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The Origin and Evolution of Metallicity Gradients: Probing the Mode of Mass Assembly at z ≃ 2

Jones, Tucker and Ellis, Richard S. and Richard, Johan and Jullo, Eric (2013) The Origin and Evolution of Metallicity Gradients: Probing the Mode of Mass Assembly at z ≃ 2. Astrophysical Journal, 765 (1). Art. No. 48. ISSN 0004-637X.

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We present and discuss measurements of the gas-phase metallicity gradient in four gravitationally lensed galaxies at z = 2.0-2.4 based on adaptive optics-assisted imaging spectroscopy with the Keck II telescope. Three galaxies with well-ordered rotation reveal metallicity gradients with lower gas-phase metallicities at larger galactocentric radii. Two of these display gradients much steeper than found locally, while a third has one similar to that seen in local disk galaxies. The fourth galaxy exhibits complex kinematics indicative of an ongoing merger and reveals an "inverted" gradient with lower metallicity in the central regions. By comparing our sample to similar data in the literature for lower redshift galaxies, we determine that, on average, metallicity gradients must flatten by a factor of 2.6 ± 0.9 between z = 2.2 and the present epoch. This factor is in rough agreement with the size growth of massive galaxies, suggesting that inside-out growth can account for the evolution of metallicity gradients. Since the addition of our new data provides the first indication of a coherent picture of this evolution, we develop a simple model of chemical evolution to explain the collective data. We find that metallicity gradients and their evolution can be explained by the inward radial migration of gas together with a radial variation in the mass loading factor governing the ratio of outflowing gas to the local star formation rate. Average mass loading factors of ≾2 are inferred from our model in good agreement with direct measurements of outflowing gas in z ≃ 2 galaxies.

Item Type:Article
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URLURL TypeDescription
Jones, Tucker0000-0001-5860-3419
Ellis, Richard S.0000-0001-7782-7071
Richard, Johan0000-0001-5492-1049
Jullo, Eric0000-0002-9253-053X
Additional Information:© 2013 American Astronomical Society. Received 2012 July 18; accepted 2013 January 9; published 2013 February 14. We thank the staff of Keck Observatory for their tireless support of these observations. T.A.J. acknowledges stimulating discussions with Shy Genel, Fabio Bresolin, Judy Cohen, Wal Sargent, Romeel Davé, and Hai Fu. We thank the referee for an excellent report which significantly improved this paper. J.R. is supported by the Marie Curie Career Integration Grant 294074. E.J. acknowledges support from the NASA Postdoctoral Program and CNRS. Most of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
Funding AgencyGrant Number
Marie Curie Career Integration Grant294074
NASA Postdoctoral ProgramUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:galaxies: abundances; galaxies: evolution; galaxies: high-redshift
Issue or Number:1
Record Number:CaltechAUTHORS:20130402-112459826
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Official Citation:The Origin and Evolution of Metallicity Gradients: Probing the Mode of Mass Assembly at z ≃ 2 Tucker Jones et al. 2013 ApJ 765 48
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37722
Deposited By: Ruth Sustaita
Deposited On:02 Apr 2013 18:41
Last Modified:09 Mar 2020 13:18

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