A New Era of Intracluster Light Studies with JWST

Abstract

Still largely unexplored, the diffuse light in clusters of galaxies traces the past and ongoing buildup of these massive structures. Here we present the first comprehensive study of the intracluster light (ICL) of the cluster SMACS J0723.3–7327 (z = 0.39) using the JWST Early Release Observations. These deep and high spatial resolution images allow the study of the ICL with a high signal-to-noise ratio up to a radial distance of ∼400 kpc, twice as far with respect to previous HST studies of intermediate-redshift clusters. This opens up the possibility of exploring the rich mixture of processes that are building the ICL. We find that the inner parts of this cluster (R < 100 kpc) are built through a major merger, while the outer parts (R > 100 kpc) are mainly produced by the tidal stripping of Milky Way–like satellites. We also find that the slope of the stellar mass density radial profile of the ICL of this cluster (α 3D = −2.47 ± 0.13) closely follows the predicted dark matter halo slope (α 3D,DM = −2.6 to −2), supporting the idea that both components have a similar shape and thus the potential of using the ICL as a tracer of the dark matter distribution in clusters of galaxies. Future JWST studies of the ICL are set to revolutionize our understanding of cluster formation and will be crucial to improve the gravitational lensing mass maps of these structures and thus accurately characterize the properties of the first galaxies.

JWST’s PEARLS: A new lens model for ACT-CL J0102−4915, “El Gordo,” and the first red supergiant star at cosmological distances discovered by JWST

“…At the redshift of El Gordo, its intracluster light and stellar surface mass-density are difficult to measure, but we can approximately estimate the surface mass-density of microlenses if we conservatively assume the stellar mass contributes ≈0.2%-1% to the total mass. At the redshift of El Gordo, the ICL is still forming, so we should expect no more than 1% contribution to the projected mass from stars at 100 kpc from the BCG (Montes & Trujillo 2022). At the position of Quyllur, the convergence from our lens models κ = 0.63-0.66, and the critical surface mass-density for the redshifts of El Gordo and Quyllur is 2300 M pc −2 .…”

“…At magnification factors of several thousand, microlenses are expected to introduce temporary fluctuations in the flux even for a relatively low surface mass-density of microlenses (Σ 10 M pc −2 ). This is a typical value for the surface mass-density of stars at distances of ≈100 kpc from the BCG (Montes & Trujillo 2022), the approximate distance from Quyllur to the BCG. The total projected mass around critical curves is usually about 2500 M pc −2 , and 1% of this in the form of stars is well within the range for microlensing to be common.…”

The Cosmic Telescope That Lenses the Sunburst Arc, PSZ1 G311.65–18.48: Strong Gravitational Lensing Model and Source Plane Analysis*

“…Deep imaging may reveal a faint interloper that complicates the lensing potential, or put limits on the surface brightness of such a component if undetected. The first public JWST data already showcase its power to detect low surface brightness structures (e.g., the intracluster light; Mahler et al 2022;Montes & Trujillo 2022). Alternatively, the IFU data may reveal that one or two of these clumps differ from the main LCE source, indicating that the LCE clump is actually composed of several distinct LyC leaking regions.…”

Precision Modeling of JWST's First Cluster Lens SMACS J0723.3–7327*

“…The intracluster light (ICL) represents an important component of the cluster mass distribution. In addition, it is a unique tracer of a system's dynamical history and its underlying darkmatter distribution, as demonstrated in recent works (e.g., Montes & Trujillo 2014, 2022a, 2022bMontes 2019;Deason et al 2021;Gonzalez et al 2021). While the ICL has so far proven extremely difficult to detect and study with ground-and space-based telescopes, the exceptional sensitivity of JWSTʼs detectors holds great promise for the detection of these extended yet extremely low-surface-brightness features.…”