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Date and Time of the Query: 2019-06-26 T01:27:58 PDT
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For refcode 2015ApJ...804L..21C:
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Copyright by American Astronomical Society. Reproduced by permission
2015ApJ...804L..21C Small Scatter and Nearly Isothermal Mass Profiles to Four Half-light Radii from Two-dimensional Stellar Dynamics of Early-type Galaxies Cappellari, Michele; Romanowsky, Aaron J.; Brodie, Jean P.; Forbes, Duncan A.; Strader, Jay; Foster, Caroline; Kartha, Sreeja S.; Pastorello, Nicola; Pota, Vincenzo; Spitler, Lee R.; Usher, Christopher; Arnold, Jacob A. Abstract. We study the total mass--density profile for a sample of 14 fast-rotator early-type galaxies (stellar masses 10.2<~ log {{M}_*_}/{{M}_o_}<~ 11.7). We combine observations from the SLUGGS and ATLAS^3D^ surveys to map out the stellar kinematics in two dimensions, out to a median radius for the sample of four half-light radii R_e_ (or 10 kpc) and a maximum radius of 2.0--6.2 R_e_ (or 4--21 kpc). We use axisymmetric dynamical models based on the Jeans equations, which allow for a spatially varying anisotropy; employ quite general profiles for the dark halos; and, in particular, do not place any restrictions on the profile slope. This is made possible by the availability of spatially extended two-dimensional kinematics. We find that our relatively simple models provide a remarkably good description of the observed kinematics. The resulting total density profiles are well described by a nearly isothermal power law {{rho}_tot_}(r) is proportional to {{r}^-gamma^} from R_e_/10 to at least 4R_e_, the largest average deviation being 11%. The average logarithmic slope is < gamma > =2.19+/- 0.03 with observed rms scatter of just {{sigma}_gamma_}=0.11. This scatter out to large radii, where dark matter dominates, is as small as previously reported by lensing studies around r ~ R_e_/2, where the stars dominate. Our bulge--halo conspiracy places much tighter constraints on galaxy formation models. It illustrates the power of two-dimensional stellar kinematics observations at large radii. It is now important to test the generality of our results for different galaxy types and larger samples. Key words: galaxies: elliptical and lenticular, cD, galaxies: formation, galaxies: kinematics and dynamics, galaxies: structure
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