We study the star formation rate ( SFR ) - stellar mass ( M _ { \star } ) relation in a self-consistent manner from 0 < z < 2.5 with a sample of galaxies selected from the NEWFIRM Medium-Band Survey .
We find a significant non-linear slope of the relation , \mathrm { SFR } \propto \mathrm { M } _ { \star } ^ { 0.6 } , and a constant observed scatter of 0.34 dex , independent of redshift and M _ { \star } .
However , if we select only blue galaxies we find a linear relation \mathrm { SFR } \propto \mathrm { M } _ { \star } , similar to previous results at z = 0 by Peng et al .
( 35 ) .
This selection excludes red , dusty , star-forming galaxies with higher masses , which brings down the slope .
By selecting on \mathrm { L _ { IR } / L _ { UV } } ( a proxy for dust obscuration ) and the rest-frame U – V colors , we show that star-forming galaxies fall in three distinct regions of the log ( SFR ) -log ( M _ { \star } ) plane : 1 ) actively star-forming galaxies with “ normal ” dust obscuration and associated colors ( 54 % for \mathrm { log ( M _ { \star } ) > 10 } at 1 < z < 1.5 ) , 2 ) red star-forming galaxies with low levels of dust obscuration and low specific SFRs ( 11 % ) , and 3 ) dusty , blue star-forming galaxies with high specific SFRs ( 7 % ) .
The remaining 28 % comprises quiescent galaxies .
Galaxies on the “ normal ” star formation sequence show strong trends of increasing dust attenuation with stellar mass and a decreasing specific SFR , with an observed scatter of 0.25 dex ( 0.17 dex intrinsic scatter ) .
The dusty , blue galaxies reside in the upper envelope of the star formation sequence with remarkably similar spectral shapes at all masses , suggesting that the same physical process is dominating the stellar light .
The red , low-dust star-forming galaxies may be in the process of shutting off and migrating to the quiescent population .