Metal-line System at z=2.18 in Quasar System

This image shows lines from a metal-line system at redshift z = 2.18 towards HE22-28.

Although the Lyman-alpha absorption line (bottom) shows only one component, with the metal lines blueshifted by ~ 40 km/sec, the corresponding Lyman-beta line (the observed wavelength is 326 nm near the atmospheric cut-off!) reveals that the complex consists of two components (clouds), separated by ~ 83 km/sec, at z = 2.1795 and at z = 2.1804.

The Voigt profile fitting gives a total column density of N(HI) = 1.3 x 10 16 cm -2 and accurate values for the column densities of SiIV, SiII, CIV, SiIII and CII. The SiIV/CIV ratio, an indicator of the temperature of the ionizing background for the z = 2.1795 component gives ~ 0.23 which is similar to what has been found in higher-z systems, suggesting little evolution in the shape of the spectrum of the ionizing background .

Credit:

ESO

About the Image

Id:eso0013h
Type:Chart
Release date:6 April 2000
Related releases:eso0013
Size:520 x 712 px

About the Object

Name:QSO HE22-28
Type:• Early Universe : Galaxy : Activity : AGN : Quasar
• X - Quasars & Black Holes
Distance:z=2.4 (redshift)

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