Galaxy And Mass Assembly (GAMA): Spectroscopic analysis

A.M. Hopkins, Simon Driver, S. Brough, M.S. Owers, A.E. Bauer, M.L.P. Gunawardhana, M.E. Cluver, M. Colless, C. Foster, M.A. Lara-López, I. Roseboom, R. Sharp, O. Steele, D. Thomas, I.K. Baldry, M.J.I. Brown, J. Liske, P. Norberg, Aaron Robotham, S. BamfordJ. Bland-Hawthorn, M.J. Drinkwater, J. Loveday, Martin Meyer, J. Peacock, R. Tuffs, N. Agius, M. Alpaslan, E. Andrae, E. Cameron, S. Cole, J.H.Y. Ching, L. Christodoulou, C. Conselice, S. Croom, N.J.G. Cross, R. De Propris, J. Delhaize, L. Dunne, S. Eales, S. Ellis, C.S. Frenk, A.W. Graham, M.W. Grootes, B. Häußler, C. Heymans, D. Hill, B. Hoyle, M. Hudson, M. Jarvis, J. Johansson, D.H. Jones, E. Van Kampen, L.S. Kelvin, K. Kuijken, A. López-Sánchez, S. Maddox, B. Madore, C. Maraston, T. Mcnaught-Roberts, R.C. Nichol, S. Oliver, H. Parkinson, S. Penny, S. Phillipps, K.A. Pimbblet, T. Ponman, C.C. Popescu, M. Prescott, R. Proctor, E.M. Sadler, A.E. Sansom, M. Seibert, Lister Staveley-Smith, W. Sutherland, E. Taylor, L. Van Waerbeke, J.A. Vázquez-Mata, S. Warren, D.B. Wijesinghe, V. Wild, S. Wilkins

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    Abstract

    The Galaxy And Mass Assembly (GAMA) survey is a multiwavelength photometric and spectroscopic survey, using the AAOmega spectrograph on the Anglo-Australian Telescope to obtain spectra for up to ~300 000 galaxies over 280 deg2, to a limiting magnitude of rpet <19.8 mag. The target galaxies are distributed over 0 <z ≲ 0.5 with a median redshift of z ≈ 0.2, although the redshift distribution includes a small number of systems, primarily quasars, at higher redshifts, up to and beyond z = 1. The redshift accuracy ranges from σv ≈ 50 km s-1 to σv ≈ 100 km s-1 depending on the signal-to-noise ratio of the spectrum. Here we describe the GAMA spectroscopic reduction and analysis pipeline. We present the steps involved in taking the raw two-dimensional spectroscopic images through to flux-calibrated one-dimensional spectra. The resulting GAMA spectra cover an observed wavelength range of 3750 λ 8850Å at a resolution of R ≈ 1300. The final flux calibration is typically accurate to 10-20 per cent, although the reliability is worse at the extreme wavelength ends, and poorer in the blue than the red. We present details of the measurement of emission and absorption features in the GAMA spectra. These measurements are characterized through a variety of quality control analyses detailing the robustness and reliability of the measurements. We illustrate the quality of the measurements with a brief exploration of elementary emission line properties of the galaxies in the GAMA sample. We demonstrate the luminosity dependence of the Balmer decrement, consistent with previously published results, and explore further how Balmer decrement varies with galaxy mass and redshift. We also investigate the mass and redshift dependencies of the [NII]/Hα versus [OIII]/Hβ spectral diagnostic diagram, commonly used to discriminate between star forming and nuclear activity in galaxies. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
    Original languageEnglish
    Pages (from-to)2047-2066
    JournalMonthly Notices of the Royal Astronomical Society
    Volume430
    Issue number3
    DOIs
    Publication statusPublished - 2013

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    Hopkins, A. M., Driver, S., Brough, S., Owers, M. S., Bauer, A. E., Gunawardhana, M. L. P., Cluver, M. E., Colless, M., Foster, C., Lara-López, M. A., Roseboom, I., Sharp, R., Steele, O., Thomas, D., Baldry, I. K., Brown, M. J. I., Liske, J., Norberg, P., Robotham, A., ... Wilkins, S. (2013). Galaxy And Mass Assembly (GAMA): Spectroscopic analysis. Monthly Notices of the Royal Astronomical Society, 430(3), 2047-2066. https://doi.org/10.1093/mnras/stt030