Dynamically tagged groups of very metal-poor halo stars from the HK and Hamburg/ ESO surveys

Guilherme Limberg; Silvia Rossi; Timothy C. Beers; Hélio D. Perottoni; Angeles Pérez-Villegas; Rafael M. Santucci; Yuri Abuchaim; Vinicius M. Placco; Young Sun Lee; Norbert Christlieb; John E. Norris; Michael S. Bessell; Sean G. Ryan; Ronald Wilhelm; Jaehyon Rhee; Anna Frebel

doi:10.3847/1538-4357/abcb87

Dynamically tagged groups of very metal-poor halo stars from the HK and Hamburg/ ESO surveys

Guilherme Limberg
, Silvia Rossi
, Timothy C. Beers
, Hélio D. Perottoni
, Angeles Pérez-Villegas
, Rafael M. Santucci
, Yuri Abuchaim
, Vinicius M. Placco
, Young Sun Lee
, Norbert Christlieb
, John E. Norris
, Michael S. Bessell
, Sean G. Ryan
, Ronald Wilhelm
, Jaehyon Rhee
, Anna Frebel

Research output: Contribution to journal › Article › peer-review

59 Scopus citations

Abstract

We analyze the dynamical properties of ∼1500 very metal-poor (VMP; [Fe/H] ≲ −2.0) halo stars, based primarily on medium-resolution spectroscopic data from the HK and Hamburg/ESO surveys. These data, collected over the past 30 yr, are supplemented by a number of calibration stars and other small samples, along with astrometric information from Gaia DR2. We apply a clustering algorithm to the 4D energy-action space of the sample, and identify a set of 38 dynamically tagged groups (DTGs), containing between 5 and 30 member stars. Many of these DTGs can be associated with previously known prominent substructures such as Gaia-Sausage/Enceladus (GSE), Sequoia, Helmi Stream (HStr), and Thamnos. Others are associated with previously identified smaller dynamical groups of stars and streams. We identify 10 new DTGs as well, many of which have strongly retrograde orbits. We also investigate possible connections between our DTGs and ∼300 individual r-process-enhanced (RPE) stars from a recent literature compilation. We find that several of these objects have similar dynamical properties to GSE (5), the HStr (4), Sequoia (1), and Rg5 (1), indicating that their progenitors might have been important sources of RPE stars in the Galaxy. Additionally, a number of our newly identified DTGs are shown to be associated with at least two RPE stars each (DTG-2: 3, DTG-7: 2; DTG-27: 2). Taken as a whole, these results are consistent with ultra-faint and/or dwarf spheroidal galaxies as birth environments in which r-process nucleosynthesis took place, and then were disrupted by the Milky Way.

Original language	English
Article number	10
Journal	Astrophysical Journal
Volume	907
Issue number	1
DOIs	https://doi.org/10.3847/1538-4357/abcb87
State	Published - Jan 20 2021

Bibliographical note

Publisher Copyright:
© 2021. The American Astronomical Society. All rights reserved.

Funding

acknowledges funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project-ID 138713538 —SFB 881 (“The Milky Way System”, subproject A04). J.R. acknowledges support from the AAS Small Research Grant, awarded by the American Astronomical Society (AAS) in 2001 and 2002. A.F. acknowledges partial support from NSF grant AST-1716251. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www. cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC,https://www.cosmos.esa.int/ web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. George Preston and Stephen Shectman are recognized for the original conception of an objective-prism search for very metal-poor halo stars at a time when their existence in any great numbers was still very much in question. Dieter Reimers and Lutz Wisotzki are recognized for their initiation of the Hamburg/ESO survey and development of the automated scanning techniques for the HES objective-prism plates. T.C.B. and N.C. extend heartfelt thanks to all of the observers, telescope facilities, support staff, and time-allocation committees who enabled the hundreds of nights of photometric and spectroscopic follow-up of candidate metal-poor stars from the HK survey and the HES over the past three decades. We thank the anonymous referee for useful comments and suggestions that helped improve the manuscript. G.L. acknowledges CAPES (PROEX) for the funding of his Ph.D (Proc. 88887.481172/2020-00). S.R. would like to acknowledge partial financial support from FAPESP (Proc. 2015/50374-0 and 2014/18100-4), CAPES, and CNPq. G.L., S.R., T.C.B., H. D.P., A.P.V., R.M.S., Y.A., V.M.P., and A.F. acknowledge partial support from grant PHY 14-30152, Physics Frontier Center/JINA Center for the Evolution of the Elements (JINA-CEE), awarded by the US National Science Foundation. H.D.P. thanks FAPESP Proc. 2018/21250-9. A.P.V. acknowledges FAPESP for the postdoctoral fellowship No. 2017/15893-1 and the DGAPA-PAPIIT grant IG100319. R.M.S. acknowledges CNPq (Project 436696/2018-5). Y.S.L. acknowledges support from the National Research Foundation (NRF) of Korea grant funded by the Ministry of Science and ICT (No. 2017R1A5A1070354 and NRF-2018R1A2B6003961). N.C.

