The MOSDEF Survey: The strong agreement between H-alpha and UV-to-FIR star formation rates for z~2 star-forming galaxies

Abstract

We present the first direct comparison between Balmer line and panchromatic SED-based SFRs for z~2 galaxies. For this comparison we used 17 star-forming galaxies selected from the MOSFIRE Deep Evolution Field (MOSDEF) survey, with $3\ddot{I}ƒ$ detections for H$\hat{I}\pm$ and at least two IR bands (Spitzer/MIPS 24$\hat{I}¼$m and Herschel/PACS 100 and 160$\hat{I}¼$m, and in some cases Herschel/SPIRE 250, 350, and 500$\hat{I}¼$m). The galaxies have total IR (8-1000$\hat{I}¼$m) luminosities of $\sim 10^{11.4}-10^{12.4}{\text{L}}_{\odot }$ and star-formation rates (SFRs) of $\sim 30-250{\text{M}}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$. We fit the UV-to-far-IR SEDs with flexible stellar population synthesis (FSPS) models - which include both stellar and dust emission - and compare the inferred SFRs with the SFR(H$\hat{I}\pm$,H${\hat{I}}^2$) values corrected for dust attenuation using Balmer decrements. The two SFRs agree with a scatter of 0.17 dex. Our results imply that the Balmer decrement accurately predicts the obscuration of the nebular lines and can be used to robustly calculate SFRs for star-forming galaxies at z~2 with SFRs up to $\sim 200{\text{M}}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$. We also use our data to assess SFR indicators based on modeling the UV-to-mid-IR SEDs or by adding SFR(UV) and SFR(IR), for which the latter is based on the mid-IR only or on the full IR SED. All these SFRs show a poorer agreement with SFR(H$\hat{I}\pm$,H${\hat{I}}^2$) and in some cases large systematic biases are observed. Finally, we show that the SFR and dust attenuation derived from the UV-to-near-IR SED alone are unbiased when assuming a delayed exponentially declining star-formation history.

7 pages, 5 figures, to be published in ApJ Letters