- Question:
- Understanding the chemical processes during starless core and prestellar core evolution is an important step in understanding the initial stages of star and disk formation. Deteratium fraction is thought to be a good tracer of evolutionary stages. There are a lack of surveys that focus on the chemistry of the entire dense core population within a single cloud.
- Method:
- ARO 12m o-NH2D at 85.9 GHz.
- Aims:
- To quantify HI/H2 abundance ratio.
- results:
- 1/4 period shift between velocity and column density profiles -- core formation flow motions. physical oscillating? long filaments with enough resolutions would be better to distinguish the two mechanisms.
- very low accretion rates similar to those found in my paper about the Serpens filament.
- They found blue and red profiles in low density regions. They interpreted that axial flows might affect the line shape. red profiles may indicate expansion (nicely illustrated in Fig. 22).
- subsonic motions: gas flows collide and their turbulent motions are dissipated to form a quiescent filament at the earlier stage where individual dense core forms. -Comments:
- axial and radial flows should be taken into account simultaneously. Probably, a radiative transfer model of these filaments can well reproduce the observed line shapes.
- Question:
- Filament formation and evolution remains a hot topic.
- Method:
- ROHSA decomposite HC5N from GAS.
- Aims:
- TMC-1 an ideal candidate to investigate the kinematic properties of a molecular cloud filament that may soon form stars.
- progress:
- They found three components. The two brightest components extend the length of the filament, while the third component is fainter and clumpier. The brightest component shows a prominent transverse velocity gradient of 2.7+-0.1 km/s /pc that we show to be indicative of gravitationally induced inflow. regularly spaced emission peaks along its length. The local minima between pairs of adjacent HC$_5$N peaks line up closely with submillimetre continuum emission peaks, which we argue is evidence for fragmentation along the spine of TMC-1.They argue that the two bright components identified in HC$_5$N emission in TMC-1 are tracing two layers in one filament: a lower density outer layer whose material is flowing under gravity towards the higher density inner layer of the filament.