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GALFA Meeting 3 August 29, 2994 Arecibo Observatory Note: These notes were taken by Di Li, and edited by Paul Goldsmith. We apologize for their rough nature, but it seemed more important to get something out that would give the flavor of the meeting, even if it were not perfect. Please send corrections and/or comments to PG. This meeting was held on the day before the start of the "Heiles Fest" Conference at Arecibo. Consequently, a number of interested astronomers, who were not members of GALFA Consortium were present, as well as some people who just happened to drop by. The GALFA Consortium thanks the members of the Arecibo Staff who put a lot of time into organizing the logistics for this meeting, and also the Organizing Committee itself, which helped ensure that key topics were fitted properly into the agenda. The following is brief summary of presentations and discussion. 8:30 Paul Goldsmith Review of the Agenda. Pointed out that GALFA is still open to new members. 8:45 Paul Goldsmith Powerpoint presentation reviewing highlights of GALFA Science. This should be available on the web. Three "subgroups", Continuum (CON), Recombination Lines (RRL) and HI. Due to realities and membership size, the first two will be considered to be on par with subprojects contained within GALFA-HI. Science: CON (esp. polarimetry): "disembodied" polarization features confusion limited 20 micro Jy /beam => rapid scan RRL (radio recombination lines): multiple lines in ALFA passband, but weak 300s /pointing => 10mK RMS HI various projects at high and low latitude beam spacing 125", 22deg rotation of dewar turbulence: need lbv cube HI/H2: relationship of atomic and molecular clouds & ISM phases ISM cold HI: why temperature range Halo clouds: HVC origins High Velocity line wings High latitude clouds Low latitude surveys: HISA |b|<5 9:00 Steve Torchinsky ALFA status Frontend installed and generally working satisfactorily WAPPs used as spectrometer and for pulsar work cold testing, Mar 2004 delivery, April 1, on time lift/installation, April 21 OH possible with front end filter off, May 2004 New pulsar, Aug 1 intermittent short circuit in one of the two LNAs of the central beam, Aug 5 (still off-line, but can sometimes be revived) 9:15 A. Deshpande ALFA testing and performance Precommissioning testing well underway. Some selected results (much information available on web) Frequency channel correlation with common noise input, some channels fall out with longer integration time, unstable. Dynamic range, ~40 dB and 30 dB head room for RFI SEFD for the central pixel vs ZA, FWHM Motor door shielding important Coma very clearly seen in beam maps; level not far from that expected Rotation in RA DEC; underlying ellipses does not rotate TO DO: beam maps at ZAs, gains at ZAs, polarization calibrations 9:33 Ellen Howell OH Observations Comet Linear: 2-4 km/s outflow, 140 mJy, ALFA gave 2.4 times lower line intensity 3-level sampling of ALFA vs 9-level for AO, Tsys(ALFA)?>30 K Spider scans, off-center pixels have ~8db sidelobe, with one up to 6 db, SEFD of off-center pixels is 1.33 times that of the center. Conclusion: beam 0 has 75% sensitivity of L-wide, off-center pixels have 55% of L-wide sensitivity. For extended sources, net improvement is factor of 2 to 3. More if you consider value of simultaneous observations. 9:47 Dan Werthimer GALFA spectrometer Jeff Mock, builder (TIVO designer) 100 MHz bandwidth + 7 MHz (highres) in each of 14 channels 35-45 dB image rejection Digital spectrometers board: Xilinx FPGA chip, compact PCI format Two spectrometers in the chip: 256 channels (broadband for removing standing wave) and 8192 channels (for real spectroscopy) Fixed integration time: 988ms (99% efficiency) File written every 15s: 2*8K+2*256K ADC on same board: spurs at +-25 MHz Dynamic range, overflow Unknown LO phase shift see: http://seti.berkeley.edu/GALFA 10:00 Giacomo Comes P-ALFA backend Polyphase filter, 1024 FFT, demuxer Ready in 6 months (?) 