All Figures

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{2149fig1.eps}} \end{figure}$ Figure 1: Spectral region about the CH⁺ absorption towards the template star HD 205637, emphasizing the absence of telluric features at airmasses of 1.05-1.08.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{2149fig2.eps}} \end{figure}$ Figure 2: The ratio of measured to expected noise, Q, as a function of the order of the Legendre polynomial used to define the baselines, l. The data are for 25 exposures of HD 170740 on June 15th, for two 1.5 $\AA$ spectral regions centred on $\lambda$ 4232 (solid line), and on $\lambda$ 3957 (dotted line).
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In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{2149fig3.eps} \end{figure}$ Figure 3: $\zeta$ Oph spectra. Wavelengths are in Angstroms, and flux densities in arbitrary units. The individual Gaussian components comprising the fit, prior to folding with the instrumental response, are shown only on ¹²CH⁺ as light gray lines, but are omitted from ¹³CH⁺ for clarity (see text for details). The vertical dashed lines mark the line centroids, at the average of the Gaussian centroids weighted by their equivalent widths. The units of the y-axis are arbitrary, and are scaled so that the median of the object spectrum is unity. Also shown is a magnified version of the object spectrum, by the factor indicated on the figure, and offset for clarity. The residual spectrum is shown on top of the object spectrum, and is also magnified by the factor indicated on figure. The noise used to compute the significance of the fits is labelled on the top right. The noise is the rms dispersion of the residual spectrum, and is in the same units as the y-axis. The height of the shaded rectangles on top of the x-axis indicates the relative weights used in the baseline definition.
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In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{2149fig4.eps} \end{figure}$ Figure 4: Same as Fig. 3. The fits on the $\lambda$ 3957 lines are excluded from the combined measurement of R.
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In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{2149fig5.eps} \end{figure}$ Figure 5: Same as Fig. 3. The fits on $\lambda$ 3957 for June 15th and 16th are excluded from the combined measurement of R.
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In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{2149fig6.eps} \end{figure}$ Figure 6: Same as Fig. 8. No excess absorption is detected on the blue edge of $\lambda 4232 ~^{12}$ CH⁺.
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In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{2149fig7.eps} \end{figure}$ Figure 7: Same as Fig. 8. ¹³CH⁺ is visible as excess absorption on the blue edge of $\lambda 4232 ~^{12}$ CH⁺.
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In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{2149fig8.eps} \end{figure}$ Figure 8: Same as Fig. 3. This line of sight has blended ¹²CH⁺ and ¹³CH⁺ absorption at $\lambda$ 4232. We extrapolate the ¹²CH⁺ profile at $\lambda$ 3957 (see text for details). ¹³CH⁺ is visible as excess absorption on the blue edge of ¹²CH⁺.
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In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{2149fig9.eps} \end{figure}$ Figure 9: Same as Fig. 8. The fit for ¹³CH⁺ absorption on the blue edge of $\lambda 4232 ~^{12}$ CH⁺ gives a 3 $\sigma$ detection, but is barely visible in the figure.
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In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{2149fig10.eps} \end{figure}$ Figure 10: Same as Fig. 3. None of the $\lambda$ 4232 spectra were used to combine individual measurements of R. There is excess absorption bridging the two isotopes at $\lambda$ 4232. The origin of the additional absorption, whether a telluric or a stellar feature, is unclear.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{2149fig11.eps} \end{figure}$ Figure 11: Same as Fig. 8. The information from $\lambda$ 4232 is not used because f is spuriously negative, and neither is that from $\lambda$ 3957 on June 14th because of a non-ISM absorption feature at 3957.3 $~\AA$ .
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In the text

