Dynamics of
Planatary
Rings and Galaxies
Dynamics of Planetary Rings and Galaxies
(Dr. Heikki Salo, Division of Astronomy, Department of Physical Sciences, University of Oulu, Finland)
Lyhyt suomenkielinen kuvaus tutkimuksista
The current research topics of our group include:
- Planetary ring dynamics
- Satellite resonances
- Dynamics and observations of interacting galaxies
- Dynamics of barred galaxies
- Development of numerical N-body simulation methods
At the moment the group consists of following members:
- Dos. Heikki Salo (planetary rings, galaxy dynamics and observations)
- Dos. Eija Laurikainen (galaxy dynamics and observations)
- Dr. Ryuji Morishima (planetary rings)
- Dr. Pertti Rautiainen (galaxy dynamics and observations)
- M.Sc. Raine Karjalainen (planetary rings)
- + 3 undergraduate students
The most important current collaborations are with the University of
Alabama (Ron Buta), the Wellesley College (Richard French), and the
University of Potsdam (Jürgen Schmidt, Frank Spahn).
Our recent planetary ring studies have concentrated on dense
rings, especially the role of self-gravity. The most important result
has been the numerical prediction of small-scale wake structure in
Saturns's rings (Nature 359, 619). We are investigating the
observational implications of such wakes with photometric
MC-simulation, and comparing the results to Voyager data, and to HST
observations by Dick French. Other current interest is the apparantly
irregular density variations in Saturn's B-ring: we are studying the
properties of such extremely dense rings both with N-body simulations
and with hydrodynamical stability analysis, in collaboration with
Frank Spahns's group in Potsdam.
Our previous satellite resonance studies have dealt with the
angular momentum exchange between rings and satellites, confirming
numerically the validity of Goldreich-Tremaine predictions, and to
some degree extending them to non-linear regime. Also, we have
demonstrated the possibility of one-sided confinement of narrow
ringlet in the 2:1 ILR of external satellite. Our recent studies have
dealt with the azimuthally incomplete ring arcs of Neptune. We have
shown (Science 282, 1102) that self-gravity of massive arc particles
can stabilize them agains mutual impacts, and help to confine dust to
the arc region in general. We are currently seaking for possible
explanations for the recently observed shift between the locations of
the arcs and the predictions of the Porco-Goldreich-Tremaine-model.
Our studies of interacting galaxies concentrate on the
observed properties and N-body modelling of M51-type closely
interacting galaxies. Observations include both visual and IR
broad-band imaging, and Fabry-Perot velocity fields. Fairly detailed
tidal models have been constructed for two systems, Arp 86 and the M51
itself. Our current interests concentrate on the innermost spiral
structures, and the interplay between intrinsic spiral modes and
externally induced tidal waves.
The other main application of our N-body modelling of galaxies
have been the barred galaxies , especially the ring structures related
to the resonances of the rotating bar. For example, a detailed N-body
model has been developed for IC 4214, a prototypical weakly barred
galaxy, using ring morphology and kinematics as diagnostics for the
bar strength and pattern speed. Recent studies concentrate on the
outer spiral modes, and their relation to the dominant bar mode: for
example we address the non-linear mode coupling.
We are also studying the observed properties of bars
in collaboration with Ron Buta, and their correlations with the
gravitational perturbations associated with bars, derived from near IR-images.
Starting almost 20 years ago, various N-body methods have
been developed in our group, first for planetary ring simulations and
later also for galaxy studies. The main current methods include
- Local simulations of planetary rings, including dissipative
collisions and self-gravity.
- Numerical codes for long-term integration of particle-satellite
interactions, including radiative pressure.
- 3D multi-grid code for simulation of interacting galaxies, composed
of self-consistent disk+bulge+halo systems with both stars and gas.
Recent Publications:
-
Salo, H. & Hänninen, J. (1998): Neptune's Partial Rings:
Action of Galatea on Self-Gravitating Particles. Science 282,
1102-1104.
-
Moss, D., Korpi, M., Rautiainen, P. & H. Salo (1998): The
evolution of dynamo maintained magnetic fields in a barred spiral
galaxy. Astron. Astrophys. 329, 895-905.
-
Laurikainen, E. & Salo, H. & Aparacio, A. (1998): BVRI Imaging
of M51-type Interacting Galaxy Pairs. Astron. Astrophys. Suppl. 129,
517-540.
-
Moss, D., Rautiainen, P. & H. Salo (1999): A dynamo model for
the magnetic field of the weakly barred galaxy IC 4214.
MNRAS, 303, 125-132.
