All Figures

$\begin{figure} \par\includegraphics[width=9cm,clip]{9727fig1.eps}\end{figure}$ Figure 1: A sample of molecular and heavy element absorption lines associated with the damped Lyman- $\alpha$ system toward SDSS J143912.04+111740.5. The normalized flux is given on a velocity scale with the origin at $z_{\rm abs} = 2.41837$ . Smooth curves in each panel show our Voigt profile fits to the data. The dashed profiles shown for $J\le 1$ H₂ lines are the 1 $\sigma$ ranges. Tick marks in each panel indicate the locations of the 6 components that are used to fit the J=3 H₂ absorption lines. The symbol ``CO'' marks the locations of two components detected in S I and CO.
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In the text

$\begin{figure} \par\includegraphics[width=9cm,clip]{9727fig2.eps}\end{figure}$ Figure 2: Voigt profile fits to ¹²[]CO A-X bands detected at $z_{\rm abs} = 2.4185$ towards SDSS J143912.04+111740.5. The vertical lines mark the locations of CO absorptions from different J levels at the redshift of the main component. The profiles in dashed and dotted lines are, respectively, for the first and second components (at $z_{\rm abs}$ = 2.41837 and 2.41847) and the total profile is shown in solid line.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{9727fig3.eps}\end{figure}$ Figure 3: The CO excitation diagram. A straight line with slope 1/( $T_{\rm ex}$ ln 10) indicates thermalization of the levels. The diagram is given for the main CO component at $z_{\rm abs} = 2.41837$ . The three lines give the mean and 1 $\sigma$ range obtained from T₀₁, T₀₂, and T₁₂. The diagram is compatible with thermalization by a black-body radiation of temperature $9.15 \pm 0.72$ K when $T_{\rm CMBR} = 9.315\pm 0.007$ K (long dashed line) is expected at $z_{\rm abs} = 2.4185$ from the hot big-bang theory.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{9727fig5.eps}\end{figure}$ Figure 4: Comparison of rotational excitation temperatures of CO and H₂. Filled circles are for the measurements from Galactic diffuse ISM (Burgh et al. 2007). The filled triangle is for our measurement at z = 2.4183towards SDSS J143912.04+111740.5.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{9727fig4.eps}\end{figure}$ Figure 5: Measurements of T(CMBR) at various z. The star with errorbars is for the measurement based on CO presented here. Our earlier measurement using fine-structure lines of neutral carbon, $6.0<T_{\rm CMBR}<14.0$ K, at z = 2.33771 is indicated by the long vertical bar (Srianand et al. 2000). Measurement by Molaro et al. (2002) is marked by an open circle. Upper limits are measurements using C I or C II^* from the literature (squares) and using C I from our UVES sample (hexagons). The dashed line is the prediction from the hot big-bang theory, $T_{\rm CMBR}(z)=T_{\rm CMBR}(z=0)\times (1+z)$ . $T_{\rm CMBR}$ measurement at z=0 is based on the COBE determination (Mather et al. 1999).
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{9727fig5.eps}\end{figure}$	Figure 4: Comparison of rotational excitation temperatures of CO and H₂. Filled circles are for the measurements from Galactic diffuse ISM (Burgh et al. 2007). The filled triangle is for our measurement at z = 2.4183towards SDSS J143912.04+111740.5.
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