Varsha P. Kulkarni, Joseph Meiring, Debopam Som, Celine Peroux, Donald G. York, Pushpa Khare, James T. Lauroesch
We report the discovery of a "super-damped" Lyman-alpha absorber at
$z_{abs}=2.2068$ toward QSO Q1135-0010 in the Sloan Digital Sky Survey, and
follow-up VLT UVES spectroscopy. Voigt profile fit to the DLA line indicates
log $N_{\rm H I} = 22.05 \pm 0.1$. This is the second QSO DLA discovered to
date with such high $N_{\rm H I}$. We derive element abundances [Si/H] = $-1.10
\pm 0.10$, [Zn/H] = $-1.06 \pm 0.10$, [Cr/H] = $-1.55 \pm 0.10$, [Ni/H] =
$-1.60 \pm 0.10$, [Fe/H] = $-1.76 \pm 0.10$, [Ti/H] = $-1.69 \pm 0.11$, [P/H] =
$-0.93 \pm 0.23$, and [Cu/H] = $-0.75 \pm 0.14$. Our data indicate detection of
Ly-$\alpha$ emission in the DLA trough, implying a star formation rate of
$\sim$10 $M_{\odot}$ yr$^{-1}$ in the absence of dust attenuation. C II$^{*} \,
\lambda 1336$ absorption is also detected, suggesting SFR surface density $-2 <
{\rm log} \, \dot{\psi_{*}} < 0$ $M_{\odot}$ yr$^{-1}$ kpc$^{-2}$. We estimate
electron density in the range $3.5 \times 10^{-4}$ to 24.7 cm$^{-3}$ from C
II$^{*}$/C II, and $\sim$0.5-0.9 cm$^{-3}$ from Si II$^{*}$/Si II. Overall,
this is a robustly star-forming, moderately enriched absorber, but with
relatively low dust depletion. Fitting of the SDSS spectrum yields low
reddening for Milky Way, LMC, or SMC extinction curves. No CO absorption is
detected, and C I absorption is weak. The low dust and molecular content,
reminiscent of some SMC sight-lines, may result from the lower metallicity, and
a stronger radiation field (due to higher SFR). Finally, we compare this
absorber with other QSO and GRB DLAs.
View original:
http://arxiv.org/abs/1202.0882
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