Integral field spectroscopy of the extended emission-line region of 4C 37.43

We present Gemini integral field spectroscopy and Keck II long-slit spectroscopy of the extended emission-line region (EELR) around the quasar 4C 37.43. The velocity structure of the ionized gas is complex and cannot be explained globally by a simple dynamical model. The spectra from the clouds are inconsistent with shock or shock + precursor'' ionization models, but they are consistent with photoionization by the quasar nucleus. The best-fit photoionization model requires a low-metallicity [ 12 + log(O/H) less than or similar to 8.7] two-phase medium, consisting of a matter-bounded diffuse component with a unity filling factor ( N similar to 1 cm(-3), T similar to 15; 000 K), in which are embedded small, dense clouds ( N similar to 400 cm(-3), T similar to 104 K). The high-density clouds are transient and can be regenerated through compressing the diffuse medium by low-speed shocks (V-S less than or similar to 100 km s(-1)). Our photoionization model gives a total mass for the ionized gas of about 3 x 10(10) M circle dot, and the total kinetic energy implied by this mass and the observed velocity field is similar to 2 x 10(58) erg. The fact that luminous EELRs are confined to steep-spectrum radio-loud QSOs, yet show no morphological correspondence to the radio jets, suggests that the driving force producing the 4C 37.43 EELR was a roughly spherical blast wave initiated by the production of the jet. That such a mechanism seems capable of ejecting a mass comparable to that of the total interstellar medium of the Milky Way suggests that quasar-mode'' feedback may indeed be an efficient means of regulating star formation in the early universe.