====== Challenge 4: M4 ======

===== Method comparison: N-body model of M4 =====


The mock data is a snapshots of large N-body simulation of the globular cluster M4 are [[http://datashare.is.ed.ac.uk/handle/10283/618?show=full|available here]]. Full lists of data for all particles (mass, position, velocity, stellar type, stellar radius, V magnitude, B-V colour) are given at almost 400 instants in the lifetime of the model. The simulation is described in this paper [[http://arxiv.org/abs/1409.5597]], which should be cited when making use of this data.


We selected the snapshot at t = 12023.9 Myr. A distance modulus of 11.35 mag was adopted (i.e. D=1862.1 pc). The cluster properties are:
  - Mtot = 69144.5 M_sun
  - L_V = 35547.1 L_V_sun
  - M/L_V = 1.95 Msun/L_V_sun
  - <m> = 0.495 Msun
  - r_h = 3.14 pc
  - r_eff = 1.43 pc
  - N neutron stars = 130
  - N black holes = 2
  - Mass in remnants = 27176.4 Msun


We do the comparison in 3 steps:
  - Step 1: Surface brightness profile + RVs
  - Step 2: Surface brightness profile + RVs + PMs ('HST')
  - Step 3: Surface brightness profile + RVs + PMs ('HST' + 'Gaia')
(+ local mass function for methods allowing it).

** DOWNLOAD NEW M4 MOCK DATA (updated 21/03/2017)**: All the mock data you will need (and more!) are available and bundled [[https://www.dropbox.com/s/8kish5scgry2nbh/M4_mocks.tar.gz?dl=0|here]]. You can find a summary of the list of files in 'ReadMe_M4_mocks'.

Included are the surface brightness profile, line-of-sight dispersion profile and discrete velocities for RGB stars, HST-like PM dispersion profiles and discrete velocities, Gaia-like (end-of-mission) PM dispersion profiles and discrete velocities (for M4, bulge and halo-like backgrounds), number density profile for bright stars, and local mass function. Mass profiles and the M/L_V profiles (in projection and 3d) are also available. Predictions from best-fit models should be compared to the 3d M/L_V profile.