Optical imaging and spectroscopic investigations of supernova remnant G190.9−2.2

Radio observations have shown that G190.9−2.2 is a barrel-shaped, low surface-brightness supernova remnant (SNR), with a large angular size and a shell-type morphology. In this work, we present the first comprehensive optical investigation of the SNR G190.9−2.2, aiming to determine its physical characteristics based on imaging and spectroscopic observations obtained with the 1-m Turkish Telescope (T100) and 1.5-m Russian-Turkish Telescope (RTT150). The Hα and [S ii] images show sharp, long and curved filamentary structures within the southern radio shell of the SNR. The presence of forbidden line emission ([O iii], [O i], [N ii], and [S ii]) from the SNR indicates that there is strong cooling behind the shock front. [S ii]/Hα line ratios measured from both long-slit spectra and imaging analysis support the interpretation that the emission originates from a shock-heated gas. We estimate that the electron density ranges from 17 to 1899 cm−3, based on the [S ii] λ6716/λ6731 line ratio. The [O iii] λ5007/Hβ ratio suggests the presence of relatively slow shocks with velocities Vs ∼ 80 km s−1. Both the optical morphology and the spectra of G190.9−2.2 are consistent with radiative shocks. Significant variations in physical parameters, including electron density, pre-shock density, and extinction, were observed across the studied regions, indicating a highly inhomogeneous ambient medium.