3D CMZ. III. Constraining the 3D structure of the Central Molecular Zone via molecular line emission and absorption

Daniel L. Walker; Cara Battersby; Dani Lipman; Mattia C. Sormani; Adam Ginsburg; Simon C. O. Glover; Jonathan D. Henshaw; Steven N. Longmore; Ralf S. Klessen; Katharina Immer; Danya Alboslani; John Bally; Ashley Barnes; H. Perry Hatchfield; Elisabeth A. C. Mills; Rowan Smith; Robin G. Tress; Qizhou Zhang

doi:10.3847/1538-4357/adb5ef

3D CMZ. III. Constraining the 3D structure of the Central Molecular Zone via molecular line emission and absorption

Daniel L. Walker^*, Cara Battersby, Dani Lipman, Mattia C. Sormani, Adam Ginsburg, Simon C. O. Glover, Jonathan D. Henshaw, Steven N. Longmore, Ralf S. Klessen, Katharina Immer, Danya Alboslani, John Bally, Ashley Barnes, H. Perry Hatchfield, Elisabeth A. C. Mills, Rowan Smith, Robin G. Tress, Qizhou Zhang

^*Corresponding author for this work

School of Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

Abstract

The Milky Way’s Central Molecular Zone (CMZ) is the largest concentration of dense molecular gas in the Galaxy, the structure of which is shaped by the complex interplay between Galactic-scale dynamics and extreme physical conditions. Understanding the 3D geometry of this gas is crucial, as it determines the locations of star formation and subsequent feedback. We present a catalog of clouds in the CMZ using Herschel data. Using archival data from the APEX and MOPRA CMZ surveys, we measure averaged kinematic properties of the clouds at 1 and 3 mm. We use archival ATCA data of the H2CO (1_1,0–1_1,1) 4.8 GHz line to search for absorption towards the clouds, and 4.85 GHz Green Bank Telescope (GBT) C-band data to measure the radio continuum emission. We measure the absorption against the continuum to provide new constraints for the line-of-sight positions of the clouds relative to the Galactic Center, and find a highly asymmetric distribution, with most clouds residing in front of the Galactic Center. The results are compared with different orbital models, and we introduce a revised toy model of a vertically oscillating closed elliptical orbit. We find that most models describe the position–position–velocity structure of the gas reasonably well, but find significant inconsistencies in all cases regarding the near versus far placement of individual clouds. Our results highlight that the CMZ is likely more complex than can be captured by these simple geometric models, along with the need for new data to provide further constraints on the true 3D structure of the CMZ.

Original language	English
Article number	158
Number of pages	24
Journal	Astrophysical Journal
Volume	984
Issue number	2
Early online date	8 May 2025
DOIs	https://doi.org/10.3847/1538-4357/adb5ef
Publication status	Published - 10 May 2025

Keywords

Galactic center
Molecular clouds

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Walker, D. L., Battersby, C., Lipman, D., Sormani, M. C., Ginsburg, A., Glover, S. C. O., Henshaw, J. D., Longmore, S. N., Klessen, R. S., Immer, K., Alboslani, D., Bally, J., Barnes, A., Hatchfield, H. P., Mills, E. A. C., Smith, R., Tress, R. G., & Zhang, Q. (2025). 3D CMZ. III. Constraining the 3D structure of the Central Molecular Zone via molecular line emission and absorption. Astrophysical Journal, 984(2), Article 158. https://doi.org/10.3847/1538-4357/adb5ef

@article{f1b8ccdb7c5d499898c3014517c4e863,

title = "3D CMZ. III. Constraining the 3D structure of the Central Molecular Zone via molecular line emission and absorption",

abstract = "The Milky Way{\textquoteright}s Central Molecular Zone (CMZ) is the largest concentration of dense molecular gas in the Galaxy, the structure of which is shaped by the complex interplay between Galactic-scale dynamics and extreme physical conditions. Understanding the 3D geometry of this gas is crucial, as it determines the locations of star formation and subsequent feedback. We present a catalog of clouds in the CMZ using Herschel data. Using archival data from the APEX and MOPRA CMZ surveys, we measure averaged kinematic properties of the clouds at 1 and 3 mm. We use archival ATCA data of the H2CO (11,0–11,1) 4.8 GHz line to search for absorption towards the clouds, and 4.85 GHz Green Bank Telescope (GBT) C-band data to measure the radio continuum emission. We measure the absorption against the continuum to provide new constraints for the line-of-sight positions of the clouds relative to the Galactic Center, and find a highly asymmetric distribution, with most clouds residing in front of the Galactic Center. The results are compared with different orbital models, and we introduce a revised toy model of a vertically oscillating closed elliptical orbit. We find that most models describe the position–position–velocity structure of the gas reasonably well, but find significant inconsistencies in all cases regarding the near versus far placement of individual clouds. Our results highlight that the CMZ is likely more complex than can be captured by these simple geometric models, along with the need for new data to provide further constraints on the true 3D structure of the CMZ.",

