Star-forming, rotating spheroidal galaxies in the GAMA and SAMI surveys

Amanda Moffett, Steven Phillipps, Aaron Robotham, Simon Driver, Malcolm Bremer, et al

Research output: Contribution to journalArticle (Academic Journal)

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Abstract

The Galaxy And Mass Assembly (GAMA) survey has morphologically identified a class of “Little Blue Spheroid” (LBS) galaxies whose relationship to other classes of galaxies we now examine in detail. Considering a sample of 868 LBSs, we find that such galaxies display similar but not identical colours, specific star formation rates, stellar population ages, mass-to-light ratios, and metallicities to Sd-Irr galaxies. We also find that LBSs typically occupy environments of even lower density than those of Sd-Irr galaxies, where ∼65% of LBS galaxies live in isolation. Using deep, highresolution imaging from VST KiDS and the new Bayesian, two-dimensional galaxy profile modeling code PROFIT, we further examine the detailed structure of LBSs and find that their S´ersic indices, sizes, and axial ratios are compatible with those of low-mass elliptical galaxies. We then examine SAMI Galaxy survey integral field emission line kinematics for a subset of 62 LBSs and find that the majority (42) of these galaxies display ordered rotation with the remainder displaying disturbed/non-ordered dynamics. Finally, we consider potential evolutionary scenarios for a population with this unusual combination of properties, concluding that LBSs are likely formed by a mixture of merger and accretion processes still recently active in low-redshift dwarf populations. We also infer that if LBS-like galaxies were subjected to quenching in a rich environment, they would plausibly resemble cluster dwarf ellipticals.
Original languageEnglish
Article numberstz2237
Pages (from-to)2830-2843
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Volume489
Issue number2
Early online date12 Aug 2019
DOIs
Publication statusE-pub ahead of print - 12 Aug 2019

Keywords

  • galaxies: fundamental parameters
  • galaxies: structure
  • galaxies: dwarf
  • surveys

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