Oral Presentation
New measurement of the near-infrared extragalactic background light by evaluation of isotropic interplanetary dust
Presenter: Kei Sano (Kyushu Institute of Technology)
Near-infrared extragalactic background light (EBL) is thought to be crucial to study astrophysics during the dark age because it can include redshifted radiation from first stellar objects or primordial blackholes. To measure the EBL intensity, zodiacal light, sunlight scattered by interplanetary dust (IPD) in our solar system, needs to be subtracted accurately. The IPD concentrated on the ecliptic plane has been investigated robustly, but the IPD of isotopic spatial distribution has not been observed and it has been one uncertainty in the EBL measurement. To search for the isotropic IPD, we perform new analysis in terms of solar elongation angle, because we expect zodiacal light intensity from the isotropic IPD to decrease as a function of the angle. We use infrared all-sky maps of Diffuse Infrared Background Experiment (DIRBE), which cover wide solar elongation, and investigate the residual intensity after subtracting conventional IPD components. As the result, we find the solar-elongation dependence of the residuals, indicating the presence of the isotropic IPD. Assuming that the entire mid-infrared residuals originate from the isotropic IPD, we estimate density distribution of that component and derive the near-infrared EBL intensity by subtracting the isotropic IPD. As has been reported so far, the resultant EBL is a few times larger than integrated light of known galaxies, suggesting contribution from unaccounted extragalactic sources. We plan to reveal the origin of the excess by future projects.
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