Journal
ASTROPHYSICAL JOURNAL
Volume 916, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.3847/1538-4357/ac0443
Keywords
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Categories
Funding
- Texas AM University
- George P. and Cynthia Woods Institute for Fundamental Physics and Astronomy
- NSF [AST-1813881, AST-1412792]
- 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
- National Science Foundation [AST-1138766, AST-1536171]
- MINECO [AYA2015-71825, ESP2015-66861, FPA2015-68048, SEV-2016-0588, SEV-2016-0597, MDM-2015-0509]
- ERDF funds from the European Union
- CERCA program of the Generalitat de Catalunya
- European Research Council under the European Union [240672, 291329, 306478]
- Brazilian Instituto Nacional de Ciencia e Tecnologia (INCT) e-Universe (CNPq) [465376/2014-2]
- U.S. Department of Energy, Office of Science, Office of High Energy Physics [DE-AC02-07CH11359]
- 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
- DES-Brazil 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
- University of Michigan
- National Optical Astronomy Observatory
- University of Nottingham
- Ohio State University
- University of Pennsylvania
- University of Portsmouth
- SLAC National Accelerator Laboratory
- Stanford University
- University of Sussex
- OzDES Membership Consortium
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This study presents deep g- and r-band Magellan/Megacam photometry of two dwarf galaxy candidates, Grus I and Indus II. Grus I is found to be an old, metal-poor dwarf galaxy, with updated distance and structural parameters. However, Indus II is likely a false positive detection due to chance alignment of stars along the line of sight.
We present deep g- and r-band Magellan/Megacam photometry of two dwarf galaxy candidates discovered in the Dark Energy Survey (DES), Grus I and Indus II (DES J2038-4609). For the case of Grus I, we resolved the main sequence turn-off (MSTO) and similar to 2 mags below it. The MSTO can be seen at g(0) similar to 24 with a photometric uncertainty of 0.03 mag. We show Grus I to be consistent with an old, metal-poor (similar to 13.3 Gyr, [Fe/H] similar to -1.9) dwarf galaxy. We derive updated distance and structural parameters for Grus I using this deep, uniform, wide-field data set. We find an azimuthally-averaged halflight radius more than two times larger (similar to 151(-31)(+21) pc; similar to 4'. 16(-0.74)(+0.54)) and an absolute V-band magnitude similar to-4.1 that is similar to 1 magnitude brighter than previous studies. We obtain updated distance, ellipticity, and centroid parameters that are in agreement with other studies within uncertainties. Although our photometry of Indus II is similar to 2-3 magnitudes deeper than the DES Y1 public release, we find no coherent stellar population at its reported location. The original detection was located in an incomplete region of sky in the DES Y2Q1 data set and was flagged due to potential blue horizontal branch member stars. The best-fit isochrone parameters are physically inconsistent with both dwarf galaxies and globular clusters. We conclude that Indus II is likely a false positive, flagged due to a chance alignment of stars along the line of sight.
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