Spitzer Documentation & Tools
WARM IRAC ONLY: Aperture Corrections

We have derived corrections for aperture photometry performed on data taken during the warm mission. These corrections differ very slightly (less than 1%) from the corrections given in the IRAC Instrument Handbook section 4.10, Table 4.7. To use the table of warm corrections, perform your photometry with an aperture of radius given in native IRAC pixels (the size of which in arcseconds is given in Table 2.1 in Section 2.2.1 "IRAC Image Quality" in the IRAC Instrument Handbook) and measure the sky background in an annulus limited by the radii given by the two latter two numbers in the first column of the new table. Thus, for example, aperture entry 2_2_6 corresponds to performing aperture photometry in a radius of two native IRAC pixels and measuring the subtracted background in an annulus between two and six native IRAC pixels. Please note that for crowded regions, performing PRF-fitting may yield more accurate results. Please refer to the IRAC Instrument Handbook, MOPEX documentation and the Spitzer Data Analysis Cookbook for instruction on how to perform PRF-fitting photometry.

The aperture corrections should be multiplied by the measured aperture photometry total flux densities to derive corrected flux densities.

The first number in the lefternmost column gives the aperture radius in pixels, and the second and third numbers give the background annulus inner and outer radii in pixels.

2_2_6 1.2132 1.2322
2_12_20 1.2026 1.2228
3_3_7 1.1233 1.1336
3_12_20 1.1132 1.1126
4_12_20 1.0736 1.0809
5_5_10 1.0588 1.0625
5_12_20 1.0482 1.0500
6_12_20 1.0315 1.0349
8_12_20 1.0112 1.0125
12_12_20 0.9931 0.9913