Journal Article

The Subaru FMOS Galaxy Redshift Survey (FastSound). III. The mass–metallicity relation and the fundamental metallicity relation at z ∼ 1.4

Kiyoto Yabe, Kouji Ohta, Masayuki Akiyama, Andrew Bunker, Gavin Dalton, Richard Ellis, Karl Glazebrook, Tomotsugu Goto, Masatoshi Imanishi, Fumihide Iwamuro, Hiroyuki Okada, Ikkoh Shimizu, Naruhisa Takato, Naoyuki Tamura, Motonari Tonegawa and Tomonori Totani

in Publications of the Astronomical Society of Japan

Volume 67, issue 6 Published in print December 2015 | ISSN: 0004-6264
Published online September 2015 | e-ISSN: 2053-051X | DOI: https://dx.doi.org/10.1093/pasj/psv079
The Subaru FMOS Galaxy Redshift Survey (FastSound). III. The mass–metallicity relation and the fundamental metallicity relation at z ∼ 1.4

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We present the results from a large near-infrared spectroscopic survey made with Subaru/FMOS (FastSound) consisting of ∼ 4000 galaxies at z ∼ 1.4 with significant Hα detection. We measure the gas-phase metallicity from the [N ii]λ6583/Hα emission line ratio of the composite spectra in various stellar mass and star-formation rate bins. The resulting mass–metallicity relation generally agrees with previous studies obtained in a similar redshift range to that of our sample. No clear dependence of the mass–metallicity relation on star-formation rate is found. Our result at z ∼ 1.4 is roughly in agreement with the fundamental metallicity relation at z ∼ 0.1 with a fiber aperture corrected star-formation rate. We detect significant [S ii]λλ6716,6731 emission lines from the composite spectra. The electron density estimated from the [S ii]λλ6716,6731 line ratio ranges from 10–500 cm−3, which generally agrees with that of local galaxies. On the other hand, the distribution of our sample on [N ii]λ6583/Hα vs. [S ii]λλ6716,6731/Hα is different to that found locally. We estimate the nitrogen-to-oxygen abundance ratio (N/O) from the N2S2 index, and find that the N/O in galaxies at z ∼ 1.4 is significantly higher than the local values at a fixed metallicity and stellar mass. The metallicity at z ∼ 1.4 recalculated with this N/O enhancement taken into account decreases by 0.1–0.2 dex. The resulting metallicity is lower than the local fundamental metallicity relation.

Keywords: galaxies: abundances; galaxies: evolution; galaxies: high-redshift; galaxies: ISM

Journal Article.  8623 words.  Illustrated.

Subjects: Galaxies

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