MOPEX User's Guide - IRSA

Appendix D. Some Tips for MOPEX with Spitzer Data:
Version 1 (3/16/2012)
D.1 Mosaics (IRAC and MIPS)
Some Tips for MOPEX with Spitzer Data:
Version 1 (3/16/2012)
MOPEX User’s Guide
The end result of a normal Mosaic run is mosaic files in output_dir/Combine-mosaic (Combine
in command-line). Generally no weighting of the pixel stack is used, and especially no sigma
weighting if sources are present. You can combine data with different exposure times and weight
them by time if the FITS keyword that has the time in it is provided. For Spitzer data, this is
'EXPTIME'. It should be set in the GUI Mosaic Coadd Settings. (In command-line, put
INTEG_TIME_KWD = 'EXPTIME', in the Coadd block of the namelist.nl file.)
The coverage mosaic is always the number of good pixels in the final stack. The total
exposure time for a pixel (when time-weighting) is not available as a mosaic, but can be found
per tile in the output_dir/Coadd-mosaic directory. (If there's only one tile, it is like the final
mosaic.)
D.2 Fluxes and Uncertainties (IRAC and MIPS)
The end result of a normal point-source fitting run (Apex or Apex 1frame) is a table in the
Output directory called *extract.tbl. It's in IPAC table format, readable by many common tools.
A tool for reading an IPAC table into an IDL structure is available at
http://irsa.ipac.caltech.edu/tools/irsa_idl.html.
The point-source fitted fluxes (in microJy for Spitzer data) are in the "flux" column. For the
uncertainty, use the signal-to-noise column called "SNR", i.e. uncertainty = flux/SNR (for a
quick discussion, see the file in the Mopex directory
readme/README_new_snr_option_081108.pdf). The aperture fluxes and uncertainties (in
microJy) have obvious names in *extract.tbl. (If you ran only aperture photometry, they are in
aperture.tbl.)
There are some small correction factors needed for the highest accuracy. Aperture corrections
for apertures other than the standard calibration aperture and annnulus can be found in the IRAC
and MIPS Data Handbboks. Some corrections for PSF-fitted fluxes can be found in Appendix C.
250 D.1 Mosaics (IRAC and MIPS)