N A W G ======= NRAO Algorithms Working Group Meeting - DRAFT MINUTES Date: 2005-4-13 (Wednesday) Time: 1300 MDT = 1500 EDT Video Hub: CV-conf (others call in) Rooms: SOC317/CV311/GB241/TUCN505 =============================================================================== Send additions and corrections to smyers 1. Organizational issues o solicitation of topics for future meetings (Steve) 2. Project-related (ALMA, EVLA, GBT, VLBA, &c.) issues o contributed topics 3. ***Short Topics*** - Presentations and Discussion Items ******************************************************************* o Steve Myers - summary of meeting "ALMA and SZ" Paris, 7-8 April 2005 This was an EU RadioNet sponsored meeting. The focus was on the Sunyaev-Zeldovich (SZ) effect and what ALMA could do in this area. Most participants were theorists or observers not familiar with radio/millimeter interferometry, and it was clear that the ALMA project (and likely EVLA also) will need to provide a clear way to let potential users know what to expect in sensitivity for extended low-surface brightness distributions (like the SZ effect). For example, the ESO ALMA sensitivity calculator is misleading for this application. Some sort of mini-simulator or model calculator should be developed. The consensus was that the main SZ science that ALMA will do will be to measure the substructure in the SZ effect corresponding to the shocks, fronts and bubbles seen in the new Chandra and XMM-Newton images. These effects can be tiny (<10 microK!) and thus some of the more subtle targets will be too faint even to be seen by ALMA. Note that the bulk of the SZ effect (about 0.5-1 mK) is resolved out by interferometry due to its shallow profile: ~1/theta ==> ~exp(-u/u_0) so interpretation of the highly filtered SZ image is tricky as it is dominated by the bright emission seen on the shortest baselines (some sort of anti-taper would seem to be in order). For my talk at the meeting... See: http://www.aoc.nrao.edu/~smyers/nawg/presentations/ File: NAWG20050413-Myers-ALMASZ.pdf Discussion: - Mark Holdway said he had some sort of glish-based sensitivity calculator that we should look at. - I think that a short memo on what you can expect to see from ALMA's compact configuration (plus ACA) for some model cases (point, Gaussians, disks=optically thick spheres, optically thin spheres) might be useful. ******************************************************************* 4. ***Main Event*** - Presentations and Discussion Items ******************************************************************* o Sanjay Bhatnagar - an update on pointing calibration and correction Correcting for pointing errors one of the most basic of the "direction dependent" calibration terms, and involves solving for a sky offset for each antenna in each solution interval. See: http://www.aoc.nrao.edu/~smyers/nawg/presentations/ File: NAWG20050413-Sanjay-Pointing.pdf ******************************************************************* 5. Future events (please sign up!) o George Moellenbrock - an update on frequency-dependent polcal (main) o Walter Brisken - a proposed self-cal modification (short) 6. Relevant reading: o Paper & Memos: - Beyond the isoplanatic patch in the VLA Low-frequency Sky Survey (W.D. Cotton et al.) Abstract: http://link.aip.org/link/%3FPSISDG/5489/180/1 - Solving for the Antenna Based Pointing Errors (Bhatnagar, Cornwell & Golap) http://www.aoc.nrao.edu/evla/geninfo/memoseries/evlamemo84.pdf - EVLA and SKA Computing Costs for Wide Field Imaging (Cornwell) http://www.aoc.nrao.edu/evla/geninfo/memoseries/evlamemo77.pdf - W Projection: A New Algorithm for Non-Coplanar Baselines (Cornwell, Golap, Bhatnagar) http://www.aoc.nrao.edu/evla/geninfo/memoseries/evlamemo67.pdf - Effects of Atmospheric Emission Fluctuations and Gain Fluctuations on Continuum Total Power Observations with ALMA (Holdaway) http://www.mma.nrao.edu/memos/html-memos/abstracts/abs490.html http://www.mma.nrao.edu/memos/html-memos/alma490/memo490.pdf o Post-processing requirements: - ALMA Offline Data Processing Requirements http://www.alma.nrao.edu/development/computing/docs/joint/0018/ALMAoffline-sw-18.pdf - EVLA Offline Data Processing Requirements http://www.aoc.nrao.edu/~smyers/evla/evla_offline.pdf o GBT: - GBT Software Review Agenda & Presentations http://wiki.gb.nrao.edu/bin/view/Software/ReviewAgenda2004 - GBT Standard Observing Modes http://wiki.gb.nrao.edu/bin/view/Observing/StandardObservingModes 7. Upcoming meetings and deadlines: o 2005 May 11 NAWG meeting o 2005 Jun 8-10 OSA Signal Recovery and Synthesis (Charlotte) o 2005 Jun 22-24 SKA Wide-field Imaging Workshop (Dwingeloo) ******************************************************************* o NAWG Website: http://www.aoc.nrao.edu/~smyers/nawg/ *******************************************************************