Thermal Pressures in the Interstellar Medium of the Magellanic Clouds
  We discuss the thermal pressures ($n_H T$) in predominantly cold, neutral
interstellar gas in the Magellanic Clouds, derived from analyses of the
fine-structure excitation of neutral carbon, as seen in high-resolution
HST/STIS spectra of seven diverse sight lines in the LMC and SMC. Detailed fits
to the line profiles of the absorption from C I, C I*, and C I** yield
consistent column densities for the 3--6 C I multiplets detected in each sight
line. In the LMC and SMC, $N$(C I$_{\rm tot}$) is consistent with Galactic
trends versus $N$(Na I) and $N$(CH), but is slightly lower versus $N$(K I) and
$N$(H$_2$). As for $N$(Na I) and $N$(K I), $N$(C I$_{\rm tot}$) is generally
significantly lower, for a given $N$(H$_{\rm tot}$), in the LMC and
(especially) in the SMC, compared to the local Galactic relationship. For the
LMC and SMC components with well determined column densities for C I, C I*, and
C I**, the derived thermal pressures are typically factors of a few higher than
the values found for most cold, neutral clouds in the Galactic ISM. Such
differences are consistent with the predictions of models for clouds in systems
(like the LMC and SMC) that are characterized by lower metallicities, lower
dust-to-gas ratios, and enhanced radiation fields -- where higher pressures are
required for stable cold, neutral clouds. The pressures may be further enhanced
by energetic activity (e.g., due to stellar winds, star formation, and/or
supernova remnants) in several of the regions probed by these sight lines.
Comparisons are made with the C I observed in some quasar absorption-line
systems.
