Testable Predictions of Outside-in Age Gradients in Dwarf Galaxies of All Types
We use a sample of 73 simulated satellite and central dwarf galaxies spanning a stellar mass range of 10 ^5.3 –10 ^9.1 M _⊙ to investigate the origin of their stellar age gradients. We find that dwarf galaxies often form their stars “inside-out,” i.e., the stars form at successively larger radii ove...
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2024-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ad8b1e |
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| author | Claire L. Riggs Alyson M. Brooks Ferah Munshi Charlotte R. Christensen Roger E. Cohen Thomas R. Quinn James Wadsley |
| author_facet | Claire L. Riggs Alyson M. Brooks Ferah Munshi Charlotte R. Christensen Roger E. Cohen Thomas R. Quinn James Wadsley |
| author_sort | Claire L. Riggs |
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| description | We use a sample of 73 simulated satellite and central dwarf galaxies spanning a stellar mass range of 10 ^5.3 –10 ^9.1 M _⊙ to investigate the origin of their stellar age gradients. We find that dwarf galaxies often form their stars “inside-out,” i.e., the stars form at successively larger radii over time. However, the oldest stars get reshuffled beyond the star-forming radius by fluctuations in the gravitational potential well caused by stellar feedback (the same mechanisms that cause dwarfs to form dark matter cores). The result is that many dwarfs appear to have an “outside-in” age gradient at z = 0, with younger stellar populations more centrally concentrated. However, for the reshuffled galaxies with the most extended star formation, young stars can form out to the large radii to which the old stars have been reshuffled, erasing the age gradient. We find that major mergers do not play a significant role in setting the age gradients of dwarfs. We find similar age gradient trends in satellites and field dwarfs, suggesting that environment plays only a minor role, if any. Finally, we find that the age gradient trends are imprinted on the galaxies at later times, suggesting that the stellar reshuffling dominates after the galaxies have formed 50% of their stellar mass. The later reshuffling is at odds with results from the fire-2 simulations. Hence, age gradients offer a test of current star formation and feedback models that can be probed via observations of resolved stellar populations. |
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| institution | Kabale University |
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| language | English |
| publishDate | 2024-01-01 |
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| spelling | doaj-art-672f531e04294264b859bd5faf0cb4572024-11-29T08:56:06ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-0197712010.3847/1538-4357/ad8b1eTestable Predictions of Outside-in Age Gradients in Dwarf Galaxies of All TypesClaire L. Riggs0https://orcid.org/0000-0001-8894-5671Alyson M. Brooks1https://orcid.org/0000-0002-0372-3736Ferah Munshi2https://orcid.org/0000-0002-9581-0297Charlotte R. Christensen3https://orcid.org/0000-0001-6779-3429Roger E. Cohen4https://orcid.org/0000-0002-2970-7435Thomas R. Quinn5https://orcid.org/0000-0001-5510-2803James Wadsley6Department of Physics and Astronomy, Rutgers, The State University of New Jersey , 136 Frelinghuysen Road, Piscataway, NJ 08854, USA ; riggs@physics.rutgers.eduDepartment of Physics and Astronomy, Rutgers, The State University of New Jersey , 136 Frelinghuysen Road, Piscataway, NJ 08854, USA ; riggs@physics.rutgers.edu; Center for Computational Astrophysics , Flatiron Institute, 162 5th Avenue, New York, NY 10010, USADepartment of Physics & Astronomy, George Mason University , 4400 University Drive, MSN: 3F3, Fairfax, VA 22030-4444, USAPhysics Department, Grinnell College , 1116 Eighth Avenue, Grinnell, IA 50112, USADepartment of Physics and Astronomy, Rutgers, The State University of New Jersey , 136 Frelinghuysen Road, Piscataway, NJ 08854, USA ; riggs@physics.rutgers.eduAstronomy Department, University of Washington , Seattle, WA 98195, USADepartment of Physics and Astronomy, McMaster University , Hamilton, ON L8S 4M1, Canada; Origins Institute, McMaster University , Hamilton, ON L8S 4M1, CanadaWe use a sample of 73 simulated satellite and central dwarf galaxies spanning a stellar mass range of 10 ^5.3 –10 ^9.1 M _⊙ to investigate the origin of their stellar age gradients. We find that dwarf galaxies often form their stars “inside-out,” i.e., the stars form at successively larger radii over time. However, the oldest stars get reshuffled beyond the star-forming radius by fluctuations in the gravitational potential well caused by stellar feedback (the same mechanisms that cause dwarfs to form dark matter cores). The result is that many dwarfs appear to have an “outside-in” age gradient at z = 0, with younger stellar populations more centrally concentrated. However, for the reshuffled galaxies with the most extended star formation, young stars can form out to the large radii to which the old stars have been reshuffled, erasing the age gradient. We find that major mergers do not play a significant role in setting the age gradients of dwarfs. We find similar age gradient trends in satellites and field dwarfs, suggesting that environment plays only a minor role, if any. Finally, we find that the age gradient trends are imprinted on the galaxies at later times, suggesting that the stellar reshuffling dominates after the galaxies have formed 50% of their stellar mass. The later reshuffling is at odds with results from the fire-2 simulations. Hence, age gradients offer a test of current star formation and feedback models that can be probed via observations of resolved stellar populations.https://doi.org/10.3847/1538-4357/ad8b1eDwarf galaxiesN-body simulationsStellar feedbackGalaxy formationGalaxy agesGalaxy evolution |
| spellingShingle | Claire L. Riggs Alyson M. Brooks Ferah Munshi Charlotte R. Christensen Roger E. Cohen Thomas R. Quinn James Wadsley Testable Predictions of Outside-in Age Gradients in Dwarf Galaxies of All Types The Astrophysical Journal Dwarf galaxies N-body simulations Stellar feedback Galaxy formation Galaxy ages Galaxy evolution |
| title | Testable Predictions of Outside-in Age Gradients in Dwarf Galaxies of All Types |
| title_full | Testable Predictions of Outside-in Age Gradients in Dwarf Galaxies of All Types |
| title_fullStr | Testable Predictions of Outside-in Age Gradients in Dwarf Galaxies of All Types |
| title_full_unstemmed | Testable Predictions of Outside-in Age Gradients in Dwarf Galaxies of All Types |
| title_short | Testable Predictions of Outside-in Age Gradients in Dwarf Galaxies of All Types |
| title_sort | testable predictions of outside in age gradients in dwarf galaxies of all types |
| topic | Dwarf galaxies N-body simulations Stellar feedback Galaxy formation Galaxy ages Galaxy evolution |
| url | https://doi.org/10.3847/1538-4357/ad8b1e |
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