrometers capable of processing a 300 MHz-wide band, and divide it in 1024 channels, dumping such spectra every 64 μs. • The search volume for millisecond pulsars in such a survey would be unprecedented. • This comes at a huge processing/storage cost: total data produced by the major PALFA survey of the Galactic plane: ~1 PBy.

4. Proposed WAPP/ALFA surveys • Such capable spectrometers do not exist yet. They are being built at Arecibo (B. Sisk and J. Hagen), using FPGA technology. The software loaded into the gates will make them act as a polyphase filterbank. • Estimated completion: Mid-2005 • However, ALFA is already here. And the 4 WAPPs now have two correlator boards each. They can process a total of 16 100-MHz channels. Can we take advantage of it now? • Yes, we can! This is the aim of the preliminary PALFA surveys.

5. Proposed WAPP/ALFA surveys The objectives of these surveys are: • Understand observing system, mainly its sensitivity, learn how to operate it. • Develop and end-to-end data processing pipeline, including bookkeeping, processing software and archival strategies. The latter are very important for the “main” survey that will start in about 1-year time. • If possible, start new science as soon as possible.

6. Proposed WAPP/ALFA surveys Scientific case for a preliminary shallow survey: • To find brightest undiscovered millisecond pulsars (i.e., get the cream of the crop NOW). These are the best timers, and they are the ones that will benefit most from extended timing baselines. • To find energetic, radio-loud young pulsars in the Galactic disk • Compare yield of this survey with previous surveys of similar sensitivity (i.e., Parkes multi-beam survey) and with the results of our simulations. This data will help optimize the large survey.

7. Proposed WAPP/ALFA surveys What do we mean by a “shallow” survey? • “Only” 100 MHz bandwidth centered at 1420 MHz, divided in 256 channels • Integrations last only 134 seconds (221 64-μs samples), summed polarization mode • Sensitivity to normal pulsars is slightly better than that of the Parkes multi-beam survey • Much increased sensitivity to millisecond pulsars at high DMs

8. Proposed WAPP/ALFA surveys Area of the Galaxy to be covered: • Center: |b| < 0.35°, 40° < l < 77° (total time: 67 h) • Anti-center: |b| < 0.6°, 170° < l < 186° (total time: 33h)

9. Proposed WAPP/ALFA surveys Things we don’t particularly care about: • Band shapes, small gain variations • Polarization characteristics • Coma, sidelobes, etc • Time-constant RFI • Feed rotation • Commensality – lack of second back-end prevents this. So we WAPP it our way… Things we care about: • Sensitivity

10. Proposed WAPP/ALFA surveys Proposed tiling leaves some small holes behind:

11. The ongoing ALFA surveys The ongoing surveys differ from the proposed surveys in two main respects: • Use of sparse tiling pattern (Freire) • Galactic latitude limit of 1 degree for the galactic center survey, instead of 0.35 degrees Survey simulations at Cornell (W. Vlemings) and McGill (Guiguere) indicate that we can increase our detection rate by 50% by making our survey “sparse”, i.e., by fully harnessing the great power of Arecibo’s sidelobes. These are about as sensitive as the GBT!

12. The ongoing ALFA surveys The proposed tiling pattern would look like this:

13. The ongoing ALFA surveys What we are really using looks more like this:

14. The ongoing ALFA surveys The advantages of this are: • We keep the same detection volume for faint pulsars, • We triple (for free!) the detection volume for stronger pulsars, because of the 3-times extended Galactic latitude range that can be covered at that lower sensitivity in the same amount of time (more bright MSPs!) • Don’t have to worry about feed rotation at all! When we started out survey, the feed rotation was still not available, but thanks to the survey strategy, this was not a problem.

15. The ongoing ALFA surveys Another important innovation in the present survey is the real time processing (D. Lorimer) • We have been using the Arecibo Signal Processor (ASP) to FTP the survey observation files to its local disks • Data is then split (each of the 4 WAPPs records total power for two beams) and degraded in time and frequency by a factor of 16 • Search for slow pulsars in all the DMs then takes about 1 second/beam! • On-line reduction of data speeds up science and improves morale!

16. Results • 1st observing session from the 1st to the 10th of August. Second ongoing. • Everything working perfectly: GUI observing mode, ALFA IF/LO system, WAPPs. Feed rotation now being tested. • Pulsar MySQL database (J. Hessels) and python scripts used to interface with it (Ramachandran, Nice, Hessels, Reid, et al.) were installed, tested. • PHP/MySQL web browsing programs (D. Champion) made viewing of results of fast processing very easy.

17. Results • Three new pulsars were found to date, after ~12 hours (4 sq. degrees) of observations in the center and ~12 in the anti-center (8 sq. deg.) • The first new pulsar is a relatively young 68-ms object, not detectable at 430 MHz!

18. Near-term plans • Understand the observing system better, like survey sensitivity (are we finding as many pulsars as we should?) and feed rotation (the latter will be necessary for dense surveys and repeated passes) • Incrementally improve survey software, implement processing software for full resolution data • Increase data storage and handling capacity and computing, in order to prepare full-scale surveys

19. Near-term plans • Help test 300-MHz back-ends • Start 300-s, 300-MHz “Main” survey of the Galactic plane – most recent simulations indicate that there is some slight advantage in doing this as compared to two 150-second passes • First two years – make a sparse covering of the 19-20H Galactic plane visible from Arecibo with |b| < 5°. Simulations indicate that we will be able to make 600 of the total expected 900 detections. Spend following 4 years filling in the holes.

20. Commensality • The proposed tiling scheme for the main survey of the Galactic plane should be compatible with EALFA requirements • Some specialized GALFA projects might also make good use of it (e.g., recombination line search) • Pointing scheme should also be fine for SETI surveys • Probably not a good idea for mapping projects • We are open to discussion on these issues. What we are doing now is not necessarily what will be done for main survey.

21. It will be challenging to make the 900 detections we proposed ourselves to do…

22. The pulsar consortium thanks… …the people that made it possible: • Jeff Hagen and Bill Sisk for the magnificent work with the WAPP and CIMA gui • Avinash Deshpande, and the electronics department for all their great work on the ALFA system • Arun Venkataraman, for all of his efficient data transferring and archiving • Steve Torchinsky, for managing it all and maintaining the irreplaceable ALFA website • NAIC and Bob Brown for pursuing ALFA, a great research instrument, and ATNF for building it.

23. Thank you for your time! For questions, comments, etc., contact me at pfreire@naic.edu, or visit my website: http://www2.naic.edu/~pfreire The National Astronomy and Ionosphere Center is operated by Cornell University, under a cooperative agreement with the National Science Foundation.