Spatially extended star formation in merger-driven and secular starbursts in dwarf galaxies

Galaxy interactions can induce bursts of star formation, while internal or secular processes can also trigger starbursts. Recent studies of the spatial distribution of star formation in high-mass (M_* $>$ 10 10 $ M_⊙) starburst galaxies show that star formation is centrally concentrated in merger-driven starbursts, whereas in secularly driven starburst systems, it is uniformly enhanced across the system. However, it is not clear whether such distinct spatial signatures are present in low-mass (M_* <10¹0M_⊙) starburst galaxies. We studied the star formation properties of a sample of 272 isolated starburst dwarf galaxies (i.e. with no massive galaxy, M_* $>$ 10^10 M_⊙, within a 1 Mpc^3 volume) consisting of 17 post-merger and 255 non-interacting starburst galaxies, spanning a stellar mass range of $ 10^ 7 - 10^ 9.6 M_⊙ and a redshift range of 0.01 -- 0.12. We used far-ultraviolet imaging data from the GALEX mission to estimate the star formation rates of our sample galaxies. We investigated the spatial variation of starburst activity by comparing the star formation rate surface density (SFRD) across radial bins for the post-merger and non-interacting dwarf samples. We find an enhanced SFRD across all radial bins for both samples, with the enhancement approximately uniform across the galaxy, within uncertainties. This indicates that star formation in low-mass starburst galaxies is uniformly enhanced throughout the galaxy, regardless of the mechanism that triggers the starburst. This contrasts with massive galaxies, where star formation is centrally concentrated in merger-driven starburst systems. The lack of central star-formation concentration in low-mass merger systems could result from their shallow gravitational potentials and from the compression of extended gaseous envelopes during interactions, which triggers star formation across these galaxies. Deeper, higher-spatial-resolution observations are essential for better understanding the spatial distribution of star formation in low-mass galaxies.