Abstract
We present results on the SFR-$M_*$ relation (i.e., the "main sequence")
among star-forming galaxies at $1.37z łeq2.61$ using the MOSFIRE Deep
Evolution Field (MOSDEF) survey. Based on a sample of 261 star-forming galaxies
with observations of H$\alpha$ and H$\beta$ emission lines, we have estimated
robust dust-corrected instantaneous star-formation rates (SFRs) over a large
dynamic range in stellar mass ($10^9.0-10^11.5M_ødot$). We find a
tight correlation between SFR(H$\alpha$) and $M_*$ with an intrinsic scatter of
0.36 dex, 0.05 dex larger than that of UV-based SFRs. This increased scatter is
consistent with predictions from numerical simulations of 0.03 - 0.1 dex, and
is attributed to H$\alpha$ more accurately tracing SFR variations. The slope of
the $łog(SFR)-łog(M_*)$ relation, using SFR(H$\alpha$), at $1.4<
z<2.6$ and over the stellar mass range of $10^9.5$ to $10^11.5M_ødot$ is
$0.650.09$. We find that different assumptions for the dust correction,
such as using the stellar $E(B-V)$ with a Calzetti et al. (2000) attenuation
curve, as well as the sample biases against red and dusty star-forming galaxies
at large masses, could yield steeper slopes. Moreover, not correcting the
Balmer emission line fluxes for the underlying Balmer absorption results in
overestimating the dust extinction of H$\alpha$ and SFR(H$\alpha$) at the
high-mass end by 2.1 (2.5) at $10^10.6 M_ødot$ ($10^11.1 M_ødot$) and
artificially increases the slope of the main-sequence. The shallower
main-sequence slope found here compared to that of galaxy evolution simulations
may be indicative of different feedback processes governing the low- and/or
high-mass end of the main sequence.
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