Mapping CO Ice in a Star-Forming Filament in the 3 kpc Arm with JWST

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Main Authors: Gramze, Savannah, Ginsburg, Adam, Budaiev, Nazar, Bulatek, Alyssa, Richardson, Theo, Barnes, A. T., Santa-Maria, Miriam G., Sormani, Mattia C., Lu, Xing, Nogueras-Lara, Francisco, Gaches, Brandt A. L., Battersby, Cara D., Wallace, Jennifer, Walker, Daniel L., Mills, Elisabeth A. C., Mattern, Michael
Format: Preprint
Published: 2025
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author Gramze, Savannah
Ginsburg, Adam
Budaiev, Nazar
Bulatek, Alyssa
Richardson, Theo
Barnes, A. T.
Santa-Maria, Miriam G.
Sormani, Mattia C.
Lu, Xing
Nogueras-Lara, Francisco
Gaches, Brandt A. L.
Battersby, Cara D.
Wallace, Jennifer
Walker, Daniel L.
Mills, Elisabeth A. C.
Mattern, Michael
author_facet Gramze, Savannah
Ginsburg, Adam
Budaiev, Nazar
Bulatek, Alyssa
Richardson, Theo
Barnes, A. T.
Santa-Maria, Miriam G.
Sormani, Mattia C.
Lu, Xing
Nogueras-Lara, Francisco
Gaches, Brandt A. L.
Battersby, Cara D.
Wallace, Jennifer
Walker, Daniel L.
Mills, Elisabeth A. C.
Mattern, Michael
contents CO gas emission is a fundamental tool for measuring column density, but in cold, dark clouds, much of the CO is locked away in ice. We present JWST results from observations of a star forming filament (G0.342+0.024) that that appears to be associated with the 3 kpc arm. This filament is backlit by the Galactic Center, which has allowed us to construct a high-resolution extinction map (mean separation between stars of ~1" outside the filament, ~2" in the filament). ALMA Band 3 data reveals embedded star formation within the cloud. Using the CO ice feature covered by the F466N band, we map the CO ice column density of the filament. By combining the extinction map, CO ice column density map, and archival CO observations, we examine the efficacy of standard CO X-factor measurements of mass in star forming gas. We find that 50-88% of the CO is locked away in ice at large column densities ($N_{\rm \rm H_2} \gtrsim 10^{22} \rm ~cm^{-2}, 200 \rm ~M_{\odot} \rm ~pc^{-2}$) in the filament. The primary sources of uncertainty in this estimate are due to uncertainty in the ice composition and lab measurements of ice opacities. This shows that systematic corrections are needed for mass measurements in the Milky Way and nearby galaxies at high column densities.
format Preprint
id arxiv_https___arxiv_org_abs_2509_21763
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Mapping CO Ice in a Star-Forming Filament in the 3 kpc Arm with JWST
Gramze, Savannah
Ginsburg, Adam
Budaiev, Nazar
Bulatek, Alyssa
Richardson, Theo
Barnes, A. T.
Santa-Maria, Miriam G.
Sormani, Mattia C.
Lu, Xing
Nogueras-Lara, Francisco
Gaches, Brandt A. L.
Battersby, Cara D.
Wallace, Jennifer
Walker, Daniel L.
Mills, Elisabeth A. C.
Mattern, Michael
Astrophysics of Galaxies
CO gas emission is a fundamental tool for measuring column density, but in cold, dark clouds, much of the CO is locked away in ice. We present JWST results from observations of a star forming filament (G0.342+0.024) that that appears to be associated with the 3 kpc arm. This filament is backlit by the Galactic Center, which has allowed us to construct a high-resolution extinction map (mean separation between stars of ~1" outside the filament, ~2" in the filament). ALMA Band 3 data reveals embedded star formation within the cloud. Using the CO ice feature covered by the F466N band, we map the CO ice column density of the filament. By combining the extinction map, CO ice column density map, and archival CO observations, we examine the efficacy of standard CO X-factor measurements of mass in star forming gas. We find that 50-88% of the CO is locked away in ice at large column densities ($N_{\rm \rm H_2} \gtrsim 10^{22} \rm ~cm^{-2}, 200 \rm ~M_{\odot} \rm ~pc^{-2}$) in the filament. The primary sources of uncertainty in this estimate are due to uncertainty in the ice composition and lab measurements of ice opacities. This shows that systematic corrections are needed for mass measurements in the Milky Way and nearby galaxies at high column densities.
title Mapping CO Ice in a Star-Forming Filament in the 3 kpc Arm with JWST
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2509.21763