Astrophysics Seminar

Ultra-diffuse galaxies (UDGs) exhibit morphological similarities with other low luminosity galaxies indicating a possible evolutionary connection. We investigate for a common dynamical origin of isolated, HI-rich UDGs with other low luminosity field galaxies, namely the low surface brightness galaxies (LSBs) and the dwarf irregulars (dIrrs). Obtaining the scaling relations between (i) central stellar surface density and exponential stellar disk scale length, (ii) stellar and atomic hydrogen mass, and (iii) stellar and dynamical mass for LSBs and dIrr populations separately, and superposing the data for UDGs on them, we note that UDGs evolve fairly akin to dIrrs. We next construct distribution function-based stellar-dynamical models of these galaxies. Comparison of the ratios of the modelled radial-to-vertical velocity dispersion, and the rotational velocity-to-total stellar velocity dispersion also indicates that the stellar kinematics of UDGs and dIrrs are fairly similar. Finally, we conducted principal component analyses to identify the key parameters accounting for the variance in the structure and kinematical data for the respective galaxy populations. We observe that the total HI and stellar mass mostly regulate the variance for the UDGs and dIrrs, while the ratio of radial-to-vertical velocity dispersion, and the compactness of the mass distribution dominate the same in LSBs. We therefore conclude that isolated, HI-rich UDGs and dIrrs possibly share a common dynamical lineage.