Determination of the Mean HI Absorption of the Intergalactic Medium for luminous quasars

In the spectrum of distant QSOs and in a region with wavelengths shorter than Lyα emission radiation, many absorption lines are being seen which relate to neutral hydrogen in the IGM. These absorption lines are numerous and belong to the hydrogen Lyα transition, called Lyα forest. In order to determine this absorption by IGM in different redshifts, the QSO continuum in the Lyα forest must be determined. The purpose of this paper is to predict the continuum of bright QSOs in this region by wavelengths longer than the Lyα emission line of the QSO using the statistical methods of PCA. Therefore a mathematical technique to predict the QSO continuum of the bright SDSS-DR7 QSO at 2.7 4.7 has been applied and measures the amount of absorption, known as the flux decrement, DA. The end our measured flux decrement with the other works to check the accuracy of this method has been compared.

Keywords:

Observational Cosmology , QSO Continuum , Intergalactic Medium (IGM) , Principal Component Analysis (PCA)