The Arp 240 Galaxy Merger: A Detailed Look at the Molecular Kennicutt–Schmidt Star Formation Law on Subkiloparsec Scales
The molecular Kennicutt–Schmidt Law has been key for understanding star formation (SF) in galaxies across all redshifts. However, recent subkiloparsec observations of nearby galaxies reveal deviations from the nearly unity slope ( N ) obtained with disk-averaged measurements. We study SF and molecul...
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| author | A. Saravia E. Rodas-Quito L. Barcos-Muñoz A. S. Evans D. Kunneriath G. Privon Y. Song I. Yoon K. L. Emig M. Sánchez-García S. T. Linden K. Green M. Johnstone J. Nagarajan-Swenson G. A. Meza E. Momjian L. Armus V. Charmandaris T. Diaz-Santos C. Eibensteiner J. Howell H. Inami J. Kader C. Ricci E. Treister V. U T. Bohn D. B. Sanders |
| author_facet | A. Saravia E. Rodas-Quito L. Barcos-Muñoz A. S. Evans D. Kunneriath G. Privon Y. Song I. Yoon K. L. Emig M. Sánchez-García S. T. Linden K. Green M. Johnstone J. Nagarajan-Swenson G. A. Meza E. Momjian L. Armus V. Charmandaris T. Diaz-Santos C. Eibensteiner J. Howell H. Inami J. Kader C. Ricci E. Treister V. U T. Bohn D. B. Sanders |
| author_sort | A. Saravia |
| collection | DOAJ |
| description | The molecular Kennicutt–Schmidt Law has been key for understanding star formation (SF) in galaxies across all redshifts. However, recent subkiloparsec observations of nearby galaxies reveal deviations from the nearly unity slope ( N ) obtained with disk-averaged measurements. We study SF and molecular gas (MG) distribution in the early-stage luminous infrared galaxy merger Arp 240 (NGC 5257-8). Using Very Large Array radio continuum (RC) and Atacama Large Millimeter/submillimeter Array CO(2–1) observations at 500 pc scale, with a uniform grid analysis, we estimate SF rates and MG surface densities (Σ _SFR and ${{\rm{\Sigma }}}_{{{\rm{H}}}_{2}}$ , respectively). In Arp 240, N is sublinear at 0.52 ± 0.17. For NGC 5257 and NGC 5258, N is 0.52 ± 0.16 and 0.75 ± 0.15, respectively. We identify two SF regimes: high surface brightness (HSB) regions in RC with N ~ 1, and low surface brightness (LSB) regions with shallow N (ranging 0.15 ± 0.09–0.48 ± 0.04). Median CO(2–1) linewidth and MG turbulent pressure ( P _turb ) are 25 km s ^−1 and 9 × 10 ^5 K cm ^−3 . No significant correlation was found between Σ _SFR and CO(2–1) linewidth. However, Σ _SFR correlates with P _turb , particularly in HSB regions ( ρ > 0.60). In contrast, SF efficiency moderately anticorrelates with P _turb in LSB regions but shows no correlation in HSB regions. Additionally, we identify regions where peaks in SF and MG are decoupled, yielding a shallow N (≤0.28 ± 0.18). Overall, the range of N reflects distinct physical properties and distribution of both the SF and MG, which can be masked by disk-averaged measurements. |
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| spelling | doaj-art-e7ec2df916f64c59b448510fb43e5de72025-08-20T02:08:12ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01979221710.3847/1538-4357/ad9babThe Arp 240 Galaxy Merger: A Detailed Look at the Molecular Kennicutt–Schmidt Star Formation Law on Subkiloparsec ScalesA. Saravia0https://orcid.org/0000-0003-4546-3810E. Rodas-Quito1https://orcid.org/0000-0001-6956-0987L. Barcos-Muñoz2https://orcid.org/0000-0003-0057-8892A. S. Evans3https://orcid.org/0000-0003-2638-1334D. Kunneriath4https://orcid.org/0000-0002-1568-579XG. Privon5https://orcid.org/0000-0003-3474-1125Y. Song6https://orcid.org/0000-0002-3139-3041I. Yoon7https://orcid.org/0000-0001-9163-0064K. L. Emig8https://orcid.org/0000-0001-6527-6954M. Sánchez-García9https://orcid.org/0000-0003-4286-4475S. T. Linden10https://orcid.org/0000-0002-1000-6081K. Green11https://orcid.org/0009-0002-2049-9470M. Johnstone