{
  "id": "1504.05589",
  "version": "v1",
  "published": "2015-04-21T20:01:34.000Z",
  "updated": "2015-04-21T20:01:34.000Z",
  "title": "Physical conditions of the interstellar medium in star-forming galaxies at z~1.5",
  "authors": [
    "Masao Hayashi",
    "Chun Ly",
    "Kazuhiro Shimasaku",
    "Kentaro Motohara",
    "Matthew A. Malkan",
    "Tohru Nagao",
    "Nobunari Kashikawa",
    "Ryosuke Goto",
    "Yoshiaki Naito"
  ],
  "comment": "Accepted for publication in the PASJ, April 20, 2015. 23 pages, 14 figures, 3 tables",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We present results from Subaru/FMOS near-infrared (NIR) spectroscopy of 118 star-forming galaxies at $z\\sim1.5$ in the Subaru Deep Field. These galaxies are selected as [OII]$\\lambda$3727 emitters at $z\\approx$ 1.47 and 1.62 from narrow-band imaging. We detect H$\\alpha$ emission line in 115 galaxies, [OIII]$\\lambda$5007 emission line in 45 galaxies, and H$\\beta$, [NII]$\\lambda$6584, and [SII]$\\lambda\\lambda$6716,6731 in 13, 16, and 6 galaxies, respectively. Including the [OII] emission line, we use the six strong nebular emission lines in the individual and composite rest-frame optical spectra to investigate physical conditions of the interstellar medium in star-forming galaxies at $z\\sim$1.5. We find a tight correlation between H$\\alpha$ and [OII], which suggests that [OII] can be a good star formation rate (SFR) indicator for galaxies at $z\\sim1.5$. The line ratios of H$\\alpha$/[OII] are consistent with those of local galaxies. We also find that [OII] emitters have strong [OIII] emission lines. The [OIII]/[OII] ratios are larger than normal star-forming galaxies in the local Universe, suggesting a higher ionization parameter. Less massive galaxies have larger [OIII]/[OII] ratios. With evidence that the electron density is consistent with local galaxies, the high ionization of galaxies at high redshifts may be attributed to a harder radiation field by a young stellar population and/or an increase in the number of ionizing photons from each massive star.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-04-21T20:01:34.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "star-forming galaxies",
      "interstellar medium",
      "physical conditions",
      "strong nebular emission lines",
      "local galaxies"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 23,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}