The Eastern Filament of W50

TL;DR

This study presents detailed spectral observations of the Eastern filament of W50, revealing complex emission line regions, high-velocity motions, and proposing shock waves in low-density gas as the filament's power source.

Contribution

It provides new high-resolution spectral data and analysis of the physical conditions and kinematics of the W50 filament, suggesting shock waves as the energy source.

Findings

Different emission lines originate from regions with distinct physical conditions.

Ionized gas exhibits moderately high, supersonic velocities (~100 km/s).

Evidence suggests very low gas densities (~0.1 cm^{-3}).

Abstract

We present new spectral (FPI and long-slit) data on the Eastern optical filament of the well known radionebula W50 associated with SS433. We find that on sub-parsec scales different emission lines are emitted by different regions with evidently different physical conditions. Kinematical properties of the ionized gas show evidence for moderately high (V ~ 100 km/s) supersonic motions. [OIII]5007 emission is found to be multi-component and differs from lower-excitation [SII]6717 line both in spatial and kinematical properties. Indirect evidence for very low characteristic densities of the gas (n ~ 0.1cm^{-3}) is found. We propose radiative (possibly incomplete) shock waves in low-density, moderately high metallicity gas as the most probable candidate for the power source of the optical filament. Apparent nitrogen over-abundance is better understood if the location of W50 in the Galaxy is taken into account.