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A relationship between specific star formation rate and metallicity gradient within z ∼ 1 galaxies from KMOS-HiZELS.

Stott, J.P. and Sobral, D. and Swinbank, A.M. and Smail, I. and Bower, R. and Best, P.N. and Sharples, R.M. and Geach, J.E. and Matthee, J. (2014) 'A relationship between specific star formation rate and metallicity gradient within z ∼ 1 galaxies from KMOS-HiZELS.', Monthly notices of the Royal Astronomical Society., 443 (3). pp. 2695-2704.


We have observed a sample of typical z ∼ 1 star-forming galaxies, selected from the HiZELS survey, with the new K-band Multi-Object Spectrograph (KMOS) near-infrared, multi-integral field unit instrument on the Very Large Telescope (VLT), in order to obtain their dynamics and metallicity gradients. The majority of our galaxies have a metallicity gradient consistent with being flat or negative (i.e. higher metallicity cores than outskirts). Intriguingly, we find a trend between metallicity gradient and specific star formation rate (sSFR), such that galaxies with a high sSFR tend to have relatively metal poor centres, a result which is strengthened when combined with data sets from the literature. This result appears to explain the discrepancies reported between different high-redshift studies and varying claims for evolution. From a galaxy evolution perspective, the trend we see would mean that a galaxy's sSFR is governed by the amount of metal-poor gas that can be funnelled into its core, triggered either by merging or through efficient accretion. In fact, merging may play a significant role as it is the starburst galaxies at all epochs, which have the more positive metallicity gradients. Our results may help to explain the origin of the fundamental metallicity relation, in which galaxies at a fixed mass are observed to have lower metallicities at higher star formation rates, especially if the metallicity is measured in an aperture encompassing only the central regions of the galaxy. Finally, we note that this study demonstrates the power of KMOS as an efficient instrument for large-scale resolved galaxy surveys.

Item Type:Article
Keywords:Galaxies: abundances, Galaxies: evolution, Galaxies: kinematics and dynamics.
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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:03 July 2014
Date deposited:18 November 2014
Date of first online publication:04 August 2014
Date first made open access:No date available

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