The growing number of Milky Way satellites detected in recent years has introduced a new focus for stellar abundance analysis. Abundances of stars in satellites have been used to probe the nature of these systems and their chemical evolution. However, for most satellites, only centrally located stars have been examined. This paper presents an analysis of three stars in the Tucana V system, one in the inner region and two at ∼10' (7–10 half-light radii) from the center. We find a remarkable chemical diversity between the stars. One star exhibits enhancements in rapid neutron-capture elements (an r-I star), and another is highly enhanced in C, N, and O but with low neutron-capture abundances (a CEMP-no star). The metallicities of the stars analyzed span more than 1 dex from [Fe/H] = −3.55 to −2.46. This, combined with a large abundance range of other elements like Ca, Sc, and Ni, confirms that Tuc V is an ultrafaint dwarf (UFD) galaxy. The variation in abundances, highlighted by [Mg/Ca] ratios ranging from +0.89 to −0.75, among the stars demonstrates that the chemical enrichment history of Tuc V was very inhomogeneous. Tuc V is only the second UFD galaxy in which stars located at large distances from the galactic center have been analyzed, along with Tucana II. The chemical diversity seen in these two galaxies, driven by the composition of the noncentral member stars, suggests that distant member stars are important to include when classifying faint satellites and that these systems may have experienced more complex chemical enrichment histories than previously anticipated.
Chemical Diversity on Small Scales: Abundance Analysis of the Tucana V Ultrafaint Dwarf Galaxy
Abstract
Copyright and License
© 2024. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Acknowledgement
The authors thank the referee, Dr. Ricardo Schiavon, for the careful read of the paper and useful comments, which have improved the manuscript. T.T.H. acknowledges support from the Swedish Research Council (VR 2021-05556). A.P.J. acknowledges support by the National Science Foundation under grants AST-2206264 and AST-2307599. T.S.L. acknowledges financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC) through grant RGPIN-2022-04794. J.Y.G. acknowledges support from a Carnegie Fellowship. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory. This research made extensive use of the SIMBAD database operated at CDS, Straasburg, France (Wenger et al. 2000), https://arxiv.org/, and NASA's Astrophysics Data System for bibliographic information. We thank Adrian Price-Whelan for assistance with binary fitting using TheJoker.
This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular, the institutions participating in the Gaia Multilateral Agreement.
This project used public archival data from the Dark Energy Survey (DES). Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência, Tecnologia e Inovação, the Deutsche Forschungsgemeinschaft, and the Collaborating Institutions in the Dark Energy Survey. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgenössische Technische Hochschule (ETH) Zürich, Fermi National Accelerator Laboratory, the University of Illinois at Urbana-Champaign, the Institut de Ciències de l'Espai (IEEC/CSIC), the Institut de Física d'Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig-Maximilians Universität München and the associated Excellence Cluster Universe, the University of Michigan, the National Optical Astronomy Observatory, the University of Nottingham, The Ohio State University, the OzDES Membership Consortium, the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, and Texas A&M University. Based in part on observations at Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation.
Facilities
Magellan:Clay - Magellan II Landon Clay Telescope, Magellan:Baade - Magellan I Walter Baade Telescope
Software References
MOOG (Sneden 1973; Sobeck et al. 2011), IRAF (Tody 1986, 1993), ATLAS9 (Castelli & Kurucz 2003), linemake (Placco et al. 2021), NumPy (van der Walt et al. 2011), Matplotlib (Hunter 2007), AstroPy (Astropy Collaboration et al. 2013, 2018), CarPy (Kelson 2003), SMHR (Casey 2014)
Files
Hansen_2024_ApJ_968_21.pdf
Additional details
Identifiers
- ISSN
- 1538-4357
Funding
- Swedish Research Council
- VR 2021-05556
- National Science Foundation
- AST-2206264
- National Science Foundation
- AST-2307599
- Natural Sciences and Engineering Research Council
- RGPIN-2022-04794
- Carnegie Institution for Science
- European Space Agency
- Gaia Multilateral Agreement
- United States Department of Energy
- Ministerio de Ciencia, Innovación y Universidades
- Science and Technology Facilities Council
- National Center for Supercomputing Applications
- University of Chicago
- The Ohio State University
- Texas A&M University
- Financiadora de Estudos e Projetos
- Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro
- National Council for Scientific and Technological Development
- Ministry of Science, Technology and Innovation
- Deutsche Forschungsgemeinschaft