CDM cusps in LSB galaxies by means of

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

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

Introduction LSB μB, 0 > 22. 6 mag/”” v They are believed to be dark matter dominated v Test the prediction of cosmological simulations (Navarro et al. 1997, Ap. J, 490, 493). gas velocity curves. However this approach turned out to give ambiguous results. Ø stellar disk and the dark halo produce rotation curves very similar in shape; Ø it is never very clear up to which point the disk is responsible for the inner part of the rotation curve (de Blok, Mc. Gaugh & Rubin, 2001, AJ 122, 2396).

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

Data for 11 galaxies: LSB with a bulge

2. 5’x 2. 5’ ESO 234 – 13 V=4703 km/s Sbc

FORS 2 Spectroscopy (~2 h integration)

Dynamical models of the stellar kinematics ü ü ü ü 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

2. 5’x 2. 5’ ESO 186 – 55 V=4640 km/s Sa

Dynamical model for ESO 186 -55 Major axis minor axis

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

Circular velocities predicted from model Ionized gas

continuum ESO 186 -55 IFU-VIMOS Velocity field H flux [NII] flux Velocity field

Ionized gas turbulent motion Circular model Residual

Summary 1. Gas kinematics: non circular motions are significative in the ionized gas kinematics when studying the inner regions. Evidence from a. long-slit minor axis b. IFU velocity field c. Comparision with stellar kinematics mass models 2. Stellar kinematics (2 models untill now): in the inner region a. mass follows light b. DM is not cuspy

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ESO 446 -17 V=4193 km/s Sb 1’=16 kpc