Stellar populations in the Galactic bulge

Modelling the Galactic bulge with TRILEGAL

¹ Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium e-mail: evelien@ster.kuleuven.be
² Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium
³ Padova Osservatorio Astronomia, Vicolo dell'Osservatorio 5, 35122 Padova, Italy

Received: 13 August 2007
Accepted: 30 January 2009

Abstract

Aims. The aim of this paper is to study the characteristics of the stellar populations and the metallicity distribution in the Galactic bulge. We study the entire stellar population, but also retrieve information using only the red clump stars.

Methods. To study the characteristics of the stellar populations and the metallicity distribution in the Galactic bulge, we compared the output of the galaxy model TRILEGAL, which implements the Binney et al. (1997, MNRAS, 288, 365) bulge model, with observations from 2MASS and OGLE-II. A minimisation procedure has been set up to retrieve the best fitting model with different stellar populations and metallicity distributions.

Results. Using the TRILEGAL code we find that the best model resembling the characteristics of the Galactic bulge is a model with the distance to the Galactic centre  kpc, the major axis ratios of the bar , and the angle between the Sun-centre line and the bar . Using these parameters the best model is found for a burst of 8 Gyr, although it is almost indistinguishable from models with ages of 9 and 10 Gyr. The metallicity distribution found is consistent with metallicity distributions in the literature based on spectroscopic results.