3D-HST Emission Line Galaxies at z ~ 2: Discrepancies in the Optical/UV Star Formation Rates

Abstract

We use Hubble Space Telescope near-IR grism spectroscopy to examine the H-beta line strengths of 260 star-forming galaxies in the redshift range 1.90 < z < 2.35. We show that at these epochs, the H-beta star formation rate (SFR) is a factor of ~1.8 higher than what would be expected from the systems' rest-frame UV flux density, suggesting a shift in the standard conversion between these quantities and star formation rate. We demonstrate that at least part of this shift can be attributed to metallicity, as H-beta is more greatly enhanced in systems with lower oxygen abundance. This offset must be considered when measuring the star formation rate history of the universe. We also show that the relation between stellar and nebular extinction in our z ~ 2 sample is consistent with that observed in the local universe.

15 pages, 11 figures, Accepted to ApJ

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Cited by in corpus (9)

• Investigating H$\alpha$, UV, and IR star-formation rate diagnostics for a large sample of z ~ 2 galaxies
• HST Emission Line Galaxies at z ~ 2: The Mystery of Neon
• HST Emission Line Galaxies at z ~ 2: The Ly-alpha Escape Fraction
• CLEAR: High-Ionization [Ne V] $\lambda$3426 Emission-line Galaxies at $1.4<z<2.3$
• The HETDEX Survey: The Ly$\alpha$ Escape Fraction from 3D-HST Emission Line Galaxies at $z\sim 2$
• Galaxies of the $z\sim 2$ Universe. I. Grism-Selected Rest-Frame Optical Emission Line Galaxies
• Measuring Stellar Masses of Emission Line Galaxies at 1.2<z<1.9
• The H$\alpha$ and [O III] $\lambda 5007$ Luminosity Functions of $1.2<z<1.9$ Emission-Line Galaxies from HST Grism Spectroscopy
• The $z\sim 2$ $[\mathrm{O}\mathrm{III}]$ Luminosity Function of Grism-selected Emission-line Galaxies