DISCOVERY of A STELLAR OVERDENSITY in ERIDANUS-PHOENIX in the DARK ENERGY SURVEY

T. S. Li; E. Balbinot; N. Mondrik; J. L. Marshall; B. Yanny; K. Bechtol; A. Drlica-Wagner; D. Oscar; B. Santiago; J. D. Simon; A. K. Vivas; A. R. Walker; M. Y. Wang; T. M.C. Abbott; F. B. Abdalla; A. Benoit-Lévy; G. M. Bernstein; E. Bertin; D. Brooks; D. L. Burke; A. Carnero Rosell; M. Carrasco Kind; J. Carretero; L. N.Da Costa; D. L. Depoy; S. Desai; H. T. Diehl; P. Doel; J. Estrada; D. A. Finley; B. Flaugher; J. Frieman; D. Gruen; R. A. Gruendl; G. Gutierrez; K. Honscheid; D. J. James; K. Kuehn; N. Kuropatkin; O. Lahav; M. A.G. Maia; M. March; P. Martini; R. Ogando; A. A. Plazas; K. Reil; A. K. Romer; A. Roodman; E. Sanchez; V. Scarpine; M. Schubnell; I. Sevilla-Noarbe; R. C. Smith; M. Soares-Santos; F. Sobreira; E. Suchyta; M. E.C. Swanson; G. Tarle; D. Tucker; Y. Zhang

doi:10.3847/0004-637X/817/2/135

DISCOVERY of A STELLAR OVERDENSITY in ERIDANUS-PHOENIX in the DARK ENERGY SURVEY

T. S. Li, E. Balbinot, N. Mondrik, J. L. Marshall, B. Yanny, K. Bechtol, A. Drlica-Wagner, D. Oscar, B. Santiago, J. D. Simon, A. K. Vivas, A. R. Walker, M. Y. Wang, T. M.C. Abbott, F. B. Abdalla, A. Benoit-Lévy, G. M. Bernstein, E. Bertin, D. Brooks, D. L. BurkeA. Carnero Rosell, M. Carrasco Kind, J. Carretero, L. N.Da Costa, D. L. Depoy, S. Desai, H. T. Diehl, P. Doel, J. Estrada, D. A. Finley, B. Flaugher, J. Frieman, D. Gruen, R. A. Gruendl, G. Gutierrez, K. Honscheid, D. J. James, K. Kuehn, N. Kuropatkin, O. Lahav, M. A.G. Maia, M. March, P. Martini, R. Ogando, A. A. Plazas, K. Reil, A. K. Romer, A. Roodman, E. Sanchez, V. Scarpine, M. Schubnell, I. Sevilla-Noarbe, R. C. Smith, M. Soares-Santos, F. Sobreira, E. Suchyta, M. E.C. Swanson, G. Tarle, D. Tucker, Y. Zhang

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Abstract

We report the discovery of an excess of main-sequence turnoff stars in the direction of the constellations of Eridanus and Phoenix from the first-year data of the Dark Energy Survey (DES). The Eridanus-Phoenix (EriPhe) overdensity is centered around l ∼ 285° and b ∼ -60° and spans at least 30° in longitude and 10° in latitude. The Poisson significance of the detection is at least 9s. The stellar population in the overdense region is similar in brightness and color to that of the nearby globular cluster NGC 1261, indicating that the heliocentric distance of EriPhe is about d ∼ 16 kpc. The extent of EriPhe in projection is therefore at least ∼4 kpc by ∼3 kpc. On the sky, this overdensity is located between NGC 1261 and a new stellar stream discovered by DES at a similar heliocentric distance, the so-called Phoenix Stream. Given their similar distance and proximity to each other, it is possible that these three structures may be kinematically associated. Alternatively, the EriPhe overdensity is morphologically similar to the Virgo overdensity and the Hercules-Aquila cloud, which also lie at a similar Galactocentric distance. These three overdensities lie along a polar plane separated by ∼120° and may share a common origin. Spectroscopic follow-up observations of the stars in EriPhe are required to fully understand the nature of this overdensity.

