UNCOVERing the extended strong lensing structures of Abell 2744 with the deepest JWST imaging

Abstract

We present a new parametric lens model for the massive galaxy cluster Abell 2744 based on new ultra-deep JWST imaging taken in the framework of the UNCOVER program. These observations constitute the deepest JWST images of a lensing cluster to date, adding to existing deep Hubble Space Telescope (HST) images and the recent JWST ERS and DDT data taken for this field. The wide field-of-view of UNCOVER (∼45 arcmin2) extends beyond the cluster’s well-studied central core and reveals a spectacular wealth of prominent lensed features around two massive cluster sub-structures in the north and north-west, where no multiple images were previously known. We identify 75 new multiple images and candidates of 17 sources, 43 of which allow us, for the first time, to constrain the lensing properties and total mass distribution around these extended cluster structures using strong lensing (SL). Our model yields an effective Einstein radius of θE, main = 23.2″ ± 2.3″ for the main cluster core (for zs = 2), enclosing a mass of M( < θE, main) = (7.7 ± 1.1) × 1013 M⊙, and θE, NW = 13.1″ ± 1.3″ for the newly discovered north-western SL structure enclosing M( < θE, NW) = (2.2 ± 0.3) × 1013 M⊙. The northern clump is somewhat less massive with θE, N = 7.4″ ± 0.7″ enclosing M( < θE, N) = (0.8 ± 0.1) × 1013 M⊙. We find the northern sub-structures of Abell 2744 to broadly agree with the findings from weak lensing (WL) analyses and align with the filamentary structure found by these previous studies. Our model in particular reveals a large area of high magnification values between the various cluster structures, which will be paramount for lensed galaxy studies in the UNCOVER field. The model is made publicly available to accompany the first UNCOVER data release.

JWST UNCOVER: Extremely Red and Compact Object at z phot ≃ 7.6 Triply Imaged by A2744

“…Three distinct red point-like objects stand out in the central core of the cluster (see Figure 1). These follow the lensing symmetry observed for other lensed systems, and our lens model (Furtak et al 2023c) indeed predicts these to be counter images of the same object at a high redshift, namely z model  7 (but see Section 3.4 for more details). Two of the images reported here were in fact already designated as highredshift z ∼ 7-8 multiple-image candidates by Atek et al (2014Atek et al ( , 2015b in the HFF data (see also Lam et al 2014) and were included in the Mahler et al (2018) SL model of A2744.…”

“…A photometric catalog of objects detected in the whole UNCOVER field is also generated in the UNCOVER program and is released with its other data products (Weaver et al 2023). The catalog includes photometric redshift estimates for each identified object and lists the lensing magnifications from the UNCOVER lensing model (Furtak et al 2023c), which is described in more detail in Section 3.4. We refer the reader to Bezanson et al (2022) and Weaver et al (2023) for more details of the data reduction, field depth in the different bands, source extraction, and catalog assembly.…”

“…For bands in which the images are not detected, we list the 1σ upper limit. The magnifications are computed from our UNCOVER-based SL model of A2744 published in Furtak et al (2023c).…”

“…To estimate the delensed properties of the object presented here as well as to corroborate the photometric redshift estimates, we use an updated fully parametric SL model of A2744 that we recently constructed in the framework of the UNCOVER program (Furtak et al 2023c; see also Roberts-Borsani et al 2023). The model uses a long list of spectroscopically confirmed multiply imaged systems (e.g., Mahler et al 2018;Bergamini et al 2023) and additional photometric systems identified in the new UNCOVER data, in particular in the two northern subclusters.…”

“…The final model used in this work reproduces the >60 multipleimage systems, which span a wide redshift range from z ∼ 1.7 to z ; 10 very well with a lens plane rms of 0 66. Full details of the model are given in Furtak et al (2023c). The critical curves from the model for various redshifts can be seen in Figure 1.…”