2021ApJ...908L...8A

Query : 2021ApJ...908L...8A

2021ApJ...908L...8A - Astrophys. J., 908, L8-L8 (2021/February-2)

Elevated r-process enrichment in Gaia Sausage and Sequoia.

AGUADO D.S., BELOKUROV V., MYEONG G.C., EVANS N.W., KOBAYASHI C., SBORDONE L., CHANAME J., NAVARRETE C. and KOPOSOV S.E.

Abstract (from CDS):

The Gaia Sausage (GS) and the Sequoia represent the major accretion events that formed the stellar halo of the Milky Way. A detailed chemical study of these main building blocks provides a pristine view of the early steps of the Galaxy's assembly. We present the results of the analysis of the UVES high-resolution spectroscopic observations at the 8.2 m VLT of nine Sausage/Sequoia members selected kinematically using Gaia DR2. We season this set of measurements with archival data from Nissen & Schuster and GALAH DR3 (2020). Here, we focus on the neutron-capture process by analyzing Sr, Y, Ba, and Eu behavior. We detect clear enhancement in Eu abundance ([Eu/Fe] ∼ 0.6-0.7) indicative of large prevalence of the r-process in the stellar n-capture makeup. We are also able to trace the evolution of the heavy element production across a wide range of metallicity. The barium to europium changes from a tight, flat sequence with [Ba/Eu] = -0.7 reflecting dominant contribution from exploding massive stars, to a clear upturn at higher iron abundances, betraying the onset of contamination from asymptotic giant branch (AGB) ejecta. Additionally, we discover two clear sequences in the [Fe/H]-[Ba/Fe] plane likely caused by distinct levels of s-process pollution and mixing within the GS progenitor.

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

Journal keyword(s): Population II stars - Galaxy formation - Halo stars - Milky Way stellar halo - Nuclear astrophysics - Nuclear abundances - Galaxy chemical evolution - Chemical abundances - Dwarf galaxies

Simbad objects: 24

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Number of rows : 24
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 HD 20 Pe* 00 05 15.3242691048 -27 16 18.140091852   9.65 9.40 8.865 8.377 F2V 80 0
2 BD-16 251 RG* 01 29 31.1311443552 -16 00 45.495314460 12.527 12.427 11.642 11.189 10.713 CEMP 318 0
3 MCG-06-07-001 G 02 39 59.3 -34 26 57   9.02 7.4     ~ 1894 1
4 NAME Reticulum II G 03 35 42.1 -54 02 57           ~ 375 0
5 CD-29 2277 PM* 05 28 50.9297117788 -29 53 47.778591790   12.13 11.61     F6 70 0
6 CD-37 2255 PM* 05 31 48.3313838448 -36 59 51.587534976   11.42 10.65     ~ 12 0
7 ESO 206-20A G 06 41 36.7 -50 57 58   22.14 11.0 19.47   ~ 1190 0
8 TYC 756-964-1 PM* 06 58 29.2335914448 +11 51 39.781090512   10.85 9.95     ~ 2 0
9 BD-16 2232 * 07 59 46.8292304640 -17 23 08.354569164   11.04 9.89     ~ 2 0
10 CPD-43 3058 HV* 08 51 17.1769663632 -44 14 50.358131016   11.82 11.27     ~ 10 0
11 NAME UMa II Galaxy G 08 51 30.0 +63 07 48     13.3     ~ 410 0
12 NAME Segue 1 G 10 07 03.2 +16 04 25     15.3     ~ 517 1
13 NAME Leo IV LSB 11 32 57.0 -00 32 00     15.1     ~ 419 1
14 CD-40 6808 Pe* 11 34 17.9232608880 -41 20 57.441061572   12.328 11.214     ~ 15 0
15 NAME Coma Dwarf Galaxy G 12 26 59.0 +23 54 15     14.1     ~ 482 1
16 TYC 6712-1166-1 PM* 13 18 42.7399734144 -28 50 31.144653312   12.45 11.71     ~ 4 0
17 TYC 1458-499-1 PM* 13 27 30.7178808168 +17 11 28.632207336   12.56 11.47 11.2   ~ 3 0
18 NAME Bootes Dwarf Spheroidal Galaxy G 14 00 00.0 +14 30 00     12.8     ~ 491 0
19 Z 300-12 G 17 20 14.335 +57 55 16.39   12.40 10.6     ~ 1428 1
20 NAME Sequoia Cluster GlC 17 31 12.0 -39 48 30           ~ 154 0
21 NAME SDG G 18 55 19.0 -30 32 43   4.5 3.6     ~ 2438 2
22 HD 220127 Pe* 23 21 43.5876197122 -49 29 15.113713857   10.81 10.410     G3/5 61 0
23 NAME Gaia Enceladus-Sausage St* ~ ~           ~ 860 0
24 NAME S2 Stream St* ~ ~           ~ 10 0

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