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

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

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.

Galaxy: halo, Globular clusters: general
0035-8711
2006-2018
Luque, E.
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Marshall, J. L.
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dal Ponte, M.
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da Costa, L. N.
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Eifler, T. F.
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Honscheid, K.
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Scarpine, V.
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Schindler, R.
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Sevilla-Noarbe, I.
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Smith, M.
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Soares-Santos, M.
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Suchyta, E.
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Tarle, G.
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Thomas, D.
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Luque, E.
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Santiago, B.
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Pieres, A.
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Marshall, J. L.
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Pace, A. B.
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Kron, R.
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Drlica-Wagner, A.
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Queiroz, A.
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Balbinot, E.
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dal Ponte, M.
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Fausti Neto, A.
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Maia, M. A.G.
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Walker, A. R.
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Abdalla, F. B.
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Allam, S.
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Annis, J.
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Bechtol, K.
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Benoit-Lévy, A.
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Bertin, E.
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Brooks, D.
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Carnero Rosell, A.
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Carrasco Kind, M.
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Carretero, J.
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Crocce, M.
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Davis, C.
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Doel, P.
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Eifler, T. F.
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Flaugher, B.
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García-Bellido, J.
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Gerdes, D. W.
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Honscheid, K.
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Kuehn, K.
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Kuropatkin, N.
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Miquel, R.
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Sanchez, E.
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Scarpine, V.
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Schindler, R.
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Sevilla-Noarbe, I.
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Smith, M.
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Soares-Santos, M.
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Sobreira, F.
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Suchyta, E.
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Tarle, G.
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Thomas, D.
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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., Bertin, E., Brooks, D., Carnero Rosell, A., Carrasco Kind, M., Carretero, J., Crocce, M., Davis, C., Doel, P., Eifler, T. F., Flaugher, B., García-Bellido, J., Gerdes, D. W., Gruen, D., Gruendl, R. A., Gutierrez, G., Honscheid, K., James, D. J., Kuehn, K., Kuropatkin, N., Miquel, R., Nichol, R. C., Plazas, A. A., Sanchez, E., Scarpine, V., Schindler, R., Sevilla-Noarbe, I., Smith, M., Soares-Santos, M., Sobreira, F., Suchyta, E., Tarle, G. and 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. (doi:10.1093/mnras/sty1039).

Record type: Article

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.

Full text not available from this repository.

More information

Accepted/In Press date: 19 April 2018
e-pub ahead of print date: 25 April 2018
Published date: 1 August 2018
Keywords: Galaxy: halo, Globular clusters: general

Identifiers

Local EPrints ID: 425801
URI: https://eprints.soton.ac.uk/id/eprint/425801
ISSN: 0035-8711
PURE UUID: a3831448-4bfc-45d6-80f4-84220c7eafac
ORCID for M. Smith: ORCID iD orcid.org/0000-0002-3321-1432

Catalogue record

Date deposited: 02 Nov 2018 17:30
Last modified: 17 May 2019 00:30

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Contributors

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

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