Deep SOAR follow-up photometry of two Milky Way outer-halo companions discovered with Dark Energy Survey

E. Luque; B. Santiago; A. Pieres; J. L. Marshall; A. B. Pace; R. Kron; A. Drlica-Wagner; A. Queiroz; E. Balbinot; M. dal Ponte; A. Fausti Neto; L. N. da Costa; M. A.G. Maia; A. R. Walker; F. B. Abdalla; S. Allam; J. Annis; K. Bechtol; A. Benoit-Lévy; E. Bertin; D. Brooks; A. Carnero Rosell; M. Carrasco Kind; J. Carretero; M. Crocce; C. Davis; P. Doel; T. F. Eifler; B. Flaugher; J. García-Bellido; D. W. Gerdes; D. Gruen; R. A. Gruendl; G. Gutierrez; K. Honscheid; D. J. James; K. Kuehn; N. Kuropatkin; R. Miquel; R. C. Nichol; A. A. Plazas; E. Sanchez; V. Scarpine; R. Schindler; I. Sevilla-Noarbe; M. Smith; M. Soares-Santos; F. Sobreira; E. Suchyta; G. Tarle; D. Thomas

doi:10.1093/mnras/sty1039

Deep SOAR follow-up photometry of two Milky Way outer-halo companions discovered with Dark Energy Survey

E. Luque, B. Santiago, A. Pieres, J. L. Marshall, A. B. Pace, R. Kron, A. Drlica-Wagner, A. Queiroz, E. Balbinot, M. dal Ponte, A. Fausti Neto, L. N. da Costa, M. A.G. Maia, A. R. Walker, F. B. Abdalla, S. Allam, J. Annis, K. Bechtol, A. Benoit-Lévy, E. BertinD. Brooks, A. Carnero Rosell, M. Carrasco Kind, J. Carretero, M. Crocce, C. Davis, P. Doel, T. F. Eifler, B. Flaugher, J. García-Bellido, D. W. Gerdes, D. Gruen, R. A. Gruendl, G. Gutierrez, K. Honscheid, D. J. James, K. Kuehn, N. Kuropatkin, R. Miquel, R. C. Nichol, A. A. Plazas, E. Sanchez, V. Scarpine, R. Schindler, I. Sevilla-Noarbe, M. Smith, M. Soares-Santos, F. Sobreira, E. Suchyta, G. Tarle, D. Thomas

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Abstract

We report the discovery of a new star cluster, DES 3, in the constellation of Indus, and deeper observations of the previously identified satellite DES J0222.7-5217 (Eridanus III). DES 3 was detected as a stellar overdensity in first-year Dark Energy Survey data, and confirmed with deeper photometry from the 4.1-m Southern Astrophysical Research (SOAR) telescope. The new system was detected with a relatively high significance and appears in the DES images as a compact concentration of faint blue point sources. We determine that DES 3 is located at a heliocentric distance of ≃76.2 kpc and it is dominated by an old (≃9.8Gyr) and metal-poor ([Fe/H] ≃ -1.84) population. While the age and metallicity values of DES 3 are comparable to typical globular clusters (objects with a high stellar density, stellar mass of ~105 M_⊙ and luminosity M_V ~ -7.3), its half-light radius (r_h ~ 6.87 pc) and luminosity (M_V ~ -1.7) are more indicative of faint star cluster. Based on the angular size, DES 3, with a value of r_h ~ 0'.31, is among the smallest faint star clusters known to date. Furthermore, using deeper imaging of DES J0222.7-5217 taken with the SOAR telescope, we update structural parameters and perform the first isochrone modelling. Our analysis yields the first age (≃12.6Gyr) and metallicity ([Fe/H] ≃ -2.01) estimates for this object. The half-light radius (r_h ≃ 11.24 pc) and luminosity (M_V ≃ -2.4) of DES J0222.7-5217 suggest that it is likely a faint star cluster. The discovery of DES 3 indicates that the census of stellar systems in the MilkyWay is still far from complete, and demonstrates the power of modern wide-field imaging surveys to improve our knowledge of the Galaxy's satellite population.

