English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

We investigate the physical conditions of ionized gas in high-z star-forminggalaxies using diagnostic diagrams based on the rest-frame optical emissionlines. The sample consists of 701 galaxies with an Ha detection at $1.4\lesssimz\lesssim1.7$, from the FMOS-COSMOS survey, that represent the normalstar-forming population over the stellar mass range $10^{9.6} \lesssimM_\ast/M_\odot \lesssim 10^{11.6}$ with those at $M_\ast>10^{11}~M_\odot$ beingwell sampled. We confirm an offset of the average location of star-forminggalaxies in the BPT diagram ([OIII]/Hb vs. [NII]/Ha), primarily towards higher[OIII]/Hb, compared with local galaxies. Based on the [SII] ratio, we measurean electron density ($n_e=220^{+170}_{-130}~\mathrm{cm^{-3}}$), that is higherthan that of local galaxies. Based on comparisons to theoretical models, weargue that changes in emission-line ratios, including the offset in the BPTdiagram, are caused by a higher ionization parameter both at fixed stellar massand at fixed metallicity with additional contributions from a higher gasdensity and possibly a hardening of the ionizing radiation field. Ionizationdue to AGNs is ruled out as assessed with Chandra. As a consequence, we revisitthe mass-metallicity relation using [NII]/Ha and a new calibration including[NII]/[SII] as recently introduced by Dopita et al. Consistent with ourprevious results, the most massive galaxies ($M_\ast\gtrsim10^{11}~M_\odot$)are fully enriched, while those at lower masses have metallicities lower thanlocal galaxies. Finally, we demonstrate that the stellar masses, metallicitiesand star formation rates of the FMOS sample are well fit with aphysically-motivated model for the chemical evolution of star-forming galaxies.

The FMOS-COSMOS survey of star-forming galaxies at z~1.6. IV: Excitation state and chemical enrichment of the interstellar medium