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Issue A&A
Volume 421, Number 3, July III 2004
Page(s) 863 - 876
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20034269



A&A 421, 863-876 (2004)
DOI: 10.1051/0004-6361:20034269

Photometric and dynamic evolution of an isolated disc galaxy simulation

L. Michel-Dansac1 and H. Wozniak1, 2

1  Observatoire de Marseille-Provence, Laboratoire d'Astrophysique de Marseille, 2 Place Le Verrier, 13248 Marseille Cedex 4, France
2  Present address: Centre de Recherche Astronomique de Lyon, 9 Av. Charles André, 69561 Saint-Genis Laval Cedex, France

(Received 2 September 2003 / Accepted 20 March 2004)

Abstract
We present a detailed analysis of the evolution of a simulated isolated disc galaxy. The simulation includes stars, gas, star formation and simple chemical yields. Stellar particles are split in two populations: the old one is present at the beginning of the simulation and is calibrated according to various ages and metallicities; the new population is born in the course of the simulation and inherits the metallicity of the gas particles. The result has been calibrated in four wavebands with the spectrophotometric evolutionary model GISSEL2000 (Bruzual & Charlot 1993). Dust extinction has also been taken into account. A rest-frame morphological and bidimensional photometric analysis has been performed on simulated images, with the same tools as for observations. The effects of the stellar bar formation and the linked star formation episode on the global properties of the galaxy (mass and luminosity distribution, colours, isophotal radii) have been analysed. In particular, we have disentangled the effects of stellar evolution from dynamic evolution to explain the cause of the isophotal radii variations. We show that the dynamic properties (e.g. mass) of the area enclosed by any isophotal radius depends on the waveband and on the level of star formation activity. It is also shown that the bar isophotes remain thinner than mass isodensities a long time ( >0.7 Gyr) after the maximum of star formation rate. We show that bar ellipticity is very wavelength dependent as suggested by real observations. Effects of dust extinction on photometric and morphological measurements are systematically quantified. For instance, it is shown that, when the star formation rate is maximum, no more than 20% of the B band luminosity can escape from the bar region whereas, without dust extinction, bar B band luminosity accounts for 80% of the total B band luminosity. Moreover, the extinction is not uniformly distributed inside the bar.


Key words: galaxies: evolution -- galaxies: kinematics and dynamics -- galaxies: spiral -- galaxies: structure -- methods: N-body simulations

Offprint request: L. Michel-Dansac, leo.michel-dansac@oamp.fr




© ESO 2004


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