Ionized Gas in the Smith Cloud

TL;DR

This study uses WHAM observations to analyze the ionized and neutral gas components of the Smith Cloud, revealing its ionized mass, temperature, and nitrogen abundance, which are crucial for understanding its origin and evolution.

Contribution

It provides detailed measurements of ionized gas properties in the Smith Cloud, highlighting the significance of ionized mass and non-primordial nitrogen abundance.

Findings

Ionized mass is at least as large as neutral mass (> 10^6 M_sun)

Electron temperature ranges from 6000 K to 16000 K

Nitrogen abundance is between 0.1 and 1 times solar

Abstract

We present WHAM observations of Halpha, [N II], and [S II] in the Smith Cloud. A map of Halpha emission from the cloud shows ionized gas coincident with the brightest H I emission, but nearly-as-bright Halpha in some regions with faint H I. The ionized mass of the cloud is at least as large as the neutral mass, > 10^6 M_sun. Ionized gas in the core of the Smith Cloud has an electron temperature 6000 K < T < 16000 K. The observed ratio [N II] / Halpha = 0.39 \pm 0.09 shows that the cloud has a non-primordial nitrogen abundance, 0.1 - 1 times solar.