PASSAGES: The Discovery of a Strongly Lensed Protocluster Core Candidate at Cosmic Noon

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Abstract
Investigating the processes by which galaxies rapidly build up their stellar mass during the peak of their star formation ( z = 2–3) is crucial to advancing our understanding of the assembly of large-scale structures. We report the discovery of one of the most gas- and dust-rich protocluster core candidates, PJ0846+15 (J0846), from the Planck All-Sky Survey to Analyze Gravitationally lensed Extreme Starbursts (PASSAGES) sample. The exceedingly high total star formation rate (SFR) uncorrected for lensing magnification ( μ ) of μ SFR = 3990 0 − 12900 + 23000 M ⊙ yr −1 is the result of a foreground cluster lensing at least 11 dusty star-forming galaxies between z = 2.660 and 2.669, where the intrinsic value is estimated to be SFR = 520 0 − 2000 + 3200 M ⊙ yr −1 . Atacama Large Millimeter/submillimeter Array observations uncovered 18 CO(3–2) emission-line detections, some of which are multiply imaged systems, lensed by a foreground cluster at z = 0.77. We present the first multiwavelength characterization of this field, constructing a lens model that predicts that these 11 galaxies ( μ ≃ 1.5–25) are contained within a projected physical extent of 280 × 150 kpc, with a velocity dispersion of σ v = 246 ± 72 km s −1 . J0846 exhibits the rare case of a protocluster candidate whose core is strongly lensed, offering a magnified view of the rapid stellar buildup within an overdense environment at Cosmic Noon.
Funding Information
  • National Radio Astronomy Observatory (1519126)
  • Arizona Space Grant Consortium (80NSSC20M0041)

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