April 2005 ALMA Offline software test NAME: James Di Francesco (NRC-HIA) Questionnaire on testing experience 1. Please list briefly your background in the following areas: A. Radio Interferometry ((sub)millimeter or centimeter) - yes, about 10 years of both B. Experience with VLA and/or PdBI data - yes, see above C. Astronomical Data Reduction packages: - AIPS, yes - MIRIAD, yes - MMA, yes - Gildas/Clic, yes - AIPS++, yes D. How much experience have you had with the AIPS++ software package before this test? - I participated in ALMA TST1.1 2. Please identify which dataset you processed during this test: B. BIMA CO(1-0) observations of NGC 4928 3. Were you able to combine the single dish and interferometric data using feather and deconvolution techniques? If not, why? Please comment on specific steps if desired (comments can be positive or negative, you may not have tried all steps): A. Feather images or image cubes provided by Offline subsystem - yes, successfully feathered together "n4826_bima.im" and "n4826_12mchan.im". The latter was not explicitly given in the package I received but I was able to create it using a FITS file that was within the package. One aspect that could be improved is introducing a way to determine a scaling factor between the interferometer and single-dish data, e.g., over the same range of spatial frequencies. This step can be done in the MIRIAD task IMMERGE. B. Feather single dish image provided and interferometer image that you created from the dataset provided. - no, I did not perform this combination since it seemed only necessary to per- form the above combination using interferometer data I received. C. Deconvolve the single dish and interferometer data using the single dish image to create an input model. - yes, successfully produced combination images using single dish models made "directly" or through deconvolution. Again, I am not sure if it would be appropriate to introduce a scaling factor in this step. Please identify any problems you had during imaging. - Beyond the scaling factor issue, I encountered no obvious problems with the combination, e.g., no crashes or hang ups. - The resulting datacubes seem quite similar to each other (i.e., within ~20%), and quite similar to the interferometer-only data, suggesting that not much extended flux was added to the final datasets. I was surprised at the differ- ences in the total fluxes found for each cube, however, so I'm not sure if the beams were appropriatlely defined in the final images. Given the similarities between the interferometer and combined data, I'm not sure if this was the best case to use as an example for testing single-dish and interferometer data com- bination. - The BIMA SONG team used the linear combination method for their data, since they thought the S/N was not good enough to perform reliably the IMMERGE method that is most similar to the feathering tested here. It may be useful to construct a similar "linear combination" method for low S/N data in aips++, especially if this is regarded as the norm for submillimeter datasets. 4. Were you able to analyze the images adequately to determine if the results you obtained were scientifically reasonable (e.g. display the image, calculate RMS and peak, make a moment map or take a spectrum)? If not, why? - Yes, I used the data viewer I learned about during the last test. Although I was able to define regions on a given plane, and determine statistics from that region, I couldn't figure out how to extend a region over a range of channels. Furthermore, I had difficulty knowing which dataset I was viewing when multiple datasets were loaded in the viewer and I was "blinking" between them to compare their appearances (using the same colormap of course). 5. Please summarize the final results of your image(s): - Note: full data cubes examined using img.stats() not data viewer i) BIMA-only image - RMS: 0.0906 Jy/beam - Peak and Total Flux Density: 1.889 Jy/beam and 61.50 Jy ii) feathered image - RMS: 0.0929 Jy/beam - Peak and Total Flux Density: 1.980 Jy/beam and 132.4 Jy iii) jointly deconvolved image (single-dish model made directly) - RMS: 0.219 Jy/beam - Peak and Total Flux Density: 2.339 Jy/beam and 167.5 Jy iv) jointly deconvolved image (single-dish model made through deconvolution) - RMS: 0.224 Jy/beam - Peak and Total Flux Density: 2.621 Jy/beam and 68.36 Jy 6. Did you have adequate support during your test? If you contacted the AIPS++ groups for questions or to fix a bug, please comment on the interaction and whether it was helpful. - Yes, I had a small difficulty with the installation and solutions were provided quickly and simply. Also, questions I had about determining the statistics were answered quickly. 7. Was AIPS++ easy to install? If not, why? - Yes, AIPS++ was easy to install, although I had to do some extra steps: 1) I had to have the load-casa script modified to reflect my local flavour of Linux (mandrake 10) 2) I had to install have some libraries installed locally for the rpms to install. 8. The Synthesis Reduction Cookbook you used for this test is the second version of a comprehensive cookbook for ALMA users. Please evaluate the organization, content, and presentation of the cookbook. It is meant to be the first documentation users will see when they want to reduce ALMA data, it provides background on the code capabilities, and extensive examples. The on-line documentation provides more details and code descriptions. With this in mind, please answer the questions below. If you have detailed comments, please attach them to the end of this questionnaire. - Was the documentation adequate for you to complete your test? - Yes, the documentation provided a very straight-forward path that allowed me to complete the test, although specific example scripts were not provided as they were in the last test. (I didn't use them before, however.) - Do you have any suggestions for how to improve the cookbook? - There are a couple of typos still in the cookbook, on the level of missing usages of ";" at the end of commands, and should be fixed when encountered. - Was the on-line documentation helpful: * User Reference Manual? - did not use * Supporting documentation? - if by this you mean the goals/scope of the test, I must confess I was a bit confused as to how far I should take the test. Was it OK to just make images, or should we play with the data to make the "best" combination and evaluate which was the "best"? 9. Roughly how much time did you take to perform the following steps: - Installing aips++: 2 hours - Imaging: 3 hours - Analysis: 4 hours - Filling out this questionnaire: 0.5 hours - Evaluating and grading the scientific requirements: 0.5 (estimate) - Total time: 10 hours 10.Please rate your overall testing experience: - good 11.Was the test well designed and executed by those in the ALMA offline subsystem (e.g. the subsystem scientist and the Offline subsystem group). If not, can you provide any suggestions for improving the next test? - I think the test was a good demonstration of the combination software, but the dataset I used may not have been the best example of how adding single- dish data can improve the science extracted from high-resolution data. - Also, the tests should have a more sharply defined cut-off. Extra play can be encouraged of course, but I want to be able to know if I have addressed the minimum of what is expected from the test. 12.Do you have any additional comments that may help improve test of the offline software in the future? - see above.