2025ApJ...987..217Z

Query : 2025ApJ...987..217Z

2025ApJ...987..217Z - Astrophys. J., 987, 217 (2025/July-2)

GHOST Commissioning Science Results. IV. Chemodynamical Analyses of Milky Way Satellites Sagittarius II and Aquarius II.

ZAREMBA D., VENN K., HAYES C.R., ERRANI R., CORNEJO T., GLOVER J., JENSEN J., McCONNACHIE A.W., NAVARRO J.F., PAZDER J., SESTITO F., ANTHONY A., ANDERSEN D., BAKER G., CHIN T., CHURILOV V., DIAZ R., FARRELL T., FIRPO V., GOMEZ-JIMENEZ M., HENDERSON D., KALARI V.M., LAWRENCE J., MARGHEIM S., MILLER B., ROBERTSON J.G., RUIZ-CARMONA R., SILVERSIDES K., SILVA K., YOUNG P.J. and ZHELEM R.

Abstract (from CDS):

We present Gemini/GHOST high-resolution spectra of five stars observed in two low surface brightness Milky Way satellites, Sagittarius II (Sgr2) and Aquarius II (Aqu2). For Aqu2, the velocities and metallicities of the two stars are consistent with membership in a dark-matter-dominated ultra-faint dwarf galaxy (UFD). The chemical abundance ratios suggest inefficient star formation from only one or a few supernovae (e.g., low Na, Sr, Ba), and enriched potassium (K) from super-AGB stars. For Sgr2, the velocity and metallicity dispersions of its members are not clearly resolved, and our detailed chemical abundances show typical ratios for metal-poor stars, with low dispersions. There is only one exception-we report the discovery of an r-process enhanced star (Sgr 2584, [Eu/Fe] = +0.7 ± 0.2; thus, an r-I star). As r-I stars are found in both UFDs (Tuc III, Tuc IV, and Grus II) and globular clusters (M15 and M92), then this does not help to further classify the nature of Sgr2. Our exploration of Sgr2 demonstrates the difficulty in classifying some of the faintest (ambiguous) satellites. We advocate for additional diagnostics in analyzing the ambiguous systems, such as exploring radial segregation (by mass and/or chemistry), N-body simulations, and the need for dark matter to survive Galactic tidal effects. The spectra analyzed in this paper were taken as part of the GHOST commissioning observations, testing faint observation limits (G < 18.8) and the single and double integrated field unit observing modes.

Abstract Copyright: © 2025. The Author(s). Published by the American Astronomical Society.

Journal keyword(s): the Milky Way - Dwarf galaxies - Star clusters - Stellar abundances - Astronomical instrumentation

Status at CDS : Large table(s) will be appraised for possible ingestion in VizieR.

Simbad objects: 40

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Number of rows : 40
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 NAME Tuc IV G 00 02.9 -60 51           ~ 90 0
2 M 31 AGN 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 13622 1
3 NAME Cetus II G 01 17.9 -17 25           ~ 56 0
4 NAME Tri II G 02 13 17.40 +36 10 42.4           ~ 164 0
5 NAME Segue 2 G 02 19 16.0 +20 10 31     15.2     ~ 299 0
6 NAME Eri III G 02 22 45.480 -52 17 04.92           ~ 79 0
7 NAME Hor I G 02 55 31.7 -54 07 08           ~ 169 0
8 NAME Reticulum II G 03 35 42.1 -54 02 57           ~ 375 0
9 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 19090 0
10 NAME Carina II Dwarf Galaxy G 07 36 25.6 -57 59 57           ~ 86 0
11 NGC 2419 GlC 07 38 08.51 +38 52 54.9     10.05     ~ 998 0
12 NAME Car III Dwarf Galaxy G 07 38 31.2 -57 53 59           ~ 81 0
13 NAME UMa II Galaxy G 08 51 30.0 +63 07 48     13.3     ~ 410 0
14 NAME Segue 1 G 10 07 03.2 +16 04 25     15.3     ~ 517 1
15 NAME UMa I Galaxy G 10 34 52.80 +51 55 12.0     14.4     ~ 355 1
16 NAME Leo IV LSB 11 32 57.0 -00 32 00     15.1     ~ 419 1
17 NAME UMa III Cl* 11 38 49.8 +31 04 42           ~ 22 0
18 NAME Coma Dwarf Galaxy G 12 26 59.0 +23 54 15     14.1     ~ 482 1
19 [IMM2021] C-19 St* 12 46 +01.           ~ 33 0
20 NAME Bootes II G 13 58 00.0 +12 51 00     15.4     ~ 269 0
21 NAME Bootes Dwarf Spheroidal Galaxy G 14 00 00.0 +14 30 00     12.8     ~ 491 0
22 HD 122563 Pe* 14 02 31.8455084952 +09 41 09.944391876 7.47 7.10 6.19 5.37 4.79 G8:III:Fe-5 920 0
23 DELVE 1 Cl* 16 30 54 -00 58.3     16.19     ~ 19 0
24 NAME Hercules Dwarf Galaxy G 16 31 02.0 +12 47 30     14.0     ~ 379 1
25 M 92 GlC 17 17 07.39 +43 08 09.4     6.52     ~ 2240 0
26 [LMS2020] J298.15344-22.04959 Pe* 19 52 36.8254505712 -22 02 58.526722248           ~ 3 0
27 PSO J298.1623-22.0774 Pe* 19 52 38.9719922418 -22 04 38.909377973           ~ 2 0
28 NAME Sagittarius II Gl? 19 52 40.5 -22 04 05           ~ 97 0
29 [LMS2020] J298.18145-22.07735 Pe* 19 52 43.5550658760 -22 04 38.439847308           ~ 3 0
30 M 15 GlC 21 29 58.33 +12 10 01.2           ~ 3274 0
31 NAME Gru II G 22 04.1 -46 26           ~ 110 0
32 [TKB2016] RGB8 RG* 22 33 52.6961446440 -09 17 09.068914536           ~ 3 0
33 NAME Aquarius 2 G 22 33 55.5 -09 19 39           ~ 66 0
34 Gaia DR3 2609061687357323776 * 22 34 08.4561411411 -09 19 40.067317626           ~ 2 0
35 NAME Tuc II G 22 51 55.1 -58 34 08           ~ 192 0
36 NAME Grus I G 22 56 42.4 -50 09 48           ~ 126 0
37 NAME Pisces II G 22 58 31.0 +05 57 09     16.3     ~ 283 0
38 NAME Tuc V G 23 37.4 -63 16           ~ 84 0
39 HD 222925 Pe* 23 45 17.6074777008 -61 54 42.835286016   9.56 9.03     ApSrEu 83 0
40 NAME Tuc III G 23 56.6 -59 36           ~ 229 0

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