12https://orcid.org/0000-0001-7690-3976J. Nagarajan-Swenson13https://orcid.org/0009-0002-6248-3688G. A. Meza14https://orcid.org/0009-0006-6594-1516E. Momjian15https://orcid.org/0000-0003-3168-5922L. Armus16https://orcid.org/0000-0003-3498-2973V. Charmandaris17https://orcid.org/0000-0002-2688-1956T. Diaz-Santos18https://orcid.org/0000-0003-0699-6083C. Eibensteiner19https://orcid.org/0000-0002-1185-2810J. Howell20https://orcid.org/0000-0001-6028-8059H. Inami21https://orcid.org/0000-0003-4268-0393J. Kader22https://orcid.org/0000-0002-6650-3757C. Ricci23https://orcid.org/0000-0001-5231-2645E. Treister24https://orcid.org/0000-0001-7568-6412V. U25https://orcid.org/0000-0002-1912-0024T. Bohn26https://orcid.org/0000-0002-4375-254XD. B. Sanders27https://orcid.org/0000-0002-1233-9998Department of Astronomy, University of Virginia , 530 McCormick Road, Charlottesville, VA 22903, USA ; mas6um@virginia.eduUniversidad Nacional Autónoma de Honduras , Ciudad Universitaria, Tegucigalpa, HondurasDepartment of Astronomy, University of Virginia , 530 McCormick Road, Charlottesville, VA 22903, USA ; mas6um@virginia.edu; National Radio Astronomy Observatory , 520 Edgemont Road, Charlottesville, VA 22903, USADepartment of Astronomy, University of Virginia , 530 McCormick Road, Charlottesville, VA 22903, USA ; mas6um@virginia.edu; National Radio Astronomy Observatory , 520 Edgemont Road, Charlottesville, VA 22903, USANational Radio Astronomy Observatory , 520 Edgemont Road, Charlottesville, VA 22903, USADepartment of Astronomy, University of Virginia , 530 McCormick Road, Charlottesville, VA 22903, USA ; mas6um@virginia.edu; National Radio Astronomy Observatory , 520 Edgemont Road, Charlottesville, VA 22903, USA; Department of Astronomy, University of Florida , 1772 Stadium Road, Gainesville, FL 32611, USAEuropean Southern Observatory , Alonso de Córdova, 3107, Vitacura, Santiago 763-0355, Chile; Joint ALMA Observatory , Alonso de Córdova, 3107, Vitacura, Santiago 763-0355, ChileNational Radio Astronomy Observatory , 520 Edgemont Road, Charlottesville, VA 22903, USANational Radio Astronomy Observatory , 520 Edgemont Road, Charlottesville, VA 22903, USAInstitute of Astrophysics , Foundation for Research and Technology-Hellas (FORTH), Heraklion, 70013, GreeceSteward Observatory, University of Arizona , 933 N Cherry Avenue, Tucson, AZ 85721, USADepartment of Astronomy, University of Virginia , 530 McCormick Road, Charlottesville, VA 22903, USA ; mas6um@virginia.eduDepartment of Astronomy, University of Virginia , 530 McCormick Road, Charlottesville, VA 22903, USA ; mas6um@virginia.eduDepartment of Astronomy, University of Virginia , 530 McCormick Road, Charlottesville, VA 22903, USA ; mas6um@virginia.eduUniversidad Nacional Autónoma de Honduras , Ciudad Universitaria, Tegucigalpa, HondurasNational Radio Astronomy Observatory , P.O. Box O, Socorro, NM 87801, USAIPAC , California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125, USAInstitute of Astrophysics , Foundation for Research and Technology-Hellas (FORTH), Heraklion, 70013, Greece; School of Sciences, European University Cyprus , Diogenes Street, Engomi, 1516 Nicosia, Cyprus; Department of Physics, University of Crete , Heraklion, 71003, GreeceInstitute of Astrophysics , Foundation for Research and Technology-Hellas (FORTH), Heraklion, 70013, GreeceNational Radio Astronomy Observatory , 520 Edgemont Road, Charlottesville, VA 22903, USAIPAC , California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125, USAHiroshima Astrophysical Science Center, Hiroshima University , 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, JapanDepartment of Physics and Astronomy, University of California , 4129 Frederick Reines Hall, Irvine, CA 92697, USANúcleo de Astronomía de la Facultad de