On the nature of H$α$ emitters at $z \sim 2$ from the HiZELS survey: physical properties, Ly$α$ escape fraction, and main sequence

I. Oteo; D. Sobral; R. J. Ivison; I. Smail; P. N. Best; J. Cepa; A. M Pérez-García

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arXiv · 1506.02670

On the nature of H$α$ emitters at $z \sim 2$ from the HiZELS survey: physical properties, Ly$α$ escape fraction, and main sequence

I. Oteo·D. Sobral·R. J. Ivison·I. Smail·P. N. Best·J. Cepa·A. M Pérez-García

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Abstract

We present a detailed multi-wavelength study (from rest-frame UV to far-IR) of narrow-band (NB) selected, star-forming (SF) H$α$ emitters (HAEs) at $z \sim 2.23$ taken from the High Redshift(Z) Emission Line Survey (HiZELS). We find that HAEs have similar SED-derived properties and colors to $sBzK$ galaxies and probe a well-defined portion of the SF population at $z \sim 2$. This is not true for Ly$α$ emitters (LAEs), which are strongly biased towards blue, less massive galaxies (missing a significant percentage of the SF population). Combining our H$α$ observations with matched, existing Ly$α$ data we determine that the Ly$α$ escape fraction ($f_{\rm esc}$) is low (only $\sim$ 4.5\% of HAEs show Ly$α$ emission) and decreases with increasing dust attenuation, UV continuum slope, stellar mass, and star formation rate (SFR). This suggests that Ly$α$ preferentially escapes from blue galaxies with low dust attenuation. However, a small population of red and massive LAEs is also present in agreement with previous works. This indicates that dust and Ly$α$ are not mutually exclusive. Using different and completely independent measures of the total SFR we show that the H$α$ emission is an excellent tracer of star formation at $z \sim 2$ with deviations typically lower than 0.3 dex for individual galaxies. We find that the slope and zero-point of the HAE main-sequence (MS) at $z \sim 2$ strongly depend on the dust correction method used to recover SFR, although they are consistent with previous works when similar assumptions are made.

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I. Oteo, D. Sobral, R. J. Ivison, I. Smail, P. N. Best, J. Cepa, A. M Pérez-García. 2015-06-08. On the nature of H$α$ emitters at $z \sim 2$ from the HiZELS survey: physical properties, Ly$α$ escape fraction, and main sequence. https://arxiv.org/abs/1506.02670

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