Spitzer Documentation & Tools
Spitzer Data Analysis Cookbook


Recipe 13.            IRSFRINGE: Remove fringes in data of HH 46/47

This is a demonstration of using IRSFRINGE to correct a spectral extraction from IRS data for the object Herbig-Haro 46/47 for fringing. We outline the basic steps for using IRSFRINGE as a generic example for correcting spectra of any point source data obtained with Spitzer IRS-Staring Mode. This specific example involves correcting a spectrum from the Long-High (LH) module, but it is generally applicable to any of the IRS modules which suffer from fringing. IRSFRINGE was developed and tested to run under IDL 5.6, and no guarantees are made of it running under other IDL versions.

13.1            Requirements

For this demo you will need the IRSFRINGE package http://irsa.ipac.caltech.edu/data/SPITZER/docs/dataanalysistools/tools/irsfringe/, and BCD and post-BCD long-high IRS data from AOR 7130112. See Recipe 1 for instructions on downloading the data.

13.2            Extract the spectrum using SPICE

First, extract the spectrum of interest, in this case from the LH module, using SPICE. (See the SPICE demo for HH 46/47.) You will produce a *_spect.tbl from the extraction. Or, use post-BCD pipeline output (*_tune.tbl, *_spect.tbl, or *_spect2.tbl files). See Recipe 13 for details on using SPICE.

13.3            Start IRSFRINGE and load in data

To start IRSFRINGE type the following alias command in the running directory:

unix% irsfringe

Read in the IRS data product, either from the pipeline or from SPICE output. In this example, it is the SPITZER_S3_7130112_8_1_E181777_coa2d.spect.tbl in the output/ directory, generated from a SPICE extraction. The spectrum is in IPAC table format and must be read into IRSFRINGE using the 'ipac2irs' command. The spectrum will have the name 'irs' in memory.

IDL> irs=ipac2irs('/output/SPITZER_S3_7130112_8_1_E181777_coa2d.spect.tbl')

13.4            Run IRSFRINGE

To run IRSFRINGE on, e.g., order 18 of the spectrum, using the GUI, enter the following command:

IDL> irsd=irsfringe(irs,order=18,/GUI)

The resulting defringed spectrum will have the name 'irsd' in memory.

1. The GUI will have the appearance as in the figure below. We can see that IRSFRINGE will act on order 18 (circled in red). The green curve shows the original ('previous') spectrum and, since we have not yet acted on the spectrum, the updated ('current') spectrum, the white curve, is the same as the original. Pressing the 'Defringe test' button (circled in blue) will perform the defringing.

2. The following screen (see figure below) will pop up. The green line in the upper panel is the original ('previous') spectrum. The blue line in the lower panel is the best (sinusoidal) fit to the fringing pattern, represented by the white points, determined by the cycle finding routine in IRSFRINGE. The red line in the upper panel is the resulting defringing model. The white line in the upper panel is then the original spectrum corrected for the defringing model.

3. In the main GUI window (see figure below) will then appear the result of the defringe test, i.e., the original spectrum corrected for the defringing model. If satisfied with the test results, then press the 'Save defringed' button (circled in red in the figure below). The updated, defringed spectrum appears as the white line (the 'current' spectrum) in the window. Press the "Exit with Current" to exit the GUI with the saved defringed spectrum still in memory.



4. An output file of the defringed spectrum can then be written to local disk from the IDL prompt. In this example, we write the contents of memory, 'irsd,' to the output file SPITZER_S3_7130112_8_1_E181777_coa2d.spect.defringed.tbl in the directory output/. The defringed spectrum in memory needs to be written out once again to IPAC table format, hence, the command 'irs2ipac.' You're done! To exit IRSFRINGE, type 'exit' at the IDL prompt. All of the above, of course, can also be done on the IRSFRINGE command line, without using the GUI. See the IRSFRINGE documentation for command syntax.

IDL> irs2ipac, irsd, /output/SPITZER_S3_7130112_8_1_E181777_coa2d.spect.defringed.tbl

IDL> exit