HI cloud formation

Jonas Syed

Poster -- Star-forming regions

The structure and composition of the interstellar medium (ISM) might hold important insights into early formation processes of molecular clouds. One particularly interesting aspect when studying initial conditions of cloud formation is the emission of cold atomic hydrogen that is often seen as HI self absorption (HISA, e.g., Gibson et al. 2000). Therefore, the identification of HISA features in a large portion of the Galactic plane is subject of this analysis. Using HI and continuum data of The HI/OH/Recombination line survey of the Milky Way (THOR, Beuther et al. 2015) as well as GRS CO data (Jackson et al. 2006), I aim to characterize HISA features to trace the cold and dense phases of atomic hydrogen. As a first sample, the analysis is performed on a region covering Galactic longitudes from 17.6 to 20.7 deg and latitudes between -1.25 and +0.5 deg. First results show apparent HI self absorption where molecular line emission increases, as seen in CO emisson. Further analysis might give constraints on HI column densities and the close association of HISA's and molecular line emission could further hint at the conversion processes of atomic to molecular gas.