The Connection Between Different Tracers Of The Diffuse Interstellar Medium: Kinematics

TL;DR

This study compares various tracers of the diffuse interstellar medium across multiple wavelengths to understand their relationships and kinematic connections, enhancing the unified picture of atomic and molecular gas in space.

Contribution

It provides a detailed component-by-component comparison of absorption and emission tracers, linking different phases of interstellar gas and exploring their kinematic relationships.

Findings

Components in emission and absorption are correlated, aiding in mapping interstellar gas.

The tracers reveal the presence of CO-dark H₂ gas in the diffuse medium.

Kinematic connections among different species are established.

Abstract

Using visible, radio, microwave, and sub-mm data, we study several lines of sight toward stars generally closer than 1 kpc on a component-by-component basis. We derive the component structure seen in absorption at visible wavelengths from Ca II, Ca I, K I, CH, CH$^{+}\!,$ and CN and compare it to emission from H I, CO and its isotopologues, and C$^{+}$ from the GOT C+ survey. The correspondence between components in emission and absorption help create a more unified picture of diffuse atomic and molecular gas in the interstellar medium. We also discuss how these tracers are related to the CO-dark H$_{2}$ gas probed by C$^{+}$ emission and discuss the kinematic connections among the species observed.