Spitzer and DIRBE Studies of the Infrared Background
Abstract
The Extragalactic Background Light (EBL) is defined as the sky surface brightness of all radiation arising from outside the Milky Way. At 1-5 microns the EBL carries the imprints of the emission from the nearby Universe, and red-shifted light from the first galaxies and any possible pre-galactic contributions. The DIRBE instrument on the COBE satellite has measured the total sky brightness, the Infrared Background (IRB), over the entire sky at 3.5 microns, 4.9 microns, and other wavelengths. The IRB is the sum of the zodiacal light, Galactic starlight, radiation from the ISM, and the EBL. The foreground Galactic stars are a major contaminant of the low resolution DIRBE data at 1-5 microns. The ultimate objective of this study is to get a more precise measurement of the 3.5-4.9 microns EBL by improving the subtraction of the Galactic starlight from the IRB, while simultaneously getting a measurement of the Integrated Galaxy Light (IGL) which is the sum total contribution of all galaxies which can be detected by the Spitzer Space Telescope. A significant difference between the IGL and the EBL may indicate IGL sources not detected by Spitzer or an as yet unresolved component to the EBL. We will present preliminary results from Spitzer observations of one of six 2x2 degree regions of sky to determine the point source components of the IRB at 3.6 and 4.5 microns. These wavelengths are near the minimum brightness of the foreground from interplanetary dust (which is also a serious limitation to measuring the EBL, but is being addressed by other experiments). In this program, we will execute the following steps aimed at reducing the uncertainties in the EBL: 1. Cross calibrating DIRBE and Spitzer point sources at both 3.5/3.6 microns and 4.9/4.5 microns so that the EBL and the IGL are on the same flux scale; 2. Reducing uncertainties in the EBL by measuring stars as faint as 19th mag and subtracting their contribution from the measured IRB. 3. Determining the EBL and the IGL at six widely separated positions in the sky to assess their consistency with each other and to assess their isotropy and hence their cosmological significance.
- Publication:
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American Astronomical Society Meeting Abstracts #221
- Pub Date:
- January 2013
- Bibcode:
- 2013AAS...22134108G