$\begin{figure} \par\includegraphics[width=15cm,clip]{2149fig12.eps} \end{figure}$ Figure 12: Same as Fig. 8. The spectra around $\lambda$ 3957 have ragged baselines, presumably due to instrumental fringing. Only the coadded spectrum at $\lambda$ 3957 is used for subsequent averaging of R with that from $\lambda$ 4232.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{2149fig13.eps}} \end{figure}$ Figure 13: A plot of individual R values for the lines of sight studied in this work. The thick lines are $\pm$ $\sigma _1$ uncertainties, from the weighted average uncertainty of individual measurements. The thin lines are $\pm$ $\sigma _2$ uncertainties, from the scatter of measurements for a given line of sight, and are set equal to $\sigma _1$ if $\sigma _2 < \sigma _1$ . The hatched box is the weighted average of the measurements in the figure, and should be representative of the local ISM. This value is $78.27 \pm 1.83$ . The height of the hatched rectangle is $\pm$ $1\sigma$ . Galactic longitude and distance in parsec are indicated to the bottom right of each target.
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In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{online/2149fig3.eps} \end{figure}$ Figure 3: $\zeta$ Oph spectra. Wavelengths are in Angstroms, and flux densities in arbitrary units. The individual Gaussian components comprising the fit, prior to folding with the instrumental response, are shown only on ¹²CH⁺ as light gray lines, but are omitted from ¹³CH⁺ for clarity (see text for details). The vertical dashed lines mark the line centroids, at the average of the Gaussian centroids weighted by their equivalent widths. The units of the y-axis are arbitrary, and are scaled so that the median of the object spectrum is unity. Also shown is a magnified version of the object spectrum, by the factor indicated on the figure, and offset for clarity. The residual spectrum is shown on top of the object spectrum, and is also magnified by the factor indicated on figure. The noise used to compute the significance of the fits is labelled on the top right. The noise is the rms dispersion of the residual spectrum, and is in the same units as the y-axis. The height of the shaded rectangles on top of the x-axis indicates the relative weights used in the baseline definition.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{online/2149fig4.eps} \end{figure}$ Figure 4: Same as Fig. 3. The fits on the $\lambda$ 3957 lines are excluded from the combined measurement of R.
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In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{online/2149fig5.eps} \end{figure}$ Figure 5: Same as Fig. 3. The fits on $\lambda$ 3957 for June 15th and 16th are excluded from the combined measurement of R.
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In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{online/2149fig10.eps} \end{figure}$ Figure 10: Same as Fig. 3. None of the $\lambda$ 4232 spectra were used to combine individual measurements of R. There is excess absorption bridging the two isotopes at $\lambda$ 4232. The origin of the additional absorption, whether a telluric or a stellar feature, is unclear.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{online/2149fig11.eps} \end{figure}$ Figure 11: Same as Fig. 8. The information from $\lambda$ 4232 is not used because f is spuriously negative, and neither is that from $\lambda$ 3957 on June 14th because of a non-ISM absorption feature at 3957.3 $~\AA$ .
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{online/2149fig12.eps} \end{figure}$ Figure 12: Same as Fig. 8. The spectra around $\lambda$ 3957 have ragged baselines, presumably due to instrumental fringing. Only the coadded spectrum at $\lambda$ 3957 is used for subsequent averaging of R with that from $\lambda$ 4232.
Open with DEXTER

In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{2149fig1.eps}} \end{figure}$	Figure 1: Spectral region about the CH⁺ absorption towards the template star HD 205637, emphasizing the absence of telluric features at airmasses of 1.05-1.08.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{2149fig2.eps}} \end{figure}$	Figure 2: The ratio of measured to expected noise, Q, as a function of the order of the Legendre polynomial used to define the baselines, l. The data are for 25 exposures of HD 170740 on June 15th, for two 1.5 $\AA$ spectral regions centred on $\lambda$ 4232 (solid line), and on $\lambda$ 3957 (dotted line).
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$\begin{figure} \par\includegraphics[width=16cm,clip]{2149fig4.eps} \end{figure}$	Figure 4: Same as Fig. 3. The fits on the $\lambda$ 3957 lines are excluded from the combined measurement of R.
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$\begin{figure} \par\includegraphics[width=16cm,clip]{2149fig5.eps} \end{figure}$	Figure 5: Same as Fig. 3. The fits on $\lambda$ 3957 for June 15th and 16th are excluded from the combined measurement of R.
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$\begin{figure} \par\includegraphics[width=16cm,clip]{2149fig6.eps} \end{figure}$	Figure 6: Same as Fig. 8. No excess absorption is detected on the blue edge of $\lambda 4232 ~^{12}$ CH⁺.
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$\begin{figure} \par\includegraphics[width=16cm,clip]{2149fig7.eps} \end{figure}$	Figure 7: Same as Fig. 8. ¹³CH⁺ is visible as excess absorption on the blue edge of $\lambda 4232 ~^{12}$ CH⁺.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=16cm,clip]{2149fig8.eps} \end{figure}$	Figure 8: Same as Fig. 3. This line of sight has blended ¹²CH⁺ and ¹³CH⁺ absorption at $\lambda$ 4232. We extrapolate the ¹²CH⁺ profile at $\lambda$ 3957 (see text for details). ¹³CH⁺ is visible as excess absorption on the blue edge of ¹²CH⁺.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=16cm,clip]{2149fig9.eps} \end{figure}$	Figure 9: Same as Fig. 8. The fit for ¹³CH⁺ absorption on the blue edge of $\lambda 4232 ~^{12}$ CH⁺ gives a 3 $\sigma$ detection, but is barely visible in the figure.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=16cm,clip]{2149fig10.eps} \end{figure}$	Figure 10: Same as Fig. 3. None of the $\lambda$ 4232 spectra were used to combine individual measurements of R. There is excess absorption bridging the two isotopes at $\lambda$ 4232. The origin of the additional absorption, whether a telluric or a stellar feature, is unclear.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{2149fig11.eps} \end{figure}$	Figure 11: Same as Fig. 8. The information from $\lambda$ 4232 is not used because f is spuriously negative, and neither is that from $\lambda$ 3957 on June 14th because of a non-ISM absorption feature at 3957.3 $~\AA$ .
Open with DEXTER

$\begin{figure} \par\includegraphics[width=15cm,clip]{2149fig12.eps} \end{figure}$	Figure 12: Same as Fig. 8. The spectra around $\lambda$ 3957 have ragged baselines, presumably due to instrumental fringing. Only the coadded spectrum at $\lambda$ 3957 is used for subsequent averaging of R with that from $\lambda$ 4232.
Open with DEXTER