JWST's PEARLS: Dust Attenuation and Gravitational Lensing in the Backlit-galaxy System VV 191
Grogin, Norman A.; Hathi, Nimish P.; Koekemoer, Anton M.; Pirzkal, Nor; Holwerda, Benne; Frye, Brenda L.; Conselice, Christopher J.; Rutkowski, Michael J.; Yan, Haojing; Wang, Lifan; Cheng, Cheng; Willmer, Christopher N. A.; Keel, William C.; Zitrin, Adi; Coe, Dan; Ryan, Russell E.; Driver, Simon P.; Summers, Jake; Windhorst, Rogier A.; Cohen, Seth H.; Willner, S. P.; Jansen, Rolf A.; Marshall, Madeline A.; Robotham, Aaron; Diego, Jose M.; Petric, Andreea; Broadhurst, Thomas J.; Ferrami, Giovanni; Bradford, Sarah T.; Robertson, Clayton D.; Wyithe, Stuart
United States, Australia, United Kingdom, Canada, Spain, China, Israel
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.