By L. Girardi et al. (2005)
What it does
TRILEGAL (TRIdimensional modeL of thE GALaxy) describes the Galaxy as components, each with a density law, a star-formation history and an age-metallicity relation: thin disc, thick disc, halo and bulge, plus an optional extra object such as a cluster or a dwarf galaxy. For a field, it integrates each component along the line of sight, draws stars from isochrones with an initial mass function, and applies extinction.
It returns a catalogue with each star's age, metallicity, mass, luminosity, temperature, surface gravity, distance, extinction and apparent magnitudes. The code is by L. Girardi, M. A. T. Groenewegen, E. Hatziminaoglou and L. da Costa (2005). The web form is hosted by INAF, Osservatorio Astronomico di Padova.
How I used it
I used TRILEGAL to generate synthetic stellar populations of multiple globular clusters as part of the HAYDNsim pipeline, for the noise forecasts of the proposed HAYDN space mission, as shown on my TASC10/KASC17 poster (2026).
The animation
The animation illustrates TRILEGAL's method after Girardi et al. (2005). No TRILEGAL run produced it. Each star's temperature, gravity and luminosity are points of a public grid of stellar isochrones computed with MESA, and their Gaia magnitudes come from the Casagrande and VandenBerg tables.
The density shapes of the components (laws and scales after Girardi et al. 2005, stretched to read), the distances, masses, extinction, the number of stars per component, the field (arbitrary, unrelated to any HAYDN target), the colours and the camera are drawn.