Original language	English
Article number	135
Journal	Astrophysical Journal
Volume	817
Issue number	2
DOIs	https://doi.org/10.3847/0004-637X/817/2/135
State	Published - Feb 1 2016
Externally published	Yes

Funding

The DES data management system is supported by the National Science Foundation under Grant Number AST- 1138766. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2012- 39559, ESP2013-48274, FPA2013-47986, and Centro de Excelencia Severo Ochoa SEV-2012-0234. Research leading to these results has received funding from the European Research Council under the European Unions Seventh Framework Programme (FP7/2007-2013), including ERC grant agreements 240672, 291329, and 306478.

Funders	Funder number
Centro de Excelencia Severo Ochoa	SEV-2012-0234
National Science Foundation	AST- 1138766
Seventh Framework Programme
Engineering Research Centers	240672, 306478, 291329
Science and Technology Facilities Council	ST/M001334/1
European Research Council
Ministerio de Economía y Competitividad	AYA2012- 39559, FPA2013-47986, ESP2013-48274
Seventh Framework Programme

Keywords

galaxy: formation
galaxy: halo
galaxy: structure
local group

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10.3847/0004-637X/817/2/135

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Li, T. S., Balbinot, E., Mondrik, N., Marshall, J. L., Yanny, B., Bechtol, K., Drlica-Wagner, A., Oscar, D., Santiago, B., Simon, J. D., Vivas, A. K., Walker, A. R., Wang, M. Y., Abbott, T. M. C., Abdalla, F. B., Benoit-Lévy, A., Bernstein, G. M., Bertin, E., Brooks, D., ... Zhang, Y. (2016). DISCOVERY of A STELLAR OVERDENSITY in ERIDANUS-PHOENIX in the DARK ENERGY SURVEY. Astrophysical Journal, 817(2), Article 135. https://doi.org/10.3847/0004-637X/817/2/135

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title = "DISCOVERY of A STELLAR OVERDENSITY in ERIDANUS-PHOENIX in the DARK ENERGY SURVEY",

abstract = "We report the discovery of an excess of main-sequence turnoff stars in the direction of the constellations of Eridanus and Phoenix from the first-year data of the Dark Energy Survey (DES). The Eridanus-Phoenix (EriPhe) overdensity is centered around l ∼ 285° and b ∼ -60° and spans at least 30° in longitude and 10° in latitude. The Poisson significance of the detection is at least 9s. The stellar population in the overdense region is similar in brightness and color to that of the nearby globular cluster NGC 1261, indicating that the heliocentric distance of EriPhe is about d ∼ 16 kpc. The extent of EriPhe in projection is therefore at least ∼4 kpc by ∼3 kpc. On the sky, this overdensity is located between NGC 1261 and a new stellar stream discovered by DES at a similar heliocentric distance, the so-called Phoenix Stream. Given their similar distance and proximity to each other, it is possible that these three structures may be kinematically associated. Alternatively, the EriPhe overdensity is morphologically similar to the Virgo overdensity and the Hercules-Aquila cloud, which also lie at a similar Galactocentric distance. These three overdensities lie along a polar plane separated by ∼120° and may share a common origin. Spectroscopic follow-up observations of the stars in EriPhe are required to fully understand the nature of this overdensity.",

