All Figures

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{0807fig1.eps} \end{figure}$ Figure 1: L-band image as obtained with ISAAC on the VLT UT1. The four slit positions chosen for the spectroscopic observations are also shown. They all include the position of SgrA*. The position of the CO-star used for the calibration along the line of sight is shown as well.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=15cm,clip]{0807fig5.eps} \end{figure}$ Figure 5: Our ISAAC L-band map combined with the spectra of the central sources corrected for the line of sight extinction.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{0807fig8.eps} \end{figure}$ Figure 8: Wavelength distribution of the line of sight extinction towards the Galactic Center.
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In the text

$\begin{figure} \par\includegraphics[width=8cm]{0807fg12.eps} \end{figure}$ Figure 12: Optical depths of the Galactic Center sources normalized to unity at $3.0~{\mu}$ m.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{0807fg13.eps} \end{figure}$ Figure 13: Mean L-band normalized spectra. The black and grey (or red in the colour version) spectra are obtained by averaging the dusty sources and the stellar (He-stars, IRS 7 and IRS 9) optical depth spectra, respectively.
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In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{0807fg14.eps} \end{figure}$ Figure 14: Mean isolated and normalized ice spectra of the dusty sources (in black) and He-stars, IRS 7 and IRS 9 sources (in grey, or red in the colour version).
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In the text

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{0807fg15.eps} \end{figure}$ Figure 15: Mean isolated and normalized $3.4~\mu$ m feature of the dusty sources (in black) and He-stars, IRS 7 and IRS 9 sources (in grey, or red in the colour version). The location of the $3.3~\mu$ m feature is indicated.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{0807fg16.eps} \end{figure}$ Figure 16: Mean isolated and normalized $3.4~\mu$ m feature of the dusty sources.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{0807fg17.eps} \end{figure}$ Figure 17: L-band intrinsic spectrum (i.e. corrected for extinction along the line of sight as explained in Sect. 3.2) at the position of SgrA* taken through a 0.6'' wide slit using ISAAC on the VLT UT1. The continuum of a blackbody of 22 200 K is also shown. The locations of hydrogen lines are marked.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{0807fg18.eps} \end{figure}$ Figure 18: Optical depth of the hydrocarbon absorption at the $3.4~\mu$ m versus the $3.48~\mu$ m absorption feature for all observed Galactic Center sources (the IRS 16 sources are represented by stars and the remaining sources by triangles).
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{0807fg19.eps} \end{figure}$ Figure 19: Optical depth of the hydrocarbon absorption at $3.4~\mu$ m versus the depth in the $3.0~{\mu}$ m absorption feature for all observed Galactic Center sources (the IRS 16 sources are represented by stars and the remaining sources by triangles). The values obtained by Chiar et al. (2002) are also shown (in circles) but are not considered in the linear regression fit.
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In the text

$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0807fig2.eps} \end{figure}$ Figure 2: Best fits of the K- and L-band spectra with single reddened blackbody continua. When no K-band spectrum was available, the flux density at $2.2~\mu$ m represented by a diamond was considered in the fitting procedure.
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In the text

$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0807fig3.eps} \end{figure}$ Figure 3: Fitting spectra with single reddened blackbody continua (cont.).
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In the text

$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0807fig4.eps} \end{figure}$ Figure 4: Fitting spectra with single reddened blackbody continua (cont.).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{0807fig6.eps} \end{figure}$ Figure 6: The H- and K-band spectrum of the late-type CO-star whose L-band spectrum is used for the line of sight absorption correction.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{0807fig7.eps} \end{figure}$ Figure 7: The L-band spectrum of the late-type CO-star used for the line of sight absorption correction.
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In the text

$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0807fig9.eps} \end{figure}$ Figure 9: L-band spectra corrected for line of sight absorption using the optical depth spectrum shown in Fig. 8. Blackbody continua (not reddened) of temperatures listed in Table 1 are also plotted for comparison.
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In the text

$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0807fg10.eps} \end{figure}$ Figure 10: L-band spectra corrected for line of sight absorption (cont.).
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In the text

