The Impact of Temperature Fluctuations on the Lyα Forest Power Spectrum

We explore the impact of spatial fluctuations in the intergalactic mediumtemperature on the Lyman-alpha forest flux power spectrum near z ~ 3. Wedevelop a semianalytic model to examine temperature fluctuations resulting frominhomogeneous HI and incomplete HeII reionizations. Detection of thesefluctuations might provide insight into the reionization histories of hydrogenand helium. Furthermore, these fluctuations, neglected in previous analyses,could bias constraints on cosmological parameters from the Lyman-alpha forest.We find that the temperature fluctuations resulting from inhomogeneous HIreionization are likely to be very small, with an rms amplitude of < 5%,$\sigma_{T_0}/ < 0.05$. More important are the temperature fluctuationsthat arise from incomplete HeII reionization, which might plausibly be as largeas 50%, $\sigma_{T_0}/ ~ 0.5$. In practice, however, these temperaturefluctuations have only a small effect on flux power spectrum predictions. Thesmallness of the effect is possibly due to density fluctuations dominating overtemperature fluctuations on the scales probed by current measurements. On thelargest scales currently probed, k ~ 0.001 s/km (~0.1 h/Mpc), the effect on theflux power spectrum may be as large as ~10% in extreme models. The effect islarger on small scales, up to ~20% at k = 0.1 s/km, due to thermal broadening.Our results suggest that the omission of temperature fluctuations effects fromprevious analyses does not significantly bias constraints on cosmologicalparameters.Comment: 11 pages, 5 figures, ApJ accepte