Original language	English
Pages (from-to)	2006-2018
Number of pages	13
Journal	Monthly Notices of the Royal Astronomical Society
Volume	478
Issue number	2
DOIs	https://doi.org/10.1093/mnras/sty1039
State	Published - Aug 1 2018

Funding

We thank the anonymous referee for interesting remarks. This paper has gone through internal review by the DES collaboration. Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, theMinistry of Science and Education of Spain, the Science and Technology FacilitiesCouncil of theUnitedKingdom, theHigher Education Funding Council for England, theNationalCenter 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 Universit ät 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 University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, TexasA&MUniversity, and theOzDES Membership Consortium. 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. The DES data management system is supported by the National Science Foundation under Grant Numbers AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2015-71825, ESP2015-88861, FPA2015-68048, SEV-2012-0234, SEV-2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA programme of the Generalitat de Catalunya. Research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013) including ERC grant agreements 240672, 291329, and 306478.We acknowledge support from the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020. This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. TheUnited StatesGovernment retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. Based on observations obtained at the SOAR telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), andMichigan State University (MSU). EB acknowledges financial support from the European Research Council (StG-335936)

Funders	Funder number
Collaborating Institutions are Argonne National Laboratory
Collaborating Institutions in the Dark Energy Survey
Fermi Research Alliance, LLC	DE-AC02-07CH11359
Institut de Ciències de l'Espai
Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University
TexasA&MUniversity
United States Government
National Science Foundation	1138766, AST-1138766, 240672, 306478, 291329, AST-1536171
U.S. Department of Energy
University of Illinois at Urbana-Champaign
Stanford University
Office of Science
High Energy Physics
Fermilab
Lawrence Berkeley National Laboratory
University of California, Santa Cruz
University of North Carolina
University of Pennsylvania
Ohio State University
University of Chicago
Virginia Polytechnic Institute and State University
University of Michigan
University of North Carolina at Chapel Hill
University of Portsmouth
Seventh Framework Programme
SLAC National Accelerator Laboratory
Science and Technology Facilities Council
University College London
European Commission
European Research Council	335936
University of Nottingham
University of Sussex
University of Edinburgh
Australian Research Council	CE110001020
Deutsche Forschungsgemeinschaft
Generalitat de Catalunya
Eidgenössische Technische Hochschule Zürich
Ministerio de Economía y Competitividad	ESP2015-88861, SEV-2016-0597, MDM-2015-0509, FPA2015-68048, SEV-2012-0234, AYA2015-71825
Ministério da Ciência, Tecnologia e Inovação
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro
Financiadora de Estudos e Projetos
Seventh Framework Programme
Ludwig-Maximilians-Universität München
European Regional Development Fund
National Science Foundation	1536171
Ministério da Ciência, Tecnologia, Inovações e Comunicações
Midlands State University	StG-335936
Institut de Física d'Altes Energies

Keywords

Galaxy: halo
Globular clusters: general

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10.1093/mnras/sty1039

Cite this

Luque, E., Santiago, B., Pieres, A., Marshall, J. L., Pace, A. B., Kron, R., Drlica-Wagner, A., Queiroz, A., Balbinot, E., dal Ponte, M., Fausti Neto, A., da Costa, L. N., Maia, M. A. G., Walker, A. R., Abdalla, F. B., Allam, S., Annis, J., Bechtol, K., Benoit-Lévy, A., ... Thomas, D. (2018). Deep SOAR follow-up photometry of two Milky Way outer-halo companions discovered with Dark Energy Survey. Monthly Notices of the Royal Astronomical Society, 478(2), 2006-2018. https://doi.org/10.1093/mnras/sty1039

@article{7115600af5174f26bfc9c1b019dd9c74,

title = "Deep SOAR follow-up photometry of two Milky Way outer-halo companions discovered with Dark Energy Survey",

abstract = "We report the discovery of a new star cluster, DES 3, in the constellation of Indus, and deeper observations of the previously identified satellite DES J0222.7-5217 (Eridanus III). DES 3 was detected as a stellar overdensity in first-year Dark Energy Survey data, and confirmed with deeper photometry from the 4.1-m Southern Astrophysical Research (SOAR) telescope. The new system was detected with a relatively high significance and appears in the DES images as a compact concentration of faint blue point sources. We determine that DES 3 is located at a heliocentric distance of ≃76.2 kpc and it is dominated by an old (≃9.8Gyr) and metal-poor ([Fe/H] ≃ -1.84) population. While the age and metallicity values of DES 3 are comparable to typical globular clusters (objects with a high stellar density, stellar mass of ~105 M⊙ and luminosity MV ~ -7.3), its half-light radius (rh ~ 6.87 pc) and luminosity (MV ~ -1.7) are more indicative of faint star cluster. Based on the angular size, DES 3, with a value of rh ~ 0'.31, is among the smallest faint star clusters known to date. Furthermore, using deeper imaging of DES J0222.7-5217 taken with the SOAR telescope, we update structural parameters and perform the first isochrone modelling. Our analysis yields the first age (≃12.6Gyr) and metallicity ([Fe/H] ≃ -2.01) estimates for this object. The half-light radius (rh ≃ 11.24 pc) and luminosity (MV ≃ -2.4) of DES J0222.7-5217 suggest that it is likely a faint star cluster. The discovery of DES 3 indicates that the census of stellar systems in the MilkyWay is still far from complete, and demonstrates the power of modern wide-field imaging surveys to improve our knowledge of the Galaxy's satellite population.",

