We propose observations of L1689B in the Ophiuchus molecular cloud (~ 125 pc). The observations will cover the Class 0 core of L1689B and the filament in which the core sits. The goal is to trace the kinematics from the filament to the core. In order to achieve this goal, we propose to observe NH_3 (1, 1) and (2, 2) line emission. By combining data from the proposed VLA observation and the GBT data planned to be taken as part of our ongoing Green Bank Ammonia Survey (GAS; GBT/15A-430), the final maps will be sensitive to spatial scales from 6 arcmin (~ 0.26 pc) to 4 arcsec (~ 500 AU). The combined (VLA+GBT) set of data will have a spectral resolution of 0.1 km/s. The spectral and angular resolution will allow us to probe fragmentation and infall motion within the core. Meanwhile, the spatial coverage will allow us to trace the any flow motion from the filament onto the core, as has been recently found in molecular line observations (for example, 12CO 1-0 and 13CO 1-0) at larger scales. Being a Class 0 (very young) core sitting on a filamentary structure with large-scale velocity gradient, L1689B appears to be an ideal place to test the theory of star formation through accretion along/across filaments.
