Poster abstract
Physical Conditions of a Low-Mass Class 0 Source in Ophiuchus
Abstract
The outflow driven by the Class 0 protostar, IRAS 16253-2429, is associated with bipolar cavities visible in scattered mid-infrared light, which we refer to as the Wasp-Waist Nebula. IRS scan mapping with Spitzer reveals an S-shaped morphology in six different pure rotational transitions of H$_2$.
This is the least luminous Class 0 flow mapped in the pure rotational H$_2$ lines by three orders of magnitude. Spatially resolved excitation analysis shows remarkably constant temperatures of $\sim$ 1000K in the shocked gas. The mass of hot H$_2$ is of order 10$^{-3}$ of the cold (30K) CO in the outflow. Comparison of the H$_2$ data with detailed shock models shows the emitting gas is passing through J-shocks. Pre-shock densities of 10$^{4}$ cm$^{-3}\ \le\ n_H\ \le$ 10$^{5}$ cm$^{-3} are inferred for the red-shifted lobe and $n_H\ \le\ 10^3$ cm$^{-3}$ for the blue-shifted lobe. Shock velocities are 5 km s$^{-1}\ \le\ v_s\ \le 10$ km s$^{-1}$ for the red-shifted gas and $v_s\ =$ 10 km s$^{-1}$ for the blue-shifted gas. Initial transverse (to the shock) magnetic field strengths for the red-shifted lobe are in the range 10$\mu$G-32$\mu$G, and just 3 $\mu$G for the blue-shifted lobe. Additionally, a map of the protostellar envelope in absorption in the 11.3 $\mu$m PAH feature is presented for the first time.
This is the least luminous Class 0 flow mapped in the pure rotational H$_2$ lines by three orders of magnitude. Spatially resolved excitation analysis shows remarkably constant temperatures of $\sim$ 1000K in the shocked gas. The mass of hot H$_2$ is of order 10$^{-3}$ of the cold (30K) CO in the outflow. Comparison of the H$_2$ data with detailed shock models shows the emitting gas is passing through J-shocks. Pre-shock densities of 10$^{4}$ cm$^{-3}\ \le\ n_H\ \le$ 10$^{5}$ cm$^{-3} are inferred for the red-shifted lobe and $n_H\ \le\ 10^3$ cm$^{-3}$ for the blue-shifted lobe. Shock velocities are 5 km s$^{-1}\ \le\ v_s\ \le 10$ km s$^{-1}$ for the red-shifted gas and $v_s\ =$ 10 km s$^{-1}$ for the blue-shifted gas. Initial transverse (to the shock) magnetic field strengths for the red-shifted lobe are in the range 10$\mu$G-32$\mu$G, and just 3 $\mu$G for the blue-shifted lobe. Additionally, a map of the protostellar envelope in absorption in the 11.3 $\mu$m PAH feature is presented for the first time.