Sheets and Filaments as the Origin of the High-Velocity Tail of the Lyman-Alpha Forest

Abstract

Simulations of large-scale structure formation predict the formation of sheet- and filamentary structures, which are often invoked as the origin of the Lyman-alpha forest. In their simplest description, these sheets and filaments require a differential distribution of observed line-of-sight velocity widths ($b$) which will decrease as power-laws at velocities well above the observed peak in this distribution: for filaments, the differential distribution is $dN/db\propto b^{-3}$, while for sheets it is $dN/db\propto b^{-2}$. These functional dependences on $b$ arise a priori due to the geometry of these absorbing structures -- assuming random orientations relative to the line-of-sight -- and are otherwise unrelated to the physical state in the absorbing structure. We find the the distribution at $b>35$ in three previously published data sets to be steeper than $dN/dB\propto b^{-3}$ (99.99% confidence). This implies that evidence of the finite length of these kinds of absorbing structures is present in the $b$-distribution data.

arXiv comment12 pages, 2 figures, Latex, requires aaspp4.sty,12pt.sty,flushrt.sty; Submitted, ApJ Letters

References in corpus (17)

• Gravitational Collapse of Small-Scale Structure as the Origin of the Lyman Alpha Forest
• The Lyman-alpha Forest in the Cold Dark Matter Model
• The Lyman Alpha Forest from Gravitational Collapse in the CDM+Lambda Model
• Evolution of Structure in the Intergalactic Medium and the Nature of the Ly-alpha Forest
• A Multi-Species Model for Hydrogen and Helium Absorbers in Lyman-Alpha Forest Clouds
• The Distribution of Column Densities and b Values in the Lyman-Alpha Forest
• Damped Lyman-alpha and Lyman Limit Absorbers in the Cold Dark Matter Model
• The Statistics of Density Peaks and the Column Density Distribution of the Lyman-Alpha Forest
• Intrinsic Properties of the <z>=2.7 Lyman Alpha Forest from Keck Spectra of QSO HS 1946+7658
• Spectral Analysis of the Lyman Alpha Forest in a Cold Dark Matter Cosmology
• The Redshift Evolution of the Lyman Alpha Forest
• Voigt-Profile Analysis of the Lyman-alpha Forest in a Cold Dark Matter Universe
• The Lyman-alpha Forest at z~4: Keck HIRES Observations of Q 0000-26
• Properties of High-Redshift Lyman Alpha Clouds II. Statistical Properties of the Clouds
• Sizes, Shapes, and Correlations of Lyman Alpha Clouds and Their Evolution in the CDM$+\Lambda$ Universe
• Lyman Alpha Forest towards B2 1225+317
• Lyman alpha absorption lines from mini pancakes

Cited by in corpus (4)

• Resolving the Lyman-alpha Forest
• On the connection between the intergalactic medium and galaxies: The HI-galaxy cross-correlation at z < 1
• The b Distribution and the Velocity Structure of Absorption Peaks in the Lyman-Alpha Forest
• Hydrodynamical Simulations of the Lyman Alpha Forest: Model Comparisons