Types of Trees in the Lyman Alpha Forest

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Session 25 -- QSO Absorption-Line Studies with HST and Keck
Oral presentation, Tuesday, June 13, 1995, 8:30am - 12:30pm

[25.02] Types of Trees in the Lyman Alpha Forest

David Kirkman, David Tytler (CASS/UCSD)

We have obtained a very high SNR spectrum of QSO HS 1946+7658 (z = 3.051, V = 15.9) at a resolution of 7.8 km ${\displaystyle s^{-1}}$. We have full wavelength coverage over the Lyman Alpha forest region of the spectrum, with a signal-to-noise-ratio per pixel of 0.03\AA \space from 10 at 3960\AA \space to 100 at 4925\AA. There are approximately 900 Lyman Alpha lines in this spectrum, which we have empirically categorized into six distinct types of lines. We have discovered two types of lines which have not been seen before; wave-like regions 500-1500 km ${\displaystyle s^{-1}}$ long caused by groups of relatively low column density lines ($N(H~I) \simeq 10^{12.8}$), and local depressions in the continuum caused by single lines with extremely high temperatures ($T \simeq 10^6~K$). We have fit the data with Voigt profiles, and from this analysis we present characteristic column densities, velocity dispersions, associated temperatures, and occurence frequency of different types of lines in the data.

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