The Astrophysical Journal Letters (Jan 2023)

A SPectroscopic Survey of Biased Halos in the Reionization Era (ASPIRE): JWST Discovers an Overdensity around a Metal Absorption-selected Galaxy at z ∼ 5.5

  • Yunjing Wu,
  • Feige Wang,
  • Zheng Cai,
  • Xiaohui Fan,
  • Kristian Finlator,
  • Jinyi Yang,
  • Joseph F. Hennawi,
  • Fengwu Sun,
  • Jaclyn B. Champagne,
  • Xiaojing Lin,
  • Zihao Li,
  • Zuyi Chen,
  • Eduardo Bañados,
  • George D. Becker,
  • Sarah E. I. Bosman,
  • Gustavo Bruzual,
  • Stephane Charlot,
  • Hsiao-Wen Chen,
  • Jacopo Chevallard,
  • Anna-Christina Eilers,
  • Emanuele Paolo Farina,
  • Xiangyu Jin,
  • Hyunsung D. Jun,
  • Koki Kakiichi,
  • Mingyu Li,
  • Weizhe Liu,
  • Maria A. Pudoka,
  • Wei Leong Tee,
  • Zhang-Liang Xie,
  • Siwei Zou

DOI
https://doi.org/10.3847/2041-8213/acfee3
Journal volume & issue
Vol. 956, no. 2
p. L40

Abstract

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The launch of JWST opens a new window for studying the connection between metal-line absorbers and galaxies at the end of the Epoch of Reionization. Previous studies have detected absorber–galaxy pairs in limited quantities through ground-based observations. To enhance our understanding of the relationship between absorbers and their host galaxies at z > 5, we utilized the NIRCam wide-field slitless spectroscopy to search for absorber-associated galaxies by detecting their rest-frame optical emission lines (e.g., [O III ] + H β ). We report the discovery of a Mg ii -associated galaxy at z = 5.428 using data from the JWST ASPIRE program. The Mg ii absorber is detected on the spectrum of quasar J0305–3150 with a rest-frame equivalent width of 0.74 Å. The associated galaxy has an [O III ] luminosity of 10 ^42.5 erg s ^−1 with an impact parameter of 24.9 pkpc. The joint Hubble Space Telescope–JWST spectral energy distribution (SED) implies a stellar mass and star formation rate of M _* ≈ 10 ^8.8 M _⊙ , star-formation rate ≈ 10 M _⊙ yr ^−1 . Its [O III ] equivalent width and stellar mass are typical of [O III ] emitters at this redshift. Furthermore, connecting the outflow starting time to the SED-derived stellar age, the outflow velocity of this galaxy is ∼300 km s ^−1 , consistent with theoretical expectations. We identified six additional [O III ] emitters with impact parameters of up to ∼300 pkpc at similar redshifts (∣ dv ∣ < 1000 km s ^−1 ). The observed number is consistent with that in cosmological simulations. This pilot study suggests that systematically investigating the absorber–galaxy connection within the ASPIRE program will provide insights into the metal-enrichment history in the early Universe.

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