Monte Carlo inversion of hydrogen and metal lines from QSO absorption spectra

TL;DR

This paper introduces a novel Monte Carlo-based method using simulated annealing to analyze complex intergalactic spectra, enabling detailed estimation of physical parameters and structures of absorbing gas from spectral lines.

Contribution

It generalizes previous methods to account for both velocity and density fluctuations, improving the analysis of complex spectral line profiles in astrophysical data.

Findings

Successfully recovered physical parameters from synthetic spectra with high accuracy

Demonstrated the method's effectiveness on complex HI and metal line profiles

Encourages application to real observational data

Abstract

A new method, based on the simulated annealing algorithm and aimed at the inverse problem in the analysis of intergalactic (interstellar) complex spectra of hydrogen and metal lines, is presented. We consider the process of line formation in clumpy stochastic media accounting for fluctuating velocity and density fields (mesoturbulence). This approach generalizes our previous Reverse Monte Carlo and Entropy-Regularized Minimization methods which were applied to velocity fluctuations only. The method allows one to estimate, from an observed system of spectral lines, both the physical parameters of the absorbing gas and appropriate structures of the velocity and density distributions along the line of sight. The validity of the computational procedure is demonstrated using a series of synthetic spectra that emulate the up-to-date best quality data. HI, CII, SiII, CIV, SiIV, and OVI lines, exhibiting complex profiles, were fitted simultaneously. The adopted physical parameters have been recovered with a sufficiently high accuracy. The results obtained encourage the application of the proposed procedure to the analysis of real observational data.