keywords = "galaxy: formation, galaxy: halo, galaxy: structure, local group",

author = "Li, {T. S.} and E. Balbinot and N. Mondrik and Marshall, {J. L.} and B. Yanny and K. Bechtol and A. Drlica-Wagner and D. Oscar and B. Santiago and Simon, {J. D.} and Vivas, {A. K.} and Walker, {A. R.} and Wang, {M. Y.} and Abbott, {T. M.C.} and Abdalla, {F. B.} and A. Benoit-L{\'e}vy and Bernstein, {G. M.} and E. Bertin and D. Brooks and Burke, {D. L.} and Rosell, {A. Carnero} and Kind, {M. Carrasco} and J. Carretero and Costa, {L. N.Da} and Depoy, {D. L.} and S. Desai and Diehl, {H. T.} and P. Doel and J. Estrada and Finley, {D. A.} and B. Flaugher and J. Frieman and D. Gruen and Gruendl, {R. A.} and G. Gutierrez and K. Honscheid and James, {D. J.} and K. Kuehn and N. Kuropatkin and O. Lahav and Maia, {M. A.G.} and M. March and P. Martini and R. Ogando and Plazas, {A. A.} and K. Reil and Romer, {A. K.} and A. Roodman and E. Sanchez and V. Scarpine and M. Schubnell and I. Sevilla-Noarbe and Smith, {R. C.} and M. Soares-Santos and F. Sobreira and E. Suchyta and Swanson, {M. E.C.} and G. Tarle and D. Tucker and Y. Zhang",

year = "2016",

month = feb,

day = "1",

doi = "10.3847/0004-637X/817/2/135",

language = "English",

volume = "817",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "American Astronomical Society",

number = "2",

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Li, TS, Balbinot, E, Mondrik, N, Marshall, JL, Yanny, B, Bechtol, K, Drlica-Wagner, A, Oscar, D, Santiago, B, Simon, JD, Vivas, AK, Walker, AR, Wang, MY, Abbott, TMC, Abdalla, FB, Benoit-Lévy, A, Bernstein, GM, Bertin, E, Brooks, D, Burke, DL, Rosell, AC, Kind, MC, Carretero, J, Costa, LND, Depoy, DL, Desai, S, Diehl, HT, Doel, P, Estrada, J, Finley, DA, Flaugher, B, Frieman, J, Gruen, D, Gruendl, RA, Gutierrez, G, Honscheid, K, James, DJ, Kuehn, K, Kuropatkin, N, Lahav, O, Maia, MAG, March, M, Martini, P, Ogando, R, Plazas, AA, Reil, K, Romer, AK, Roodman, A, Sanchez, E, Scarpine, V, Schubnell, M, Sevilla-Noarbe, I, Smith, RC, Soares-Santos, M, Sobreira, F, Suchyta, E, Swanson, MEC, Tarle, G, Tucker, D & Zhang, Y 2016, 'DISCOVERY of A STELLAR OVERDENSITY in ERIDANUS-PHOENIX in the DARK ENERGY SURVEY', Astrophysical Journal, vol. 817, no. 2, 135. https://doi.org/10.3847/0004-637X/817/2/135

TY - JOUR

T1 - DISCOVERY of A STELLAR OVERDENSITY in ERIDANUS-PHOENIX in the DARK ENERGY SURVEY

AU - Li, T. S.

AU - Balbinot, E.

AU - Mondrik, N.

AU - Marshall, J. L.

AU - Yanny, B.

AU - Bechtol, K.

AU - Drlica-Wagner, A.

AU - Oscar, D.

AU - Santiago, B.

AU - Simon, J. D.

AU - Vivas, A. K.

AU - Walker, A. R.

AU - Wang, M. Y.

AU - Abbott, T. M.C.

AU - Abdalla, F. B.

AU - Benoit-Lévy, A.

AU - Bernstein, G. M.

AU - Bertin, E.

AU - Brooks, D.

AU - Burke, D. L.

AU - Rosell, A. Carnero

AU - Kind, M. Carrasco

AU - Carretero, J.

AU - Costa, L. N.Da

AU - Depoy, D. L.

AU - Desai, S.

AU - Diehl, H. T.

AU - Doel, P.

AU - Estrada, J.

AU - Finley, D. A.

AU - Flaugher, B.

AU - Frieman, J.

AU - Gruen, D.

AU - Gruendl, R. A.

