Thèse soutenue

Evolution des propriétés structurelles des galaxies de type précoce dans différents environnements
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Auteur / Autrice : Lauriane Delaye
Direction : Simona MeiMarc Huertas-Portocarrero Company
Type : Thèse de doctorat
Discipline(s) : [Astronomie et] astrophysique
Date : Soutenance en 2013
Etablissement(s) : Paris 7

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Résumé

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A large debate takes place about the evolution leading to the formation of massive early-type galaxies (ETGs) observed today, since the discovery of massive passive galaxies at z~l-2 more compact than their local counterparts. Gas expulsion or dry minor mergers are invoked to explain the size growth of these galaxies, but none of them can reproduce all the observed trends. Environment is an extra variable used to disentangle the two scenarios and has been poorly explored up to now. Z>l is an interesting epoch to study environmental dependence of ETG sizes since massive clusters start to appear. If galaxies ending-up in these massive structures have been processed differently than galaxies in the field, the effects should be visible at that time. I analyze the mass-size relation (MSR) and size evolution of passive ETGs in a sample of 9 clusters at 0. 8 < z < 1. 6 and compare it to an homogeneous sample of field galaxies. . All properties are derived on the same way. Cluster and field galaxy selections include galaxies classified as ETGs with stellar masses;above 3. 10¹⁰ M☼ Msun, on the red sequence. We do not detect any significant differences in the MSR and size evolution of field and cluster ETGs. Oui results, with previous works, suggest a very weak imprint of environment on galaxy sizes from at leas z~1. 5. This is independent of the stellar mass range. We find a morphological dependence of the MSR for elliptical (E) and lenticular (SO) galaxies. SOs appear on average more compact at fixed stellar mass than Ellipticals and evolve faster from z~1. 5 to z=0. We compare our results with the predictions of two semi-analytica models which show a behaviour consistent with ours at l-2σ.