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The FMOS-COSMOS Survey of Star-forming Galaxies at z ~ 1.6. IV. Excitation State and Chemical Enrichment of the Interstellar Medium

Kashino, D. and Silverman, J. D. and Sanders, D. and Kartaltepe, J. S. and Daddi, E. and Renzini, A. and Valentino, F. and Rodighiero, G. and Juneau, S. and Kewley, L. J. and Zahid, H. J. and Arimoto, N. and Nagao, T. and Chu, J. and Sugiyama, N. and Civano, F. and Ilbert, O. and Kajisawa, M. and Le Fèvre, O. and Maier, C. and Masters, D. and Miyaji, T. and Onodera, M. and Puglisi, A. and Taniguchi, Y. (2017) The FMOS-COSMOS Survey of Star-forming Galaxies at z ~ 1.6. IV. Excitation State and Chemical Enrichment of the Interstellar Medium. Astrophysical Journal, 835 (1). Art. No. 88. ISSN 0004-637X. doi:10.3847/1538-4357/835/1/88.

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We investigate the physical conditions of ionized gas in high-z star-forming galaxies using diagnostic diagrams based on the rest-frame optical emission lines. The sample consists of 701 galaxies with an Hα detection at 1.4 ≾ z ≾ 1.7, from the Fiber Multi-Object Spectrograph (FMOS)-COSMOS survey, that represent the normal star-forming population over the stellar mass range 10^(9.6) ≾ M_*/M_⊙ ≾ 10^(11.6), with those at M_* > 10^(11) M_⊙ being well sampled. We confirm an offset of the average location of star-forming galaxies in the Baldwin–Phillips–Terlevich (BPT) diagram ([O III]/Hβ versus [N II]/Hα), primarily toward higher [O III]/Hβ, compared with local galaxies. Based on the [S ii] ratio, we measure an electron density n_e 220_(-130)^(+170) cm^(-3)), which is higher than that of local galaxies. Based on comparisons to theoretical models, we argue that changes in emission-line ratios, including the offset in the BPT diagram, are caused by a higher ionization parameter both at fixed stellar mass and at fixed metallicity, with additional contributions from a higher gas density and possibly a hardening of the ionizing radiation field. Ionization due to active galactic nuclei is ruled out as assessed with Chandra. As a consequence, we revisit the mass–metallicity relation using [N II]/Hα and a new calibration including [N II]/[S II] as recently introduced by Dopita et al. Consistent with our previous results, the most massive galaxies (M_* ≳ 10^(11) M_⊙ are fully enriched, while those at lower masses have metallicities lower than local galaxies. Finally, we demonstrate that the stellar masses, metallicities, and star formation rates of the FMOS sample are well fit with a physically motivated model for the chemical evolution of star-forming galaxies.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Kashino, D.0000-0001-9044-1747
Silverman, J. D.0000-0002-0000-6977
Sanders, D.0000-0002-1233-9998
Kartaltepe, J. S.0000-0001-9187-3605
Daddi, E.0000-0002-3331-9590
Renzini, A.0000-0002-7093-7355
Rodighiero, G.0000-0002-9415-2296
Kewley, L. J.0000-0001-8152-3943
Nagao, T.0000-0002-7402-5441
Chu, J.0000-0003-3955-2470
Civano, F.0000-0002-2115-1137
Ilbert, O.0000-0002-7303-4397
Kajisawa, M.0000-0002-1732-6387
Le Fèvre, O.0000-0001-5891-2596
Masters, D.0000-0001-5382-6138
Puglisi, A.0000-0001-9369-1805
Taniguchi, Y.0000-0003-2247-3741
Additional Information:© 2017. The American Astronomical Society. Received 2016 April 15; revised 2016 November 25; accepted 2016 December 4; published 2017 January 20. We are grateful to the referee for careful reading and useful comments, M. Dopita for kindly providing us with the photoionization model data, and M. Fukugita, K. Yabe, T. Kojima, and R. Shimakawa for useful discussions. We thank the Subaru telescope staff, especially K. Aoki, for their great help in the observations. This paper is based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. We appreciate the MPA/JHU team for making their catalog public. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is T.M. is supported by CONACyT Grants 179662, 252531 and UNAM-DGAPA PAPIIT IN104216. A.R. is grateful to the National Astronomical Observatory of Japan for its support and hospitality while this paper was prepared. Partial support by the INAF-PRIN 2012 grant is also acknowledged. This work was supported in part by KAKENHI (YT: 23244031 and 16H02166) through Japan Society for the Promotion of Science (JSPS). J.D.S. is supported by JSPS KAKENHI grant Number 26400221 and the World Premier International Research Center Initiative (WPI), MEXT, Japan. D.K. is supported through the Grant-in-Aid for JSPS Research Fellows (No. 26-3216).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
Participating InstitutionsUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Consejo Nacional de Ciencia y Tecnología (CONACyT)179662
Consejo Nacional de Ciencia y Tecnología (CONACyT)252531
Universidad Nacional Autónoma de México (UNAM)IN104216
National Astronomical Observatory of JapanUNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)PRIN 2012
Japan Society for the Promotion of Science (JSPS)23244031
Japan Society for the Promotion of Science (JSPS)16H02166
Japan Society for the Promotion of Science (JSPS)26400221
Ministry of Education, Culture, Sports, Science and Technology (MEXT)UNSPECIFIED
Japan Society for the Promotion of Science (JSPS)26-3216
Subject Keywords:galaxies: abundances; galaxies: evolution; galaxies: high-redshift; galaxies: ISM; galaxies: star formation
Issue or Number:1
Record Number:CaltechAUTHORS:20170127-145733022
Persistent URL:
Official Citation:D. Kashino et al 2017 ApJ 835 88
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:73791
Deposited By: George Porter
Deposited On:27 Jan 2017 23:24
Last Modified:11 Nov 2021 05:22

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