keywords = "Galaxy: halo, Globular clusters: general",

author = "E. Luque and B. Santiago and A. Pieres and Marshall, {J. L.} and Pace, {A. B.} and R. Kron and A. Drlica-Wagner and A. Queiroz and E. Balbinot and {dal Ponte}, M. and {Fausti Neto}, A. and {da Costa}, {L. N.} and Maia, {M. A.G.} and Walker, {A. R.} and Abdalla, {F. B.} and S. Allam and J. Annis and K. Bechtol and A. Benoit-L{\'e}vy and E. Bertin and D. Brooks and {Carnero Rosell}, A. and {Carrasco Kind}, M. and J. Carretero and M. Crocce and C. Davis and P. Doel and Eifler, {T. F.} and B. Flaugher and J. Garc{\'i}a-Bellido and Gerdes, {D. W.} and D. Gruen and Gruendl, {R. A.} and G. Gutierrez and K. Honscheid and James, {D. J.} and K. Kuehn and N. Kuropatkin and R. Miquel and Nichol, {R. C.} and Plazas, {A. A.} and E. Sanchez and V. Scarpine and R. Schindler and I. Sevilla-Noarbe and M. Smith and M. Soares-Santos and F. Sobreira and E. Suchyta and G. Tarle and D. Thomas",

note = "Publisher Copyright: {\textcopyright} 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.",

year = "2018",

month = aug,

day = "1",

doi = "10.1093/mnras/sty1039",

language = "English",

volume = "478",

pages = "2006--2018",

journal = "Monthly Notices of the Royal Astronomical Society",

issn = "0035-8711",

publisher = "Oxford University Press",

number = "2",

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Luque, E, Santiago, B, Pieres, A, Marshall, JL, Pace, AB, Kron, R, Drlica-Wagner, A, Queiroz, A, Balbinot, E, dal Ponte, M, Fausti Neto, A, da Costa, LN, Maia, MAG, Walker, AR, Abdalla, FB, Allam, S, Annis, J, Bechtol, K, Benoit-Lévy, A, Bertin, E, Brooks, D, Carnero Rosell, A, Carrasco Kind, M, Carretero, J, Crocce, M, Davis, C, Doel, P, Eifler, TF, Flaugher, B, García-Bellido, J, Gerdes, DW, Gruen, D, Gruendl, RA, Gutierrez, G, Honscheid, K, James, DJ, Kuehn, K, Kuropatkin, N, Miquel, R, Nichol, RC, Plazas, AA, Sanchez, E, Scarpine, V, Schindler, R, Sevilla-Noarbe, I, Smith, M, Soares-Santos, M, Sobreira, F, Suchyta, E, Tarle, G & Thomas, D 2018, 'Deep SOAR follow-up photometry of two Milky Way outer-halo companions discovered with Dark Energy Survey', Monthly Notices of the Royal Astronomical Society, vol. 478, no. 2, pp. 2006-2018. https://doi.org/10.1093/mnras/sty1039

TY - JOUR

T1 - Deep SOAR follow-up photometry of two Milky Way outer-halo companions discovered with Dark Energy Survey

AU - Luque, E.

AU - Santiago, B.

AU - Pieres, A.

AU - Marshall, J. L.

AU - Pace, A. B.

AU - Kron, R.

AU - Drlica-Wagner, A.

AU - Queiroz, A.

AU - Balbinot, E.

AU - dal Ponte, M.

AU - Fausti Neto, A.

AU - da Costa, L. N.

AU - Maia, M. A.G.

AU - Walker, A. R.

AU - Abdalla, F. B.

AU - Allam, S.

AU - Annis, J.

AU - Bechtol, K.

AU - Benoit-Lévy, A.

AU - Bertin, E.

AU - Brooks, D.

AU - Carnero Rosell, A.

AU - Carrasco Kind, M.

AU - Carretero, J.

AU - Crocce, M.

AU - Davis, C.

AU - Doel, P.

AU - Eifler, T. F.

AU - Flaugher, B.

AU - García-Bellido, J.

AU - Gerdes, D. W.

