{
  "id": "1809.07675",
  "version": "v1",
  "published": "2018-09-20T15:32:22.000Z",
  "updated": "2018-09-20T15:32:22.000Z",
  "title": "Slow-then-rapid quenching as traced by enhanced metallicities of cluster galaxies at z~0.2 in the slow quenching phase",
  "authors": [
    "C. Maier",
    "B. L. Ziegler",
    "C. P. Haines",
    "G. P. Smith"
  ],
  "comment": "11 pages, 7 figures; submitted on 20 Sep 2018 to A&A",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "(Abridged) We explore 7 clusters from LoCuSS at z~0.2 with spectra of ~2700 cluster members from the ACReS Hectospec survey covering a region which corresponds to about three virial radii for each cluster. We measure fluxes of five emission lines of cluster members enabling us to unambiguously derive O/H gas metallicities, and also SFRs from extinction corrected Halpha fluxes. We compare our cluster galaxy sample with a field sample of ~1000 galaxies at similar redshifts observed with Hectospec. We find that star-forming cluster and field galaxies show similar median specific SFRs in a given mass bin, but their O/H values are displaced to higher values at projected radii of R<R200 compared with galaxies at larger radii and in the field. The comparison with metallicity-SFR-mass model predictions with inflowing gas indicates a slow-quenching scenario in which strangulation is initiated when galaxies pass R~R200 by stopping the inflow of gas. The metallicities of cluster members inside R200 are thereby increasing, but their SFRs are hardly affected for a period of time, because these galaxies consume available disk gas. We use the fraction of star-forming cluster galaxies as a function of clustercentric radius compared to predictions from the Millennium simulation to constrain quenching timescales to be 1-2Gyrs. This is consistent with a slow-then-rapid quenching scenario. Slow quenching (strangulation) starts when the gas inflow is stopped when the galaxy passes R200 with a phase in which cluster galaxies are still star-forming, but they show elevated metallicities tracing the ongoing quenching. This phase lasts for 1-2Gyrs, meanwhile the galaxies travel to denser inner regions of the cluster, and is followed by a \"rapid\" phase: a rapid complete quenching of star formation due to the increasing ram-pressure towards the cluster center which can also strip the cold gas in massive galaxies.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2018-09-20T15:32:22.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "cluster galaxy",
      "slow quenching phase",
      "slow-then-rapid quenching",
      "enhanced metallicities",
      "derive o/h gas metallicities"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 11,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}