THE MOSDEF SURVEY: DISSECTING THE STAR FORMATION RATE VERSUS STELLAR MASS RELATION USING HαAND HβEMISSION LINES ATz∼ 2

We present results on the star-formation rate (SFR) versus stellar mass (M_*) relation (i.e., the "main sequence") among star-forming galaxies at 1.37≤z≤2.61 using the MOSFIRE Deep Evolution Field (MOSDEF) survey. Based on a sample of 261 galaxies with Hα and Hβ spectroscopy, we have estimated robust dust-corrected instantaneous SFRs over a large range in M_* (~109.5-1011.5M_). We find a correlation between log(SFR(Hα)) and log(M_*) with a slope of 0.65±0.08 (0.58±0.10) at 1.4<z<2.6 (2.1<z<2.6). We find that different assumptions for the dust correction, such as using the color-excess of the stellar continuum to correct the nebular lines, sample selection biases against red star-forming galaxies, and not accounting for Balmer absorption can yield steeper slopes of the log(SFR)-log(M_*) relation. Our sample is immune from these biases as it is rest-frame optically selected, Hα and Hβ are corrected for Balmer absorption, and the Hα luminosity is dust-corrected using the nebular color-excess computed from the Balmer decrement. The scatter of the log(SFR(Hα))-log(M_*) relation, after accounting for the measurement uncertainties, is 0.31 dex at 2.1<z<2.6, which is 0.05 dex larger than the scatter in log(SFR(UV))-log(M_*). Based on comparisons to a simulated SFR-M_* relation with some intrinsic scatter, we argue that in the absence of direct measurements of galaxy-to-galaxy variations in the attenuation/extinction curves and the IMF, one cannot use the difference in the scatter of the SFR(Hα)- and SFR(UV)-M_* relations to constrain the stochasticity of star formation in high-redshift galaxies.