Letter to the Editor

The distribution of stellar population age in galactic bars

¹ Université de Lyon, 69000 Lyon, France
² Université Lyon 1, 69622 Villeurbanne, France
³ Centre de Recherche Astronomique de Lyon, Observatoire de Lyon, 9 avenue Charles André, 69561 Saint-Genis Laval Cedex, France
⁴ CNRS, UMR 5574 – École Normale Supérieure de Lyon, Lyon, France e-mail: herve.wozniak@obs.univ-lyon1.fr

Received: 23 December 2006
Accepted: 22 January 2007

Abstract

Context.Recent analysis of stellar populations in barred galaxies have focused on the spatial distribution of stellar population ages and metallicities. However, barred galaxies are complex objects where dynamical instabilities play a leading role in shaping any spatial distribution.

Aims.The age distribution of stellar populations should thus be analyzed from the two points of view of stellar population evolution and dynamical secular evolution.

Methods.Chemodynamical simulations of single barred galaxies with simple but realistic star formation and feedback recipes are used to produce face-on mass-weighted maps of stellar population ages. Luminosity-weighted maps in V-band are also displayed after calibrating the simulation with mass-to-light ratios provided by a synthesis population model.

Results.It is shown that inside a stellar bar two persistent diametrically opposed regions display a mean age lower than the surrounding average. These two low-age regions are due to the accumulation of young stellar populations trapped on elliptical-like orbits along the bar, near the ultra-harmonic resonance. Age gradients along the bar major-axis are comparable to recent observations. Another low-age region is the outer ring located near the Outer Lindblad Resonance, but the presence and strength of this structure is very time-dependent.