The HST/LCO measurement of the mean flux of the extragalactic background light (3000-8000Å)

Citation

Bernstein, Rebecca A. (1998) The HST/LCO measurement of the mean flux of the extragalactic background light (3000-8000Å). Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/4cy1-bw30. https://resolver.caltech.edu/CaltechETD:etd-09242008-105539

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. We present the first detection of the optical extragalactic background light (EBL) at 3000, 5500, and 8000[...] using simultaneous observations taken from Hubble Space Telescope (HST) and the du Pont 2.5m telescope at Las Campanas Observatory (LCO). The total background flux of the night sky was measured from space using the Wide Field Planetary Camera 2 (WFPC2), thereby avoiding terrestrial airglow which is the dominant foreground component from the ground and the primary obstacle in previous efforts to measure the EBL. Foregrounds which contribute to the surface brightness of the night sky from HST are zodiacal light and diffuse galactic light. We have measured the absolute surface brightness of the zodiacal light using spectrophotometry taken with the du Pont 2.5m telescope at LCO and using the Faint Object Spectrograph (FOS) on HST. We minimize the contribution from diffuse galactic light by conducting the measurement in a target field with a low column density of galactic dust and neutral hydrogen, both of which are traced by 100μ emission in the IRAS maps. The small remaining galactic contribution has been modeled using known correlations between the diffuse thermal emission from the dust at 100μ and the diffuse optical light due to starlight scattered off the same dust. Because galaxies brighter than V = 23 AB mag are statistically poorly sampled in the WFPC2 field of view, we define the EBL as the total flux from objects fainter than V = 23 AB mag. We find the following mean levels for the EBL as a function of wavelength (in units of ergs s[superscript -1]cm[superscript -2]sr[superscript -1][...][superscript -1], with 1 σ rms errors): Iλ(3000[...])=4.0(±1.9)x10[superscript -9], Iλ(5500[...])=2.8 (±0.8)x10(superscript -9], Iλ(8000[...])=2.3 (±0.6)x10[superscript -9], with systematic errors of 1-2x10[superscript -9] at each wavelength. The total flux detected at each wavelength is at least 2-3 times the integrated flux in published galaxy counts. The implications of this detection are discussed.

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