User's Guide to MSX6C Infrared Point Source Catalog

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The Midcourse Space Experiment Point Source Catalog Version 2.3 (October 2003)
Egan, M.P., Price, S.D., Kraemer, K.E., Mizuno, D.R., Carey, S.J., 
Wright, C.O., Engelke, C.W., Cohen, M., and Gugliotti, G. M.
Air Force Research Laboratory Technical Report AFRL-VS-TR-2003-1589
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Description:

Version 2.3 of the Midcourse Space Experiment (MSX) Point Source Catalog (PSC), which supercedes the version (1.2) that was released in 1999, contains over 100,000 more sources than the previous version. The photometry is based on co-added image plates, as opposed to single-scan data, which results in improved sensitivity and hence reliability in the fluxes. Comparison with Tycho-2 positions indicates that the astrometric accuracy of the new catalog is more than 1'' better than that in Version 1.2. In addition to the Galactic plane, Areas Missed by the Infrared Astronomical Satellite (IRAS), and the Large Magellanic Cloud, which were included in the previous catalog, Version 2.3 includes data from the Small Magellanic Cloud, eight nearby galaxies, and several molecular clouds and star forming regions.

The infrared instrument on MSX was named SPIRIT III; it was a 35cm clear aperture off-axis telescope with five line scanned infrared focal plane arrays of 18.3 arcsec square pixels, with a high sensitivity (0.1 Jy at 8.3 microns). The 6 bands are B1 (4.29 microns, FWHM 4.22-4.36 microns), B2 (4.25 microns, 4.24-4.45 microns), A (8.28 microns, 6.8-10.8 microns), C (12.13 microns, 11.1-13.2 microns), D (14.65 microns, 13.5-15.9 microns), and E (21.34 microns, 18.2-25.1 microns).

The MSX catalog names of the sources have been defined according to International Astronomical Union (IAU) conventions with a unique identifier combined with the position of the source. In this case, the MSX PSC V2.3 sources are named using the convention MSX6C GLLL.llll+/-BB.bbbb, where MSX6C denotes that this is MSX data run using Version 6.0 of the CONVERT software, and GLLL.llll+/-BB.bbbb gives the Galactic coordinates of the source. (Names in the minicatalogs may differ slightly from those given in Kraemer et al. 2002, 2003.)

The MSX6C catalogs were delivered to IPAC as a set of 45 data files with each region of sky imaged by MSX contained in one or more files. The description of the original delivery containing a breakdown of the regions covered can be found here. The original primary catalogs for each field have been merged into one all-inclusive catalog.

In addition to the primary catalog files, most regions also have low-reliability and singleton catalogs. The low-reliability catalogs contain sources with signal-to-noise values of 3-5. Singleton catalogs consist of sources that were detected once when multiple coverages of a field were taken. Most singletons occur at the edges of surveyed regions where overlapping coverage was not always realized. No singleton catalogs exist for the galaxy minicatalogs and some star-formation minicatalogs. All singleton and low-reliability catalogs have been combined into a reject source catalog. Users will need to confirm the validity of sources extracted from the reject source catalog.

Byte-by-byte Description of file: *.cat

Note (1): fluxes in the infrared bands:
                 When the number of sightings is zero, the fluxes are set to the
                 negative value of the sensitivity limit.

Note (2): The Quality flags in each band are:
                 4 = excellent, SNim >= 10.0
                 3 = good,      7.0  <= SNim < 10.0
                     or SNim  = -800 and SNpsx >= 10.0
                 2 = fair,      5.0  <= SNim < 7.0
                     or SNim  = -800 and 5.0 <= SNpsx < 10.0
                 1 = limit,     SNim < 5.0
                 0 = not detected

Note (3): SNim can take on a value of -800 if no image plate exists at the 
                 source location and -999 if the image-based PRF fitting was unable to 
                 extract a positive irradiance value. In these cases, we default to the 
                 SNpsx to set the flux quality flag.

Note (4): the variabilility flag is set to 1 when the variation of the 
                 measurements over the mission exceeds the 3{sigma} limit. The confusion
                 flag is set to 1 if there is a potential confusion issue.

Note (5): a value of 0 means that the measurements fit the point source
                 function and that all measurements were of adequate signal-to-noise.
                 A value of R=9 is assigned when the source is not detected in the band.

Links to Detailed MSX Documents

MSX PSC V2.3 Explanatory Guide

MSX PSC V1.2 Explanatory Guide superceded by V2.3 guide, but still contains useful information in the appendices that is not duplicated in the newer document.

Original delivery file description

For ease of handling, the main catalog is broken into six files: five for the Galactic plane survey, plus the primary high latitude regions (the IRAS gaps and the LMC). The supplementary catalogs are the singleton catalog, the low-reliability catalog, and minicatalogs for 19 selected regions. All catalogs have the same format. However, the minicatalogs for the galaxies (except the SMC) and Orion do not have all the fields filled in because they were solely created from the images, not from the Point Source Extractor; there are no singleton files for these regions. Also, the minicatalogs may not have singleton or low-reliability counterparts if no sources met the inclusion criteria. All told, there are a total of 45 data files.

File Summary:

Data Format

The catalog files are in ASCII format with entries as given in Table 11 of the Explanatory Guide. The columns are space delimited (except for the variability, confusion, and measurement reliability flags, which are each given as a block), and were written out using the following FORTRAN format statement:

2002 format(a23,1x,f9.4,1x,f9.4,2(1x,f4.1),1x,f5.1,1x,i3, 6(1x,1pe12.4,i2,1x,0pf5.1,1x,f6.1,1x,f6.1,1x,i3,1x,f5.1),1x,6i1,1x, 6i1,1x,6i1)