Funders	Funder number
American Astronomical Society
African Academy of Sciences
National Aeronautics and Space Administration
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Fundação de Amparo à Pesquisa do Estado de São Paulo
National Science Foundation Arctic Social Science Program	AST-1716251
PROEX	88887.481172/2020-00
Deutsche Forschungsgemeinschaft	138713538

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.3847/1538-4357/abcb87

Cite this

Limberg, G., Rossi, S., Beers, T. C., Perottoni, H. D., Pérez-Villegas, A., Santucci, R. M., Abuchaim, Y., Placco, V. M., Lee, Y. S., Christlieb, N., Norris, J. E., Bessell, M. S., Ryan, S. G., Wilhelm, R., Rhee, J., & Frebel, A. (2021). Dynamically tagged groups of very metal-poor halo stars from the HK and Hamburg/ ESO surveys. Astrophysical Journal, 907(1), Article 10. https://doi.org/10.3847/1538-4357/abcb87

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title = "Dynamically tagged groups of very metal-poor halo stars from the HK and Hamburg/ ESO surveys",

abstract = "We analyze the dynamical properties of ∼1500 very metal-poor (VMP; [Fe/H] ≲ −2.0) halo stars, based primarily on medium-resolution spectroscopic data from the HK and Hamburg/ESO surveys. These data, collected over the past 30 yr, are supplemented by a number of calibration stars and other small samples, along with astrometric information from Gaia DR2. We apply a clustering algorithm to the 4D energy-action space of the sample, and identify a set of 38 dynamically tagged groups (DTGs), containing between 5 and 30 member stars. Many of these DTGs can be associated with previously known prominent substructures such as Gaia-Sausage/Enceladus (GSE), Sequoia, Helmi Stream (HStr), and Thamnos. Others are associated with previously identified smaller dynamical groups of stars and streams. We identify 10 new DTGs as well, many of which have strongly retrograde orbits. We also investigate possible connections between our DTGs and ∼300 individual r-process-enhanced (RPE) stars from a recent literature compilation. We find that several of these objects have similar dynamical properties to GSE (5), the HStr (4), Sequoia (1), and Rg5 (1), indicating that their progenitors might have been important sources of RPE stars in the Galaxy. Additionally, a number of our newly identified DTGs are shown to be associated with at least two RPE stars each (DTG-2: 3, DTG-7: 2; DTG-27: 2). Taken as a whole, these results are consistent with ultra-faint and/or dwarf spheroidal galaxies as birth environments in which r-process nucleosynthesis took place, and then were disrupted by the Milky Way.",

author = "Guilherme Limberg and Silvia Rossi and Beers, \{Timothy C.\} and Perottoni, \{H{\'e}lio D.\} and Angeles P{\'e}rez-Villegas and Santucci, \{Rafael M.\} and Yuri Abuchaim and Placco, \{Vinicius M.\} and Lee, \{Young Sun\} and Norbert Christlieb and Norris, \{John E.\} and Bessell, \{Michael S.\} and Ryan, \{Sean G.\} and Ronald Wilhelm and Jaehyon Rhee and Anna Frebel",

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Limberg, G, Rossi, S, Beers, TC, Perottoni, HD, Pérez-Villegas, A, Santucci, RM, Abuchaim, Y, Placco, VM, Lee, YS, Christlieb, N, Norris, JE, Bessell, MS, Ryan, SG, Wilhelm, R, Rhee, J & Frebel, A 2021, 'Dynamically tagged groups of very metal-poor halo stars from the HK and Hamburg/ ESO surveys', Astrophysical Journal, vol. 907, no. 1, 10. https://doi.org/10.3847/1538-4357/abcb87

TY - JOUR

T1 - Dynamically tagged groups of very metal-poor halo stars from the HK and Hamburg/ ESO surveys

AU - Limberg, Guilherme

AU - Rossi, Silvia

AU - Beers, Timothy C.

