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L. R. Levenson, E. L. Wright (UCLA)
Using Spitzer images of the Bootes region and the Extended Groth Strip (EGS), Fazio et al. (2004) report a total contribution of resolved galaxies to the CIRB of 5.4 nW m-2 sr-1 at 3.6 microns, less than half of the 13.8 ± 3.4 nW m-2 sr-1 CIRB detected at this wavelength by Wright and Johnson (2001). However, due to the fuzzy fringes of galaxies, especially in crowded fields, aperture photometry can be insufficient for measuring the total flux from closely neighboring galaxies. We have analyzed 11,045 sources in the Bootes region and 1043 sources in the EGS from the same Spitzer surveys used in the above analysis. Here we use the surface photometry package GIM2D (Simard et al. 2002), fitting a bulge+disk model to each source. A direct comparison of photometry done with SExtractor (Bertin and Arnouts 1996) mag{_auto} and GIM2D on the sources in Bootes, we find mag{_auto} to be missing approximately 25% of the flux from each source. Continuing our analysis to deeper magnitudes in the EGS, we calculate number counts adjusted to the brighter magnitudes determined with GIM2D. We show a comparison of the total flux from galaxies at 3.6 microns determined from our number counts and those reported in Fazio et al. The integrated contribution of the sources from the 15th to the 18th magnitudes from surface photometry is 28% higher than that from aperture photometry.
This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.