Browsing by Author "Prescott, M."
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Item Galaxy And Mass Assembly (GAMA): Resolving the role of environment in galaxy evolution(Oxford University Press, 2013) Brough, S.; Croom, S. M.; Prescott, M.We present observations of 18 galaxies from the Galaxy And Mass Assembly (GAMA) survey made with the SPIRAL optical integral field unit (IFU) on the Anglo- Australian Telescope. The galaxies are selected to have a narrow range in stellar mass (6 × 109M < M∗ < 2 × 1010M ) in order to focus on the effects of environment. Local galaxy environments are measured quantitatively using 5th nearest neighbour surface densities. We find that the total star formation rates (SFR) measured from the IFU data are consistent with total SFRs measured from aperture correcting either GAMA or Sloan Digital Sky Survey single-fibre observations. The mean differences are SFRGAMA/SFRIFU = 1.26 ± 0.23, σ = 0.90 and for the Sloan Digital Sky Sur- vey we similarly find SFRBrinchmann/SFRIFU = 1.34 ± 0.17, σ = 0.67. Examining the relationships with environment, we find off-centre and clumpy Hα emission is not sig- nificantly dependent on environment, being present in 2/7 (29+20 per cent) galaxies in high-density environments (> 0.77 Mpc−2), and 5/11 (45+15 per cent) galaxies in low-density environments (< 0.77 Mpc−2). We find a weak but not significant relationship of the total star formation rates of star-forming galaxies with environment. Due to the size of our sample and the scatter observed we do not draw a definitive conclusion about a possible SFR dependence on environment. Examining the spatial distribution of the Hα emission, we find no evidence for a change in shape or amplitude of the ra- dial profile of star-forming galaxies with environment. If these observations are borne out in larger samples this would infer that any environment-driven star-formation sup- pression must either act very rapidly (the ‘infall-and-quench’ model) or that galaxies must evolve in a density-dependent manner (an ‘in-situ evolution’ model).Item Galaxy and mass assembly: evolution of the Hα luminosity function and star formation rate density up to z < 0.35(OUP, 2013) Gunawardhana, M.L.P.; Hopkins, A.M.; Bland–Hawthorn, J.; Prescott, M.Measurements of the low-z Hα luminosity function, Φ, have a large dispersion in the local number density of sources (∼0.5–1 Mpc−3 dex−1), and correspondingly in the star formation rate density (SFRD). The possible causes for these discrepancies include limited volume sampling, biases arising from survey sample selection, different methods of correcting for dust obscuration and active galactic nucleus contamination. The Galaxy And Mass Assembly (GAMA) survey and Sloan Digital Sky Survey (SDSS) provide deep spectroscopic observations over a wide sky area enabling detection of a large sample of star-forming galaxies spanning 0.001 < SFRHα (M⊙ yr− 1) < 100 with which to robustly measure the evolution of the SFRD in the low-z Universe. The large number of high-SFR galaxies present in our sample allow an improved measurement of the bright end of the luminosity function, indicating that the decrease in Φ at bright luminosities is best described by a Saunders functional form rather than the traditional Schechter function. This result is consistent with other published luminosity functions in the far-infrared and radio. For GAMA and SDSS, we find the r-band apparent magnitude limit, combined with the subsequent requirement for Hα detection leads to an incompleteness due to missing bright Hα sources with faint r-band magnitudes.