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Discussion on 19-23 Aug, 2013

These are ideas and initial results of the challenges discussed in the Surrey workshop week. However, please feel free to post your mock data, grab the data and do your own challenge. Please also feel free to discuss off-line and build up collaborations.


Sharing the mock data.

Comparison among different dynamical modelling methods using various mock data.

Challenge A:

Who expressed their interests in participating

Bovy, McMillan, Chemin, Hunt, Buedenbender, Sharma, Roca-Fabrega, Monari, Inoue, Read, Steger


deriving 3D force fields from the mock data: measure force in 3D, F$_R$, F$_{\phi}$, F$_z$ as a function of R, $\phi$, z grid points


Grid in Galactic R, $\phi$, z

R: 3-20 kpc in radius

|z|: 0-4 kpc

$\phi$: +-45 deg (for Paper 1 below, no $\phi$ grid)

whoever got the first results can decide bin size.

mock data:

Smooth disc: McMillan model

Smooth N-body simulation: GD1 (1M particles, see above), D'Onghia disk (100 M)

input data:

- heliocentric equatorial coordinate: R.A. DEC, parallax, proper motion (mas/yr), radial velocity (km/s)

- position and motion (w.r.t. GC) of the Sun (R$_{Sun}$=8 kpc, z=0)

- selection function

  • RC tracer, solar metallicity with and without Gaia error G < 20.
  • Use radial velocity data for only G_RVS < 17
  • RC stars: M_G=1 mag, V-I=1.0, sig M_G=0
  • no extinction

data format:

ascii data

Challenge B:

Who expressed their interests in participaiting

Pfenniger, Monari, Hunt, Roca-Fabriga, Chemin


Recovering the pattern speed of the bar.

Mock Data

N-body Barred galaxy

-GD1 (Hunt)

-Debattista bar model

UB Test particle simulation with a bar potential

Input Data

* RC tracers

* with or without Gaia error

* with or without extinction

Challenge C:

1D vertical force field reconstruction


Cosmological simulations, multiple populations, dust extinction


Mock data available?

Cosmological simulations:


N-body: smooth, structured, barred, multi-compents, bulge

Test particles: bar potential, spiral arms

Analytic: smooth disk


GUMS: kinematic model, multiple populations, dust extinction

Challenges: what we want to analysis?

starting: GD1 without error

selection function - cutting within sphere - cutting |z|<1~0.1 kpc - known dust extinction

  1. - smooth disk exponential
  2. - Schlegel(?) map, Galaxia type dust
  3. - 3D extinction

- multiple populations

- Who is interested in what?

L. Chemin … derive rotation curve, DM vs. disk potential. Location of bar, resonance.

P. McMillan … N-body with error, the local+whole potential

S. Roca-Fabrega … Moment of distribution function, vertex deviation, bar pattern speed, spiral arm (number) position and perturbation

J. Bovy … vertical force.

J. Hunt … M2M modelling. disc structure, DM potential?

S. Sharma … analysing rotation curve

S. Inoue … vertical disc structure, local DM density

G. Monari … velocity distribution, local and radial gradient, with structures

Read/Steger … vertical force; local DM density

Challenge suggested by Barcelona team

Who expressed their interests in participating

Figueras, Antoja, Romero-Gomez, Monari, Aguilar, Mateu, Abedi, Roca-Fàbrega


To test which tools are useful to obtain information about spiral arms properties, in samples where extinction and Gaia errors have been implemented.

Following the work that L. Chemin started in the last year in Surrey, we can try to study the feasibility of using the TW method to find pattern speed of spirals. We can evaluate the method first in a pure simulation (without errors and extinction) and then in more realistic data that include Gaia errors and extinction.

It would be interesting to test when other tools like Fourier based ones are also useful.

mock data (will be uploaded soon):

Test particle simulations with single spirals and also with spirals + bar.

Tools to add realistic extinction and Gaia errors.

tests/discs/gc2013_discussion.txt · Last modified: 2014/11/03 09:25 by kawata