The Impact of Bar-induced Noncircular Motions on the Measurement of Galactic Rotation Curves
We study the impact of bar-induced noncircular motions on the derivation of galactic rotation curves (RCs) using hydrodynamic simulations and observational data from the PHANGS-ALMA survey. We confirm that noncircular motions induced by a bar can significantly bias RCs derived from the conventional...
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IOP Publishing
2025-01-01
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| author | Jie Liu Zhi Li Juntai Shen |
| author_facet | Jie Liu Zhi Li Juntai Shen |
| author_sort | Jie Liu |
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| description | We study the impact of bar-induced noncircular motions on the derivation of galactic rotation curves (RCs) using hydrodynamic simulations and observational data from the PHANGS-ALMA survey. We confirm that noncircular motions induced by a bar can significantly bias RCs derived from the conventional tilted-ring method, consistent with previous findings. The shape of the derived RC depends on the difference in position angle (Δ ϕ ) between the major axes of the bar and the disk in the face-on plane. For $\left|{\rm{\Delta }}\phi \right|\lesssim 40^\circ $ , noncircular motions produce a bar-induced “dip” feature (rise–drop–rise pattern) in the derived RC, which shows higher velocities near the nuclear ring and lower velocities in the bar region compared to the true RC (RC _true ). We demonstrate convincingly that such dip features are very common in the PHANGS-ALMA sample of barred galaxies. Hydrodynamical simulations reveal that the “dip” feature is caused by the perpendicular orientation of the gas flows in the nuclear ring and the bar; at low $\left|{\rm{\Delta }}\phi \right|$ streamlines in the nuclear ring tend to enhance V _los , while those in the bar tend to suppress V _los . We use a simple “misaligned ellipses” model to qualitatively explain the general trend of RCs from the tilted-ring method (RC _tilted ) and the discrepancy between RC _tilted and RC _true . Furthermore, we propose a straightforward method to implement a first-order correction to the RC derived from the tilted-ring method. Our study is the first to systematically discuss the bar-induced “dip” feature in the RCs of barred galaxies by combining both simulations and observations. |
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| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-142d01c8326b458c9b62d40a57e621042025-02-10T07:50:58ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01980114610.3847/1538-4357/adabe0The Impact of Bar-induced Noncircular Motions on the Measurement of Galactic Rotation CurvesJie Liu0https://orcid.org/0000-0003-4052-8785Zhi Li1https://orcid.org/0000-0002-0627-8009Juntai Shen2https://orcid.org/0000-0001-5604-1643Shanghai Astronomical Observatory, Chinese Academy of Sciences , 80 Nandan Road, Shanghai 200030, People’s Republic of China; School of Astronomy and Space Sciences, University of Chinese Academy of Sciences , 19A Yuquan Road, Beijing 100049, People’s Republic of ChinaShanghai Key Lab for Astrophysics, Shanghai Normal University , 100 Guilin Road, Shanghai 200234, People’s Republic of China ; [email protected]; Department of Astronomy, School of Physics and Astronomy, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai 200240, People’s Republic of China ; [email protected] of Astronomy, School of Physics and Astronomy, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai 200240, People’s Republic of China ; [email protected]; State Key Laboratory of Dark Matter Physics, School of Physics and Astronomy, Shanghai Jiao Tong University , Shanghai 200240, People’s Republic of ChinaWe study the impact of bar-induced noncircular motions on the derivation of galactic rotation curves (RCs) using hydrodynamic simulations and observational data from the PHANGS-ALMA survey. We confirm that noncircular motions induced by a bar can significantly bias RCs derived from the conventional tilted-ring method, consistent with previous findings. The shape of the derived RC depends on the difference in position angle (Δ ϕ ) between the major axes of the bar and the disk in the face-on plane. For $\left|{\rm{\Delta }}\phi \right|\lesssim 40^\circ $ , noncircular motions produce a bar-induced “dip” feature (rise–drop–rise pattern) in the derived RC, which shows higher velocities near the nuclear ring and lower velocities in the bar region compared to the true RC (RC _true ). We demonstrate convincingly that such dip features are very common in the PHANGS-ALMA sample of barred galaxies. Hydrodynamical simulations reveal that the “dip” feature is caused by the perpendicular orientation of the gas flows in the nuclear ring and the bar; at low $\left|{\rm{\Delta }}\phi \right|$ streamlines in the nuclear ring tend to enhance V _los , while those in the bar tend to suppress V _los . We use a simple “misaligned ellipses” model to qualitatively explain the general trend of RCs from the tilted-ring method (RC _tilted ) and the discrepancy between RC _tilted and RC _true . Furthermore, we propose a straightforward method to implement a first-order correction to the RC derived from the tilted-ring method. Our study is the first to systematically discuss the bar-induced “dip” feature in the RCs of barred galaxies by combining both simulations and observations.https://doi.org/10.3847/1538-4357/adabe0Barred spiral galaxiesGalaxy rotation curvesGalaxy dynamicsHydrodynamical simulations |
| spellingShingle | Jie Liu Zhi Li Juntai Shen The Impact of Bar-induced Noncircular Motions on the Measurement of Galactic Rotation Curves The Astrophysical Journal Barred spiral galaxies Galaxy rotation curves Galaxy dynamics Hydrodynamical simulations |
| title | The Impact of Bar-induced Noncircular Motions on the Measurement of Galactic Rotation Curves |
| title_full | The Impact of Bar-induced Noncircular Motions on the Measurement of Galactic Rotation Curves |
| title_fullStr | The Impact of Bar-induced Noncircular Motions on the Measurement of Galactic Rotation Curves |
| title_full_unstemmed | The Impact of Bar-induced Noncircular Motions on the Measurement of Galactic Rotation Curves |
| title_short | The Impact of Bar-induced Noncircular Motions on the Measurement of Galactic Rotation Curves |
| title_sort | impact of bar induced noncircular motions on the measurement of galactic rotation curves |
| topic | Barred spiral galaxies Galaxy rotation curves Galaxy dynamics Hydrodynamical simulations |
| url | https://doi.org/10.3847/1538-4357/adabe0 |
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