We give an overview and describe the rationale, methods, and first results from NIRCam images of the JWST “Prime Extragalactic Areas for Reionization and Lensing Science” (PEARLS) project. PEARLS uses up to eight NIRCam filters to survey several prime extragalactic survey areas: two fields at the North Ecliptic Pole (NEP); seven gravitationally lensing clusters; two high redshift protoclusters; and the iconic backlit VV 191 galaxy system to map its dust attenuation. PEARLS also includes NIRISS spectra for one of the NEP fields and NIRSpec spectra of two high-redshift quasars. The main goal of PEARLS is to study the epoch of galaxy assembly, active galactic nucleus (AGN) growth, and First Light. Five fields—the JWST NEP Time-Domain Field (TDF), IRAC Dark Field, and three lensing clusters—will be observed in up to four epochs over a year. The cadence and sensitivity of the imaging data are ideally suited to find faint variable objects such as weak AGN, high-redshift supernovae, and cluster caustic transits. Both NEP fields have sightlines through our Galaxy, providing significant numbers of very faint brown dwarfs whose proper motions can be studied. Observations from the first spoke in the NEP TDF are public. This paper presents our first PEARLS observations, their NIRCam data reduction and analysis, our first object catalogs, the 0.9–4.5 μm galaxy counts and Integrated Galaxy Light. We assess the JWST sky brightness in 13 NIRCam filters, yielding our first constraints to diffuse light at 0.9–4.5 μm. PEARLS is designed to be of lasting benefit to the community.

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Brightest cluster galaxies (BCGs), particularly those at the centers of cool-core clusters, can exhibit star formation over spatial extents of up to 100 kpc at inferred rates of up to 100 M yr −1 . Is their star formation also extended over time, as might be expected if fuelled by cooling of the surrounding hot intracluster gas -a residual cooling flow -as demonstrated hitherto only for the BCG in the Perseus cluster? Here, to infer the formation history of relatively young stars in the BCG of MACS J0329.7−0211, we fit model single-stellar-populations to the spectral energy distributions (spanning near-UV to near-IR) measured along different sightlines towards its young stellar population. Employing a Markov Chain Monte Carlo method, we show that star formation in this BCG has persisted at a relatively constant rate of ∼ 2 M yr −1 (factors of 10-40 below the rates previously inferred using simpler methods and/or ad hoc assumptions) over the past ∼400 Myr, beyond which any star formation falls below the observational detection threshold. Such persistent star formation from a residual cooling flow can contribute up to ∼10% of the original stellar mass of this BCG if its progenitor was among the most massive red nuggets known at z ∼2 having masses of ∼ 1 × 10 11 M , but only a few percent of its overall growth in stellar mass to ∼ 8 × 10 11 M at z = 0.45. Although constituting only a minor pathway for the stellar growth of this BCG, persistent star formation from a residual cooling flow can nevertheless contribute significantly to the enormous number of globular clusters found around BCGs in the local Universe.

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