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CDM cusps in LSB galaxies by means of stellar kinematics

CDM cusps in LSB galaxies by means of stellar kinematics. Pizzella, E.M.Corsini, F. Bertola Università di Padova And J. Magorrian, M. Sarzi University of Oxford. Summary. Introduction Observational results Long-slit spectroscopy (FORS2) IFU-VIMOS Dynamical modeling

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CDM cusps in LSB galaxies by means of stellar kinematics

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  1. CDM cusps in LSB galaxies by means of stellar kinematics Pizzella, E.M.Corsini, F. Bertola Università di Padova And J. Magorrian, M. Sarzi University of Oxford

  2. Summary • Introduction • Observational results • Long-slit spectroscopy (FORS2) • IFU-VIMOS • Dynamical modeling • Does gas move in circular orbits in the inner regions ? • Cursy or not cuspy DM profiles ?

  3. Introduction LSB  μB,0 > 22.6 mag/”” • They are believed to be dark matter dominated • Test the prediction of cosmological simulations (Navarro et al. 1997, ApJ, 490, 493).  gas velocity curves. However this approach turned out to giveambiguousresults. • stellar disk and the dark halo produce rotation curves very similar in shape; • it is never very clear up to which point the disk is responsible for the inner part of the rotation curve (deBlok, McGaugh & Rubin, 2001, AJ 122, 2396).

  4. Additional osservational problems are: • Centering of the slit; • Non circular motion of the ionized gas; A way to solve this problems is: • 2-D spectroscopy of the nuclear region • Use the stellar kinematics:  Stellar and gaseous kinematics of major and minor axes (+ IFU for 2D gas kinematics).

  5. Data for 11 galaxies: LSB with a bulge

  6. 2.5’x2.5’ ESO 234 –13 V=4703km/s Sbc

  7. FORS2 Spectroscopy (~2h integration)

  8. Dynamical models of the stellar kinematics • Galaxy is assumed to be axisymmetric (biggest assumption in the whole process) • Stellar light distribution by deprojecting the galaxy image. • Constant M/L of the stellar component • DM halo r • Velocity ellipsoid shape/orientation free parameter. • Jeans equations give kinematics • Fit parameter using Metropolis algorithm NOTE:no use of gas kinematics

  9. 2.5’x2.5’ ESO 186 –55 V=4640km/s Sa

  10. Dynamical model for ESO 186-55 Major axis minor axis

  11. The density radial profile Total Mass density (model) Last data point seeing Deprojected Light

  12. Circular velocities predicted from model Ionized gas

  13. continuum Velocity field H flux [NII] flux Velocity field  field ESO 186-55 IFU-VIMOS

  14. Ionized gas turbulent motion Circular model Residual

  15. Summary • Gas kinematics: non circular motions are significative in the ionized gas kinematics when studying the inner regions. Evidence from • long-slit minor axis • IFU velocity field • Comparision with stellar kinematics mass models • Stellar kinematics (2 models untill now): in the inner region • mass follows light • DM is not cuspy

  16. The End

  17. end

  18. ESO 446-17V=4193km/sSb 1’=16kpc

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