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Title: On the Metallicities and Kinematics of the Circumgalactic Media of Damped Lyα Systems at z ∼ 2.5*

We use medium- and high-resolution spectroscopy of close pairs of quasars to analyze the circumgalactic medium (CGM) surrounding 32 damped Lyαabsorption systems (DLAs). The primary quasar sightline in each pair probes an intervening DLA in the redshift range 1.6 <zabs< 3.5, such that the secondary sightline probes absorption from Lyαand a large suite of metal-line transitions (including Oi, Cii, Civ, Siii, and Siiv) in the DLA host galaxy’s CGM at transverse distances 24 kpc ≤R≤ 284 kpc. Analysis of Lyαin the CGM sightlines shows an anticorrelation betweenRand Hicolumn density (NHI) with 99.8% confidence, similar to that observed around luminous galaxies. The incidences of Ciiand SiiiwithN> 1013cm−2within 100 kpc of DLAs are larger by 2σthan those measured in the CGM of Lyman break galaxies (Cf(NCII) > 0.89 andCf(NSiII)=0.750.17+0.12). Metallicity constraints derived from ionic ratios for nine CGM systems with negligible ionization corrections andNHI> 1018.5cm−2show a significant degree of scatter (with metallicities/limits across the range2.06logZ/Z0.75), suggesting inhomogeneity in the metal distribution in these environments. Velocity widths of Civλ1548 and low-ionization metal species in the DLA versus CGM sightlines are strongly (>2σ) correlated, suggesting that they trace the potential well of the host halo overR≲ 300 kpc scales. At the same time, velocity centroids for Civλ1548 differ in DLA versus CGM sightlines by >100 km s−1for ∼50% of velocity components, but few components have velocities that would exceed the escape velocity assuming dark matter host halos of ≥1012M.

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DOI PREFIX: 10.3847
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Journal Name:
The Astrophysical Journal
Medium: X Size: Article No. 135
["Article No. 135"]
Sponsoring Org:
National Science Foundation
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