The scatter of the spatially resolved star formation main sequence ( SFMS ) is investigated in order to reveal signatures about the processes of galaxy formation and evolution .
We have assembled a sample of 355 nearby galaxies with spatially resolved H \alpha and mid-infrared fluxes from the Survey for Ionized Neutral Gas in Galaxies and the Wide-field Infrared Survey Explorer , respectively .
We examine the impact of various star formation rate ( SFR ) and stellar mass transformations on the SFMS .
Ranging from 10 ^ { 6 } to 10 ^ { 11.5 } M _ { \odot } and derived from color to mass-to-light ratio methods for mid-infrared bands , the stellar masses are internally consistent within their range of applicability and inherent systematic errors ; a constant mass-to-light ratio also yields representative stellar masses .
The various SFR estimates show intrinsic differences and produce noticeable vertical shifts in the SFMS , depending on the timescales and physics encompassed by the corresponding tracer .
SFR estimates appear to break down on physical scales below 500 pc .
We also examine the various sources of scatter in the spatially resolved SFMS and find morphology does not play a significant role .
We identify three unique tracks across the SFMS by individual galaxies , delineated by a critical stellar mass density of log ( \Sigma _ { \mbox { $M _ { * } $ } } ) \sim 7.5 .
Below this scale , the SFMS shows no clear trend and is likely driven by local , stochastic internal processes .
Above this scale , all spatially resolved galaxies have comparable SFMS slopes but exhibit two different behaviors , resulting likely from the rate of mass accretion at the center of the galaxy .