All Figures

$\begin{figure} \resizebox{8.8cm}{!}{\includegraphics{7640f2.eps}} \end{figure}$ Figure 2: Normalized histograms of total C IV line width and absolute velocity offset among our DLA/sub-DLA sample. The distribution of both $\Delta v$ (dotted) and v₊-v_- (solid) is shown in the top panel. The peak of the v₊-v_- distribution is $\approx$ 100 km s^-1 broader than the peak of the $\Delta v$ distribution, reflecting the presence of low optical depth satellite components. There is an extended tail of line widths reaching >1000 km s^-1. We have treated the upper limits to $\Delta v$ as data points when forming the distribution. The distribution of the absolute C IV velocity offset (i.e., the mean C IV velocity relative to the neutral gas) is shown in the lower panel.
Open with DEXTER

In the text

$\begin{figure} \resizebox{8.8cm}{!}{\includegraphics{7640f3.eps}} \end{figure}$ Figure 3: Comparison of the normalized C IV column density distributions: (i) in DLAs and sub-DLAs (solid line, this work); (ii) in the IGM at $z\approx 2{-}3$ (dashed line; Boksenberg et al. 2003); (iii) around LBGs at $z\approx 2{-}3$ (dotted line; Adelberger et al. 2005). In each case, $N_{\rm C {\sc iv}}$ is integrated over all components. Note how a typical DLA/sub-DLA shows (a) considerably stronger C IV than a typical IGM C IV absorber, but (b) a C IV column similar to the mean seen in the LBG distribution. These two findings support our interpretation that the C IV in DLAs and sub-DLAs is galactic rather than intergalactic. We have included the saturated C IV absorbers as data points in the DLA/sub-DLA distribution, using the measured lower limits; this has the effect of artificially truncating the high $N_{\rm C {\sc iv}}$ tail of the solid line.
Open with DEXTER

In the text

$\begin{figure} \resizebox{8.8cm}{!}{\includegraphics{7640f4.eps}} \end{figure}$ Figure 4: Comparison of high-ion and low-ion total line width for DLAs (filled circles) and sub-DLAs (open circles). Absorbers at <5000 km s^-1 from the QSO redshift are highlighted in square symbols. The dashed line shows where $\Delta v_{\rm C {\sc iv}}=\Delta v_{\rm Neut}$ . In 69 of 74 cases the C IV absorption is broader than the neutral absorption. There is a large scatter in $\Delta v_{\rm C {\sc iv}}$ at low $\Delta v_{\rm Neut}$ , but the scatter decreases with increasing $\Delta v_{\rm Neut}$ . Saturated C IV absorbers are shown with upper limits to $\Delta v_{\rm C {\sc iv}}$ .
Open with DEXTER

In the text

$\begin{figure} \resizebox{8.8cm}{!}{\includegraphics{7640f5.eps}} \end{figure}$ Figure 5: Correlations between the measured C IV properties for both DLAs (filled circles) and sub-DLAs (open circles). Proximate absorbers are highlighted in square symbols. We use v₊-v_- rather than $\Delta v$ to measure the line width, since it is defined even in the saturated cases. We annotate the Kendall rank correlation coefficient $\tau$ and its significance on the panel, for various sub-samples. Solid lines show linear least-square bisector fits for the case where all data points are treated equally (including limits). Top panel: C IV column density vs. C IV line width. A correlation is found even when excluding the saturated C IV absorbers (the lower limits on $N_{\rm C {\sc iv}}$ ), although in this case the slope of the fit (shown as a dashed line) is shallower. Bottom panel: comparison between total C IV line width and C IV absolute velocity offset, also showing a significant correlation. These trends show that the stronger C IV absorbers tend to be broader and more offset from the neutral gas than the weaker absorbers.
Open with DEXTER

In the text

$\begin{figure} \resizebox{8.5cm}{!}{\includegraphics{7640f6.eps}} \end{figure}$ Figure 6: Dependence of C IV properties in DLAs (filled circles) and sub-DLAs (open circles) with neutral-phase metallicity. Proximate absorbers are highlighted in square symbols. In each panel, we annotate the Kendall rank correlation coefficient $\tau$ and its significance, and we show a linear least-square bisector fit (solid line), for the case where all data points are treated equally (including the limits). In panel a), we find a significant correlation between $N_{\rm C {\sc iv}}$ and [Z/H]. This remains true (at 2.5 $\sigma$ ) even in the case where the saturated points are excluded, though in this case the slope is slightly shallower (dashed line). In panel b), we show a 3.4 $\sigma$ correlation between $\Delta v_{\rm C {\sc iv}}$ and [Z/H], but this correlation is not found when the saturated points are excluded (hence there is no dashed line in this panel). However, if we instead use $(v_+-v_-)_{\rm C {\sc iv}}$ to measure the line width ( bottom panel), since this statistic is not affected by saturation, a significant (4.1 $\sigma$ ) metallicity-line width correlation does exist. The detected correlations show that high-metallicity systems tend to exhibit strong and broad C IV absorption.
Open with DEXTER

