Physical and Chemical Characterization of GY 91's Multi-ringed Protostellar Disk with ALMA

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Main Authors: Jiang, Sally D., Huang, Jane, Czekala, Ian, Trapman, Leon, Aikawa, Yuri, Andrews, Sean M., Bae, Jaehan, Bergin, Edwin A., Law, Charles J., Gal, Romane Le, Long, Feng, Ménard, François, Öberg, Karin I., Qi, Chunhua, Teague, Richard, Wilner, David, Zhang, Ke
Format: Preprint
Published: 2026
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author Jiang, Sally D.
Huang, Jane
Czekala, Ian
Trapman, Leon
Aikawa, Yuri
Andrews, Sean M.
Bae, Jaehan
Bergin, Edwin A.
Law, Charles J.
Gal, Romane Le
Long, Feng
Ménard, François
Öberg, Karin I.
Qi, Chunhua
Teague, Richard
Wilner, David
Zhang, Ke
author_facet Jiang, Sally D.
Huang, Jane
Czekala, Ian
Trapman, Leon
Aikawa, Yuri
Andrews, Sean M.
Bae, Jaehan
Bergin, Edwin A.
Law, Charles J.
Gal, Romane Le
Long, Feng
Ménard, François
Öberg, Karin I.
Qi, Chunhua
Teague, Richard
Wilner, David
Zhang, Ke
contents GY 91, commonly categorized as a Class I young stellar object, is notable for disk dust substructures that have been hypothesized to trace early planet formation. Using the ALMA 12-m and ACA arrays, we present new Band 7 dust continuum and molecular line observations of GY 91 at an angular resolution of (~40 au). We report detections of CS $J=6-5$, N$_2$H$^+$ $J=3-2$, C$^{18}$O $J=3-2$, H$_2$CS $J_{K_a, K_c} = 8_{1,7}-7_{1,6}$, H$_2$CO $J_{K_a, K_c} = 4_{0,4}-3_{0,3}$, and H$_2$CO $J_{K_a, K_c} = 4_{2,3}-3_{2,2}$, as well as a tentative detection of $^{13}$C$^{18}$O $J=3-2$. We observe azimuthal asymmetry in CS and H$_2$CS emission, as well as radially structured H$_2$CO $4_{0,4}-3_{0,3}$ emission outside the dust continuum. C$^{18}$O and H$_2$CO 4$_{0,4}-3_{0,3}$ show significant cloud contamination, while CS and N$_2$H$^+$ are good tracers of Keplerian rotation originating from the disk. Envelope emission does not appear to contribute significantly either to the continuum or molecular line observations. GY 91's chemical properties appear in large part to resemble those of Class II disks, although observations of additional molecular probes should be obtained for a fuller comparison. With CS, we estimated a dynamical stellar mass of 0.58 $M_\odot$, which is higher than previous estimates from stellar evolutionary models (0.25 $M_\odot$). Using both radiative transfer modeling of the dust continuum and comparison of the C$^{18}$O and N$_2$H$^+$ fluxes to literature thermochemical models, we estimate a disk mass of $\sim0.01$ $M_\odot$.
format Preprint
id arxiv_https___arxiv_org_abs_2601_18884
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Physical and Chemical Characterization of GY 91's Multi-ringed Protostellar Disk with ALMA
Jiang, Sally D.
Huang, Jane
Czekala, Ian
Trapman, Leon
Aikawa, Yuri
Andrews, Sean M.
Bae, Jaehan
Bergin, Edwin A.
Law, Charles J.
Gal, Romane Le
Long, Feng
Ménard, François
Öberg, Karin I.
Qi, Chunhua
Teague, Richard
Wilner, David
Zhang, Ke
Earth and Planetary Astrophysics
Astrophysics of Galaxies
Solar and Stellar Astrophysics
GY 91, commonly categorized as a Class I young stellar object, is notable for disk dust substructures that have been hypothesized to trace early planet formation. Using the ALMA 12-m and ACA arrays, we present new Band 7 dust continuum and molecular line observations of GY 91 at an angular resolution of (~40 au). We report detections of CS $J=6-5$, N$_2$H$^+$ $J=3-2$, C$^{18}$O $J=3-2$, H$_2$CS $J_{K_a, K_c} = 8_{1,7}-7_{1,6}$, H$_2$CO $J_{K_a, K_c} = 4_{0,4}-3_{0,3}$, and H$_2$CO $J_{K_a, K_c} = 4_{2,3}-3_{2,2}$, as well as a tentative detection of $^{13}$C$^{18}$O $J=3-2$. We observe azimuthal asymmetry in CS and H$_2$CS emission, as well as radially structured H$_2$CO $4_{0,4}-3_{0,3}$ emission outside the dust continuum. C$^{18}$O and H$_2$CO 4$_{0,4}-3_{0,3}$ show significant cloud contamination, while CS and N$_2$H$^+$ are good tracers of Keplerian rotation originating from the disk. Envelope emission does not appear to contribute significantly either to the continuum or molecular line observations. GY 91's chemical properties appear in large part to resemble those of Class II disks, although observations of additional molecular probes should be obtained for a fuller comparison. With CS, we estimated a dynamical stellar mass of 0.58 $M_\odot$, which is higher than previous estimates from stellar evolutionary models (0.25 $M_\odot$). Using both radiative transfer modeling of the dust continuum and comparison of the C$^{18}$O and N$_2$H$^+$ fluxes to literature thermochemical models, we estimate a disk mass of $\sim0.01$ $M_\odot$.
title Physical and Chemical Characterization of GY 91's Multi-ringed Protostellar Disk with ALMA
topic Earth and Planetary Astrophysics
Astrophysics of Galaxies
Solar and Stellar Astrophysics
url https://arxiv.org/abs/2601.18884