cdm cusps in lsb galaxies by means of stellar kinematics a.pizzella, e.m.corsini, f. bertola...
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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