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The case for low surface brightness galaxies as absorbers in QSO Mg II systems

Phillipps, S., Disney, Michael John and Davies, Jonathan Ivor 1993. The case for low surface brightness galaxies as absorbers in QSO Mg II systems. Monthly Notices of the Royal Astronomical Society 260 (2) , pp. 453-462.

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We re-examine the case for numerous invisible low surface brightness galaxies (LSBGs), rather than rare but huge galactic haloes, as the absorbers responsible for a large fraction of the metal-line systems in the spectra of distant QSOs. In particular we find that the supposed best evidence for huge haloes, i.e. the direct observation of giant galaxies at projected distances of a few Holmberg radii from the QSO line of sight, can be explained by the normal clustering of galaxies near an (invisible) LSBG absorber directly in the line of sight to the QSO. We further point out that the most recent observations of the LSBG population indicate that we should expect a very high total cross-section for this population compared to the conventional population of 'normal' galaxies. In addition, adoption of the LSBG hypothesis removes several difficulties which occur in the 'conventional' picture, such as the unaccountably high average luminosity of the giant absorbers, the enormous size of the haloes required and the lack of correlation of the metal-line equivalent width and the QSO-giant galaxy separation. Perhaps most compelling of all, though, is the fact that the LSBG hypothesis simply explains the fact that searches for bright galaxies near QSOs with metal-line systems usually succeed (there is usually a bright galaxy somewhere near the absorbing LSBG), while searches for metal-line systems in QSOs projected a few Holmberg radii from a giant galaxy usually fail (no neighbouring LSBG happens to be in precisely the right place).

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: absorption spectra ; galactic clusters ; halos ; interstellar matter ; luminous intensity ; quasars ; line of sight ; magnesium
Publisher: Wiley
ISSN: 0035-8711
Last Modified: 04 Jun 2017 04:26

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