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Rotation Curves of Disk Galaxies New
Perspectives
A. Burkert LMU G. Gentile UNM G. Józsa AIfA F.
Kenn AIfA U. Klein AIfA C. Niemczyk
AIfA T. Oosterloo ASTRON A. Pizzella Padova P. Sa
llucci SISSA C. Struve AIfA

• DM and rotation curves
• centres cores or cusps?
• peripheries warps!

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History

• J. Oort (1933) vz of stars
• F. Zwicky (1933) sv in the Coma cluster of
  galaxies
• V. Rubin (1980) galaxies H? rotation curves
• A. Bosma (1981) galaxies HI rotation curves
• COBE (1992) CMB DM on cosmic scales

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disk galaxies circular velocities
expected Kepler rotation
observed
Dark Halo
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DM potential measure circular rotation speed
VDM(R) and infer ?DM(R) using
for circular orbits in a spherical dark halo. So
measure Vtot (R), V (R), Vgas (R), and deduce
VDM (R)
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DM models

• 90s numerical models of cold dark matter
  (?CDM) Navarro et al. (1996), Moore et al.
  (1998)
• very successful on large scales
• ? possibility to test (verify / falsify)
  something!
• ? larger number of observational efforts / more
  focussed

• problems CDM crises
• 1. predicted cusps in galaxy centres not
  favoured by observations (gt 30 papers over
  last years)
• 2. angular momentum (simulated baryonic disks
  too small)
• 3. missing satellites
• cemented H0, O0, O?, Om, Ob ,

• Burkert (1995) empirical law, complying with
  observations of dwarf galaxies

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NFW
Burkert
Moore et al. (1999)
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• shortcomings on the observational side
  limitations of observed rotation curves (van den
  Bosch et al. 2000 Swaters et al. 2003)
• - optical (H?) extinction, limited radial
  extents, poor spectral resolution (?V ? 20 km
  s-1), mostly slit spectroscopy
• slit orientation
• - radio (HI) poor spatial resolution in the
  central regions
• - sensitivity HI still the best ...

• one can do better optimum combination of CO and
  H? (inner parts) and HI (outer parts), ?V ? 6
  km s-1

?DM(r) !
DM exists
MDM/Mlum

• progress

observations (HI, H?, CO) more than 30 papers
on (no) cusps ...
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Rotation curves

• Three main tracers
• HI ? 21 cm
• H? ? 6563 Å data cube
• CO ? 2.6, 1.3, ... mm

e.g. HI line velocity (peak, Gauss fit, 1st
moment) column density
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analysis in elliptical rings
PV diagramme cut along major axis
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LB 0.5 ? L
LB 0.06 ? L
LB 0.005 ? L
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• rotation curves, traditionally via
• tilted-ring analysis yields - Vsys
  - position angle - inclination

• asymmetric HI line profiles
• - tails towards systemic velocity -
  projected emission from thick disk

• need to account for - instrum. ?V
  broadening - beam smearing - interst.
  turbulence

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Tracer angular spectral resolution
resolution H?, 0.5" 1.5" 10 30 km s-1
HI 7" 30" 4 10 km s-1 CO 1.5" 8"
5 20 km s-1
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Cusps or cores? G. Gentile, P. Salucci, U.
Klein, D. Vergani, P. Kalberla (MNRAS 351, 903,
2004)

• sample of spiral galaxies with - precise optical
  RCs - moderate (L ? L) luminosities - late
  type (small bulges) - well known distances
• optical RCs and photometry from Persic Salucci
  (1995)

culled from high-quality selection of optical
rotation curves by Persic Salucci (1995)
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HI distributions (column densities)
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PV diagrams rotation curves
rotation curves out to ? 3 Ropt
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Comparison with models

• Fits to numerical models
• ?CDM - NFW - Moore
• empirical - Burkert - Salucci URC
  
• others - scaled gaseous disk (HI) -
  MOND

cusps or cores ?
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Burkert
NFW
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• Results
• Burkert profiles - better fits
  (?2) - consistent M/L and a Rc/Ropt

• NFW profiles - clearly worse (?2), in
  some cases dramatically
• - M/L flagrantly low in some cases - Mvir too
  high - observed V(R) in conflict with
  central cusps

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NGC 6822
Weldrake et al. (2003)
DDO 47
Salucci et al. (2003)
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Can vertical motions smear out cusps? harmonic
analysis of velocity field à la Schoenmakers
(1999)
C0 Vsys C1 Vrot sin i S1 Vrad sin i etc.
DDO 47
Gentile et al. (2005)
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• Conclusions
• low-luminosity / low-mass galaxies lack CDM cusps
• (empirical) Burkert profile seems to fit better
• non-circular (radial or vertical) motions not
  significant
• MOND does not provide a way out

