The negative BAO shift in the Ly$\alpha$ forest from cosmological simulations

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We present the first measurement of the Ly$\alpha$ forest BAO shift parameter from cosmological simulations.

• In particular, we generate a suite of $1000$ accurate effective field-level bias-based Ly$\alpha$ forest simulations of volume $V=(1 \, h^{-1} \, {\rm Gpc})^3$ at $z=2$, both in real and redshift space, calibrated upon two fixed-and-paired cosmological hydrodynamic simulations.
• To measure the BAO, we stack the three-dimensional power spectra of the $1000$ different realizations, compute the average, and use a model accounting for a proper smooth-peak component decomposition of the power spectrum, to fit it via an efficient Markov Chain Monte Carlo scheme estimating the covariance matrices directly from the simulations.
• We report the BAO shift parameters to be $\alpha=0.9969^{+0.0014}_{-0.0014}$ and $\alpha=0.9905^{+0.0027}_{-0.0027}$ in real and redshift space, respectively.