User Tools

Site Tools


GC2: Challenge 3

Simulated observations and biases

PI: Antonio Sollima
Other participants: Eduardo Balbinot, Mark Gieles, Alice Zocchi, Anna Lisa Varri, Vincent Henault-Brunet

Questions to address:

  1. How different are the fits when considering: 1) all stars and 2) only visible stars?
  2. Is it better to consider luminosity weighted profiles, or number density profiles?
  3. How much can we do with 2 velocity components instead of 1 (i.e. with Gaia data)?

Snapshots from Sections C and D of the Mock data page can be used for this challenge.

Including GAIA realistic errors

Using PyGaia 0.6 and the NBODY snapshots in Sections B.


  1. Assume a position for the cluster in the Galaxy (X,Y,Z taken from Harris catalogue)
  2. Transform phase-space coordinates to observed ones (pygaia.astrometry.vectorastrometry.phaseSpaceToAstrometry)
  3. Compute errors using parallaxErrorSkyAvg and parallaxErrorSkyAvg
  4. Back to phase-space with ´astrometryToPhaseSpace

On the plots bellow the red dots are computed using error free data and the black dots using the GAIA error model. The quantity shown is the on-sky velocity dispersion versus the distance to the cluster centre.

Cluster @ 3kpc

Cluster @ 5kpc

Cluster @ 8kpc

Cluster @ 10kpc

Other plots:

CMD in GAIA photometric system for stars in the snapshot (in this example the cluster is at 3kpc)

Observed three component velocities (black) and real ones (red) as a function of observed GAIA BP magnitude

tests/collision/gc2_archive/challenge3.txt · Last modified: 2015/08/31 13:38 by v.henault-brunet