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Register a new userGas-phase metallicity of 27 galaxies at intermediate redshift
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Added by
Lorenzo Morelli Dr.
Publication date
2012
fields
Physics
and research's language is
English
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The purpose of this work is to make available new gas-phase oxygen abundance measurements for a serendipitous sample of 27 galaxies with redshift 0.35<z<0.52. We measured the equivalent widths of the [O II]{lambda}3727, H{beta}, and [O III]{lambda}{lambda}4959, 5007 emission lines observed in the galaxy spectra obtained with the Visible Multi-Object Spectrograph mounted at the Very Large Telescope. For each galaxy, we derived the metallicity-sensitive emission lines ratio R23, ionization-sensitive emission lines ratio O32, and gas-phase oxygen abundance 12+log(O/H). The values of gas-phase oxygen abundance 12+log(O/H) we obtained for the sample galaxies are consistent with previous findings for galaxies at intermediate redshift.
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Recent spatially resolved observations of galaxies at z=0.6-3 reveal that high-redshift galaxies show complex kinematics and a broad distribution of gas-phase metallicity gradients. To understand these results, we use a suite of high-resolution cosmological zoom-in simulations from the Feedback in Realistic Environments (FIRE) project, which include physically motivated models of the multi-phase ISM, star formation, and stellar feedback. Our simulations reproduce the observed diversity of kinematic properties and metallicity gradients, broadly consistent with observations at z=0-3. Strong negative metallicity gradients only appear in galaxies with a rotating disk, but not all rotationally supported galaxies have significant gradients. Strongly perturbed galaxies with little rotation always have flat gradients. The kinematic properties and metallicity gradient of a high-redshift galaxy can vary significantly on short time-scales, associated with starburst episodes. Feedback from a starburst can destroy the gas disk, drive strong outflows, and flatten a pre-existing negative metallicity gradient. The time variability of a single galaxy is statistically similar to the entire simulated sample, indicating that the observed metallicity gradients in high-redshift galaxies reflect the instantaneous state of the galaxy rather than the accretion and growth history on cosmological time-scales. We find weak dependence of metallicity gradient on stellar mass and specific star formation rate (sSFR). Low-mass galaxies and galaxies with high sSFR tend to have flat gradients, likely due to the fact that feedback is more efficient in these galaxies. We argue that it is important to resolve feedback on small scales in order to produce the diverse metallicity gradients observed.
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