A merging pair of massive quiescent galaxies at $z=3.44$ in the Cosmic Vine

Abstract

We report the spectroscopic confirmation of a merging pair of massive quiescent galaxies at $z=3.44$. Using JWST observations, we confirm that the two galaxies lie at a projected separation of 4.5 kpc with a velocity offset of $\sim 680\mathrm{km}{\mathrm{s}}^{-1}({\delta }_z\sim 0.01)$. The pair resides in the core of a known rich overdensity of galaxies, dubbed the "Cosmic Vine". For both pair members, modeling of the Spectral Energy Distributions and faint rest-frame optical emission lines indicate high stellar masses ($\log (M_{\star }/M_{\odot })\sim 10.9$) and suppressed star formation ($\log (sSFR/y{\mathrm{r}}^{-1})<-10$), more than an order of magnitude below the level of the star formation main sequence at this redshift. We then explore the Illustris-TNG simulation and the GAEA and SHARK semi-analytical models to examine whether they produce a pair of massive quiescent galaxies akin to that of the Cosmic Vine. While all models produce close pairs of massive quiescent galaxies at $2<z<4$ with comparable separations and velocity offsets, their predicted number densities are $10-80$ times lower than our observational constraint. This discrepancy cannot be fully explained by coarse time sampling in these models or the general challenge of forming early massive quiescent galaxies in simulations. Given that $>90\%$ of simulated pairs in the models that we analyzed merge by $z=0$, our findings suggest that our observed pair will likely coalesce into a single massive galaxy. The merger, occurring in the dense core of a large-scale structure, might represent a critical event in the formation of a brightest cluster galaxy and the morphological transformation of high-redshift disky quiescent galaxies into early-type ellipticals.

8 pages, 5 figures, 1 table + Appendix. Accepted for publication in A&A on Feb 28, 2025. Spectra and photometry used in this paper are available at https://doi.org/10.5281/zenodo.14883519 , See Valentino et al. (2025) on arXiv today for another result from the JWST "DeepDive" program

References in corpus (24)

• The propagation of uncertainties in stellar population synthesis modeling I: The relevance of uncertain aspects of stellar evolution and the IMF to the derived physical properties of galaxies
• The hierarchical formation of the brightest cluster galaxies
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• Simulating galaxy formation with black hole driven thermal and kinetic feedback
• The Herschel view of the dominant mode of galaxy growth from z=4 to the present day
• Full spectrum fitting with photometry in pPXF: stellar population versus dynamical masses, non-parametric star formation history and metallicity for 3200 LEGA-C galaxies at redshift z~0.8
• CEERS Epoch 1 NIRCam Imaging: Reduction Methods and Simulations Enabling Early JWST Science Results
• Quiescent galaxies 1.5 billion years after the Big Bang and their progenitors
• An Atlas of Color-selected Quiescent Galaxies at $z>3$ in Public $JWST$ Fields
• COSMOS2020: The Galaxy Stellar Mass Function: the assembly and star formation cessation of galaxies at $0.2<z\le 7.5$
• A surprising abundance of massive quiescent galaxies at 3 < z < 5 in the first data from JWST CEERS
• A massive, dead disk galaxy in the early Universe
• RUBIES: a complete census of the bright and red distant Universe with JWST/NIRSpec
• The JWST-PRIMAL Legacy Survey. A JWST/NIRSpec reference sample for the physical properties and Lyman-$\alpha$ absorption and emission of $\sim 500$ galaxies at $z=5.5-13.4$
• A population of faint, old, and massive quiescent galaxies at 3 < z < 4 revealed by JWST NIRSpec Spectroscopy
• Metal deficiency in cluster star-forming galaxies at z=2
• Quenching of star formation from a lack of inflowing gas to galaxies
• Tracing the Quenching Journey across Cosmic Time
• COSMOS2020: Discovery of a protocluster of massive quiescent galaxies at $z=2.77$
• Galaxy Merger Candidates in High-Redshift Cluster Environments
• Cosmic Vine: A z=3.44 large-scale structure hosting massive quiescent galaxies
• $JWST$ Insight Into a Lensed $HST$-dark Galaxy and its Quiescent Companion at $z=2.58$
• Hubble Space Telescope Images of Red Mergers: How Dry are They?
• JWST's first glimpse of a z > 2 forming cluster reveals a top-heavy stellar mass function

Cited by in corpus (10)

• Exploring over 700 massive quiescent galaxies at z = 2-7: Demographics and stellar mass functions
• Explaining ultra-massive quiescent galaxies at $3<z<5$ in the context of their environments
• PRIMER & JADES reveal an abundance of massive quiescent galaxies at 2 < z < 5
• Double Trouble: Two spectroscopically confirmed low-mass quiescent galaxies at z>5 in overdensities
• RUBIES spectroscopically confirms the high number density of quiescent galaxies from $2<\mathbf{z}<5$
• COSMOS-Web galaxy groups: Evolution of red sequence and quiescent galaxy fraction
• On the unique evolutionary mechanisms of massive quiescent galaxies in the epoch of reionisation
• Quantifying the Impact of Incompleteness on Identifying and Interpreting Galaxy Protocluster Populations with the TNG-Cluster Simulation
• Cosmic Vine: High abundance of massive galaxies and dark matter halos in a forming cluster at z=3.44
• Dynamical properties and star formation history of a low-mass quenched galaxy at Cosmic Noon