10:13 Carl Heiles GALFA HI calibration Try to separate G_if G_rf Baseline ripple at AO: reflection between structures => 1MHz~200km/s G_if is stable (change 0.l% day to day) Thinking in Fourier transform space - 1 microsecond peak, same height during night, changes faster in daytime There are other peaks at 2.2 to 2.5 microseconds delay It is not clear what causes them Baseline ripple due to reflections is not polarized PA of ellipse of OH varies from 50-120 degrees from beam to beam of ALFA Need to measure that for HI band too. Questions/Comments Tom: What integration time do you need for removal? Carl: 10 min at beginning of the day on a random position on the sky Mike Davis: longer time delays are likely a result of multiple reflections, perhaps including the ground screen 10:35 Chris Salter GALFA continuum transit survey HII, SNR Galactic background spectral index Faraday tomography extragalactic sources using P-ALFA, 300 MHz, 0.3 MHz channel, full stokes Problems: temporal drifts, 8-db coma, spurious polarization=> fast scanning, basket-weaving Current plans include: LBW precursor, 400 MHz, 1msec dump ALFA precursor, map the same field as LBW Part II: Full-Stokes mapping of point sources Part III: Linear polarized pulsar 10:48 Snezana Stanimirovic GALFA testing observations: A1943 Test mapping modes, reference position+freq switching, standing wave extraction, cross/spider scans Science projects: L1544, CHVC218+29+145, high latitude MBM40, forbidden velocity line wings Observing plans: 7 beam (WAPP) in 10 MHz narrow mode, 1 WAPP 100 MHz wide Driving rate 0.95d /min ~ 3.5 sidereal rate, ALFA 75 d, beam separation~ 2.8m, one up and down sweep takes 3min, int 15s/footprint 4x1deg covered in 25mins with 3 crossings per point, 10x1 deg covered in 55 mins Riccardo: How do you handle fast up, slow down? Snez: answer not recorded Mike: Fixed rotation angle? Snez: yes 11:20 Russ Taylor GALFA software group Image products: GALFA-HI narrow-band HI spectral cube galfa-rrl narrow-band multiple line cube galfa-con wide-band, polarization Phases: I data acquisition, II image formation, III scientific process, archiving GALFA-CON: Desh has written phase 1, Calgary working on phase II GALFA-HI: phase I output to "big dish" fits; phase II Josh in IDL; phase III Richard Gooch, karma? Issues: quality oversight, code base IDL? Comments/questions: Naomi: IDL cost? Russ: Not much discussion. Riccardo: much broader user base and support than just astronomy Martha: only expensive in Germany not in other European countries Tom: IDL executable is free. can run but cannot write programs 11:33 Steve Torchinsky ALFA software at NAIC Big Dish fits (ATNF) still working with GBT reduction software produced by consortia CIMA: Control Interface Module for Arecibo IF/LO, Backend, pointing (choose particular beam), observing mode On-line Data Display: waterfall plots, spectra, dump plots to files, header, real time monitoring engineering monitor:motor, total power, etc. Big Dish Fits WapRed: reduction software for WAPP Riccardo: thanks Miguel for the fits header software Tom: When is the big fits produced? Steve: only WAPP data is written in Big dish format Tom: Is there a script? Steve: command file observing. Load/save state: configuration. CIMA can be run off-line. Dan: What about commensal observing? Steve: backends can be configured independently, but software is not there yet. 11:57 Josh Goldston GALFA mapping Basket-weave vs typewriter: slow up quick down Least square gain fitting on cross points ALFA orientations depends on scanning methods Discrete scanning rate for basket weaving for Nyquist sampling Pros: Typewriter: less timing, long RA regions, better for sidereal rate BW: long dec regions, variable scan rate, preserve beam pattern Gridding: non-simple beams, preserve information, Tegmark 1997=> least square solutions Q: data loss for slow scans Josh: weight the balance between overheads Paul: what is the story with regridding? Josh: close to COBE's method 12:15 Riccardo Giovanelli E-ALFA Surveys 5 projects but will focus on the drift mode surveys DRIFT: ALFALFA VAVA Science: HI mass function Drift: no problem for point sources E-ALFA: HIPASS software, IDL minimal intrusion data taking: 900s scans Data in converted from fits to IDL "d" structure on the fly Be prepared to have less than 7 pixels Level I data product: noise calibrated IDL structure Level II: tiled structure including continuum calibration, regridding Level III: source catalogue, NVO domain HI node, etc. Current