  Galaxy integrated H{\alpha} star formation rate-stellar mass relation, or
SFR(global)-M*(global) relation, is crucial for understanding star formation
history and evolution of galaxies. However, many studies have dealt with SFR
using unresolved measurements, which makes it difficult to separate out the
contamination from other ionizing sources, such as active galactic nuclei and
evolved stars. Using the integral field spectroscopic observations from SDSS-IV
MaNGA, we spatially disentangle the contribution from different H{\alpha}
powering sources for ~1000 galaxies. We find that, when including regions
dominated by all ionizing sources in galaxies, the spatially-resolved relation
between H{\alpha} surface density ({\Sigma}H{\alpha}(all)) and stellar mass
surface density ({\Sigma}*(all)) progressively turns over at high
{\Sigma}*(all) end for increasing M*(global) and bulge dominance
(bulge-to-total light ratio, B/T). This in turn leads to the flattening of the
integrated H{\alpha}(global)-M*(global) relation in the literature. By
contrast, there is no noticeable flattening in both integrated
H{\alpha}(HII)-M*(HII) and spatially-resolved
{\Sigma}H{\alpha}(HII)-{\Sigma}*(HII) relations when only regions where star
formation dominates the ionization are considered. In other words, the
flattening can be attributed to the increasing regions powered by
non-star-formation sources, which generally have lower ionizing ability than
star formation. Analysis of the fractional contribution of non-star-formation
sources to total H{\alpha} luminosity of a galaxy suggests a decreasing role of
star formation as an ionizing source toward high-mass, high-B/T galaxies and
bulge regions. This result indicates that the appearance of the galaxy
integrated SFR-M* relation critically depends on their global properties
(M*(global) and B/T) and relative abundances of various ionizing sources within
the galaxies.
