Properties of high redshift Lyman alpha clouds. 2. Statistical properties of the clouds
Mar, 1993
35 pages
Published in:
- Astrophys.J. 418 (1993) 585
e-Print:
- astro-ph/9303017 [astro-ph]
DOI:
Report number:
- CFA-3601
View in:
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Abstract: (arXiv)
Curve of growth analysis, applied to the Lyman series absorption ratios deduced in our previous paper, yields a measurement of the logarithmic slope of distribution of \Lya\ clouds in column density . The observed exponential distribution of the clouds' equivalent widths is then shown to require a broad distribution of velocity parameters , extending up to 80 km s. We show how the exponential itself emerges in a natural way. An absolute normalization for the differential distribution of cloud numbers in , , and is obtained. By detailed analysis of absorption fluctuations along the line of sight we are able to put upper limits on the cloud-cloud correlation function on several megaparsec length scales. We show that observed values, if thermal, are incompatible, in several different ways, with the hypothesis of equilibrium heating and ionization by a background UV flux. Either a significant component of is due to bulk motion (which we argue against on several grounds), or else the clouds are out of equilibrium, and hotter than is implied by their ionization state, a situation which could be indicative of recent adiabatic collapse.References(16)
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