The ``Maggie'' filament: dynamic signatures of a giant atomic cloud

Jonas Syed

Thursday December 3rd, 14:30

The atomic phase of the interstellar medium plays a key role in the formation process of molecular clouds. Although or even on account of being ubiquitous in the Galactic plane, atomic hydrogen emission has been challenging to study. I will present the recent results of one distinct large-scale filament that was identified in HI emission at negative v_lsr velocities. ``Maggie'' - with a length of ~1200pc - has an aspect ratio of 30:1. It is purely atomic and shows no detection in other tracers or signs of active star formation. At the kinematic distance of 17kpc, Maggie is situated fairly off (~500pc) but parallel to the Galactic midplane. The velocities show a coherent structure to within +-7km/s and the line widths are dominated by turbulent motion. Assuming optically thin emission, Maggie has a mass of 10^5 solar masses. Whether Maggie is an anomaly or an object of regular occurrence is still not well understood. This novel type of filament might open up a new range of questions addressing the formation of large-scale atomic structures seen in the Milky Way.