Astrochemistry

The Edge-on Disk Tau042021: Icy Grains At High Altitudes And A Wind Containing Astronomical PAHs

By Keith Cowing

Status Report

The ISME Journal

April 1, 2025

Filed under astrochemistry, astronomy, Interstellar, JWST, organic chemistry, PAH, Protoplanetary Disk, Spectroscopy, Tau042021, The ISME Journal

The Edge-on Disk Tau042021: Icy Grains At High Altitudes And A Wind Containing Astronomical PAHs — Location of sediment sampling and pictures of resurrected species S. marinoi. (A) Map of the Baltic Sea (northern Europe) with the location of sediment core sampling (EMB262/6; 240 m water depth) in the eastern Gotland Basin (triangle). Additional sampling points of stratigraphy reference cores (points): M86-1a/36 [35], MSM62–60 [36], and P435-2-1 [34]. (B) Pictures of different Lugol-stained strains of S. marinoi. Strain SM_EGB_382_11 from 6871 ± 140 years of dormancy, SM_EGB_1_5 from 3 ± 2 years of dormancy, SM_EGB_107_1 from 1131 ± 110 years of dormancy, SM_EGB_20_4 from 58 ± 5 years of dormancy, and SM_EGB_232_2 from 3411 ± 120 years of dormancy. Scale bars = 20 μm. — The ISME Journal

Spectra of the nearly edge-on protoplanetary disks observed with the JWST have shown ice absorption bands of varying optical depths and peculiar profiles, challenging radiative transfer modelling and our understanding of dust and ice in disks.

We build models including dust grain size, shape, and composition to reproduce JWST IFU spectroscopy of the large edge-on disk Tau042021. We explore radiative transfer models using different dust grain size distributions, including grains of effective radii a_eff = 0.005-3000 microns. Scattering properties of distributions of triaxial ellipsoidal grains are calculated.

We consider compositions with silicates, amorphous carbon, and mixtures of H₂O, CO₂, and CO. We use RADMC-3D Monte Carlo radiative transfer models of Tau042021 to simulate the spectral cubes observed with JWST-NIRSpec and MIRI. We compare the results to observations, including H₂O at 3.05 microns, CO at 4.67 microns, and CO2 at 4.27 microns and to archival JWST-NIRCam and ALMA continuum images.

The observed near- to mid-infrared imply dust distributions with grain sizes up to several tens of microns. The intensity distribution perpendicular to the disk exhibits emission profile wings extending into the upper disk atmosphere at altitudes exceeding the classical scale height expected in the isothermal hydrostatic limit.

We produce ice map images demonstrating the presence of icy dust grains up to altitudes high above the disk midplane, more than three hydrostatic equilibrium scale heights. We demonstrate the presence of a wind containing the carriers of astronomical PAH bands.

The wind appears as an X-shaped emission at 3.3, 6.2, 7.7 and 11.3 microns, characteristic wavelengths of the infrared astronomical PAH bands. We associate the spatial distribution of this component with carriers of astronomical PAH bands that form a layer of emission at the interface with the H2 wind.

E. Dartois, J. A. Noble, M. K. McClure, J. A. Sturm, T. L. Beck, N. Arulanantham, M. N. Drozdovskaya, C. C. Espaillat, D. Harsono, M.-E. Palumbo, Y. J. Pendleton, K. M. Pontoppidan

Comments: Accepted for publication in Astronomy and Astrophysics
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2503.24309 [astro-ph.EP] (or arXiv:2503.24309v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2503.24309
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Submission history
From: Emmanuel Dartois
[v1] Mon, 31 Mar 2025 16:56:16 UTC (4,558 KB)
https://arxiv.org/abs/2503.24309
Astrobiology,

Astrobiology

Resurrection of a diatom after 7000 years from anoxic Baltic Sea sediment, The ISME Journal (open access)

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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