SIMBAD references

A map of the core of Orion A, with a 42" resolution in the 64α recombination line of hydrogen, covering ∼5' by ∼5', is presented. The V_lsr distribution shows a complex variation about the center of the ionized gas emission: From {DELTA}α=-200'' to +300'', the V_lsr varies from -5km/s to +2km/s then to -4km/s, finally rising to +3km/s. A search for cold (T_e∼3000K) ionized gas toward the KL nebula has revealed no measurable differences in T_e between this region and other parts of Orion A. The average T_e from our data is 8300±200K. We find no significant difference between T_e values determined from radio recombination lines and those determined from forbidden optical lines of [O III], although the T_e value from Balmer decrement data is markedly lower. The turbulent velocity varies by <5% over the region mapped. On the basis of our 2.45' resolution, high dynamic range 6cm continuum map, we find that the emission falls off faster in the East than in the West. We find support for the model in which Orion A is ionization bounded in the East but density bounded in the West. The ionized gas in the West is flowing in the direction of the Sun, while the more positive V_lsr values in the east may be caused by the flow of ionized gas off the foreground Dark Bay. This ionized region may have little fine scale structure, since there is little continuum emission in interferometer maps.