Spectral Signatures of Fast Shocks. I. Low-Density Model Grid

A high-velocity radiative shock provides an efficient means to generate a strong local UV photon field. The optical emission from the shock and precursor region is then dominated by the photoionized gas, rather than by the cooling region, and the total optical and UV emission scales as the mechanical energy flux through the shock. In addition, for reasonable values of the magnetic field, such shocks become supported by magnetic pressure in the photoionization/recombination zone of the shock. The effect of the limited compression factor has a profound influence on the output spectrum. Models without precursors apply to unresolved shocks in gas-poor environments or to fast shocks in individually resolved filaments of supernova remnants. Models with precursors should be applicable to unresolved structures in gas-rich environments. In this paper, we present extensive tabular results designed to be of maximum utility to observationalists for a grid of low-density steady-flow models covering the shock velocity range 150 ≤ VS 500 km s-1, and magnetic parameter 0 ≤ B/n½ ≤ 4 μG cm-3/2. In the next paper of this series, we will apply these models to diagnostic plots for narrow-line regions of active galactic nuclei.