$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0807fg11.eps} \end{figure}$ Figure 11: L-band spectra corrected for line of sight absorption (cont.).
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{0807fig1.eps} \end{figure}$	Figure 1: L-band image as obtained with ISAAC on the VLT UT1. The four slit positions chosen for the spectroscopic observations are also shown. They all include the position of SgrA*. The position of the CO-star used for the calibration along the line of sight is shown as well.
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$\begin{figure} \par\includegraphics[angle=90,width=15cm,clip]{0807fig5.eps} \end{figure}$	Figure 5: Our ISAAC L-band map combined with the spectra of the central sources corrected for the line of sight extinction.
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$\begin{figure} \par\includegraphics[width=7cm,clip]{0807fig8.eps} \end{figure}$	Figure 8: Wavelength distribution of the line of sight extinction towards the Galactic Center.
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$\begin{figure} \par\includegraphics[width=8cm]{0807fg12.eps} \end{figure}$	Figure 12: Optical depths of the Galactic Center sources normalized to unity at $3.0~{\mu}$ m.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{0807fg13.eps} \end{figure}$	Figure 13: Mean L-band normalized spectra. The black and grey (or red in the colour version) spectra are obtained by averaging the dusty sources and the stellar (He-stars, IRS 7 and IRS 9) optical depth spectra, respectively.
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$\begin{figure} \par\includegraphics[width=8.4cm,clip]{0807fg14.eps} \end{figure}$	Figure 14: Mean isolated and normalized ice spectra of the dusty sources (in black) and He-stars, IRS 7 and IRS 9 sources (in grey, or red in the colour version).
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$\begin{figure} \par\includegraphics[width=8.2cm,clip]{0807fg15.eps} \end{figure}$	Figure 15: Mean isolated and normalized $3.4~\mu$ m feature of the dusty sources (in black) and He-stars, IRS 7 and IRS 9 sources (in grey, or red in the colour version). The location of the $3.3~\mu$ m feature is indicated.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{0807fg16.eps} \end{figure}$	Figure 16: Mean isolated and normalized $3.4~\mu$ m feature of the dusty sources.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{0807fg17.eps} \end{figure}$	Figure 17: L-band intrinsic spectrum (i.e. corrected for extinction along the line of sight as explained in Sect. 3.2) at the position of SgrA* taken through a 0.6'' wide slit using ISAAC on the VLT UT1. The continuum of a blackbody of 22 200 K is also shown. The locations of hydrogen lines are marked.
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$\begin{figure} \par\includegraphics[width=7cm,clip]{0807fg18.eps} \end{figure}$	Figure 18: Optical depth of the hydrocarbon absorption at the $3.4~\mu$ m versus the $3.48~\mu$ m absorption feature for all observed Galactic Center sources (the IRS 16 sources are represented by stars and the remaining sources by triangles).
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$\begin{figure} \par\includegraphics[width=7cm,clip]{0807fg19.eps} \end{figure}$	Figure 19: Optical depth of the hydrocarbon absorption at $3.4~\mu$ m versus the depth in the $3.0~{\mu}$ m absorption feature for all observed Galactic Center sources (the IRS 16 sources are represented by stars and the remaining sources by triangles). The values obtained by Chiar et al. (2002) are also shown (in circles) but are not considered in the linear regression fit.
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$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0807fig2.eps} \end{figure}$	Figure 2: Best fits of the K- and L-band spectra with single reddened blackbody continua. When no K-band spectrum was available, the flux density at $2.2~\mu$ m represented by a diamond was considered in the fitting procedure.
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$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0807fig3.eps} \end{figure}$	Figure 3: Fitting spectra with single reddened blackbody continua (cont.).
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$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0807fig4.eps} \end{figure}$	Figure 4: Fitting spectra with single reddened blackbody continua (cont.).
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$\begin{figure} \par\includegraphics[width=8cm,clip]{0807fig6.eps} \end{figure}$	Figure 6: The H- and K-band spectrum of the late-type CO-star whose L-band spectrum is used for the line of sight absorption correction.
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$\begin{figure} \par\includegraphics[width=8.5cm,clip]{0807fig7.eps} \end{figure}$	Figure 7: The L-band spectrum of the late-type CO-star used for the line of sight absorption correction.
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$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0807fig9.eps} \end{figure}$	Figure 9: L-band spectra corrected for line of sight absorption using the optical depth spectrum shown in Fig. 8. Blackbody continua (not reddened) of temperatures listed in Table 1 are also plotted for comparison.
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$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0807fg10.eps} \end{figure}$	Figure 10: L-band spectra corrected for line of sight absorption (cont.).
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$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0807fg11.eps} \end{figure}$	Figure 11: L-band spectra corrected for line of sight absorption (cont.).
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