Gas Flows in a Prototypical Galactic-Scale Filament

Abstract

The study of the filamentary interstellar medium (ISM) is crucial for understanding both star formation and galactic evolution. Filamentary structures that exceed 100 parsecs present optimal conditions for studying the formation of stars, star clusters, and large-scale dynamical filamentary evolution. The work presented in this thesis mainly utilized molecular line transitions observed with the Atacama Large Millimeter Array (ALMA) to analyze the gas kinematics of the prototypical galactic-scale filament Nessie. We describe the kinematic properties of the filaments traced by the HNC and N2H+ molecules from 100-parsec to sub-parsec scales. The general structure of the Nessie filament was shown to extend even further than established in prior studies, yet remains a single coherent structure. There were also clear signs of large-scale velocity gradients indicating galactic-scale interactions with the filament. We further quantify the velocity gradients along the main spline tracing the filamentary structure to estimate the mass flows onto parsec-scale gravitationally collapsing clumps. These were characterized by a directional flip of the mass flow direction along the spline associated with a local density peak. Using these signatures, we propose 11 candidates for such clumps and estimate the mass inflow rates toward them. The resulting mass flows showed consistency with evolutionary timescales of these clumps. This clearly demonstrates that Nessie is a highly dynamic environment, rich in potential sites for star formation.