AU - Gutierrez, G.

AU - Honscheid, K.

AU - James, D. J.

AU - Kuehn, K.

AU - Kuropatkin, N.

AU - Lahav, O.

AU - Maia, M. A.G.

AU - March, M.

AU - Martini, P.

AU - Ogando, R.

AU - Plazas, A. A.

AU - Reil, K.

AU - Romer, A. K.

AU - Roodman, A.

AU - Sanchez, E.

AU - Scarpine, V.

AU - Schubnell, M.

AU - Sevilla-Noarbe, I.

AU - Smith, R. C.

AU - Soares-Santos, M.

AU - Sobreira, F.

AU - Suchyta, E.

AU - Swanson, M. E.C.

AU - Tarle, G.

AU - Tucker, D.

AU - Zhang, Y.

PY - 2016/2/1

Y1 - 2016/2/1

N2 - We report the discovery of an excess of main-sequence turnoff stars in the direction of the constellations of Eridanus and Phoenix from the first-year data of the Dark Energy Survey (DES). The Eridanus-Phoenix (EriPhe) overdensity is centered around l ∼ 285° and b ∼ -60° and spans at least 30° in longitude and 10° in latitude. The Poisson significance of the detection is at least 9s. The stellar population in the overdense region is similar in brightness and color to that of the nearby globular cluster NGC 1261, indicating that the heliocentric distance of EriPhe is about d ∼ 16 kpc. The extent of EriPhe in projection is therefore at least ∼4 kpc by ∼3 kpc. On the sky, this overdensity is located between NGC 1261 and a new stellar stream discovered by DES at a similar heliocentric distance, the so-called Phoenix Stream. Given their similar distance and proximity to each other, it is possible that these three structures may be kinematically associated. Alternatively, the EriPhe overdensity is morphologically similar to the Virgo overdensity and the Hercules-Aquila cloud, which also lie at a similar Galactocentric distance. These three overdensities lie along a polar plane separated by ∼120° and may share a common origin. Spectroscopic follow-up observations of the stars in EriPhe are required to fully understand the nature of this overdensity.

AB - We report the discovery of an excess of main-sequence turnoff stars in the direction of the constellations of Eridanus and Phoenix from the first-year data of the Dark Energy Survey (DES). The Eridanus-Phoenix (EriPhe) overdensity is centered around l ∼ 285° and b ∼ -60° and spans at least 30° in longitude and 10° in latitude. The Poisson significance of the detection is at least 9s. The stellar population in the overdense region is similar in brightness and color to that of the nearby globular cluster NGC 1261, indicating that the heliocentric distance of EriPhe is about d ∼ 16 kpc. The extent of EriPhe in projection is therefore at least ∼4 kpc by ∼3 kpc. On the sky, this overdensity is located between NGC 1261 and a new stellar stream discovered by DES at a similar heliocentric distance, the so-called Phoenix Stream. Given their similar distance and proximity to each other, it is possible that these three structures may be kinematically associated. Alternatively, the EriPhe overdensity is morphologically similar to the Virgo overdensity and the Hercules-Aquila cloud, which also lie at a similar Galactocentric distance. These three overdensities lie along a polar plane separated by ∼120° and may share a common origin. Spectroscopic follow-up observations of the stars in EriPhe are required to fully understand the nature of this overdensity.

KW - galaxy: formation

KW - galaxy: halo

KW - galaxy: structure

KW - local group

UR - http://www.scopus.com/inward/record.url?scp=84957944276&partnerID=8YFLogxK

U2 - 10.3847/0004-637X/817/2/135

DO - 10.3847/0004-637X/817/2/135

M3 - Review article

AN - SCOPUS:84957944276

SN - 0004-637X

VL - 817

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 2

M1 - 135

ER -

DISCOVERY of A STELLAR OVERDENSITY in ERIDANUS-PHOENIX in the DARK ENERGY SURVEY

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