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$\begin{figure} \par\includegraphics[angle=270,width=8.2cm,clip]{5990fig1.ps} \end{figure}$ Figure 1: The J-band spectrum of Itoh et al. (2000) containing the Paschen lines, with the estimated level of the rms noise indicated. The observations are displayed as the black histogram, whereas the smooth red line refers to the fit of the [Fe II] spectrum (for $A_{\rm V} = 5.7$ mag, Liseau et al. 2005). The wavelength positions of the recombination lines He I 1.0830 $\mu$ m, ${\rm P}\gamma~1.0938~\mu$ m and ${\rm P}\beta~1.2818~\mu$ m are indicated above and below the spectrum. This applies also to the wavelengths of the transitions to the inverted ground state of [S I], i.e. $^1{\rm D}_2{-} ^3{\rm P}_2$ 1.08212 $\mu$ m, $^1{\rm D}_2{-}^3{\rm P}_1$ 1.13058 $\mu$ m and $^1{\rm D}_2{-}^3{\rm P}_0$ at 1.15376 $\mu$ m, respectively.
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In the text

$\begin{figure} \par\includegraphics[width=8.15cm,clip]{5990fig2.ps} \end{figure}$ Figure 2: The observed X-ray spectrum of the L 1551 IRS 5 jet is shown by the big dots, omitting error bars for clarity. The data are limited to roughly 0.3-3.3 keV. The spectrum appears thermal and is consistent with temperatures of about 4-4.5 MK (including observational errors, the best fit MEKAL model yields $4 \pm 2.5$ MK, Favata et al. 2002). For the model computations, the spectral shape of the blackbody, shown by the continuous curves, has been used as input spectrum (see the text). The frequencies corresponding to the ionization edges of He I and He II are shown by the vertical dashed lines.
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In the text

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{5990fig3.ps} \end{figure}$ Figure 3: Energy level diagramme of He I. For clarity, levels for quantum numbers >4 have been omitted. The transitions, which are discussed in the text, i.e. 1.0830 $\mu$ m and 0.5876 $\mu$ m of the triplet states and 2.06 $\mu$ m of the singlets, are marked and the wavelength of He I ionization is shown next to the slanted dashed line (see also Fig. 2).
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In the text

$\begin{figure} \par\includegraphics[width=8.1cm,clip]{5990fig4.ps} \end{figure}$ Figure 4: Helium ionization structure of gas with constant density $n({\rm H})=10^5$ cm^-3, being illuminated by a 4 MK point source. The run of the temperature $T_{\rm e}$ (in units of 10⁶ K) is shown in red, that of the electron fraction $x_{\rm e}$ in green. The fractional H I density is shown by the black broken line, whereas those of He I, He II and He III in blue, cyan and magenta, respectively. Tests with the previous version Cloudy 90 gave essentially identical results, except that the temperature structure is smoother. The hump due to "ionization jumps'' for a number of species is absent, indicating that this feature does not have any major effect on the results of interest.
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In the text

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{5990fig3.ps} \end{figure}$	Figure 3: Energy level diagramme of He I. For clarity, levels for quantum numbers >4 have been omitted. The transitions, which are discussed in the text, i.e. 1.0830 $\mu$ m and 0.5876 $\mu$ m of the triplet states and 2.06 $\mu$ m of the singlets, are marked and the wavelength of He I ionization is shown next to the slanted dashed line (see also Fig. 2).
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