Ingeniería y Ciencias, Universidad Diego Portales , Santiago, 8320000, ChileInstituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile , Campus San Joaquín, 7820436, ChileDepartment of Physics and Astronomy, University of California , 4129 Frederick Reines Hall, Irvine, CA 92697, USAHiroshima Astrophysical Science Center, Hiroshima University , 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, JapanInstitute for Astronomy, University of Hawaii , 2680 Woodlawn Drive, Honolulu, HI 96822, USAThe molecular Kennicutt–Schmidt Law has been key for understanding star formation (SF) in galaxies across all redshifts. However, recent subkiloparsec observations of nearby galaxies reveal deviations from the nearly unity slope ( N ) obtained with disk-averaged measurements. We study SF and molecular gas (MG) distribution in the early-stage luminous infrared galaxy merger Arp 240 (NGC 5257-8). Using Very Large Array radio continuum (RC) and Atacama Large Millimeter/submillimeter Array CO(2–1) observations at 500 pc scale, with a uniform grid analysis, we estimate SF rates and MG surface densities (Σ _SFR and ${{\rm{\Sigma }}}_{{{\rm{H}}}_{2}}$ , respectively). In Arp 240, N is sublinear at 0.52 ± 0.17. For NGC 5257 and NGC 5258, N is 0.52 ± 0.16 and 0.75 ± 0.15, respectively. We identify two SF regimes: high surface brightness (HSB) regions in RC with N ~ 1, and low surface brightness (LSB) regions with shallow N (ranging 0.15 ± 0.09–0.48 ± 0.04). Median CO(2–1) linewidth and MG turbulent pressure ( P _turb ) are 25 km s ^−1 and 9 × 10 ^5 K cm ^−3 . No significant correlation was found between Σ _SFR and CO(2–1) linewidth. However, Σ _SFR correlates with P _turb , particularly in HSB regions ( ρ > 0.60). In contrast, SF efficiency moderately anticorrelates with P _turb in LSB regions but shows no correlation in HSB regions. Additionally, we identify regions where peaks in SF and MG are decoupled, yielding a shallow N (≤0.28 ± 0.18). Overall, the range of N reflects distinct physical properties and distribution of both the SF and MG, which can be masked by disk-averaged measurements.https://doi.org/10.3847/1538-4357/ad9babLuminous infrared galaxiesGalaxy mergersStar forming regions |
| spellingShingle | A. Saravia E. Rodas-Quito L. Barcos-Muñoz A. S. Evans D. Kunneriath G. Privon Y. Song I. Yoon K. L. Emig M. Sánchez-García S. T. Linden K. Green M. Johnstone J. Nagarajan-Swenson G. A. Meza E. Momjian L. Armus V. Charmandaris T. Diaz-Santos C. Eibensteiner J. Howell H. Inami J. Kader C. Ricci E. Treister V. U T. Bohn D. B. Sanders The Arp 240 Galaxy Merger: A Detailed Look at the Molecular Kennicutt–Schmidt Star Formation Law on Subkiloparsec Scales The Astrophysical Journal Luminous infrared galaxies Galaxy mergers Star forming regions |
| title | The Arp 240 Galaxy Merger: A Detailed Look at the Molecular Kennicutt–Schmidt Star Formation Law on Subkiloparsec Scales |
| title_full | The Arp 240 Galaxy Merger: A Detailed Look at the Molecular Kennicutt–Schmidt Star Formation Law on Subkiloparsec Scales |
| title_fullStr | The Arp 240 Galaxy Merger: A Detailed Look at the Molecular Kennicutt–Schmidt Star Formation Law on Subkiloparsec Scales |
| title_full_unstemmed | The Arp 240 Galaxy Merger: A Detailed Look at the Molecular Kennicutt–Schmidt Star Formation Law on Subkiloparsec Scales |
| title_short | The Arp 240 Galaxy Merger: A Detailed Look at the Molecular Kennicutt–Schmidt Star Formation Law on Subkiloparsec Scales |
| title_sort | arp 240 galaxy merger a detailed look at the molecular kennicutt schmidt star formation law on subkiloparsec scales |
| topic | Luminous infrared galaxies Galaxy mergers Star forming regions |
| url | https://doi.org/10.3847/1538-4357/ad9bab |
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