Unveiling the Structure and Kinematics of Rare Star-forming Elliptical Galaxies in SDSS-MaNGA

Star-forming elliptical galaxies (SF-Es) represent a rare and intriguing class of objects that challenge our understanding of galaxy evolution. This study investigates the properties and formation mechanisms of SF-Es using data from the SDSS-MaNGA survey. We identified 59 SF-Es and compared them with control samples of quenched ellipticals and star-forming spirals. Our analysis reveals that SF-Es typically have lower stellar masses than quenched ellipticals and exhibit a mix of slow and fast rotators. They show significant H-alpha emissions, particularly in their central regions, indicating ongoing star formation. The stellar populations of SF-Es display a combination of old and young stars, with many showing younger populations in the centre surrounded by older stars. Evidence suggests that SF-Es have recently acquired metal-poor gas, possibly through minor mergers or interactions, driving the observed star formation. Approximately two-thirds of SF-Es show complex velocity structures, implying recent disturbances or mergers. Based on their bulge dominance and rotation, SF-Es suggest diverse evolutionary pathways including rejuvenated ellipticals, transformed spirals, fading S0s, and analogues to primordial "red nugget" galaxies that have acquired star-forming disks. The diversity of SF-Es underscores the complex and multifaceted nature of galaxy evolution, challenging simplistic views of the Hubble sequence and supporting more nuanced models like the comb morphology diagram.