ALMaQUEST -- VII: Star Formation Scaling Relations of Green Valley Galaxies

Abstract

We utilize the ALMA-MaNGA QUEnch and STar formation (ALMaQUEST) survey to investigate the kpc-scale scaling relations, presented as the resolved star forming main sequence (rSFMS: $\Sigma_{\rm SFR}$ vs. $\Sigma_{*}$), the resolved Schmidt-Kennicutt relation (rSK: $\Sigma_{\rm SFR}$ vs. $\Sigma_{\rm H_{2}}$), and the resolved molecular gas main sequence (rMGMS: $\Sigma_{\rm H_{2}}$ vs. $\Sigma_{*}$), for 11478 star-forming and 1414 retired spaxels (oversampled by a factor of $\sim20$) located in 22 green valley (GV) and 12 main sequence (MS) galaxies. For a given galaxy type (MS or GV), the retired spaxels are found to be offset from the sequences formed by the star-forming spaxels on the rSFMS, rSK, and rMGMS planes, toward lower absolute values of sSFR, SFE, and $f_{\rm H_{2}}$ by $\sim$ 1.1, 0.6, and 0.5 dex. The scaling relations for GV galaxies are found to be distinct from that of the MS galaxies, even if the analyses are restricted to the star-forming spaxels only. It is found that for star-forming spaxels, sSFR, SFE, and $f_{\rm H_{2}}$ in GV galaxies are reduced by $\sim$0.36, 0.14, and 0.21 dex, respectively, compared to those in MS galaxies. Therefore, the suppressed sSFR/SFE/$f_{\rm H_{2}}$ in GV galaxies are associated with not only an increased proportion of retired regions in GV galaxies but also a depletion of these quantities in star-forming regions. Finally, the reduction of SFE and $f_{\rm H_{2}}$ in GV galaxies relative to MS galaxies is seen in both bulge and disk regions (albeit with larger uncertainties), suggesting that statistically, quenching in the GV population may persist from the inner to the outer regions.