The Far Ultraviolet Background

Abstract

The diffuse far-ultraviolet (FUV) background has received considerable attention from astronomers since the 1970's. The initial impetus came from the hope of detecting UV radiation from the hot intergalactic medium. The central importance of the FUV background to the physics (heating and ionization) of the diffuse atomic phases motivated the next generation of experiments. The consensus view is that the diffuse FUV emission at high latitudes has three components: stellar FUV reflected by dust grains (diffuse Galactic light or DGL), FUV from other galaxies and the intergalactic medium (extra-galactic background light or EBL) and a component of unknown origin (and referred to as the "offset" component). During the1980's, there was some discussion that decaying dark matter particles produced FUV radiation. In this paper I investigate production of FUV photons by conventional sources: line emission from Galactic Hot Ionized Medium, two-photon emission from the Galactic Warm Ionized Medium and low-velocity shocks, and Lyman-beta fluorescence of hydrogen at several locales in the Solar System (the interplanetary medium, the exosphere and the thermosphere of Earth). I conclude that two thirds and arguably all of the offset component can be explained by the sum of the radiation from the processes listed above.

Accepted by PASP (20 April 2022). Twenty one pages, 16 Figures and 3 Tables

References in corpus (11)

• Momentum Injection by Supernovae in the Interstellar Medium
• CHIANTI -- an atomic database for emission lines -- Paper XVI: Version 10, further extensions
• The Far Ultraviolet Spectroscopic Explorer Survey of OVI Absorption in the Disk of the Milky Way
• The Photon Underproduction Crisis
• The SPEAR Instrument and On-Orbit Performance
• Mapping the Diffuse Ultraviolet Sky with GALEX
• The Mystery of the Cosmic Diffuse Ultraviolet Background Radiation
• Far UV and Optical Emissions from Three Very Large Supernova Remnants Located at Unusually High Galactic Latitudes
• Far-ultraviolet fluorescent molecular hydrogen emission map of the Milky Way Galaxy
• Discovery of a Thirty-Degree Long Ultraviolet Arc in Ursa Major
• Global distribution of far-ultraviolet emissions from highly ionized gas in the Milky Way

Cited by in corpus (5)

• Science opportunities with solar sailing smallsats
• Evidence for large-scale excesses associated with low HI column densities in the sky I. Dust excess
• Excess Ultraviolet Emission at High Galactic Latitudes: A New Horizons View
• AstroSat/UVIT Study of the Diffuse Ultraviolet Radiation in the Dwarf Galaxy Holmberg II
• The Lyman alpha Sky as Observed by New Horizons