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The Evolution of the Effective Equation of State of the IGM

Massimo Ricotti·Nickolay Y. Gnedin·J. Michael Shull
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Abstract

We develop a method to extract the "effective equation of state" of the intergalactic medium from the doppler b parameter distribution of the low-density Lyman-alpha forest. We test the method on numerical simulations and then apply it to published observations of the Lyman-alpha forest at redshifts z from 0 to 4. We find that the effective equation of state is close to isothermal at redshift z=3, indicating that a second reheating of the IGM took place at z=3. This reheating can plausibly be identified with the reionization of HeII observed to occur at z about 3.

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Massimo Ricotti, Nickolay Y. Gnedin, J. Michael Shull. 1999-12-11. The Evolution of the Effective Equation of State of the IGM. https://doi.org/10.1086/308733

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