A wavelet analysis of QSO spectra

Abstract

The temperature of the intergalactic medium (IGM) is an important factor in determining the line-widths of the absorption lines in the Lyman-alpha forest. We present a method to characterise the line-widths distribution using a decomposition of a Lyman-alpha spectrum in terms of discrete wavelets. Such wavelets form an orthogonal basis so the decomposition is unique. We demonstrate using hydrodynamic simulations that the mean and dispersion of the wavelet amplitudes is strongly correlated with both the temperature of the absorbing gas and its dependence on the gas density. Since wavelets are also localised in space, we are able to analyse the temperature distribution as a function of position along the spectrum. We illustrate how this method could be used to identify fluctuations in the IGM temperature which might result from late reionization or local effects.

7 pages, MNRAS published version

References in corpus (4)

• The Evolution of the Effective Equation of State of the IGM
• Measuring the equation of state of the intergalactic medium
• Broadening of QSO Lyman-alpha forest absorbers
• Spectral Analysis of the Lyman-Alpha Forest Using Wavelets

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