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 (US)
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

Keywords

Galaxy: halo
Globular clusters: general

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

Online availability

10.1093/mnras/sty1039

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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

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

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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 (US)",

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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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

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U2 - 10.1093/mnras/sty1039

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JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

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ER -

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

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