A measurement of two-particle correlations with a high transverse momentum trigger particle (p_T^{trig} > 2.5 GeV/c) is presented for Au+Au collisions at sqrt(s_NN) = 200 GeV over the uniquely broad longitudinal acceptance of the PHOBOS detector (-4
< Deltaeta < 2). A broadening of the away-side azimuthal correlation compared to elementary collisions is observed at all Deltaeta. As in p+p collisions, the near-side is characterized by a peak of correlated partners at small angle relative to the trigger particle. However, in central Au+Au collisions an additional correlation extended in Deltaeta and known as the `ridge is found to reach at least |Deltaeta| approx 4. The ridge yield is largely independent of Deltaeta over the measured range, and it decreases towards more peripheral collisions. For the chosen p_T^{trig} cut, the ridge yield is consistent with zero for events with less than roughly 100 participating nucleons.
