CDM cusps in LSB galaxies by means of stellar kinematics

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CDM cusps in LSB galaxies by means of stellar
kinematics

• Pizzella, E.M.Corsini, F. Bertola
• Università di Padova
• J. Magorrian - Univ. of Oxford
• and
• M. Sarzi Univ. of Hertfordshire

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Summary

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

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Introduction

• LSB ? µB,0 gt 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).

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• Additional osservational problems are (McGaughs
  talk)
• Centering of the slit, beam smearing, etc.
• Non circular motion of the ionized gas
• A way to solve this problems is
• 2-D spectroscopy of the nuclear region (Simon et
  al. 2005, Kunzio de Naray et al. 2006)
• Use the stellar kinematics (thanks Anatoly)
• ?
• Stellar (and gaseous) kinematics of major and
  minor axes ( IFU for 2D gas kinematics).

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Data for 11 galaxies LSB with a bulge (like in
Beijersbergen et al. 1999)
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2.5x2.5

• ESO 186 55
• Sa

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FORS2 Spectroscopy (2h integration)
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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? in the center
• Velocity ellipsoid shape/orientation free
  parameter.
• Jeans equations give kinematics
• Fit parameter using Metropolis algorithm
• NOTE no use of gas kinematics

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Dynamical model for ESO 186-55
Major axis
minor axis
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The density radial profile
Total Mass density (model)
Last data point
seeing
Deprojected Light
20 of DM within 25
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Pressure supported ionized gas? (Bertola et al.
1995)
Circular velocities predicted from model
Ionized gas
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ESO 186-55 IFU-VIMOS
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Ionized gas - non ordered motion
Circular model
Residual
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2.5x2.5

• ESO 234 13
• Sbc

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(No Transcript)
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Major axis
minor axis
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model
Last data point
seeing
Deprojected Light
50 of DM within 25
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Circular velocities from dynamical model
Ionized gas
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Summary

• Gas kinematics non ordered 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 less scatter than the ionized
  gas data. (2 models untill now) in the inner
  region
• mass follows light
• DM with constant density core is preferred