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.
- Publication:
-
The Astronomical Journal
- Pub Date:
- April 2023
- DOI:
- 10.3847/1538-3881/acbdff
- arXiv:
- arXiv:2208.14475
- Bibcode:
- 2023AJ....165..166K
- Keywords:
-
- Interstellar dust extinction;
- Spiral galaxies;
- Strong gravitational lensing;
- 837;
- 1560;
- 1643;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted by Astron. J. Analysis redone since submission, using updated JWST calibrations. Dust reddening behavior is steeper with wavelength and lensed galaxy redshift lower than we first derived