JWST’s PEARLS: Dust Attenuation and Gravitational Lensing in the Backlit-galaxy System VV 191

Abstract

We derive the spatial and wavelength behavior of dust attenuation in the multiple-armed spiral galaxy VV 191b using backlighting by the superimposed elliptical system VV 191a in a pair with an exceptionally favorable geometry for this measurement. Imaging using the James Webb Space Telescope and Hubble Space Telescope spans the wavelength range 0.3–4.5 μm with high angular resolution, tracing the dust in detail from 0.6–1.5 μm. Distinct dust lanes continue well beyond the bright spiral arms, and trace a complex web, with a very sharp radial cutoff near 1.7 Petrosian radii. We present attenuation profiles and coverage statistics in each band at radii 14–21 kpc. We derive the attenuation law with wavelength; the data both within and between the dust lanes clearly favor a stronger reddening behavior (R = A V /E B−V ≈ 2.0 between 0.6 and 0.9 μm, approaching unity by 1.5 μm) than found for starbursts and star-forming regions of galaxies. Power-law extinction behavior ∝λ −β gives β = 2.1 from 0.6–0.9 μm. R decreases at increasing wavelengths (R ≈ 1.1 between 0.9 and 1.5 μm), while β steepens to 2.5. Mixing regions of different column density flattens the wavelength behavior, so these results suggest a different grain population than in our vicinity. The NIRCam images reveal a lens arc and counterimage from a background galaxy at z ≈ 1, spanning 90° azimuthally at 2.″8 from the foreground elliptical-galaxy nucleus, and an additional weakly lensed galaxy. The lens model and imaging data give a mass/light ratio M/L B = 7.6 in solar units within the Einstein radius 2.0 kpc.

Hidden Giants in JWST's PEARLS: An Ultramassive z = 4.26 Submillimeter Galaxy that Is Invisible to HST

“…The pixel-level SED fits for 850.2 give A V ∼ 0.3-1.0 over most of the UV-detected region, but rising to A V ∼ 3 at the red clump on the northern side. This behavior contrasts with that seen in local galaxies, where extinction typically rises toward the galaxy center (e.g., Holwerda et al 2005;Keel et al 2023). From the stellar mass map, the median stellar-mass density within the effective radius in 850.2 was (0.10 ± 0.01) × 10 10 M e kpc −2 with a peak of 0.7 × 10 10 M e kpc −2 .…”

JWST NIRCam Photometry: A Study of Globular Clusters Surrounding Bright Elliptical Galaxy VV 191a at z = 0.0513

“…This paper analyzes the GC population in the nearby elliptical VV 191a. Visual inspection of the JWST infrared data presented first in Keel et al (2023) reveals dozens of pointsource GC candidates in the VV 191 system not before seen with deep HST data (see Figure 1). Throughout we use AB magnitudes (m AB ; Oke & Gunn 1983) and the Planck flat ΛCDM cosmology with H 0 = 70 ± 0.3 km s −1 Mpc −1 , Ω Λ = 0.685, and Ω m = 0.315 ± 0.007 (Planck Collaboration et al 2020;Riess et al 2022).…”

“…PEARLS has also observed VV 191, an overlapping galaxy pair selected initially to provide a benchmark dust attenuation profile for studying higher-redshift, dusty environments. The galaxy pair consists of VV 191b, a spiral galaxy in the foreground, and VV 191a, an elliptical galaxy in the background situated at z = 0.0513 (Keel et al 2023).…”

“…Throughout we use AB magnitudes (m AB ; Oke & Gunn 1983) and the Planck flat ΛCDM cosmology with H 0 = 70 ± 0.3 km s −1 Mpc −1 , Ω Λ = 0.685, and Ω m = 0.315 ± 0.007 (Planck Collaboration et al 2020;Riess et al 2022). With the above cosmological values, we find the luminosity distance of our target galaxy to be 228 ± 10 Mpc, using a redshift of 0.0513 (Keel et al 2023) and the Wright Cosmology Calculator (Wright 2006). (See Appendix A for justification.)…”

“…Blue was assigned to two HST filters: ultraviolet data taken in 0.34 μm (F336W), and visible light in 0.61 μm (F606W). Observations show an apparent population of GCs surrounding the elliptical (Keel et al 2023). We added the white polygon to their image to outline the region usable for GC searches in VV 191a, as determined in Figure 2.…”