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

• Published in: Monthly Notices of the Royal Astronomical Society
• Main Authors: Moffett, Amanda J, Phillipps, Steven, Robotham, Aaron S G, Driver, Simon P, Bremer, Malcolm N, Cortese, Luca, Wong, O Ivy, Brough, Sarah, Brown, Michael J I, Bryant, Julia J, Conselice, Christopher J, Croom, Scott M, George, Koshy, Goldstein, Greg, Goodwin, Michael, Holwerda, Benne W, Hopkins, Andrew M, Konstantopoulos, Iraklis S, Lawrence, Jon S, Lorente, Nuria P F, Medling, Anne M, Owers, Matt S, Pimbblet, Kevin A, Richards, Samuel N, Sweet, Sarah M, Van De Sande, Jesse
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: Surveys; Galaxies: dwarf; Galaxies: structure; Galaxies: fundamental paramaters; sami
• 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

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.