Astronomy & Astrophysics

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$\begin{figure} \par\mbox{\includegraphics[width=4.7cm,clip]{0897fg1a.eps} \hspac... ...\hspace{4mm} \includegraphics[width=4.7cm,clip]{0897fg1c.eps} } \end{figure}$ Figure 1: Distribution of iron depletions for the DLA systems in Table 1. Panels a), b) and c) correspond to cases Sa, Sb and E1, respectively. Vertical lines: typical values of interstellar iron depletions in the Milky Way (dotted line: warm halo gas; dashed line: warm disk gas; dotted-dashed line: cold disk gas).
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In the text

$\begin{figure} \par\mbox{\includegraphics[width=4.7cm,angle=0]{0897fg2a.eps} \hs... ...pace{3mm} \includegraphics[width=4.7cm,angle=0]{0897fg2c.eps} } \end{figure}$ Figure 2: Iron dust fraction versus metallicity for the sample of DLA systems listed in Table 1. Panels a), b) and c) correspond to cases Sa, Sb and E1, respectively. Horizontal lines: representative values of iron dust fractions in the Galactic ISM (legenda as in Fig. 1). Solid curve: empirical law (4) describing the evolution of the dust fraction with metallicity.
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In the text

$\begin{figure} \par\includegraphics[width=6cm,clip]{0897fg3a.eps}\par\vspace{4mm} \includegraphics[width=6cm,clip]{0897fg3b.eps} \end{figure}$ Figure 3: Test of selection effects performed on a mock sample of n=1000 DLA systems with H I, Fe II and Zn II column densities rejected as explained in Sect. 3.3. a) Frequency distribution of iron depletion (after rejection) for an adopted flat distribution of $\delta$ (Fe). b) Dust fraction versus metallicity for an adopted flat distribution of $f_{\rm Fe}$ ; the solid curves represent the envelopes of the real data in Fig. 2. The depletions of the mock sample have been modeled with the set of parameters Sa (Table 1); similar results are obtained for the other cases.
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In the text

$\begin{figure} \par\mbox{ \includegraphics[height=6.2cm,width=6.8cm,clip]{0897fg... ...\includegraphics[height=6.2cm,width=6.8cm,clip]{0897fg4b.eps} } \end{figure}$ Figure 4: Time evolution of the dust content in DLA systems. a) Diamonds: $f_{\rm Fe}$ versus age of the universe; dashed area: reionization epoch $6 \leq z \leq 20$ (Fan et al. 2003; Spergel et al. 2003); solid, dotted and dashed curves: Inoue's (2003) model predictions of the evolution of the relative dust-to-metal ratio for different sets of input parameters (see text for explanations); the curves have been normalized to the present-day value and scaled assuming a formation redshift z_f=20. b) Frequency distribution of iron depletions in two bins of look-back time (shaded area: $t_{\rm l} \ge 10.5$ Gyr; empty histogram: $t_{\rm l} < 10.5$ Gyr). The fraction in dust are computed for the set of parameters Sa.
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In the text

$\begin{figure} \par\mbox{\includegraphics[width=6.7cm,angle=0]{0897fg5a.eps} \hs... ...e{0.5cm} \includegraphics[width=6.7cm,angle=0]{0897fg5d.eps} } \end{figure}$ Figure 5: Iron depletions/dust fractions versus some physical parameters measured in DLA systems. a) Cooling rate per H atom, $l_{\rm c}$ (Wolfe et al. 2003a). b) Spin temperature, $T_{\rm s}$ (Kanekar & Chengalur 2003). c) $N(C {\sc ii})/N(C {\sc i})$ ionization ratio (Liszt 2002). d) Molecular fraction $f({\rm H}_2)$ (Ledoux et al. 2003). Depletions are computed in case Sa. Horizontal lines as in Fig. 1.
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In the text

$\begin{figure} \par\mbox{\includegraphics[width=4.7cm,clip]{0897fg1a.eps} \hspac... ...\hspace{4mm} \includegraphics[width=4.7cm,clip]{0897fg1c.eps} } \end{figure}$	Figure 1: Distribution of iron depletions for the DLA systems in Table 1. Panels a), b) and c) correspond to cases Sa, Sb and E1, respectively. Vertical lines: typical values of interstellar iron depletions in the Milky Way (dotted line: warm halo gas; dashed line: warm disk gas; dotted-dashed line: cold disk gas).
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$\begin{figure} \par\mbox{\includegraphics[width=4.7cm,angle=0]{0897fg2a.eps} \hs... ...pace{3mm} \includegraphics[width=4.7cm,angle=0]{0897fg2c.eps} } \end{figure}$	Figure 2: Iron dust fraction versus metallicity for the sample of DLA systems listed in Table 1. Panels a), b) and c) correspond to cases Sa, Sb and E1, respectively. Horizontal lines: representative values of iron dust fractions in the Galactic ISM (legenda as in Fig. 1). Solid curve: empirical law (4) describing the evolution of the dust fraction with metallicity.
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