Ionised gas kinematics and star-forming clumps in extremely metal-poor galaxies

Extremely metal poor (XMP) galaxies are the least chemically evolved objects in the local Universe and provide important constraints on galaxy formation in low-metallicity environments. This work investigates the ionised gas kinematics and star formation properties of XMP galaxies to identify signatures of disturbed or multi-component gas motions and explore their connection with ongoing star formation. This approach probes the assembly and growth of low-mass galaxies. We analysed long-slit spectroscopic observations of nine XMP galaxies obtained with the Intermediate Dispersion Spectrograph on the 2.5,m Isaac Newton Telescope. We primarily used the Hα emission line to trace the ionised gas component. We used kinematic measurements to identify ordered rotation, disturbed motions, and localised deviations associated with star-forming regions. We used emission-line ratios to derive gas-phase metallicities and analyse the chemical properties of the ionised gas. The kinematic analysis reveals that a subset of galaxies exhibit ordered rotation, with the kinematic centres not always coincident with the luminous star-forming heads. Most systems show disturbed, asymmetric, or declining velocity profiles, while localised distortions near the bright star-forming heads suggest that massive star-forming clumps can influence the surrounding gas dynamics. We derived dynamical masses for the dominant clumps and investigated the mass--metallicity and size--metallicity relations. The clumps exhibit low metallicities consistent with the XMP regime and broadly comparable to those observed in low-mass dwarf galaxies. Three galaxies show counter-rotating or kinematically decoupled ionised-gas components, indicating the presence of multiple kinematic structures. These features, together with low metallicities and intense star formation in the bright head regions, point to complex gas accretion and redistribution, whereas internal processes such as outflows, mixing, and stochastic star formation may also contribute to the observed properties. The XMP galaxies in our sample are predominantly isolated systems, with metal-poor star formation concentrated in compact head regions. Three galaxies exhibit counter-rotating or kinematically distinct ionised-gas components, indicating complex gas kinematics and possible external gas acquisition. Such gas may be supplied through merger-driven or interaction-driven processes, or through the accretion of relatively metal-poor gas from the surrounding intergalactic medium and cosmic filaments. These processes may contribute to the evolution of XMP galaxies, although internal mechanisms such as gas mixing, outflows, recycling, and stochastic star formation may also shape their observed properties.