Journal
ASTRONOMICAL JOURNAL
Volume 157, Issue 1, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.3847/1538-3881/aaf4f3
Keywords
galaxies: dwarf; galaxies: individual (Sextans); galaxies:stellar content; stars: variables: general; stars: variables: RR Lyrae
Categories
Funding
- FONDECYT Iniciacin [11150916]
- Ministry of Economy, Development, and Tourism's Millennium Science Initiative [IC120009]
- NSF [AST-1312997, AST-1815403]
- U.S. Department of Energy
- U.S. National Science Foundation
- Ministry of Science and Education of Spain
- Science and Technology Facilities Council of the United Kingdom
- Higher Education Funding Council for England
- National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign
- Kavli Institute of Cosmological Physics at the University of Chicago
- Center for Cosmology and Astro-Particle Physics at the Ohio State University
- Mitchell Institute for Fundamental Physics and Astronomy at Texas AM University
- Financiadora de Estudos e Projetos
- Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro
- Conselho Nacional de Desenvolvimento Cientifico e Tecnologico
- Ministerio da Ciencia, Tecnologia e Inovacao
- Deutsche Forschungsgemeinschaft
- Dark Energy Survey
- Argonne National Laboratory
- University of California at Santa Cruz
- University of Cambridge
- Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas-Madrid
- University of Chicago
- University College London
- DESBrazil Consortium
- University of Edinburgh
- Eidgenossische Technische Hochschule (ETH) Zurich
- Fermi National Accelerator Laboratory
- University of Illinois at Urbana-Champaign
- Institut de Ciencies de l'Espai (IEEC/CSIC)
- Institut de Fisica d'Altes Energies
- Lawrence Berkeley National Laboratory
- Ludwig-Maximilians Universitat Munchen
- associated Excellence Cluster Universe
- University of Michigan
- National Optical Astronomy Observatory
- University of Pennsylvania
- University of Portsmouth
- SLAC National Accelerator Laboratory
- Stanford University
- University of Sussex
- Texas AM University
- National Aeronautics and Space Administration [NNX08AR22G]
- National Science Foundation [AST-1238877]
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A large extension of the Sextans dwarf spheroidal galaxy, 7 deg(2), has been surveyed for variable stars using the Dark Energy Camera at the Blanco Telescope at Cerro Tololo Inter-American Observatory, Chile. We report seven anomalous Cepheids, 199 RR Lyrae stars, and 16 dwarf Cepheids in the field. This is only the fifth extragalactic system in which dwarf Cepheids have been systematically searched. Henceforth, the new stars increase the census of stars coming from different environments that can be used to asses the advantages and limitations of using dwarf Cepheids as standard candles in populations for which the metallicity is not necessarily known. The dwarf Cepheids found in Sextans have a mean period of 0.066 day and a mean g amplitude of 0.87 mag. They are located below the horizontal branch, spanning a range of 0.8 mag: 21.9 < g < 22.7. The number of dwarf Cepheids in Sextans is low compared with other galaxies such as Carina, which has a strong intermediate-age population. On the other hand, the number and ratio of RR Lyrae stars to dwarf Cepheids are quite similar to those of Sculptor, a galaxy which, as Sextans, is dominated by an old stellar population. The dwarf Cepheid stars found in Sextans follow a well-constrained period-luminosity relationship with an rms = 0.05 mag in the g band, which was set up by anchoring to the distance modulus given by the RR Lyrae stars. Although the majority of the variable stars in Sextans are located toward the center of the galaxy, we have found two RR Lyrae stars and one anomalous Cepheid in the outskirts of the galaxy that may be extratidal stars and suggest that this galaxy may be undergoing tidal destruction. These possible extratidal variable stars share the same proper motions as Sextans, as seen by recent Gaia measurements. Two additional stars that we initially classified as foreground RR Lyrae stars may actually be other examples of Sextans extratidal anomalous Cepheids, although radial velocities are needed to prove that scenario.
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