problem with calibration: CIMA cal not synchronized with data records Tsys ~ 30 K Questions/Comments Dan: should fix a bad pixel quickly Jay: should work without all 7 pixels Break for lunch and discussion of separate project/observing proposal groups 15:00 Tom Bania (session chair) Tom: Is there a preference for proposals with commensal considerations? Bob: Preferred for practical reason, but not officially for review Tom: Formal proposal commensal proposal? Bob: No. Science driven, commensal later 15:11 Yervant Terzian GALFA-RRL Galactic plane, long integration, >100MHz, dv < 1km/s Will propose commensal observing with pulsar survey Desh has proposed testing with WAPP Tom: Need new backend? Yervant: Pulsar people is getting their own, but the E-ALFA backend may also be relevant Dan: reconfiguring GALFA spectrometer for multiple narrow sub bands is possible, but is not currently implemented 15:18 Russ Taylor GALFA-CON Need all sky survey, night time, 1000 hours P-ALFA spectrometer with full stokes Prefer larger bandwidth (200MHz) Precursor observations in December Commensal with GALFA HI using P-ALFA spectrometer with basket-weaving Questions/comments Bob: Typewriter? Russ: no. too slow. Mike: convenient for scheduling Desh: Winking cal issue 15:26 Paul Goldsmith Molecular clouds Basket-weaving preferred, narrow bandwidth high velocity resolution A question - OH: can it be done simultaneously? Snez: A test proposal was not well received, but there could be another precursor proposal in October? Steve: maybe use GALFA spectrometer for test observations scheduled to start this coming Friday. 15:32 Jay and Snezana Halo clouds merged with disk halo connection (?) Snez Stray radiation and standing wave are big concerns Use GBT maps for correction Will propose precursor objects Jay More careful determination of galactic HI spectra Questions/Comments Paul: independent from the pipeline development? Jay: yes. Russ: stray radiation also a concern for CON. Snez: seasonal switching. Mike: seasonal switching only works for spectral line not for continuum. Tom: Stray radiation correction? Jay: no. just for noise, gain characterization 15:39 Eric Korpela High latitude clouds Stray radiation is a major issue Commensal with DRIFT survey Might need extra observations to produce crossing points Q: How many people? Eric: 6. 15:42 Tom Bania Low latitude survey Not sure the system is good enough for a clear science case Team with pulsar and e-alfa to further study how to do galactic plane mapping May go commensal with several projects Steven Gibson: I did not get advance notice, so hard to organize CNM group. Comments and Questions Tom Bania: re. Data Rights and Access Riccardo suggests that the data is made public through NVO rather early. Is there a NAIC policy? Bob: No strict policy. But would like to only make available calibrated data. Tom: Who controls the quality? Who releases? Do not necessarily need perfect data Bob: Some group should vouch for the quality. NAIC should be playing a role. Goes into NVO as NAIC product. Ed: Would NAIC have manpower? Bob: NAIC would always involved (but would not do it [?]) Paul: No person in H2/HI has stepped forward Tom: Glimpse and Ring surveys have shown commitment to make data public immediately. We should consider that in detail. Bob: This view is consistent with NAIC attitude: data public as early as possible. Individual proposal will be assigned time in blocks. More time depends on data release. Ed: Archiving takes a lot of effort. Bob: NAIC is writing guidelines. No strict time table. Paul: Different from surveys "fully supported" by NSF and NASA. Tom: What's the division of labor of software development? Bob: Steve has a philosophy. Tom: Big surveys write their own codes. Alex: 1 km/s and 3' is ok Peter: Data reduction could be redundant between subgroups. More work will be needed 16:20 Paul Goldsmith Jigsaw Puzzle Approach Has morphed into separate continuum and RRL proposals, plus those of the HI projects NAIC => Big dish fits HI groups needs to agree on a set of observing mode that can be supported by the pipeline, a single GALFA HI pipeline Ed: Why do HI and RRL require different reduction? Paul: Pulsar spectrometer is not here. Russ: How many observing projects or science