Star-forming, rotating spheroidal galaxies in the GAMA and SAMI Surveys
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,...
Published in: | Monthly Notices of the Royal Astronomical Society |
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Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
2019
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Subjects: | |
Online Access: | https://research-portal.st-andrews.ac.uk/en/researchoutput/starforming-rotating-spheroidal-galaxies-in-the-gama-and-sami-surveys(65d3d335-5e3b-4f2f-8bca-361051b6c4e0).html https://doi.org/10.1093/mnras/stz2237 https://research-repository.st-andrews.ac.uk/bitstream/10023/18424/1/Moffett_2019_MNRAS_Star_forming_AAM.pdf |
Summary: | 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, high-resolution 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 Sérsic 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. |
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