Equation of state of the intergalactic medium in the early Universe

TL;DR

This paper develops an automated Voigt profile fitting program for Lyα forest lines in quasar spectra, enabling the estimation of the intergalactic medium's equation of state at redshifts 2-3, consistent with previous studies.

Contribution

The authors created an automatic fitting tool and applied it to high-resolution quasar spectra to measure the intergalactic medium's equation of state, providing a new, efficient analysis method.

Findings

Estimated the power law index γ of the IGM's equation of state.

Confirmed consistency with previous measurements using different techniques.

Analyzed 9 high-resolution quasar spectra from Keck archive.

Abstract

Spectroscopy of the Ly$\alpha$ forest in quasar spectra proved to be a useful tool for probing the intergalactic gas. We developed the automatic program for Voigt profile fitting of Ly$\alpha$ forest lines. We run this code on 9 high resolution ($\sim 50000$) quasars spectra with a high signal-to-noise ratio ($\sim 50 -100$) from the Keck telescope archive and obtained the sample of single well-fitted Ly$\alpha$ lines. Fitting the joint 2d distribution of column density and Doppler parameter from this sample by physically reasonable model we estimate a power law index $\gamma$ of the equation of state of the intergalactic medium in the redshift range $z\sim 2-3$. We found that our measurement is in an agreement with measurements by other groups obtained with Voigt profile fitting technique.