| Full text | |
| Author(s): |
Limberg, Guilherme
[1]
;
Santucci, Rafael M.
[2, 3]
;
Rossi, Silvia
[1]
;
Queiroz, Anna B. A.
[4, 5]
;
Chiappini, Cristina
[4, 5]
;
Souza, Stefano O.
[1]
;
Perottoni, Helio D.
[1]
;
Perez-Villegas, Angeles
[6]
;
Barbosa, Fabricia O.
[1]
Total Authors: 9
|
| Affiliation: | [1] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, Dept Astron, BR-05508090 Sao Paulo, SP - Brazil
[2] Univ Fed Goias, Inst Fis, Campus Samambaia, BR-74001970 Goiania, Go - Brazil
[3] Univ Fed Goias, Inst Estudos Socioambientais, BR-74055140 Goiania, Go - Brazil
[4] Leibniz Inst Astrophys Potsdam AIP, Sternwarte 16, D-14482 Potsdam - Germany
[5] Lab Interinst E Astron LIneA, BR-20921400 Rio De Janeiro, RJ - Brazil
[6] Univ Nacl Autonoma Mexico, Inst Astron, Apartado Postal 106, Ensenada 22800, BC - Mexico
Total Affiliations: 6
|
| Document type: | Journal article |
| Source: | Astrophysical Journal Letters; v. 913, n. 2 JUN 2021. |
| Web of Science Citations: | 0 |
| Abstract | |
We identified eight additional stars as members of the Helmi stream (HStr) in the combined GALAH+ DR3 and Gaia EDR3 catalog. By consistently reevaluating claimed members from the literature, we consolidate a sample of 22 HStr stars with parameters determined from high-resolution spectroscopy and spanning a considerably wider (by similar to 0.5 dex) metallicity interval (- 2.5 less than or similar to {[}Fe/H] < - 1.0) than previously reported. Our study focuses on alpha (Mg and Ca) and neutron-capture (Ba and Eu) elements. We find that the chemistry of HStr is typical of dwarf spheroidal (dSph) galaxies, in good agreement with previous N-body simulations of this merging event. Stars of HStr constitute a clear declining sequence in {[}alpha/Fe] for increasing metallicity up to {[}Fe/H] similar to -1.0. Moreover, stars of HStr show a median value of +0.5 dex for {[}Eu/Fe] with a small dispersion (+/- 0.1 dex). Every star analyzed with {[}Fe/H] < -1.2 belongs to the r-process enhanced ({[}Eu/Fe] > +0.3 and {[}Ba/Eu] < 0.0) metal-poor category, providing remarkable evidence that, at such a low-metallicity regime, stars of HStr experienced enrichment in neutron-capture elements predominantly via r-process nucleosynthesis. Finally, the extended metallicity range also suggests an increase in {[}Ba/Eu] for higher {[}Fe/H], in conformity with other surviving dwarf satellite galaxies of the Milky Way. (AU) | |
| FAPESP's process: | 18/21250-9 - Identification of bright ultra-metal-poor stars from Multi-Band photometry and spectroscopic follow-up |
| Grantee: | Hélio Dotto Perottoni |
| Support Opportunities: | Scholarships in Brazil - Post-Doctoral |
| FAPESP's process: | 14/18100-4 - Stellar populations in the Milky Way: bulge, halo, disk and star forming regions; instrumentation for high resolution spectroscopy |
| Grantee: | Beatriz Leonor Silveira Barbuy |
| Support Opportunities: | Research Projects - Thematic Grants |
| FAPESP's process: | 15/50374-0 - Mosaic: the multi-object spectrograph for the ESO Extremely Large Telescope |
| Grantee: | Silvia Cristina Fernandes Rossi |
| Support Opportunities: | Research Projects - Thematic Grants |
| FAPESP's process: | 18/22044-3 - Bulge globular clusters: relics of the early formation of the galaxy |
| Grantee: | Stefano Oliveira de Souza |
| Support Opportunities: | Scholarships in Brazil - Doctorate (Direct) |