The Evolution of the Effective Equation of State of the IGM
نویسندگان
چکیده
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 Lyα forest. We test the method on numerical simulations and then apply it to published observations of the Lyα forest at redshifts z ≃ 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 He ii observed to occur at z ∼ 3. Subject headings: cosmology: theory — intergalactic medium — equation of state — quasars: absorption lines
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