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Ideas for additional challenges

Weighing dark remnants using luminous stars

Explore how/if the mass function of dark remnants can be constrained from a limited set of observables, using mock data from N-body simulations. This could be part of Miklos’ project on Challenge 2. Provided that this works, we can then consider a direct application to real data (e.g. Gaia-ESO survey - some of us are members of the consortium).

Dark remnants & IMBH

Laura is applying her discrete Jeans modelling method to snapshots of N-body models that contain stellar-mass black holes. The idea is check if a concentration of dark remnants near the centre can be mistaken for an intermediate-mass black hole.

Pal 5 model from Andreas Kuepper in streams section

Same analyses as in Challenge 2 and 3, but with cluster on eccentric orbit and “polluting” stars from tidal tails. The models posted in the streams section were not evolved with stellar evolution and for a Hubble time, but Andreas sent me files for that. Will upload them if there is interest.

Models with initial rotation

Different models with angular momentum are within the group: collapsing spheres, cold fractal collapse, cluster mergers.

Collapse of homogeneous spheres with angular momentum

Below snapshots of 3 cold(ish) collapses of homogeneous spheres with angular momentum. Initial virial ratios and angular momentum were taken from the 3 models described in Gott (1972). The models contain 2e5 stars, a Kroupa IMF between 0.1 and 100 Msun and snapshots are at t=30 [NBODY]. The amount of rotation is quantified with Peebles $\lambda$ parameter in the title:

  1. rot_collapse_lam0.127.gz NEW! Tuesday August 20
  2. rot_collapse_lam0.168.gz NEW! Tuesday August 20
  3. rot_collapse_lam0.212.gz NEW! Tuesday August 20



Merger between 2 clusters of equal mass, equal containing 1e5 stars, a Kroupa IMF between 0.1 and 100 Msun. The initial orbit of the cluster pair had zero energy and different angular momentum. The

  1. rot_merger_lam0.128.gz NEW! Tuesday August 20

For both collapse and mergers collapse contain:

$M$ $X$ $Y$ $Z$ $V_x$ $V_y$ $V_z$
[$M_\odot$] [NBODY] [NBODY]

Collapse of non-homogeneous spheres with angular momentum

(Based on simulations ran by Anna Lisa Varri, see Ref1 Ref2)

Below snapshots of two cold(ish) collapses of isolated spheres with N=64k, equal mass stars, non-homogeneous initial density distribution (fractal dimension D = 2.8, 2.4, as in the file name), and approximate solid-body rotation. The configurations are characterized by the same initial values of virial ratio and global angular momentum as in the homogeneous case #3 (with $\lambda=0.212$). The simulations have been performed with STARLAB and the snapshots are taken at T=20 [NBODY].

  1. rot_collapse_fracd2.4.gz NEW! Tuesday August 20
  2. rot_collapse_fracd2.8.gz NEW! Tuesday August 20

The file header contains: N, T, coordinates and velocities of the center of mass. The file format is as follow:

$ID$ $M$ $X$ $Y$ $Z$ $V_x$ $V_y$ $V_z$

Mass modelling multiple-population GC with non-parametric method

Apply Pascal Steger's non-parametric method (developed for dwarf galaxies) to mock data from N-body simulation of globular cluster with two distinct chemical populations.

The data has the following format.

$m$ $x$ $y$ $z$ $v_x$ $v_y$ $v_z$ population
[Msun] [pc] [pc][pc] [km/s] [km/s] [km/s] [1 or 2]

More ideas (but no mock data for these yet)

  1. What is the effect of binary stars?
  2. Is there a dynamical “smoking gun” for an intermediate mass black hole?
tests/collision/new_challenges.txt · Last modified: 2022/10/24 12:27 by