AU - Gruen, D.

AU - Gruendl, R. A.

AU - Gutierrez, G.

AU - Honscheid, K.

AU - James, D. J.

AU - Kuehn, K.

AU - Kuropatkin, N.

AU - Miquel, R.

AU - Nichol, R. C.

AU - Plazas, A. A.

AU - Sanchez, E.

AU - Scarpine, V.

AU - Schindler, R.

AU - Sevilla-Noarbe, I.

AU - Smith, M.

AU - Soares-Santos, M.

AU - Sobreira, F.

AU - Suchyta, E.

AU - Tarle, G.

AU - Thomas, D.

PY - 2018/8/1

Y1 - 2018/8/1

N2 - We report the discovery of a new star cluster, DES 3, in the constellation of Indus, and deeper observations of the previously identified satellite DES J0222.7-5217 (Eridanus III). DES 3 was detected as a stellar overdensity in first-year Dark Energy Survey data, and confirmed with deeper photometry from the 4.1-m Southern Astrophysical Research (SOAR) telescope. The new system was detected with a relatively high significance and appears in the DES images as a compact concentration of faint blue point sources. We determine that DES 3 is located at a heliocentric distance of ≃76.2 kpc and it is dominated by an old (≃9.8Gyr) and metal-poor ([Fe/H] ≃ -1.84) population. While the age and metallicity values of DES 3 are comparable to typical globular clusters (objects with a high stellar density, stellar mass of ~105 M⊙ and luminosity MV ~ -7.3), its half-light radius (rh ~ 6.87 pc) and luminosity (MV ~ -1.7) are more indicative of faint star cluster. Based on the angular size, DES 3, with a value of rh ~ 0'.31, is among the smallest faint star clusters known to date. Furthermore, using deeper imaging of DES J0222.7-5217 taken with the SOAR telescope, we update structural parameters and perform the first isochrone modelling. Our analysis yields the first age (≃12.6Gyr) and metallicity ([Fe/H] ≃ -2.01) estimates for this object. The half-light radius (rh ≃ 11.24 pc) and luminosity (MV ≃ -2.4) of DES J0222.7-5217 suggest that it is likely a faint star cluster. The discovery of DES 3 indicates that the census of stellar systems in the MilkyWay is still far from complete, and demonstrates the power of modern wide-field imaging surveys to improve our knowledge of the Galaxy's satellite population.

AB - We report the discovery of a new star cluster, DES 3, in the constellation of Indus, and deeper observations of the previously identified satellite DES J0222.7-5217 (Eridanus III). DES 3 was detected as a stellar overdensity in first-year Dark Energy Survey data, and confirmed with deeper photometry from the 4.1-m Southern Astrophysical Research (SOAR) telescope. The new system was detected with a relatively high significance and appears in the DES images as a compact concentration of faint blue point sources. We determine that DES 3 is located at a heliocentric distance of ≃76.2 kpc and it is dominated by an old (≃9.8Gyr) and metal-poor ([Fe/H] ≃ -1.84) population. While the age and metallicity values of DES 3 are comparable to typical globular clusters (objects with a high stellar density, stellar mass of ~105 M⊙ and luminosity MV ~ -7.3), its half-light radius (rh ~ 6.87 pc) and luminosity (MV ~ -1.7) are more indicative of faint star cluster. Based on the angular size, DES 3, with a value of rh ~ 0'.31, is among the smallest faint star clusters known to date. Furthermore, using deeper imaging of DES J0222.7-5217 taken with the SOAR telescope, we update structural parameters and perform the first isochrone modelling. Our analysis yields the first age (≃12.6Gyr) and metallicity ([Fe/H] ≃ -2.01) estimates for this object. The half-light radius (rh ≃ 11.24 pc) and luminosity (MV ≃ -2.4) of DES J0222.7-5217 suggest that it is likely a faint star cluster. The discovery of DES 3 indicates that the census of stellar systems in the MilkyWay is still far from complete, and demonstrates the power of modern wide-field imaging surveys to improve our knowledge of the Galaxy's satellite population.

KW - Galaxy: halo

KW - Globular clusters: general

UR - http://www.scopus.com/inward/record.url?scp=85048883433&partnerID=8YFLogxK

U2 - 10.1093/mnras/sty1039

DO - 10.1093/mnras/sty1039

M3 - Article

AN - SCOPUS:85048883433

SN - 0035-8711

VL - 478

SP - 2006

EP - 2018

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 2

ER -

Deep SOAR follow-up photometry of two Milky Way outer-halo companions discovered with Dark Energy Survey

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