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KROSS: Mapping the Ha emission across the star-formation sequence at z~1

, , , , , , , , , and . (2016)cite arxiv:1601.04713Comment: Accepted for publication in MNRAS, ref. MN-15-2214-MJ.R2 14/12/15).

Abstract

We present first results from the KMOS Redshift One Spectroscopic Survey (KROSS), an ongoing large kinematical survey of a thousand, z~1 star forming galaxies, with VLT KMOS. Out of the targeted galaxies (~500 so far), we detect and spatially resolve Ha emission in ~90% and 77% of the sample respectively. Based on the integrated Ha flux measurements and the spatially resolved maps we derive a median star formation rate (SFR) of ~7.0 Msun/yr and a median physical size of <r$_e$> = 5.1kpc. We combine the inferred SFRs and effective radii measurements to derive the star formation surface densities (\SigmaSFR) and present a "resolved" version of the star formation main sequence (MS) that appears to hold at sub-galactic scales, with similar slope and scatter as the one inferred from galaxy integrated properties. Our data also yield a trend between \SigmaSFR and \Delta(sSFR) (distance from the MS) suggesting that galaxies with higher sSFR are characterised by denser star formation activity. Similarly, we find evidence for an anti-correlation between the gas phase metallicity (Z) and the \Delta(sSFR), suggesting a 0.2dex variation in the metal content of galaxies within the MS and significantly lower metallicities for galaxies above it. The origin of the observed trends between \SigmaSFR - \Sigma(sSFR) and Z - \Delta(sSFR) could be driven by an interplay between variations of the gas fraction or the star formation efficiency of the galaxies along and off the MS. To address this, follow-up observations of the our sample that will allow gas mass estimates are necessary.

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[1601.04713] KROSS: Mapping the Ha emission across the star-formation sequence at z~1

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