projects? How many proposals? Tom: No clear answer yet. Josh: We need a specific guidelines for pipeline. Carl: Spectrometer configures differently for CON, RRL, HI. Cannot use same pipeline. Phil: Consider the "pipeline" to consist of various modules. If they are done properly you can make various pipelines by hooking up various modules. You don't have to think of the various pipelines as totally different. Peter: More effort required for that. Mike: NAIC observatory should keep expertise for calibration. at least adopt existing good software. Carl: There needs to be a person at AO to maintain and update software Riccardo: Tools developed will be specifically designed Paul: one modular GALFA HI pipeline and adaptable by NAIC Outcome of all this: pipeline(s) can be configured from modules for different needs. We must not forget that NAIC will have observers who want to use ALFA, but who may not be members of any consortium. There thus must be software for them to use, which again could be configured from pipeline modules, but for this reason alone, NAIC must have software person familiar with all the pipeline procedures. This adds to NAIC responsibility, but doing this as well maintaining the software is critical. 16:47 Trish Henning Overview of E-ALFA Surveys ALFALFA (shallow) expect 7000 new galaxies AGES (mid) HI mass function, spatial distribution, 3000 galaxies at larger Z HI mass to 6e6 solar masses. Virgo, local void, NGC2903 outer region of nearby target Drift scanning, step and stare AUDS (ultra-deep) evolution of gas Z<0.15, 5e16 / 5km/s sensitivity, low column density gas in the local universe OH megamaser, HI absorption 0.36d^2 in 1000 hours, repeated drift Zone of avoidance (commensal) cuts through several known regions, Taurus, etc Commensal option 1 GALFA: double drift? 2 PALFA Paul: precursor time? P. : 70 hours drift, 35 on source 17:10 Paulo Freire ALFA Pulsar Surveys 300 MHz 1024 channels, 65 microsecond dump Search for millisec pulsar, 1PByte of data! Mid 2005 complete PALFA spectrometer; Now using WAPP: discover brightest ms pulsars, radio loud young pulsars 100 MHz 256 channels Proposed tiling leaves small holes, use sidelobes to fill in 1 degree limit for the galactic center survey ongoing ALFA surveys results: PHP/MySQL viewing, first new pulsar: 68 ms object not detectable at 430 MHz Commensality: RRL, SETI (no cal) OTHER TOPICS DISCUSSED AND CLOSING POINTS The issue of Guidelines for GALFA consortium was discussed. Although available on the web, many people present had not had a chance to read them. Thus, it was felt that adoption would have to be deferred and handled by some electronic means. There was general feeling that some guidelines would be appropriate. The guidelines as proposed were based on concept of PIs of individual projects forming a Coordinating Committee. There was discussion about this, which was not unanimous. In fact, during the lunch project group meetings, it was evident that there had been some consolidation of projects. It could be that initially there would only be 2 or 3 HI projects, but there is nothing to prevent additional ones from forming and submitting proposals later on. The feeling of chairperson was that to get people to make the effort of doing observing, working on software, etc, would require a real scientific motivation. Being part of one HUGE GALFA proposal would just not stimulate most people. While the idea of one giant survey that would produce all the data for all projects has a certain appeal, who is going to do it? That is why the Jigsaw approach seemed originally to be attractive, and why translating it into separate proposals for separate areas of the Galaxy, could work. It is obviously important that surveys be planned in a way to function as pieces of the puzzle, but the first order thing that needs to be done is to get people involved in planning the proposals and getting them committed to doing what has to be done! So far, the HI/H2 Connection group has Di Li and Hector Arce as co-PIs. For the other groups, no individuals have yet been identified (to the GALFA Chairperson), but this must be rectified in the near future. We hope to tackle the idea of GALFA Consortium Guidelines and Project PIs for GALFA Projects in the near future.