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Tutorial 2 â Data Reduction for multiple spectra
================================================ Tutorial 2 â Data Reduction for multiple spectra ================================================
.. sectionauthor:: Kate Brooks
Main goal: Handle multiple Spectral windows (IFs) and plot spectral-line catalogues
Files
- 2006-07-09_1431-M168.rpf Data file (63 Mb)
- 3mm.txt Emission line catalogue
- QuickData.py Data Reduction GUI (by Cormac Purcell)
Data Log
- ON-OFF-OFF-ON Position switching mode with Mopra
- 4 Scans (2 OFF and 2 ON)
- 4 x 2-GH bands (IF 0, 1, 2, 3)
Instructions
- Work through the list of commands given in the text file to calibrate data taken with the Mopra telescope and identify the emission lines. Commands should be typed line-by-line into ASAP. Seek help from the tutors if there are any commands you donât understand.
- The commands given in the text file are for 1 Mopra frequency band only (IF0). Now work on the other 3 bands and make a final plot showing all four frequency bands stitched together.
- Now repeat the calibration steps using the Mopra Data Reduction GUI. This GUI has been created via a python script (QuickData.py).
Commands
# Load data into memory and display short description s = scantable('2006-07-09_1431-M168.rpf') print s # Set the plotting mode plotter.set_mode(stacking='i', panelling='t') plotter.set_histogram() plotter.set_colours('black') plotter.set_linestyles('solid') # Plot all the raw data plotter.plot(s) # Form the quotient spectra q = s.auto_quotient() # Average all scans in time, weighting according to Tsys value av = q.average_time(weight='tsys') # Average the two polarisations together, weighting according to Tsys value iav = av.average_pol(weight='tsys') ### Work on IF0 only # Define a selector sel1 = selector() # Select the first IF for scantable 'iav' sel1.set_ifs(0) iav.set_selection(sel1) # Plot the first IF with x-axis in channel number iav.set_unit('channel') plotter.plot(iav) # Flag out the end channels msk1 = iav.create_mask([0,120]) iav.flag(msk1) msk1 = iav.create_mask([7900,8200]) iav.flag(msk1) # Redo the plot plotter.plot(iav) # Identify emission lines iav.set_unit('GHz') plotter.plot(iav) # Load in catalogue of emission lines and overlay on plot lc3 = linecatalog('3mm.txt') plotter.plot_lines(lc3,location='top',rotate=90,doppler=-45)
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