Astrochemistry

An Ice Age JWST Inventory Of Dense Molecular Cloud Ices

By Keith Cowing
Status Report
astro-ph.EP
January 24, 2023
Filed under , , , , ,
An Ice Age JWST Inventory Of Dense Molecular Cloud Ices
NIRSpec FS [NIRCam WFSS] and MIRI LRS spectra of NIR38 and J110621. Top: Full NIRSpec FS and MIRI LRS spectra of NIR38 (AV ∼ 60, solid navy line) and J110621 (AV ∼ 95, solid light gray line), with associated continuum fits (dotted lines). For NIR38, a preliminary NIRCam WFSS spectrum has been scaled to the NIRSpec spectrum at 3.8 µm and spliced in to cover the NIRSpec FS gap from 3.85–3.9 µm and extend the spectrum to 2.5 µm. Ice absorption features are color-coded according to species and labelled in the NIR38 spectrum. Wavelength regions used for the continuum fit are indicated by light gray bars (NIRSpec) and dark gray filled circles (MIRI) at the bottom of the top panel. Bottom: Zoom in on the weaker ice features and structure revealed by JWST. The potential dangling O-H feature is indicted by “dO-H”, and the combination modes of CO2 and H2O by “combi.”

Icy grain mantles are the main reservoir of the volatile elements that link chemical processes in dark, interstellar clouds with the formation of planets and composition of their atmospheres.

The initial ice composition is set in the cold, dense parts of molecular clouds, prior to the onset of star formation. With the exquisite sensitivity of JWST, this critical stage of ice evolution is now accessible for detailed study.

Here we show the first results of the Early Release Science program “Ice Age” that reveal the rich composition of these dense cloud ices. Weak ices, including, 13CO2, OCN−, 13CO, OCS, and COMs functional groups are now detected along two pre-stellar lines of sight. The 12CO2 ice profile indicates modest growth of the icy grains.

Column densities of the major and minor ice species indicate that ices contribute between 2 and 19% of the bulk budgets of the key C, O, N, and S elements. Our results suggest that the formation of simple and complex molecules could begin early in a water-ice rich environment.

M. K. McClure, W. R. M. Rocha, K. M. Pontoppidan, N. Crouzet, L. E. U. Chu, E. Dartois, T. Lamberts, J. A. Noble, Y. J. Pendleton, G. Perotti, D. Qasim, M.G. Rachid, Z.L. Smith, Fengwu Sun, Tracy L Beck, A. C. A. Boogert, W. A. Brown, P. Caselli, S.B. Charnley, Herma M. Cuppen, H. Dickinson, M. N. Drozdovskaya, E. Egami, J. Erkal, H. Fraser, R. T. Garrod, D. Harsono, S. Ioppolo, I. Jimenez-Serra, M. Jin, J. K. Jørgensen, L. E. Kristensen, D.C. Lis, M. R. S. McCoustra, Brett A. McGuire, G.J. Melnick, Karin I. Oberg, M. E. Palumbo, T. Shimonishi, J.A. Sturm, E.F. van Dishoeck, H. Linnartz

Comments: To appear in Nature Astronomy on January 23rd, 2023. 33 pages, 16 figures, 3 tables; includes extended and supplemental data sections. Part of the JWST Ice Age Early Release Science program’s science enabling products. Enhanced spectra downloadable on Zenodo at the following DOI: https://doi.org/10.5281/zenodo.7501239
Subjects: Astrophysics of Galaxies (astro-ph.GA); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2301.09140 [astro-ph.GA] (or arXiv:2301.09140v1 [astro-ph.GA] for this version)
Related DOI:
https://doi.org/10.1038/s41550-022-01875-w
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Submission history
From: Melissa McClure
[v1] Sun, 22 Jan 2023 15:28:37 UTC (6,950 KB)
https://arxiv.org/abs/2301.09140
Astrobiology

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