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We study the total mass-density profile for a sample of 14 fast-rotatorearly-type galaxies (stellar masses $10.2<\log M_\ast/M_\odot<11.7$). Wecombine observations from the SLUGGS and Atlas3D surveys to map out the stellarkinematics in two-dimensions, out to a median radius for the sample of fourhalf-light radii $R_e$ (or 10 kpc), and a maximum radius of 2.0-6.2 $R_e$ (or4-21 kpc). We use axisymmetric dynamical models based on the Jeans equations,which allow for a spatially varying anisotropy, and employ quite generalprofiles for the dark halos, and in particular do not place any restriction onthe profile slope. This is made possible by the availability of spatiallyextended two-dimensional kinematics. We find that our relatively simple modelsprovide a remarkably good description of the observed kinematics. The resultingtotal density profiles are well described by a nearly-isothermal power law$\rho_{\rm tot}(r)\propto r^{-\gamma}$ from $R_e$/10 to at least 4$R_e$, thelargest average deviation being 11%. The average logarithmic slope is$\langle\gamma\rangle=2.19\pm0.03$ with observed rms scatter of just$\sigma_\gamma=0.11$. This scatter out to large radii, where dark matterdominates, is as small as previously reported by lensing studies around$r\approx R_e/2$, where the stars dominate. Our bulge-halo conspiracy placesmuch tighter constraints on galaxy formation models. It illustrates the powerof two-dimensional stellar kinematics observations at large radii. It would nowbe important to test the generality of our results for different galaxy typesand larger samples.

Small scatter and nearly-isothermal mass profiles to four half-light radii from two-dimensional stellar dynamics of early-type galaxies