Browsing by Author "Owers, M. S."

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    Galaxy and Mass Assembly (GAMA): probing the merger histories of massive galaxies via stellar populations
    (2017) Ferreras, I.; Hopkins, A. M.; Gunawardhana, M. L. P.; Sansom, A. E.; Owers, M. S.; Driver, S.; Davies, L.; Robotham, A.; Taylor, E. N.; Konstantopoulos, I.; Brough, S.; Norberg, P.; Croom, S.; Loveday, J.; Wang, L.; Bremer, M.
    The merging history of galaxies can be traced with studies of dynamically close pairs. These consist of a massive primary galaxy and a less massive secondary (or satellite) galaxy. The study of the stellar populations of secondary (lower mass) galaxies in close pairs provides a way to understand galaxy growth by mergers. Here we focus on systems involving at least one massive galaxy - with stellar mass above 10(11)M(circle dot) in the highly complete Galaxy and Mass Assembly (GAMA) survey. Our working sample comprises 2692 satellite galaxy spectra (0.1 <= z <= 0.3). These spectra are combined into high S/N stacks, and binned according to both an 'internal' parameter, the stellar mass of the satellite galaxy (i. e. the secondary), and an 'external' parameter, selecting either the mass of the primary in the pair, or the mass of the corresponding dark matter halo. We find significant variations in the age of the populations with respect to environment. At fixed mass, satellites around the most massive galaxies are older and possibly more metal-rich, with age differences similar to 1-2 Gyr within the subset of lower mass satellites (similar to 10(10) M-circle dot). These variations are similar when stacking with respect to the halo mass of the group where the pair is embedded. The population trends in the lower mass satellites are consistent with the old stellar ages found in the outer regions of massive galaxies.
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    Galaxy And Mass Assembly (GAMA): the signatures of galaxy interactions as viewed from small-scale galaxy clustering
    (2018) Gunawardhan, M. L. P.; Norberg, P.; Zehavi, I.; Farrow, D. J.; Loveday, J.; Hopkins, A. M.; Davie, L. J. M.; Wang, L.; Alpaslan, M.; Bland-Hawthorn, J.; Brough, S.; Holwerda, B. W.; Owers, M. S.; Wrigh, A. H.
    Statistical studies of galaxy-galaxy interactions often utilize net change in physical properties of progenitors as a function of the separation between their nuclei to trace both the strength and the observable time-scale of their interaction. In this study, we use two-point auto-, cross-, and mark-correlation functions to investigate the extent to which small-scale clustering properties of star-forming galaxies can be used to gain physical insight into galaxy-galaxy interactions between galaxies of similar optical brightness and stellar mass. The H α star formers, drawn from the highly spatially complete Galaxy And Mass Assembly (GAMA) survey, show an increase in clustering at small separations. Moreover, the clustering strength shows a strong dependence on optical brightness and stellar mass, where (1) the clustering amplitude of optically brighter galaxies at a given separation is larger than that of optically fainter systems, (2) the small-scale-clustering properties (e.g. the strength, the scale at which the signal relative to the fiducial power law plateaus) of star-forming galaxies appear to differ as a function of increasing optical brightness of galaxies. According to cross- and mark-correlation analyses, the former result is largely driven by the increased dust content in optically bright star-forming galaxies. The latter could be interpreted as evidence of a correlation between interaction-scale and optical brightness of galaxies, where physical evidence of interactions between optically bright star formers, likely hosted within relatively massive haloes, persists over larger separations than those between optically faint star formers.