Cooling Galactic Fountain Gas
Abstract
We have calculated the time-dependent, nonequilibrium thermal and ionization history of gas cooling radiatively from 10(6) K in a one-dimensional, planar,steady-state flow model of the galactic fountain, including the effects of radiative transfer. We find that inclusion of the effects of self-ionization of the flow, combined with the requirement that the gas undergo a constant density (isochoric) phase in its evolution allows such a flow to match the observed galactic halo column densities of C IV, Si IV, and N V and UV emission from C IV and O III for a range of initial temperatures (5.5 < log T0 <6.5) and cooling regions sizes homogenous on scales of D0>15 pc.For an initial flow velocity v0 ~ 100km/s, comparable to the sound speed of a 10(6) K gas, the initial density is found to be n_{H,0} ~ 2times 10(-2) cm(-3) , in reasonable agreement with other observational estimates of ionized halo gas, and D0 ~ 40pc. We compare predicted H alpha fluxes, total ionizing flux, free-free radio emission, and broadband X-ray fluxes with observed values. Finally, we present results of 1-D hydrodynamical calculations of radiative shocks lead to the physical conditions necessary to produce such a cooling flow.
- Publication:
-
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1993
- Bibcode:
- 1993AAS...18311404B