An Analysis of Galex Observations of the Aquila Rift

Abstract

The interstellar medium (ISM) is a significant component of the Galaxy from which all the celestial bodies evolve. ISM is very tenuous consisting of interstellar matter interstellar gas (99% by mass) plus interstellar dust (1% by mass) - and interstellar radiation field. The interstellar matter is mostly conned to the Galactic plane and the regions nearer to the Galactic plane. Even though less abundant in the ISM, the interstellar dust grains play a very crucial role in regulating the energy transaction mechanism in the Galaxy. They absorb and radiate away the excess energy contained in molecular clouds, thereby aid in the star formation process. They scatter and absorb the ultraviolet radiation and re-radiate in the infrared (IR). Diffuse galactic light, reflection nebulae, X-ray halos etc are the consequences of the scattering of radiation by the interstellar dust grains. Absorption leads to the thermal emission observed at longer wavelength regions. The UV radiation emitting from bright sources are the major source of the interstellar radiation field. The radiation from stars are always messed up with many other emissions of galactic and extragalactic origins and what one observes is a diffuse background rather than direct starlight. The diffuse background is observable across almost all domains of the electromagnetic spectrum. Yet the diffuse background in the ultraviolet range ( : 10 nm - 400 nm) remains unique due to different astronomical aspects. The hot and cold components of the ISM can be traced using the information from various components of the diffuse UV background. The UV range is also important in studying the properties of interstellar gas and dust including their chemical composition, density and temperature. The components of the diffuse UV background include airglow, zodiacal light, diffuse galactic light and some contribution from the extragalactic sources at high Galactic latitudes..