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Previous measurements of a quadrupole component of azimuth correlationsdenoted by symbol $v_2$ have been interpreted to represent elliptic flow, ahydrodynamic phenomenon conjectured to play a major role in noncentralnucleus-nucleus collisions. $v_2$ measurements provide the main support forconclusions that a ``perfect liquid'' is formed in heavy ion collisions at theRelativistic Heavy Ion Collider (RHIC). However, conventional $v_2$ methodsbased on one-dimensional (1D) azimuth correlations give inconsistent resultsand may include a jet contribution. In some cases the data trends appear to beinconsistent with hydrodynamic interpretations. In this study we distinguishseveral components of 2D angular correlations and isolate a nonjet (NJ) azimuthquadrupole denoted by $v_2\{\text{2D}\}$. We establish systematic variations ofthe NJ quadrupole on $y_t$, centrality and collision energy. We adopttransverse rapidity $y_t$ as both a velocity measure and as a logarithmicalternative to transverse momentum $p_t$. Based on NJ quadrupole trends wederive a completely factorized universal parametrization of quantity$v_2\{\text{2D}\}(y_t,b,\sqrt{s_{NN}})$ which describes the centrality, $y_t$and energy dependence. From $y_t$-differential $v_2(y_t)$ data we isolate aquadrupole spectrum and infer a quadrupole source boost having unexpectedproperties. NJ quadrupole $v_2$ trends obtained with 2D model fits areremarkably simple. The centrality trend appear to be uncorrelated with a sharptransition in jet-related structure that may indicate rapid change of Au-Aumedium properties. The lack of correspondence suggests that the NJ quadrupolemay be insensitive to such a medium. Several quadrupole trends have interestingimplications for hydro interpretations.

Transverse-rapidity $\bf y_t$ dependence of the nonjet azimuth quadrupole from 62 and 200 GeV Au-Au collisions