keywords = "Galactic center, Molecular clouds",

author = "Walker, \{Daniel L.\} and Cara Battersby and Dani Lipman and Sormani, \{Mattia C.\} and Adam Ginsburg and Glover, \{Simon C. O.\} and Henshaw, \{Jonathan D.\} and Longmore, \{Steven N.\} and Klessen, \{Ralf S.\} and Katharina Immer and Danya Alboslani and John Bally and Ashley Barnes and Hatchfield, \{H. Perry\} and Mills, \{Elisabeth A. C.\} and Rowan Smith and Tress, \{Robin G.\} and Qizhou Zhang",

note = "Funding: D.L.W., C.B., and D.L. gratefully acknowledge support from the National Science Foundation under award No. 1816715. D.L.W. gratefully acknowledges support from the UK ALMA Regional Centre (ARC) Node, which is supported by the Science and Technology Facilities Council (grant Nos. ST/Y004108/1 and ST/T001488/1). C.B. also gratefully acknowledges funding from National Science Foundation (NSF) under award Nos. 2108938, 2206510, and CAREER 2145689, as well as from the National Aeronautics and Space Administration through the Astrophysics Data Analysis Program under award “3D MC: Mapping Circumnuclear Molecular Clouds from X-ray to Radio,” grant No. 80NSSC22K1125. D.L. also gratefully acknowledges funding from the National Science Foundation under award Nos. 2108938 and CAREER 2145689, as well as from the NASA Connecticut Space Grant Consortium under PTE Federal award No: 80NSSC20M0129. M.C.S. acknowledges financial support from the European Research Council under the ERC Starting Grant “GalFlow” (grant 101116226). A.G. acknowledges funding from NSF awards AST 2008101 and 2206511 and CAREER 2142300. J.D.H. gratefully acknowledges financial support from the Royal Society (University Research Fellowship; URF/R1/221620). R.S.K. and S.C.O.G. acknowledge financial support from the European Research Council via the ERC Synergy Grant “ECOGAL” (project ID 855130), from the German Excellence Strategy via the Heidelberg Cluster of Excellence (EXC 2181 - 390900948) “STRUCTURES,” and from the German Ministry for Economic Affairs and Climate Action in project “MAINN” (funding ID 50OO2206). E.A.C. Mills gratefully acknowledges funding from the National Science Foundation under award Nos. 1813765, 2115428, 2206509, and CAREER 2339670. Q.Z. acknowledges the support from the National Science Foundation under award No. 2206512.",

year = "2025",

month = may,

day = "10",

doi = "10.3847/1538-4357/adb5ef",

language = "English",

volume = "984",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "American Astronomical Society",

number = "2",

}

Walker, DL, Battersby, C, Lipman, D, Sormani, MC, Ginsburg, A, Glover, SCO, Henshaw, JD, Longmore, SN, Klessen, RS, Immer, K, Alboslani, D, Bally, J, Barnes, A, Hatchfield, HP, Mills, EAC, Smith, R, Tress, RG & Zhang, Q 2025, '3D CMZ. III. Constraining the 3D structure of the Central Molecular Zone via molecular line emission and absorption', Astrophysical Journal, vol. 984, no. 2, 158. https://doi.org/10.3847/1538-4357/adb5ef

TY - JOUR

T1 - 3D CMZ. III. Constraining the 3D structure of the Central Molecular Zone via molecular line emission and absorption

AU - Walker, Daniel L.

AU - Battersby, Cara

AU - Lipman, Dani

AU - Sormani, Mattia C.

AU - Ginsburg, Adam

AU - Glover, Simon C. O.

AU - Henshaw, Jonathan D.

AU - Longmore, Steven N.

AU - Klessen, Ralf S.

AU - Immer, Katharina

AU - Alboslani, Danya

AU - Bally, John

AU - Barnes, Ashley

AU - Hatchfield, H. Perry

AU - Mills, Elisabeth A. C.

AU - Smith, Rowan

AU - Tress, Robin G.

