CDM cusps in LSB galaxies by means of stellar kinematics

A. Pizzella, E.M.Corsini, F. Bertola

Università di Padova

And

J. Magorrian, M. SarziUniversity of Oxford

Introduction Observational results

Long-slit spectroscopy (FORS2)

IFU-VIMOS

Dynamical modelingDoes gas move in circular orbits in the inner regions ?Cursy or not cuspy DM profiles ?

Summary

IntroductionLSB 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 give ambiguous results.

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 (de Blok, McGaugh & Rubin, 2001, AJ 122, 2396).

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 regionUse the stellar kinematics:

Stellar and gaseous kinematics of major and minor

axes (+ IFU for 2D gas kinematics).

Data for 11 galaxies: LSB with a bulge

ESO 234 –13V=4703km/s

Sbc

2.5’x2.5’

FORS2Spectroscopy(~2h integration)

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

ESO 186 –55V=4640km/s

Sa

2.5’x2.5’

minor axis

Major axis

Dynamical model for ESO 186-55

Total Mass density (model)

Deprojected Light

The density radial profile

seeing

Last data point

Ionized gas

Circular velocities predicted from model

ESO 186-55 IFU-VIMOS

Velocity field

H flux [NII] flux

field

continuum

Velocity field

Circular model Residual

Ionized gas turbulent motion

Summary1. Gas kinematics: non circular motions are

significative in the ionized gas kinematics when studying the inner regions. Evidence from

a. long-slit minor axisb. IFU velocity fieldc. Comparision with stellar kinematics mass models

2. Stellar kinematics (2 models untill now): in the inner region

a. mass follows lightb. DM is not cuspy

The End

end

ESO 446-17V=4193km/sSb

1’=16kpc