Astronomy & Astrophysics

All Figures

$\begin{figure} \par\includegraphics[angle=-90,width=6.8cm,clip]{2816fig1.ps} \end{figure}$ Figure 1: NH₃ lines with a velocity scale relative to z=0.68466, observed towards B0218+357. Channel widths are 3.3 km s^-1. The ordinate is in units of the radio continuum flux. In the case of the (1,1) line a two component fit has been added accounting for NH₃ hyperfine splitting (Kukolich 1967). The fit demonstrates that the line profile is consistent with two optically thin velocity features. Limited signal-to-noise ratios do not constrain the fit sufficiently to justify an inclusion of its parameters in Table 3.
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In the text

$\begin{figure} \par\resizebox{12.3cm}{!}{\rotatebox[origin=br]{-90}{\includegraphics{2816fig2.ps}}} \end{figure}$ Figure 2: Boltzmann plot (rotation diagram) of the normalized NH₃ column density ( $g_{\rm op}$ is 1 for para-NH₃ ( K = 1, 2, 4) and 2 for ortho-NH₃ (K = 3)) divided by the excitation temperature $T_{\rm ex}$ in K within the inversion doublet as a function of excitation above the ground state. Lines connect the ( J,K) = (1,1) and (3,3) normalized column densities (the (4,4) transition was not detected). Filled squares connected by a solid line: total NH₃ absorption; open triangles connected by a dashed line: broad NH₃ absorption component; open squares connected by a dotted line: narrow NH₃ absorption component. Assuming optically thin absorption and equal excitation temperatures in the inversion doublets, rotation temperatures become $35.5\pm 2.5$ K (total), $34.0\pm 2.9$ K (broad component) and $39.0\pm 6.2$ K (narrow component).
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In the text