Comparisons of Diffuse Ionized and Neutral Hydrogen in the Galaxy

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Session 8 -- General ISM, Dust
Display presentation, Monday, 9:20-6:30, Pauley Room

[8.03] Comparisons of Diffuse Ionized and Neutral Hydrogen in the Galaxy

Stephen Tufte, R. J. Reynolds, David T. Kung (UW--Madison), \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ Peter R. McCullough, and Carl Heiles (UCB)

We compare velocity resolved maps of the diffuse Galactic H$_{\alpha}$ emission over a 10$^{\rm o} \times12^{\rm o}$ degree region of the sky centered near $l$= 144$^{\rm o}$, b= --21$^{\rm o}$ (cf. Reynolds 1980) with corresponding maps from 21 cm data taken with the Hat Creek 85-foot telescope (now destroyed). The H$_{\alpha}$ maps have about 1$^{\rm o}$ angular resolution and display the intensity distribution down to an effective emission measure of 1--2 cm$^{-6}$pc for a series of seven narrow (12 km s$^{-1}$) radial velocity intervals between --76 and +8 km s$^{-1}$ (LSR). From 21 cm data the corresponding H I column density is mapped in the same velocity intervals allowing direct comparison of neutral and ionized hydrogen in the diffuse interstellar medium at high latitude. We find both correlations and anti-correlations between the H$_{\alpha}$ and 21 cm emission regions. In particular, a $\sim$ 15$^{\rm o}$ long, high-velocity filament and an $\simeq$ 11$^{\rm o}$ diameter ring are analyzed. We also compare a 3$^{\prime}$ resolution narrow band H$_{\alpha}$ image with Aricebo 21 cm data covering the same spatial and spectral regions ($\sim$ 1$^{\rm o} \times$ 1$^{\rm o}$ and --76 to --64 km s$^{-1}$).

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