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New Temperatures of Diffuse Interstellar Gas: Thermally Unstable Gas

Carl Heiles
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Abstract

We present new Arecibo 21-cm line measurements of the temperatures of interstellar gas. Our temperatures for the Cold Neutral Medium (CNM) are significantly lower than previous single-dish results and in very good accord with theoretical models. For warm gas at T > 500 K, we find a significant fraction of gas (>47%) to lie in the thermally unstable region 500 ---> 5000 K; moreover, about 60% of all the neutral atomic gas has T > 500 K. Large amounts of thermally unstable gas are not allowed in theoretical models of the global interstellar medium.

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Carl Heiles. 2001-03-08. New Temperatures of Diffuse Interstellar Gas: Thermally Unstable Gas. https://doi.org/10.1086/319844

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