The model of stellar population synthesis built by our team for three decades
is used to elaborate a global view of the Galaxy including dynamical and evolutionary aspects.
Scenarii for the formation and evolution produces theoretical distribution functions
which are directly compared with survey observations of different types
(photometry, kinematics, abundance distributions).
We link the kinematical and dynamical point of view to an evolution scheme through a key parameter:
the stellar ages. The age distribution of stars in the solar neighbourhood
is derived from a model of galactic evolution. The stellar populations of the galactic disc
are self-consistently (locally) constrained by the Boltzmann and Poisson equations
through the potential of the mass model. Thus we directly derive observational predictions
from an overall description of galactic structure and evolution.
A complete description of the model inputs can be found in
Robin, Reylé, Derrière, Picaud (2003)
Since then, substantial changes have been performed. Their description is given below.
The new version
Several important updates
have been done recently, concerning
- the bar population, described in
Robin, Marshall, Schultheis, Reylé (2012)
- the thick disc and halo populations have been revised
in Robin et al, (2014)
The thick disc is modelled by 2 isochrones of different ages and metallicities
to mimic a long star formation period of 2 Gyr.
The bar population is the same as in version 2012,
but the extra "thick bulge" population has been removed
since the thick-disc short scale length now produces a significant
contribution in the bulge region,
leading to a negligible contribution from a classical bulge.
- the thin disc population is the same as in 2012 version with the bar.
A revised version described in Czekaj et al, 2014
with new evolutionary tracks,
star formation history and initial mass function,
taking into account binarity, will be released in a near future.
- this new version implements the computation of parallaxes
and adds observational errors on spectroscopic parameters.
- The new version allows computation on alpha over iron abundance ratios from simple
hypotheses in link with metallicity, Galactic position and population
- The extinction can be modeled by different ways:
- It can be modeled by a diffuse thin disc. This is not reliable for the galactic
plane where a more sophisticated 3D extinction model should be used instead.
- It can use the 3D map from Marshall et al (2006)
- The user can include an extinction distribution along the line of sight of his own.
- Several photometric systems are available for producing the catalogues
(UBVRIJHKL, Megacam+Wircam+Spitzer, SDSS+2MASS, GALEX)
- A new kinematical model has been constructed
from the Galactic potential approximated
by a Stackel potential Bienaymé, Robin, Famaey (2015).
The solar motion and age-velocity dispersion relations
have been fitted to RAVE and Gaia DR1.
A complete description of this new kinematics is given in
Robin, Bienaymé, Fernandez-Trincado, Reylé (2017).
- The outer disc scale lengths, warp and flare have been revised, according to 2MASS data.
The description is given in Amores, Robin, Reylé (2017)
The model is a powerful tool to constrain either evolutionary scenarii or
galactic structure hypothesis through the comparison between model predictions
and a large variety of observational constraints such as star counts,
photometry or astrometry. Model simulations are produced in the form of:
- catalogues of pseudo-stars, from Monte-Carlo simulations.
For each star, observable parameters as well as intrinsic ones are given.
- tables of statistical distributions as a function of either observables
(magnitudes, colours, proper motions, radial velocities)
or intrinsic parameters (distances, spectral type, age, absolute magnitude).
A number of quantitative results have been obtained by comparing model predictions
with suitable observations, like multidirectional photometric and astrometric star counts.
Simulations may help for preparing observations, for evaluating the galactic stellar
contamination in extragalatic studies or in star cluster fields.
The resulting model can be used for simulations of the galactic stellar populations
in any galactic field in different photometric systems.
There are limitations in the volume of the catalogues simulated (2Gb).
Your simulation can be interrupted when it reaches this limit.
Hence it is recommended to estimate the volume expected
before launching a large simulation.
If you require large amount of simulations, you might consider contacting us
directly at firstname.lastname@example.org
A web service access to the model is also available.