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.
- galaxies: fundamental parameters
- galaxies: structure
- galaxies: dwarf
Moffett, A., Phillipps, S., Robotham, A., Driver, S., Bremer, M., & et al (2019). Star-forming, rotating spheroidal galaxies in the GAMA and SAMI surveys. Monthly Notices of the Royal Astronomical Society, 489(2), 2830-2843. [stz2237]. https://doi.org/10.1093/mnras/stz2237