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Title: Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns

Abstract

We report the peculiar chemical abundance patterns of 11 atypical Milky Way (MW) field red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). These atypical giants exhibit strong Al and N enhancements accompanied by C and Mg depletions, strikingly similar to those observed in the so-called second-generation (SG) stars of globular clusters (GCs). Remarkably, we find low Mg abundances ([Mg/Fe] < 0.0) together with strong Al and N overabundances in the majority (5/7) of the metal-rich ([Fe/H] ≳ −1.0) sample stars, which is at odds with actual observations of SG stars in Galactic GCs of similar metallicities. This chemical pattern is unique and unprecedented among MW stars, posing urgent questions about its origin. These atypical stars could be former SG stars of dissolved GCs formed with intrinsically lower abundances of Mg and enriched Al (subsequently self-polluted by massive AGB stars) or the result of exotic binary systems. We speculate that the stars Mg-deficiency as well as the orbital properties suggest that they could have an extragalactic origin. This discovery should guide future dedicated spectroscopic searches of atypical stellar chemical patterns in our Galaxy, a fundamental step forward to understanding the Galactic formation and evolution.

Authors:
; ; ; ;  [1]; ; ; ;  [2]; ;  [3];  [4];  [5];  [6];  [7];  [8]; ; ;  [9];  [10] more »; « less
  1. Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción (Chile)
  2. Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife (Spain)
  3. Observatório Nacional, Rua Gal. José Cristino 77, Rio de Janeiro, RJ—20921-400 (Brazil)
  4. Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF (United Kingdom)
  5. New Mexico State University, Las Cruces, NM 88003 (United States)
  6. University of Texas at Austin, McDonald Observatory, Fort Davis, TX 79734 (United States)
  7. Centro de Investigaciones de Astronomía, AP 264, Mérida 5101-A (Venezuela, Bolivarian Republic of)
  8. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  9. Department of Astronomy, University of Virginia, Charlottesville, VA 22903 (United States)
  10. Department of Physics and JINA Center for the Evolution of the Elements, University of Notre Dame, Notre Dame, IN 46556 (United States)
Publication Date:
OSTI Identifier:
22654403
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 846; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; ALUMINIUM; CARBON; GALACTIC EVOLUTION; ISOCHRONOUS CYCLOTRONS; MAGNESIUM; METALLICITY; METALS; MILKY WAY; NITROGEN; RED GIANT STARS; STAR CLUSTERS

Citation Formats

Fernández-Trincado, J. G., Geisler, D., Tang, B., Villanova, S., Mennickent, R. E., Zamora, O., García-Hernández, D. A., Dell’Agli, F., Prieto, Carlos Allende, Souto, Diogo, Cunha, Katia, Schiavon, R. P., Hasselquist, Sten, Shetrone, M., Vieira, K., Zasowski, G., Sobeck, J., Hayes, C. R., Majewski, S. R., Placco, V. M., E-mail: jfernandezt@astro-udec.cl, E-mail: jfernandezt87@gmail.com, and and others. Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns. United States: N. p., 2017. Web. doi:10.3847/2041-8213/AA8032.
Fernández-Trincado, J. G., Geisler, D., Tang, B., Villanova, S., Mennickent, R. E., Zamora, O., García-Hernández, D. A., Dell’Agli, F., Prieto, Carlos Allende, Souto, Diogo, Cunha, Katia, Schiavon, R. P., Hasselquist, Sten, Shetrone, M., Vieira, K., Zasowski, G., Sobeck, J., Hayes, C. R., Majewski, S. R., Placco, V. M., E-mail: jfernandezt@astro-udec.cl, E-mail: jfernandezt87@gmail.com, & and others. Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns. United States. doi:10.3847/2041-8213/AA8032.
Fernández-Trincado, J. G., Geisler, D., Tang, B., Villanova, S., Mennickent, R. E., Zamora, O., García-Hernández, D. A., Dell’Agli, F., Prieto, Carlos Allende, Souto, Diogo, Cunha, Katia, Schiavon, R. P., Hasselquist, Sten, Shetrone, M., Vieira, K., Zasowski, G., Sobeck, J., Hayes, C. R., Majewski, S. R., Placco, V. M., E-mail: jfernandezt@astro-udec.cl, E-mail: jfernandezt87@gmail.com, and and others. Fri . "Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns". United States. doi:10.3847/2041-8213/AA8032.
@article{osti_22654403,
title = {Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns},
author = {Fernández-Trincado, J. G. and Geisler, D. and Tang, B. and Villanova, S. and Mennickent, R. E. and Zamora, O. and García-Hernández, D. A. and Dell’Agli, F. and Prieto, Carlos Allende and Souto, Diogo and Cunha, Katia and Schiavon, R. P. and Hasselquist, Sten and Shetrone, M. and Vieira, K. and Zasowski, G. and Sobeck, J. and Hayes, C. R. and Majewski, S. R. and Placco, V. M., E-mail: jfernandezt@astro-udec.cl, E-mail: jfernandezt87@gmail.com and and others},
abstractNote = {We report the peculiar chemical abundance patterns of 11 atypical Milky Way (MW) field red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). These atypical giants exhibit strong Al and N enhancements accompanied by C and Mg depletions, strikingly similar to those observed in the so-called second-generation (SG) stars of globular clusters (GCs). Remarkably, we find low Mg abundances ([Mg/Fe] < 0.0) together with strong Al and N overabundances in the majority (5/7) of the metal-rich ([Fe/H] ≳ −1.0) sample stars, which is at odds with actual observations of SG stars in Galactic GCs of similar metallicities. This chemical pattern is unique and unprecedented among MW stars, posing urgent questions about its origin. These atypical stars could be former SG stars of dissolved GCs formed with intrinsically lower abundances of Mg and enriched Al (subsequently self-polluted by massive AGB stars) or the result of exotic binary systems. We speculate that the stars Mg-deficiency as well as the orbital properties suggest that they could have an extragalactic origin. This discovery should guide future dedicated spectroscopic searches of atypical stellar chemical patterns in our Galaxy, a fundamental step forward to understanding the Galactic formation and evolution.},
doi = {10.3847/2041-8213/AA8032},
journal = {Astrophysical Journal Letters},
number = 1,
volume = 846,
place = {United States},
year = {Fri Sep 01 00:00:00 EDT 2017},
month = {Fri Sep 01 00:00:00 EDT 2017}
}