Systematic Continuum Errors in the Lyman-Alpha Forest and The Measured Temperature-Density Relation

Understand

Continuum fitting uncertainties are a major source of error in estimates of the temperature-density relation (usually parametrized as a power-law, $T \propto \Delta^{\gamma - 1} $) of the inter-galactic medium (IGM) through the flux probability distribution function (PDF) of the Lyman-$\alpha$ forest.

• Using a simple order-of-magnitude calculation, we show that few percent-level systematic errors in the placement of the quasar continuum due to e.g.
• a uniform low-absorption Gunn-Peterson component, could lead to errors in $\gamma$ of order unity.
• This is quantified further using a simple semi-analytic model of the Lya forest flux PDF.