AU - Perottoni, Hélio D.

AU - Pérez-Villegas, Angeles

AU - Santucci, Rafael M.

AU - Abuchaim, Yuri

AU - Placco, Vinicius M.

AU - Lee, Young Sun

AU - Christlieb, Norbert

AU - Norris, John E.

AU - Bessell, Michael S.

AU - Ryan, Sean G.

AU - Wilhelm, Ronald

AU - Rhee, Jaehyon

AU - Frebel, Anna

PY - 2021/1/20

Y1 - 2021/1/20

N2 - We analyze the dynamical properties of ∼1500 very metal-poor (VMP; [Fe/H] ≲ −2.0) halo stars, based primarily on medium-resolution spectroscopic data from the HK and Hamburg/ESO surveys. These data, collected over the past 30 yr, are supplemented by a number of calibration stars and other small samples, along with astrometric information from Gaia DR2. We apply a clustering algorithm to the 4D energy-action space of the sample, and identify a set of 38 dynamically tagged groups (DTGs), containing between 5 and 30 member stars. Many of these DTGs can be associated with previously known prominent substructures such as Gaia-Sausage/Enceladus (GSE), Sequoia, Helmi Stream (HStr), and Thamnos. Others are associated with previously identified smaller dynamical groups of stars and streams. We identify 10 new DTGs as well, many of which have strongly retrograde orbits. We also investigate possible connections between our DTGs and ∼300 individual r-process-enhanced (RPE) stars from a recent literature compilation. We find that several of these objects have similar dynamical properties to GSE (5), the HStr (4), Sequoia (1), and Rg5 (1), indicating that their progenitors might have been important sources of RPE stars in the Galaxy. Additionally, a number of our newly identified DTGs are shown to be associated with at least two RPE stars each (DTG-2: 3, DTG-7: 2; DTG-27: 2). Taken as a whole, these results are consistent with ultra-faint and/or dwarf spheroidal galaxies as birth environments in which r-process nucleosynthesis took place, and then were disrupted by the Milky Way.

AB - We analyze the dynamical properties of ∼1500 very metal-poor (VMP; [Fe/H] ≲ −2.0) halo stars, based primarily on medium-resolution spectroscopic data from the HK and Hamburg/ESO surveys. These data, collected over the past 30 yr, are supplemented by a number of calibration stars and other small samples, along with astrometric information from Gaia DR2. We apply a clustering algorithm to the 4D energy-action space of the sample, and identify a set of 38 dynamically tagged groups (DTGs), containing between 5 and 30 member stars. Many of these DTGs can be associated with previously known prominent substructures such as Gaia-Sausage/Enceladus (GSE), Sequoia, Helmi Stream (HStr), and Thamnos. Others are associated with previously identified smaller dynamical groups of stars and streams. We identify 10 new DTGs as well, many of which have strongly retrograde orbits. We also investigate possible connections between our DTGs and ∼300 individual r-process-enhanced (RPE) stars from a recent literature compilation. We find that several of these objects have similar dynamical properties to GSE (5), the HStr (4), Sequoia (1), and Rg5 (1), indicating that their progenitors might have been important sources of RPE stars in the Galaxy. Additionally, a number of our newly identified DTGs are shown to be associated with at least two RPE stars each (DTG-2: 3, DTG-7: 2; DTG-27: 2). Taken as a whole, these results are consistent with ultra-faint and/or dwarf spheroidal galaxies as birth environments in which r-process nucleosynthesis took place, and then were disrupted by the Milky Way.

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JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 1

M1 - 10

ER -

Dynamically tagged groups of very metal-poor halo stars from the HK and Hamburg/ ESO surveys

Abstract

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Funding

ASJC Scopus subject areas

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