In this recipe, we extract photometry for the FEPS Legacy Science program MIPS 70 microns observation in small-field photometry mode of the Pleiades star HII 173. This recipe continues from the mosaicking step (Recipe 24).

26.1            Requirements

You need to download MOPEX (http://irsa.ipac.caltech.edu/data/SPITZER/docs/dataanalysistools/tools/mopex/) in order to run the script apex_1frame.pl. You will need this namelist: http://irsa.ipac.caltech.edu/data/SPITZER/docs/dataanalysistools/cookbook/files/apex_1frame_MIPS70.nl. And you will use the MOPEX output from Recipe 24.

26.2            Step-by-Step Guide

1. Get set up.

 unix% cd r5315584/ch1/bcd/

 unix% mv /where/you/downloaded/apex_1frame_MIPS70.nl ./cdf/

 unix% nedit cdf/apex_1frame_MIPS70.nl

 

Edit the namelist to reflect the absolute pathnames, including the PRF (http://irsa.ipac.caltech.edu/data/SPITZER/docs/mips/calibrationfiles/) you want to start from. Normally, it's best to create your own custom PRF for your own observations, but in this case, there aren't really any bright (known) sources, so we can't construct our own from this single observation. So, we have to depend on the version that came with the MOPEX package, or the version that is available online.

 

2. Extract sources!

unix% apex_1frame.pl -n apex_1frame_MIPS70.nl

 OR

unix% mkdir pbcd70

unix% apex_1frame.pl -n apex_1frame_MIPS70.nl > pbcd70/apex.log &

 

The star that is the target of this observation should be dead on in the center, but there doesn't appear to be anything there. It's very likely that this step will not catch anything at this location. (actual apex log file: http://irsa.ipac.caltech.edu/data/SPITZER/docs/dataanalysistools/cookbook/files/apex70.log) The parameters in the namelist are set such that the extraction step is included, and the final file with extracted sources is http://irsa.ipac.caltech.edu/data/SPITZER/docs/dataanalysistools/cookbook/files/mosaic70_extract.tbl. It completes successfully, but it indeed does not find any sources even meeting our selection criteria, much less at the center of the field.

 

3. Identify sources in list.

unix% spot

unix% nedit pbcd70/Combine/mosaic70_extract.tbl

 

In theory, had we found anything, we could have used the same trick as we did with 24 microns to find the object. However, in this case, there are no detections. We can still use Spot to create a nice fade between the two observations.

 

Start up Spot, and load in the 24 microns mosaic (images menu/FITS file option) -- no AORs needed. Be sure to load the file you just created -- r5315584/ch1/bcd/pbcd24/Combine/mosaic.fits. Next, load in the 70 microns mosaic you just created: ch2/bcd/pbcd70/Combine/mosaic.fits. Click on the little "%" icon on the right side of the spot window and change the transparency of the 70 microns image to watch the 24 microns image fade into and out of 70 microns. There sure doesn't seem to be anything at our source position, but there's something nice and bright near an edge at 70 microns, and it corresponds to a source seen at 24 microns -- it was source 197 in the 24 microns source list. There is very little redundancy at 70 microns in that position, so any photometry for this source will have very high errors.

 

 

Left image is 24 microns only; right image is showing the 70 micron image though the 24 micron (adjusting the opacity in Spot).

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