Galaxy and mass assembly (GAMA): The life and times of L* galaxies

Aaron Robotham, J. Liske, Simon Driver, A.E. Sansom, I.K. Baldry, A.E. Bauer, J. Bland-Hawthorn, S. Brough, M.J.I. Brown, M. Colless, L. Christodoulou, M.J. Drinkwater, M.W. Grootes, A.M. Hopkins, L.S. Kelvin, P. Norberg, J. Loveday, S. Phillipps, R. Sharp, E.N. TaylorR.J. Tuffs

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    Abstract

    In this work, we investigate in detail the effects the local environment (groups and pairs) has on galaxies with stellar mass similar to the MilkyWay (L* galaxies). A volume limited sample of 6150 galaxies are visually classified to determine the emission features, morphological type and presence of a disc. This large sample allows for the significant characteristics of galaxies to be isolated (e.g. stellar mass and group halo mass), and their codependencies determined. We observe that galaxy-galaxy interactions play the most important role in shaping the evolutionwithin a group halo; themain role of halomass is in gathering the galaxies together to encourage such interactions. Dominant pair galaxies find their overall star formation enhanced when the pair's mass ratio is close to 1; otherwise, we observe the same galaxies as we would in an unpaired system. The minor galaxy in a pair is greatly affected by its companion galaxy, and while the star-forming fraction is always suppressed relative to equivalent stellar mass unpaired galaxies, it becomes lower still when the mass ratio of a pair system increases. We find that, in general, the close galaxy-galaxy interaction rate drops as a function of halo mass for a given amount of stellar mass. We find evidence of a local peak of interactions for Milky Way stellar mass galaxies in Milky Way halo mass groups. Low-mass haloes, and in particular Local Group mass haloes, are an important environment for understanding the typical evolutionary path of a unit of stellar mass. We find compelling evidence for galaxy conformity in both groups and pairs, where morphological type conformity is dominant in groups, and emission class conformity is dominant in pairs. This suggests that group scale conformity is the result of many galaxy encounters. over an extended period of time, while pair conformity is a fairly instantaneous response to a transitory interaction. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.
    Original languageEnglish
    Pages (from-to)167-193
    JournalMonthly Notices of the Royal Astronomical Society
    Volume431
    Issue number1
    DOIs
    Publication statusPublished - 2013

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