J/MNRAS/496/2902 Lithium and beryllium in Gaia-Enceladus galaxy (Molaro+, 2020)
Lithium and beryllium in the Gaia-Enceladus galaxy.
Molaro P., Cescutti G., Fu X.
<Mon. Not. R. Astron. Soc., 496, 2902-2909 (2020)>
=2020MNRAS.496.2902M 2020MNRAS.496.2902M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, halo ; Galaxies, dwarf ; Abundances, [Fe/H] ;
Abundances, peculiar ; Effective temperatures ; Optical
Keywords: stars: abundances - Galaxy: halo - Galaxy: stellar content -
galaxies: abundances - galaxies: individual: Gaia-Enceladus -
primordial nucleosynthesis
Abstract:
Data from Gaia DR2 and The Apache Point Observatory Galactic Evolution
Experiment surveys revealed a relatively new component in the inner
Galactic halo, which is likely the dynamical remnant of a disrupted
dwarf galaxy named Gaia-Enceladus that collided with the Milky Way
about 10Gyr ago. This merging event offers an extraordinary
opportunity to study chemical abundances of elements in a dwarf
galaxy, since they are generally hampered in external galaxies. Here,
we focus on 7Li and 9Be in dwarf stars that are out of reach even
in Local Group galaxies. Searching in GALAH, Gaia-ESO survey and in
literature, we found several existing 7Li abundance determinations
of stars belonging to the Gaia-Enceladus galaxy. The 7Li abundances
of stars at the low metallicity end overlap with those of the Galactic
halo. These are effective extragalactic 7Li measurements, which
suggest that the 7Li Spite plateau is universal, as is the
cosmological 7Li problem. We found a 7Li-rich giant out of 101
stars, which suggests a small percentage similar to that of the Milky
Way. We also collect 9Be abundance for a subsample of 25
Gaia-Enceladus stars from literature. Their abundances share the
Galactic [Be/H] values at the low metallicity end but grow slower with
[Fe/H] and show a reduced dispersion. This suggests that the scatter
observed in the Milky Way could reflect the different 9Be evolution
patterns of different stellar components that are mixed-up in the
Galactic halo.
Description:
Helmi et al. (2018Natur.563...85H 2018Natur.563...85H) provided a sample of 4644 suggested
Gaia-Enceladus member stars, a subsample of which are in the catalogue
of APOGEE with determined abundances for 18 elements (Nidever et al.
2012ApJ...755L..25N 2012ApJ...755L..25N). The Gaia-Enceladus subsample with APOGEE
measurements includes stars with [α/Fe] values lower than that
of the Milky Way halo stars in the metallicity range -1.5<[Fe/H]←0.5,
which are typical of dwarf spheroidal galaxies and are also observed
in the Damped Lyman α galaxies (Molaro 2006cams.book..256M 2006cams.book..256M;
Rafelski et al. 2012ApJ...755...89R 2012ApJ...755...89R, Cat. J/ApJ/755/89). APOGEE does
not provide 7Li abundances. Thus, we searched for the Gaia-Enceladus
component in the GALAH DR2 survey (Buder et al. 2018MNRAS.478.4513B 2018MNRAS.478.4513B,
Cat. J/MNRAS/478/4513), the Gaia-ESO DR3 survey (Gilmore et al.
2012Msngr.147...25G 2012Msngr.147...25G), and in the literature by cross-matching the
larger sample of Gaia-Enceladus stars provided by Helmi et al.
