The First Glimpse of Water Ice Absorption Map in the Milky Way
Interstellar ice plays a key role in the thermal evolution of the interstellar medium and in astrochemical pathways, yet its large-scale distribution remains poorly constrained.
We use ALLWISE and 2MASS photometry to estimate water ice absorption in the WISE band by correcting the observed colors for reddening and intrinsic stellar colors. This allows us to construct a first Milky Way water ice map.
By varying input parameters, we test the stability of the method and identify the extinction law as the dominant source of uncertainty. Using synthetic photometry, we also quantify how different physical and observational parameters influence the $\Wi$ band water ice absorption.
The strong correlation between the measurement from photometric method and spectroscopic water ice abundance confirms that the Wi band signature originates from the 3 μm ice feature. We present the relationship between ice absorption in Wi band and water ice optical depth from theory and observations.
Finally, we provide a preliminary Milky Way-scale map of water ice distribution.
The detailed map of Taurus-Orion-Perseus region. The background of the middle panel is the dust map from Edenhofer et al. (2024), indicating the extinction level (note that this map only covers the distance around 1.25 kpc). Blue colors represent a higher water ice absorption. Locations with clear water ice detections are labeled. The four panels surrounding the middle panel are magnified views of the four regions, A, B, C and D in the mid panel, and each plot shows all the tracer stars, with three different markers used to indicate the three A ice W1 levels, A ice W1 < 0.05, 0.05 < A ice W1 < 0.15 and A ice W1 > 0.15. The backgrounds for top two panels are from DSS2, while the backgrounds for the bottom two panels are from AKARI. Sub figures A, B and C show the stars with ice absorption in filament structure or core region with small angular sizes which are easily smoothed out in ice distribution map, while D shows the stars with ice absorptions in the large scale Taurus molecular cloud. The color bar of the mid panel is shared with Figure 9. — astro-ph.GA
Zhetai Cao, Biwei Jiang, Stefan Meingast
Comments: 15 pages, 12 figures. Manuscript in second revision under review
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2606.01088 [astro-ph.GA] (or arXiv:2606.01088v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2606.01088
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Submission history
From: ZheTai Cao
[v1] Sun, 31 May 2026 08:16:14 UTC (8,004 KB)
https://arxiv.org/abs/2606.01088
Astrobiology, Astrochemistry,
