A study of galactic molecular clouds through multiwavelength observations

Abstract

The ISM is one of the most important ingredients in the study of the process of the Galactic evolution. Due to the fact that the ISM is endlessly recycled (gravitationally collapse, star-formation, stellar evolution, and finally supernova explosion), there are various types of ISM which can be categorized in terms of temperature and density. This thesis focuses on two Galactic molecular clouds that are located in wholly different environments and both are observed in FUV bands. The Draco cloud is known as a translucent molecular cloud (optically thin) at high Galactic latitude. The FUV spectra show important ionic lines of C IV, Si IV+O IV], Si $II^*$ and Al II, indicating the existence of hot and warm interstellar gases in the region. The FUV continuum is mostly the starlight scattered off the dust grains in the Draco cloud. The enhanced C IV emission inside the Draco cloud region is attributable to the turbulent mixing of the interacting cold and warm/hot media, which is supported by the detection of the O III] emission line and the $H\alpha$ feature in this region. The Si $II^*$ emission covers the remainder of the region outside the Draco cloud, in agreement with previous observations of Galactic halos. Additionally, the $H_2$ fluorescent map is consistent with the morphology of the atomic neutral hydrogen and dust emission of the Draco cloud. In the Aquila Rift region near Galactic plane, FIMS observed that the FUV continuum emission from the core of the Aquila Rift suffers heavy dust extinction. The entire field is divided into three subregions that are known as the-“halo,” “diffuse,” and “star-forming” regions. The “diffuse” and “star-forming” regions show various prominent $H_2$ fluorescent emission lines, while the ‘halo” region indicates the general ubiquitous characteristics of $H_2$, as supported by previous FIMS studies. The CLOUD model and the FUV line ratio are included here to investigate the physical conditions of each subregion. Finally, the d...