-
Buta, R., Purcell, G.B., Cobb, M., Crocker, D.A., Rautiainen, P., &
Salo, H. (1999): The Structure and Dynamics of the Early-Type
Resonance Ring Galaxy IC 4214. I. Observations. Astron. J. 117,
778-791.
-
Salo, H., Rautiainen, P., Buta, R., Purcell, G.B., Cobb, M., Crocker,
D.A., & Laurikainen, E. (1999): The Structure and Dynamics of the
Early-Type Resonance Ring Galaxy IC
4214. II. Models. Astron. J. 117, 792-810.
-
Salo, H. & Laurikainen, E. (1999): Inner Structure of M51.
Astrophys. Space Sci. 269-270, 589-592.
-
Salo, H. & Laurikainen, E. (1999): A multiple encounter model of M51.
Astrophysics and Space Science 269-270: 663-664.
-
Schmidt, J., Salo, H., Petzshman, O. & Spahn, F. (1999):
Vertical distribution of temperature and density in a planetary ring.
Astron. Astrophys. 345, 646-652.
-
Rautiainen, P. & Salo, H. (1999): Multiple pattern speeds in barred
galaxies. Astron. Astrophys. 348, 737-754.
-
Laurikainen, E. & Salo, H. (2000): BVRI Imaging of M51-type
Interacting Galaxy Pairs II. Bulge and disk parameters. Astronomy
Astrophys. Suppl. 141, 103-111 (+19 pages in electronic form)
-
Spahn, F., Schmidt, J., Petzschmann, O. & Salo, H. (2000):
Stability analysis of a Keplerian disk of granular grains: influence
of thermal diffusion. Icarus 145, 657-660.
-
Rautiainen, P. & Salo, H. (2000) N-body simulations of resonance rings
in galactic disks. Astron. Astrophys. 362, 465-485.
-
Salo, H. & Laurikainen, E. (2000): N-body model for M51: I. Multiple
encounter vs. single passage?. MNRAS 319, 377-392 .
-
Salo, H. & Laurikainen, E. (2000): N-body model for M51: II. Inner
structure. MNRAS 319, 393-413.
-
Laurikainen, E. & Salo, H. (2001) : BVRI Imaging of M51-type
Interacting Galaxy Pairs III. Analysis of the photometric
parameters. MNRAS 324, 685-698.
-
Salo, H., Schmidt. J. & Spahn, F. (2001) : Viscous overstability
in Saturn's B-ring: I. Direct simulations and measurement of transport
coefficients. Icarus 153, 295-315.
-
Schmidt. J., Salo, H., Spahn, F. & Petzschmann, O. (2001) :
Viscous overstability in Saturn's B-ring: II. Hydrodynamic theory and
comparison to simulations. Icarus 153, 316-331.
-
Salo, H. & Laurikainen, E. (2001): N-body models of M51: From
extended tail to central spiral structure. Astron. Astrophys
Trans. 20, 93-101.
-
Laurikainen, E, Salo, H. & Rautiainen, P.(2002): Comparison of bar
strengths in active and non-axtive galaxies. MNRAS , 331,
880-893
-
Rautiainen, P., Salo, H & Laurikainen, (2002) : Simulations of central
structure in barred galaxies. MNRAS 337, 1233-1244.
-
Laurikainen, E, Salo, H. (2002): Bar strengths in spiral galaxies
estimated from 2MASS images. MNRAS 337, 1118-1138.
-
Schmidt, J, Salo, H. (2003) : A weakly nonlinear model for
oscillatory instability in Saturn's dense rings. Phys. Rev. Lett
90, 061102-1 - 061102-4
-
Bergvall N., Laurikainen E., Aalto S. (2003): Galaxy interactions -
poor starburst triggers: A study of a complete sample of interacting
galaxies. III. Accepted to Astron. Astrophys.
-
Salo, H, Karjalainen, R (2003): Photometric modeling of Saturn's
rings: I. Monte Carlo method and the effect of non-zero volume
filling factor. Icarus 164, 428-460.
Invited talks:
- Salo, H. (1999):
``Numerical exploration of planetary ring dynamics'', 215th WE-Hereaus Conference on Granular Gases, Bad Honnef, Germany, 8-13.3.1999
- Salo, H. and Laurikainen, E. (2000):
``Simulation modelling of M51: from extended tail to inner spiral
structure'', European Astronomical Society, JENAM-2000, Moscow, 29.5-4.6.2000
- Salo, H., Scmidt, J., Spahn, F (2002): ``Viscous stability properties of dense planetary rings'', Granular Gases: Theory-Experiments-Simulations Conference, CECAM, Lyon, France, 2-5.9.2002
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