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Warps in galaxies

• possible causes
• tidal forces
• IGM (gas infall)
• (non-spherical) DM halos

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• Warps in galaxies a frequent phenomenon!
• Reshetnikov Combes (1998 1999)
• - about 40 of late-type galaxies exhibit
  ?-shaped warps
• - tidal interaction a likely cause
• - no large-scale alignment
• García-Ruiz (2001)
• - all galaxies with an HI disk that is more
  extended than the optical are warped
  (corollary all disk galaxies are warped)
• - stronger and more asymmetric warps in more
  rich environ- ments
• - but also warps in isolated galaxies ? other
  mechanisms

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most pronounced in the HI line!
NGC 4013
NGC 5055
Battaglia et al. (2006)
Bottema et al. (1996)
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the conspicuous galaxy ESO 123-G23 HI gas 15 kpc
out of the plane??
ESO 123-G23
Gentile et al. (2003)
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Data and models
Data
Warp
Flare
2 - C
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G. Gentile, Fraternali, P., Klein, U., P.
Salucci, P. (AA 405, 969, 2003)
parameters ? 35º (strong warp!) ? ? 0º
(close to l.o.s)
view of warp
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Warp shapes
View
inclined, opaque
edge-on, opaque
edge-on, translucent
Most warps are grand-design S-shaped
warps (García-Ruiz et al. 2002, Sánchez-Saavedra
et al. 2003)
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Extracting parameters from HI data cubes of
warped galaxies
Measured (HI) data cube ? ? ?
moment 1 (or peak velocities) tilted-ring
analysis initial model - systemic
velocity - inclination - position angle
model cube ? convolution ? subtract data
cube ? check ?2 better / worse?
new parameters, each ring (Vsys , Vrot , centre,
i, p.a., w.a.)
TIRIFIC (G. Józsa, 2006)
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Kinematics and morphology of warped disk
galaxies G. Józsa, F. Kenn, T. Oosterloo, U.
Klein (in prep.) - galaxies with strong
symmetric HI warps - HI observations with
WSRT - optical photometry with INT Study
galaxies in 3 dimensions, i.e. determine - inclin
ation i (R) - position angle
p.a. (R) - systemic velocity Vsys (R) - warp
angle w.a. (R) - centre ?0 (R),
?0 (R) HI disks of galaxies were previously
deemed to have cut-off radii at NHI ? 1019
cm-2 but they are (fortunately) larger!
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Large warps e.g. NGC 5204
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NGC 5204
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NGC 755
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NGC 755
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edge-on galaxies exhibit this
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fully in line with Dekel Shlosman
(1983) Toomre (1983)
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• Conclusions
• warps are a frequent phenomenon in galaxies
• warped galaxies possess flat inner disk
• warps start where - optical disk has
  faded away
• - HI surface brightness reaches a constant,
  low level
• 4. rotation velocity changes with orientation of
  the disk
• ? non-spherical DM halo?
• 5. two coherent kinematic regimes, each with
  constant LON

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Thanks a lot for the kind hospitality!
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data cubes of
a differentially rotating galaxy
an expanding shell
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Large HI disks
DDO 54 - D 3.2 Mpc - Rho 1.4
kpc - MB -13.33 - Mtot ? 3 109 M? - MHI
/ M ? 5.1 - MDM / Mlum ? 12 Carignan
Freeman (1988) Carignan Purton (1998)
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- 4 ? 12 hrs. WSRT - fast data reduction -
warped, asymmetric!
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• NGC6946 HI mosaic
• (Oosterloo et al.)
• 16 12 hrs.
• prominent holes
• anomalous velocities
• outer spiral structure with
• large streaming motions

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UGC 2885 super-massive spiral (Lewis
1985) - D 120 Mpc - RHI 108
kpc - Mtot 2.2 1012 M?
100 kpc
100 kpc
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Outlook

• past decade has seen enormous progress in
  theory models much more realistic (baryonic
  component)
• observations are (and will be) improving
  considerably HI out to many Ropt CO
  towards inner 100 200 pc (2 ? 1 line, D ? 20
  Mpc)
• instrumental artefacts can be overcome

• giant future telescopes (ALMA, NGST, SKA,
  ...) - RCs out to z 0.5 (CO, CI) - TF
  relation out to z 3 5