(2018Natur.563...85H 2018Natur.563...85H) by considering their selection criteria, namely
a distance of <5kpc and Lz<150.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 90 53 Gaia-Enceladus candidate stars with Li and Be
abundances measured from literature with
log(g)>3.65 and Teff>5700K
table2.dat 77 53 Kinematical properties of the selected
Gaia-Enceladus candidates
galah.dat 47 121 Enceladus Candidates from the GALAH survey with
Li determinations
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/MNRAS/478/4513 : GALAH Survey DR2 (Buder+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaDR2 Gaia DR2 source identifier
21- 35 A15 --- Name Star name
37- 40 I4 K Teff Effective temperature
42- 45 F4.2 [cm/s2] logg Surface gravity
47- 51 F5.2 [-] [Fe/H] Fe/H abundance ratio
53- 57 F5.2 [-] [O/H] ? O/H abundance ratio (1)
59- 62 F4.2 [-] A(Li) ? Lithium abundance
64- 68 F5.2 [-] [Fe/H]Be ? Fe/H abundance ratio from the reference
with Beryllium abundance measurements
70- 73 F4.2 [-] e_[Fe/H]Be ? Error on [Fe/H]Be
75- 79 F5.2 [-] A(Be) ? Beryllium abundance
81- 84 F4.2 [-] e_A(Be) ? Error on A (Be)
86- 90 A5 --- Ref References (2)
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Note (1): The oxygen abundances are from Boesgaard et al. (2011ApJ...743..140B 2011ApJ...743..140B,
Cat. J/ApJ/743/140) or Smiljanic et al. (2009A&A...499..103S 2009A&A...499..103S), in this
latter case [O/H] is inferred by their [α-element/Fe]
Note (2): References as follows:
1 = Buder et al. (2018MNRAS.478.4513B 2018MNRAS.478.4513B, Cat. J/MNRAS/478/4513)
2 = Fulbright (2000AJ....120.1841F 2000AJ....120.1841F, Cat. J/AJ/120/1841)
3 = Boesgaard & Novicki (2006ApJ...641.1122B 2006ApJ...641.1122B)
4 = Boesgaard, Stephens & Deliyannis (2005ApJ...633..398B 2005ApJ...633..398B)
5 = Smiljanic et al. (2009A&A...499..103S 2009A&A...499..103S)
6 = Charbonnel & Primas (2005A&A...442..961C 2005A&A...442..961C, Cat. J/A+A/442/961)
7 = Asplund et al. (2006ApJ...644..229A 2006ApJ...644..229A)
8 = Spite et al. (2015A&A...582A..74S 2015A&A...582A..74S, Cat. J/A+A/582/A74)
9 = Siqueira-Mello et al. (2015A&A...584A..86S 2015A&A...584A..86S, Cat. J/A+A/584/A86)
10 = Ramirez et al. (2012ApJ...756...46R 2012ApJ...756...46R, Cat. J/ApJ/756/46)
11 = Delgado Mena et al. (2015A&A...576A..69D 2015A&A...576A..69D, Cat. J/A+A/576/A69)
12 = Delgado Mena et al. (2014A&A...562A..92D 2014A&A...562A..92D, Cat. J/A+A/562/A92)
13 = Placco et al. (2016ApJ...829L..24P 2016ApJ...829L..24P)
14 = Bonifacio & Molaro (1997MNRAS.285..847B 1997MNRAS.285..847B)
15 = Boesgaard et al. (2011ApJ...743..140B 2011ApJ...743..140B, Cat. J/ApJ/743/140)
16 = Smiljanic et al. (2009A&A...499..103S 2009A&A...499..103S)
17 = Rich & Boesgaard (2009ApJ...701.1519R 2009ApJ...701.1519R)
18 = Tan, Shi & Zhao (2009MNRAS.392..205T 2009MNRAS.392..205T)
19 = Roederer et al. (2014AJ....147..136R 2014AJ....147..136R, Cat. J/AJ/147/136)
20 = Melendez et al. (2010A&A...515L...3M 2010A&A...515L...3M)
21 = Charbonnel & Balachandran (2000A&A...359..563C 2000A&A...359..563C)
22 = Hosford et al. (2009A&A...493..601H 2009A&A...493..601H, Cat. J/A+A/493/601);
Aguilera-Gomez et al. (2018A&A...614A..55A 2018A&A...614A..55A, Cat. J/A+A/614/A55)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaDR2 Gaia DR2 source identifier
21- 35 A15 --- Name Star name
37- 46 F10.2 km2/s2 Energy Energy from Helmi et al.
(2018Natur.563...85H 2018Natur.563...85H)
48- 55 F8.2 kpc.km/s Lz Angular momentum in the Z direction from
Helmi et al. (2018Natur.563...85H 2018Natur.563...85H)
57- 61 F5.2 kpc rapo Apocentre distance (1)
63- 66 F4.2 kpc rperi Pericentre distance (1)
68- 71 F4.2 --- e Eccentricity (1)
73- 77 F5.2 kpc Zmax Maximum distance from the Galactic plane (1)
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Note (1): Values based on the stellar orbit in the last 1 Gyr. For this
calculation, we use the public licensed code galpot following the
method described in McMillan (2017MNRAS.465...76M 2017MNRAS.465...76M), and assume a
Galactic potential that includes thin and thick stellar discs, bulge,
halo, and a gas disc.
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Byte-by-byte Description of file: galah.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR2 Gaia DR2 source identifier
21- 22 I2 --- flagc Cannon flag form the GALAH survey (1)
24- 30 F7.2 K Teff Effective temperature
32- 35 F4.2 [cm/s2] logg Surface gravity
37- 41 F5.2 [-] [Fe/H] Fe/H abundance ratio
43- 47 F5.2 [-] A(Li) Lithium abundance
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Note (1): A flag Cannon = 0 means a reliable measurement (see Buder et al.
2018MNRAS.478.4513B 2018MNRAS.478.4513B, Cat. J/MNRAS/478/4513)
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 04-Jul-2023