Dynamically Driven Evolution of Molecular Gas in the Barred Spiral Galaxy M83 Traced by CO J = 2–1/1–0 Line Ratio Variations
We show the variations of the CO J = 2–1/1–0 line ratio ( R _21/10 ) across the barred spiral galaxy M83, using the 46 pc resolution data from the Atacama Large Millimeter/submillimeter Array. The R _21/10 map clearly evidences the systematic large-scale variations as a function of galactic structur...
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2025-01-01
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| author | Jin Koda Fumi Egusa Akihiko Hirota Amanda M Lee Tsuyoshi Sawada Fumiya Maeda |
| author_facet | Jin Koda Fumi Egusa Akihiko Hirota Amanda M Lee Tsuyoshi Sawada Fumiya Maeda |
| author_sort | Jin Koda |
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| description | We show the variations of the CO J = 2–1/1–0 line ratio ( R _21/10 ) across the barred spiral galaxy M83, using the 46 pc resolution data from the Atacama Large Millimeter/submillimeter Array. The R _21/10 map clearly evidences the systematic large-scale variations as a function of galactic structures. Azimuthally, it starts from low R _21/10 ≲ 0.7 in the interarm regions and becomes high ≳0.7 in the bar and spiral arms, suggesting that the density and/or kinetic temperature of molecular gas increase by about a factor of 2–3. This evolution is seen even in the parts of spiral arms without star formation, and R _21/10 is often elevated even higher to ∼0.8–1.0 when H ii regions exist in the vicinity. Radially, R _21/10 starts very high ≳1.0 at the galactic center, remains low ≲0.7 in the bar region, increases to ≳0.7 around the bar end, and again decreases to ≲0.7 in the rest of disk where the spiral arms dominate. The evolutionary sequence is synchronized with galactic rotation, and therefore, it is determined largely by the galactic structures and dynamics and is governed by the galactic rotation timescales. The R _21/10 map also shows that the influence of stellar feedback is localized and limited. Massive, large, and non-star-forming molecular structures have low R _21/10 , which also suggests that the bulk molecular gas in the disk is not regulated by stellar feedback, but more likely by galactic structures and dynamics. These results are consistent with suggestions by the earlier studies of the Milky Way and other barred spiral galaxies, and thus, are likely general among barred spiral galaxies in the local Universe. |
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| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-1939b14289fd4af0be5b1960d224bd2d2025-08-20T02:02:15ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198612910.3847/1538-4357/add1dcDynamically Driven Evolution of Molecular Gas in the Barred Spiral Galaxy M83 Traced by CO J = 2–1/1–0 Line Ratio VariationsJin Koda0https://orcid.org/0000-0002-8762-7863Fumi Egusa1https://orcid.org/0000-0002-1639-1515Akihiko Hirota2https://orcid.org/0000-0002-0465-5421Amanda M Lee3https://orcid.org/0000-0001-8254-6768Tsuyoshi Sawada4https://orcid.org/0000-0002-0588-5595Fumiya Maeda5https://orcid.org/0000-0002-8868-1255Stony Brook University , Stony Brook, NY 11743-3800, USAInstitute of Astronomy, Graduate School of Science, The University of Tokyo , 2-21-1 Osawa, Mitaka, Tokyo 181-0015, JapanJoint ALMA Observatory , Alonso de Córdova 3107, Vitacura, Santiago 763-0355, Chile; National Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, JapanStony Brook University , Stony Brook, NY 11743-3800, USAJoint ALMA Observatory , Alonso de Córdova 3107, Vitacura, Santiago 763-0355, Chile; National Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, JapanResearch Center for Physics and Mathematics, Osaka Electro-Communication University , 18-8 Hatsucho, Neyagawa, Osaka, 572-8530, JapanWe show the variations of the CO J = 2–1/1–0 line ratio ( R _21/10 ) across the barred spiral galaxy M83, using the 46 pc resolution data from the Atacama Large Millimeter/submillimeter Array. The R _21/10 map clearly evidences the systematic large-scale variations as a function of galactic structures. Azimuthally, it starts from low R _21/10 ≲ 0.7 in the interarm regions and becomes high ≳0.7 in the bar and spiral arms, suggesting that the density and/or kinetic temperature of molecular gas increase by about a factor of 2–3. This evolution is seen even in the parts of spiral arms without star formation, and R _21/10 is often elevated even higher to ∼0.8–1.0 when H ii regions exist in the vicinity. Radially, R _21/10 starts very high ≳1.0 at the galactic center, remains low ≲0.7 in the bar region, increases to ≳0.7 around the bar end, and again decreases to ≲0.7 in the rest of disk where the spiral arms dominate. The evolutionary sequence is synchronized with galactic rotation, and therefore, it is determined largely by the galactic structures and dynamics and is governed by the galactic rotation timescales. The R _21/10 map also shows that the influence of stellar feedback is localized and limited. Massive, large, and non-star-forming molecular structures have low R _21/10 , which also suggests that the bulk molecular gas in the disk is not regulated by stellar feedback, but more likely by galactic structures and dynamics. These results are consistent with suggestions by the earlier studies of the Milky Way and other barred spiral galaxies, and thus, are likely general among barred spiral galaxies in the local Universe.https://doi.org/10.3847/1538-4357/add1dcInterstellar mediumMolecular gasMolecular cloudsGalaxy structureGalaxy dynamicsStar formation |
| spellingShingle | Jin Koda Fumi Egusa Akihiko Hirota Amanda M Lee Tsuyoshi Sawada Fumiya Maeda Dynamically Driven Evolution of Molecular Gas in the Barred Spiral Galaxy M83 Traced by CO J = 2–1/1–0 Line Ratio Variations The Astrophysical Journal Interstellar medium Molecular gas Molecular clouds Galaxy structure Galaxy dynamics Star formation |
| title | Dynamically Driven Evolution of Molecular Gas in the Barred Spiral Galaxy M83 Traced by CO J = 2–1/1–0 Line Ratio Variations |
| title_full | Dynamically Driven Evolution of Molecular Gas in the Barred Spiral Galaxy M83 Traced by CO J = 2–1/1–0 Line Ratio Variations |
| title_fullStr | Dynamically Driven Evolution of Molecular Gas in the Barred Spiral Galaxy M83 Traced by CO J = 2–1/1–0 Line Ratio Variations |
| title_full_unstemmed | Dynamically Driven Evolution of Molecular Gas in the Barred Spiral Galaxy M83 Traced by CO J = 2–1/1–0 Line Ratio Variations |
| title_short | Dynamically Driven Evolution of Molecular Gas in the Barred Spiral Galaxy M83 Traced by CO J = 2–1/1–0 Line Ratio Variations |
| title_sort | dynamically driven evolution of molecular gas in the barred spiral galaxy m83 traced by co j 2 1 1 0 line ratio variations |
| topic | Interstellar medium Molecular gas Molecular clouds Galaxy structure Galaxy dynamics Star formation |
| url | https://doi.org/10.3847/1538-4357/add1dc |
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