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Dry minor mergers and size evolution of high-z compact massive early-type galaxies

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Title: Dry minor mergers and size evolution of high-z compact massive early-type galaxies
Authors: Oogi, Taira Browse this author
Habe, Asao Browse this author →KAKEN DB
Keywords: methods: numerical
galaxies: elliptical and lenticular, cD
galaxies: evolution
galaxies: formation
galaxies: kinematics and dynamics
galaxies: structure
Issue Date: 1-Jan-2013
Publisher: The Royal Astronomical Society (Oxford University Press)
Journal Title: Monthly Notices of the Royal Astronomical Society
Volume: 428
Issue: 1
Start Page: 641
End Page: 657
Publisher DOI: 10.1093/mnras/sts047
Abstract: Recent observations show evidence that high-z (z similar to 2-3) early-type galaxies (ETGs) are more compact than those with comparable mass at z similar to 0. Such size evolution is most likely explained by the 'dry merger sceanario'. However, previous studies based on this scenario cannot consistently explain the properties of both high-z compact massive ETGs and local ETGs. We investigate the effect of multiple sequential dry minor mergers on the size evolution of compact massive ETGs. From an analysis of the Millennium Simulation Data Base, we show that such minor (stellar mass ratio M-2/M-1 < 1/4) mergers are extremely common during hierarchical structure formation. We perform N-body simulations of sequential minor mergers with parabolic and head-on orbits, including a dark matter component and a stellar component. Typical mass ratios of these minor mergers are 1/20 < M-2/M-1 <= 1/10. We show that sequential minor mergers of compact satellite galaxies are the most efficient at promoting size growth and decreasing the velocity dispersion of compact massive ETGs in our simulations. The change of stellar size and density of the merger remnants is consistent with recent observations. Furthermore, we construct the merger histories of candidates for high-z compact massive ETGs using the Millennium Simulation Data Base and estimate the size growth of the galaxies through the dry minor merger scenario. We can reproduce the mean size growth factor between z = 2 and z = 0, assuming the most efficient size growth obtained during sequential minor mergers in our simulations. However, we note that our numerical result is only valid for merger histories with typical mass ratios between 1/20 and 1/10 with parabolic and head-on orbits and that our most efficient size-growth efficiency is likely an upper limit.
Rights: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2012 The Authors Published by Oxford University Press on behalf of The Royal Astronomical Society. All rights reserved.
Type: article
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 羽部 朝男

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