Difference: DataProcessingWorkshop2013 (32 vs. 33)

Revision 332013-06-26 - PedroGarciaLario

Line: 1 to 1

Herschel Data Processing Workshop for Newcomers, 24-27 June 2013

Line: 309 to 309
  (NOTE: you may need to remove the .txt from the filenames associated to the python scripts above so that these files can be recognized as python scripts by HIPE - the .txt suffix is added automatically by the twiki for security reasons)


PACS Spectroscopy

Q1: I have a rather specific question. I am reducing unchopped line scans. I use oversample=2 and I get a warning for the specwaveRebinTask (not enough good values etc, try oversample=1). However when I look at the final result (end interactive L2) there doesn't seem to be a problem, for instance in the plotCubesStdev display there are only low exposure pixels at the edges. Is this something to worry about? I hope I managed to explain this clearly enough....

A1: Hi xxx, in many pipeline tasks you get warning messages (actually, many are just information, but the developers seem to like to scare people with WARNING!! comments ;-). so at first glance your message seems to be just a kind warning. if the end result looks ok then you don't need to worry. there is a task at the end of the pipeline that plots little yellow? squares on the bins that are "low exposure". If these are all at the end of the spectral range, you don't need to worry. In fact, yes, the task plotStdDev is the one that tells you which bins are low exposure. so it looks like you do not need to worry. but you can also change the wavelength grid up/over sample values and overplot the different end results to compare. More about up and over sampling is in the PDRG chapter…5 or 6 or 7, I forgot, and more about comparing spectra at the end of the pipeline is also in the PDRG (chap 5 or 6 or 7 also - a section that talks about flatfielding), or use the spectrum explorer.

Q2: can I use data cubes that we get from the archive for spectroscopic AND photometric studies?

A2: well, if you have enough continuum in your cube then you can of course use it for photometry. the question is "what is enough". The thing to remember is that the continuum you get at the end of the pipeline is subject to error. This error depends on the strength of your source with respect to the teelscope. The telescope spectrum is some 100 Jy or so, and so even 1% error is a error of 1 Jy in the continuum. In the calibration document that is on the pacs calibration and instrument wiki the errors for the end cubes are given. a few Jy you should expect will be the error in the continuum level. http://herschel.esac.esa.int/twiki/pub/Public/PacsCalibrationWeb/PacsSpectroscopyPerformanceAndCalibration_v2_4.pdf For full science quality you need to re-pipeline the data - take advantage of the latest calibrations as the HSA products don't run all the pipeline tasks. This is documented in chp 1 of the PDRG. You can get fluxes (Jy/spaxel) and wavelengths (microns). Though the fits files do have a rather awkward format. They can be hard to read directly into other software - we are working on this and if you have problems it is fastest to raise a helpdesk ticket. One last thing: for unchopped mode, the flux level of the continuum is not guaranteed to be correct. That mode was never intended for continuum studies.

PACS Photometry




This site is powered by the TWiki collaboration platform Powered by Perl