The Fundamental Plane of Damped Lyα Systems

Abstract

Using a sample of 100 H I-selected damped Lyα (DLA) systems, observed with the High Resolution Echelle Spectrometer on the Keck I telescope, we present evidence that the scatter in the well-studied correlation between the redshift and metallicity of a DLA is largely due to the existence of a mass-metallicity relationship at each redshift. To describe the fundamental relations that exist between redshift, metallicity, and mass, we use a fundamental plane description, which is described by the following equation: [M/H] = (– 1.9 ± 0.5) + (0.74 ± 0.21) centerdot logΔv_90 – (0.32 ± 0.06) centerdot z. Here, we assert that the velocity width, Δv_90, which is defined as the velocity interval containing 90% of the integrated optical depth, traces the mass of the underlying dark matter halo. This description provides two significant improvements over the individual descriptions of the mass-metallicity correlation and metallicity-redshift correlation. Firstly, the fundamental equation reduces the scatter around both relationships by about 20%, providing a more stringent constraint on numerical simulations modeling DLAs. Secondly, it confirms that the dark matter halos that host DLAs satisfy a mass-metallicity relationship at each redshift between redshifts 2 through 5.

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