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Paper: The Structure of High Redshift Galactic Halos from QSO Absorption Lines
Volume: 331, Extra-Planar Gas
Page: 395
Authors: Ellison, S.L.
Abstract: By studying intervening absorption systems in the spectra of gravitationally lensed or closely separated pairs of QSOs, we can investigate the size and structure of high redshift galaxies. Here, we present results from a study of the triply imaged QSO APM08279+5255 (zem = 3.9) for which we have obtained spatially resolved, moderate resolution spectra with STIS on the Hubble Space Telescope (HST). We find that the coherence scale of high redshift absorbers depends on their ionization state, qualitatively consistent with observations of the Galactic interstellar medium (ISM) via stellar spectroscopy. For example, previous studies of high redshift absorbers have shown that high ionization systems, such as those traced by C IV, exhibit a high level of uniformity over at least ~ 100 h−170 kpc. Conversely, we find that the low ionization absorbers, such as those traced by Mg II, can exhibit variation over scales of ~ 1 h−170 kpc. By using a maximum likelihood estimation technique, we determine the most probable coherence length of weak Mg II absorbers (EW < 0.3 Å) to be 2.0 h−170 kpc.
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