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A Note on the Total Absorption Cross-section of Galaxies

M. M. Cirkovic·S. Samurovic·D. Ilic·J. Petrovic
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Abstract

In this work we shall sketch a further piece of evidence for the plausibility of hypothesis of galactic origin of Ly-$α$ forest absorption systems. Two basic premises of our discussion are (1) HDF redshift surface densities in the redshift interval 0<z<6; and (2) validity of low-redshift results on redshift coincidences, showing average absorption cross-section corresponding to radius of 160$h^{-1}$ kpc for $L^*$ galaxies. Low-redshift analysis also showed covering factor nearing unity, which will be used and discussed in further considerations. Semantic problems concerned with the interpretation of galaxy absorption cross-section are discussed in some details, and importance of distinction between size of the absorbers and absorption coherence length is emphasized. It is shown that HDF data predict huge number of absorption systems, in fact much larger than observed, which shows frequently quoted argument that number of galaxies is insufficient to account for all absorption lines to be wrong. Road to achieving higher compatibility with the empirical statistics is shown to lie in applying the luminosity scaling, possibly with cut-off. This is significant for recent attempts to explain the association of the Ly-$α$ forest systems with normal galaxies.

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M. M. Cirkovic, S. Samurovic, D. Ilic, J. Petrovic. 1997-11-13. A Note on the Total Absorption Cross-section of Galaxies. https://arxiv.org/abs/astro-ph/9711078

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