AU - Zhang, Qizhou

N1 - Funding: D.L.W., C.B., and D.L. gratefully acknowledge support from the National Science Foundation under award No. 1816715. D.L.W. gratefully acknowledges support from the UK ALMA Regional Centre (ARC) Node, which is supported by the Science and Technology Facilities Council (grant Nos. ST/Y004108/1 and ST/T001488/1). C.B. also gratefully acknowledges funding from National Science Foundation (NSF) under award Nos. 2108938, 2206510, and CAREER 2145689, as well as from the National Aeronautics and Space Administration through the Astrophysics Data Analysis Program under award “3D MC: Mapping Circumnuclear Molecular Clouds from X-ray to Radio,” grant No. 80NSSC22K1125. D.L. also gratefully acknowledges funding from the National Science Foundation under award Nos. 2108938 and CAREER 2145689, as well as from the NASA Connecticut Space Grant Consortium under PTE Federal award No: 80NSSC20M0129. M.C.S. acknowledges financial support from the European Research Council under the ERC Starting Grant “GalFlow” (grant 101116226). A.G. acknowledges funding from NSF awards AST 2008101 and 2206511 and CAREER 2142300. J.D.H. gratefully acknowledges financial support from the Royal Society (University Research Fellowship; URF/R1/221620). R.S.K. and S.C.O.G. acknowledge financial support from the European Research Council via the ERC Synergy Grant “ECOGAL” (project ID 855130), from the German Excellence Strategy via the Heidelberg Cluster of Excellence (EXC 2181 - 390900948) “STRUCTURES,” and from the German Ministry for Economic Affairs and Climate Action in project “MAINN” (funding ID 50OO2206). E.A.C. Mills gratefully acknowledges funding from the National Science Foundation under award Nos. 1813765, 2115428, 2206509, and CAREER 2339670. Q.Z. acknowledges the support from the National Science Foundation under award No. 2206512.

PY - 2025/5/10

Y1 - 2025/5/10

N2 - The Milky Way’s Central Molecular Zone (CMZ) is the largest concentration of dense molecular gas in the Galaxy, the structure of which is shaped by the complex interplay between Galactic-scale dynamics and extreme physical conditions. Understanding the 3D geometry of this gas is crucial, as it determines the locations of star formation and subsequent feedback. We present a catalog of clouds in the CMZ using Herschel data. Using archival data from the APEX and MOPRA CMZ surveys, we measure averaged kinematic properties of the clouds at 1 and 3 mm. We use archival ATCA data of the H2CO (11,0–11,1) 4.8 GHz line to search for absorption towards the clouds, and 4.85 GHz Green Bank Telescope (GBT) C-band data to measure the radio continuum emission. We measure the absorption against the continuum to provide new constraints for the line-of-sight positions of the clouds relative to the Galactic Center, and find a highly asymmetric distribution, with most clouds residing in front of the Galactic Center. The results are compared with different orbital models, and we introduce a revised toy model of a vertically oscillating closed elliptical orbit. We find that most models describe the position–position–velocity structure of the gas reasonably well, but find significant inconsistencies in all cases regarding the near versus far placement of individual clouds. Our results highlight that the CMZ is likely more complex than can be captured by these simple geometric models, along with the need for new data to provide further constraints on the true 3D structure of the CMZ.

AB - The Milky Way’s Central Molecular Zone (CMZ) is the largest concentration of dense molecular gas in the Galaxy, the structure of which is shaped by the complex interplay between Galactic-scale dynamics and extreme physical conditions. Understanding the 3D geometry of this gas is crucial, as it determines the locations of star formation and subsequent feedback. We present a catalog of clouds in the CMZ using Herschel data. Using archival data from the APEX and MOPRA CMZ surveys, we measure averaged kinematic properties of the clouds at 1 and 3 mm. We use archival ATCA data of the H2CO (11,0–11,1) 4.8 GHz line to search for absorption towards the clouds, and 4.85 GHz Green Bank Telescope (GBT) C-band data to measure the radio continuum emission. We measure the absorption against the continuum to provide new constraints for the line-of-sight positions of the clouds relative to the Galactic Center, and find a highly asymmetric distribution, with most clouds residing in front of the Galactic Center. The results are compared with different orbital models, and we introduce a revised toy model of a vertically oscillating closed elliptical orbit. We find that most models describe the position–position–velocity structure of the gas reasonably well, but find significant inconsistencies in all cases regarding the near versus far placement of individual clouds. Our results highlight that the CMZ is likely more complex than can be captured by these simple geometric models, along with the need for new data to provide further constraints on the true 3D structure of the CMZ.

KW - Galactic center

KW - Molecular clouds

UR - https://www.scopus.com/pages/publications/105004690206

U2 - 10.3847/1538-4357/adb5ef

DO - 10.3847/1538-4357/adb5ef

M3 - Article

AN - SCOPUS:105004690206

SN - 0004-637X

VL - 984

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 2

M1 - 158

ER -

3D CMZ. III. Constraining the 3D structure of the Central Molecular Zone via molecular line emission and absorption

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Keywords

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3D CMZ. I. Central Molecular Zone overview

3D CMZ. II. Hierarchical structure analysis of the Central Molecular Zone

3D CMZ. IV. Distinguishing near versus far distances in the galactic center using Spitzer and Herschel

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