  NGC 2915 is a unique nearby galaxy that is classified as an isolated blue
compact dwarf based on its optical appearance but has an extremely extended H i
gas disk with prominent Sd-type spiral arms. To unveil the starburst-triggering
mystery of NGC 2915, we performed a comprehensive analysis of deep VLT/MUSE
integral field spectroscopic observations that cover the star-forming region in
the central kiloparsec of the galaxy. We find that episodes of bursty star
formation have recurred in different locations throughout the central region,
and the most recent one peaked around 50 Myr ago. The bursty star formation has
significantly disturbed the kinematics of the ionized gas but not the neutral
atomic gas, which implies that the two gas phases are largely spatially
decoupled along the line of sight. No evidence for an active galactic nucleus
is found based on the classical line-ratio diagnostic diagrams. The ionized gas
metallicities have a positive radial gradient, which confirms the previous
study based on several individual H ii regions and may be attributed to both
the stellar feedback-driven outflows and metal-poor gas inflow. Evidence for
metal-poor gas infall or inflow includes discoveries of high-speed collisions
between gas clouds of different metallicities, localized gas metallicity drops
and unusually small metallicity differences between gas and stars. The central
stellar disk appears to be counter-rotating with respect to the extended H i
disk, implying that the recent episodes of bursty star formation have been
sustained by externally accreted gas.
