Publications

2023

1. ApJ

   Searching for C II Emission from the First Sample of z∼6 O I Absorption-associated Galaxies with the Atacama Large Millimeter/submillimeter Array

   Yunjing Wu, Zheng Cai, Jianan Li, and 13 more authors

   The Astrophysical Journal, Nov 2023

   DOI
2. ApJL

   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, and 27 more authors

   The Astrophysical Journal Letters, Oct 2023

   Abs DOI

   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] + Hβ). 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.

3. ApJL

   The Identification of a Dusty Multiarm Spiral Galaxy at z = 3.06 with JWST and ALMA

   Yunjing Wu, Zheng Cai, Fengwu Sun, and 13 more authors

   The Astrophysical Journal Letters, Jan 2023

   Abs DOI

   Spiral arms serve crucial purposes in star formation and galaxy evolution. In this paper, we report the identification of "A2744-DSG-z3," a dusty, multiarm spiral galaxy at z = 3.059 using the James Webb Space Telescope (JWST) NIRISS imaging and grism spectroscopy. A2744-DSG-z3 was discovered as a gravitationally lensed submillimeter galaxy with the Atacama Large Millimeter/submillimeter Array (ALMA). This is the most distant stellar spiral structure seen thus far, consistent with cosmological simulations that suggest z ≈ 3 as the epoch when spirals emerge. Thanks to the gravitational lensing and excellent spatial resolution of JWST, the spiral arms are resolved with a spatial resolution of ≈290 pc. Based on spectral energy distribution fitting, the spiral galaxy has a delensed star formation rate of 85 ± 30 M _⊙ yr^-1, and a stellar mass of ≈10^10.6 M _⊙, indicating that A2744-DSG-z3 is a main-sequence galaxy. After fitting the spiral arms, we find a stellar effective radius (R _e,star) of 5.0 ± 1.5 kpc. Combining with ALMA measurements, we find that the effective radii ratio between dust and stars is ≈0.4, similar to those of massive star‑forming galaxies (SFGs) at z   2, indicating a compact dusty core in A2744-DSG-z3. Moreover, this galaxy appears to be living in a group environment: including A2744-DSG-z3, at least three galaxies at z = 3.05-3.06 are spectroscopically confirmed by JWST/NIRISS and ALMA, residing within a lensing-corrected projected scale of ≈70 kpc. This, along with the asymmetric brightness profile, further suggests that the spiral arms may be triggered by minor-merger events at z ≳ 3.

2021

1. Nature Astronomy

   A [C II] 158 µm emitter associated with an O I absorber at the end of the reionization epoch

   Yunjing Wu, Zheng Cai, Marcel Neeleman, and 11 more authors

   Nature Astronomy, Nov 2021

   DOI