Strong spiral arms drive secular growth of pseudo bulges in disk galaxies

Spiral-driven instabilities may drive gas inflow to enhance central star formation in disk galaxies. We investigate this hypothesis using the Sloan Digital Sky Survey (SDSS) a sample of 2779 nearby unbarred star-forming main sequence spiral The strength arms is quantified by their average Fourier amplitude relative axisymmetric disk. properties 1–3 kpc region were derived from SDSS spectra. show that galaxies with stronger not only tend have more intense specific rates (sSFRs), larger Balmer absorption line indices, and lower 4000 Å break strengths, but also enhanced sSFRs sSFR measured for whole galaxy. This link independent redshift, stellar mass, surface density, concentration. There lack evidence strong being associated significant fraction starburst or post-starburst galaxies, implying spiral-induced likely continuous rather than bursty. an increasing pseudo bulges, relatively unchanged classical decreasing quenched bulges. Moreover, concentration hosting bulges mildly increases arms, spirals help grow. connection between bulge type partly attributed suppression driven spirals. explain our results context scenario where transport cold inward trigger formation, which facilitates buildup Spiral thus play role secular evolution