In the text

$\begin{figure} \resizebox{8.8cm}{!}{\includegraphics{7640f7.eps}} \end{figure}$ Figure 7: Illustration that the correlation between C IV total line width and metallicity exists independently in the lower and upper redshift halves of the sample, even though there is a difference between the mean metallicity of the two sub-samples (the lower-z sample shows systematically higher [Z/H]). The symbols have their same meanings as in Fig. 6. All DLAs and sub-DLAs in each redshift range were included in the correlation analysis and in the linear bisector fits, shown with solid lines.
Open with DEXTER

In the text

$\begin{figure} \resizebox{8.5cm}{!}{\includegraphics{7640f8.eps}} \end{figure}$ Figure 8: Comparison of H II column density in the C IV-bearing gas integrated over all velocities with ( top) $N_{\rm H {\sc i}}$ and ( bottom) [Z/H] for each system in our sample, assuming an ionization fraction $N_{\rm C {\sc iv}}/N_{\rm C}=0.3$ . The average value of the ratio N(H II)/N(H I) over all 74 systems is 0.1, implying that the C IV phase of DLAs and sub-DLAs typically contains >10% of the baryons and metals in the neutral phase. The mean value of $N_{\rm H {\sc ii}}$ is $\approx$ 2.5 times lower in sub-DLAs than in DLAs.
Open with DEXTER

In the text

$\begin{figure} \resizebox{8.8cm}{!}{\includegraphics{7640f9.eps}} \end{figure}$ Figure 9: Dependence of the C IV column density on the cooling rate derived from the $N_{\rm C {\sc ii}^*}/N_{\rm H {\sc i}}$ ratio, for each DLA (filled circles) and sub-DLA (open circles) where data on C IV and C II^* exist. Color-coding is used to denote the metallicity of the gas, as indicated in the legend. The seven data points with the highest $N_{\rm C {\sc iv}}$ all show above-average cooling rates. Among these seven, six show high metallicities.
Open with DEXTER

In the text

$\begin{figure} \resizebox{8.8cm}{!}{\includegraphics{7640f10.new.eps}} \end{figure}$ Figure 10: Top panel: C IV column density moving above the escape speed (i.e. wind candidate $N_{\rm C {\sc iv}}$ ) as a function of metallicity, for the 25 DLAs and 4 sub-DLAs with C IV absorption at $\vert v\vert>\vert v_{\rm esc}\vert$ , where $v_{\rm esc}=2.4\Delta v_{\rm Neut}$ . Bottom panel: wind mass outflow rate $\dot{M}_{\rm wind}$ divided by characteristic C IV radius r₄₀ (in units of 40 kpc) vs metallicity. The median mass outflow rate among these cases is 22r₄₀ $M_\odot$ yr^-1. The large diamond shows the mass outflow rate determined in the z=2.7 Lyman Break Galaxy cB58 by Pettini et al. (2000), assuming r=1 kpc. The filled triangles are the mass flow rates determined for the cool winds in the Martin (2006) sample of low-redshift ultraluminous starburst galaxies and plotted at zero metallicity for convenience. Only the DLA and sub-DLA points have been divided by r₄₀.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=15cm,clip]{7640f1a.eps} \end{figure}$ Figure 1: VLT/UVES absorption line spectra of C IV $\lambda \lambda 1548, 1550$ and an optically thin line (typically Si II or Fe II) chosen to trace the neutral phase component structure, for all DLAs and sub-DLAs in our sample. The flux is in arbitrary units, with the bottom of each panel at zero. The light (dark) shaded regions show C IV absorption below (above) $v_{\rm esc}$ , where $v_{\rm esc}=2.4\Delta v_{\rm Neut}$ (see text). The thick vertical line in each C IV panel denotes the optical-depth weighted mean velocity of the profile. The two narrow vertical lines show the velocities corresponding to 5% and 95% of the integrated optical depth; the interval between these velocities defines the total line width $\Delta v$ . A small letter "B'' within the shaded area indicates a blend; in these cases the other C IV line was used for measurement. The label "Proximate'' implies the absorber is at <5000 km s^-1 from the QSO. Note how the wind candidate absorbers (the dark regions) show no absorption in the weak neutral line shown here, implying these absorbers have low column densities of neutral gas and are highly ionized.
Open with DEXTER

In the text

$\begin{figure}\par\includegraphics[width=15cm,clip]{7640f1b.eps} \end{figure}$ Figure 1: continued.
Open with DEXTER

In the text

$\begin{figure}\par\includegraphics[width=15cm,clip]{7640f1c.eps} \end{figure}$ Figure 1: continued.
Open with DEXTER

In the text

$\begin{figure}\par\includegraphics[width=15cm,clip]{7640f1d.eps} \end{figure}$ Figure 1: continued.
Open with DEXTER

In the text

$\begin{figure}\par\includegraphics[width=15cm,clip]{7640f1b.eps} \end{figure}$	Figure 1: continued.
Open with DEXTER