The JWST Advanced Deep Extragalactic Survey: Discovery of an Extreme Galaxy Overdensity at z = 5.4 with JWST/NIRCam in GOODS-S

Publications

Feb 13, 2024·

Jakob M. Helton

Fengwu Sun

Charity Woodrum

Kevin N. Hainline

Christopher N. A. Willmer

George H. Rieke

Marcia J. Rieke

Sandro Tacchella

Brant Robertson

Benjamin D. Johnson

Stacey Alberts

Daniel J. Eisenstein

Ryan Hausen

Nina R. Bonaventura

Andrew Bunker

Stephane Charlot

Mirko Curti

Emma Curtis-Lake

Tobias J. Looser

Roberto Maiolino

Chris Willott

Joris Witstok

Kristan Boyett

Zuyi Chen

Eiichi Egami

Ryan Endsley

Raphael E. Hviding

Daniel T. Jaffe

Zhiyuan Ji

Jianwei Lyu

Lester Sandles

Cite DOI ADS Pre-Print Publication

$The distribution of spectroscopic redshifts for the {{< math >}}$N = 81${{< /math >}} objects at {{< math >}}$z = 5.2-5.5${{< /math >}} that are part of the final spectroscopic sample identified in Section 2.3. As defined in Section 3.1, the gray histograms represent the {{< math >}}$N = 42${{< /math >}} confirmed members of the field, while the turquoise histograms represent the {{< math >}}$N = 39${{< /math >}} confirmed members of the overdensity. The median redshift of the overdensity is given by the solid magenta line. Compared to the field members, the overdensity members appear much more clustered, representing a {{< math >}}$\sim 10${{< /math >}} times overdensity at {{< math >}}$z = 5.4${{< /math >}}.$ Figure 1 from Helton et al. (2024, ApJ, 962, 124).

Abstract

We report the discovery of an extreme galaxy overdensity at $z = 5.4$ in the GOODS-S field using James Webb Space Telescope (JWST)/NIRCam imaging from JADES and JEMS alongside JWST/NIRCam wide-field slitless spectroscopy from FRESCO. We identified potential members of the overdensity using Hubble Space Telescope+JWST photometry spanning $\lambda = 0.4-5.0\ \mu\mathrm{m}$ . These data provide accurate and well-constrained photometric redshifts down to $m \approx 29-30\ \mathrm{mag}$ . We subsequently confirmed $N = 81$ galaxies at $5.2 < z < 5.5$ using JWST slitless spectroscopy over $\lambda = 3.9-5.0\ \mu\mathrm{m}$ through a targeted line search for $\mathrm{H}\alpha$ around the best-fit photometric redshift. We verified that $N = 42$ of these galaxies reside in the field, while $N = 39$ galaxies reside in a density around $\sim 10$ times that of a random volume. Stellar populations for these galaxies were inferred from the photometry and used to construct the star-forming main sequence, where protocluster members appeared more massive and exhibited earlier star formation (and thus older stellar populations) when compared to their field galaxy counterparts. We estimate the total halo mass of this large-scale structure to be $12.6 \leq \mathrm{log}_{10}(M_{\mathrm{halo}}/M_{\odot}) \leq 12.8$ using an empirical stellar mass to halo mass relation, which is likely an underestimate as a result of incompleteness. Our discovery demonstrates the power of JWST at constraining dark matter halo assembly and galaxy formation at very early cosmic times.

Type

Journal article

Publication

The Astrophysical Journal, Volume 962, Issue 2, id.124, 17 pages