J/MNRAS/511/1004 Abundances study of Pristine VMP stars (Lucchesi+, 2022)
The Pristine survey.
XV. A CFHT ESPaDOnS view on the Milky Way halo and disc populations.
Lucchesi R., Lardo C., Jablonka P., Sestito F., Mashonkina L., Arentsen A.,
Suter W., Venn K., Martin N., Starkenburg E., Aguado D., Hill V.,
Kordopatis G., Navarro J.F., Gonzalez Hernandez J.I., Malhan K., Yuan Z.
<Mon. Not. R. Astron. Soc., 511, 1004-1021 (2022)>
=2022MNRAS.511.1004L 2022MNRAS.511.1004L (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, metal-deficient ; Positional data ;
Photometry ; Spectroscopy ; Optical ; Extinction ;
Radial velocities ; Effective temperatures ; Abundances
Keywords: stars: abundances - galaxies: dwarf - galaxies: formation -
Local Group
Abstract:
We present a one-dimensional, local thermodynamic equilibrium homogeneous
analysis of 132 stars observed at high resolution with ESPaDOnS. This
represents the largest sample observed at high resolution (R ∼ 40000)
from the Pristine survey. This sample is based on the first version of
the Pristine catalogue and covers the full range of metallicities from
[Fe/H] ∼ -3 to ∼ +0.25, with nearly half of our sample (58 stars)
composed of very metal-poor (VMP) stars ([Fe/H] ≤ -2). This wide
range of metallicities provides the opportunity of a new detailed
study of the Milky Way stellar population. Because it includes both
dwarf and giant stars, it also enables the analysis of any potential
bias induced by the Pristine selection process. Based on Gaia EDR3,
the orbital analysis of this Pristine-ESPaDOnS sample shows that it is
composed of 65 halo stars and 67 disc stars. After a general
assessment of the sample chemical properties with the α-elements Mg
and Ca, we focus on the abundance of carbon and the neutron capture
elements Ba and Sr. While most of our VMP subsample is carbon normal,
we also find that 14 stars out of the 38 stars with [Fe/H] ≤ -2 and
measured carbon abundances turn out to be carbon-enhanced metal-poor
(CEMP) stars. We show that these CEMP stars are nearly exclusively
(i.e. 12 stars out of 14) in the regime of low luminosity, unevolved,
dwarf stars, which we interpret as the consequence of bias of the
Pristine filter against C-rich giants. Among the VMP stars, we
identify two CEMP stars with no enhancement in neutron-capture process
elements and another one enriched in s-process element. Finally, one
VMP star is found with a very low [Sr/Fe] abundance ratio for its
metallicity, as expected if it had been accreted from an ultra-faint
dwarf galaxy.
Description:
In our work, we present the analysis of the 132 bright (V < 15.5)
metal-poor candidates from the original 1000 deg2 of the Pristine
survey, calibrated using the original SDSS gri photometry and observed
at the CFHT with the high-resolution spectrograph ESPaDOnS. Out of
this full sample, Venn et al. (2020MNRAS.492.3241V 2020MNRAS.492.3241V, Cat.
J/MNRAS/492/3241) presented the detailed abundances of 10 elements
(Na, Mg, Ca, Sc, Ti, Cr, Fe, Ni, Y, and Ba) for the 28 very metal-poor
(VMP) stars identified at the time, as well as the analysis of their
orbital properties. Because the full sample comes from the first
stages of the Pristine calibration, the confirmation of very
metal-deficient stars does not reach a success rate as high as in the
later stages. Nevertheless, near half of the present sample (58 stars)
is composed of VMP stars ([Fe/H] ≤ -2). The more metal-rich stars
offer us the opportunity of a new and detailed study of the MW halo
stellar population, (i.e see Introduction).
The targets were selected from the Pristine diagnostics originally
presented in Starkenburg et al. (2017MNRAS.471.2587S 2017MNRAS.471.2587S). Stars were
selected upon their probability to be VMP, the final sample consists
in 132 stars and including 112 stars introduce by Venn et al.
(2020MNRAS.492.3241V 2020MNRAS.492.3241V, Cat. J/MNRAS/492/3241) and 20 new stars from the
CFHT ESPaDOnS programs. After observations and data reduction
procedures (i.e see section 2.2) and stellar parameters adjustements
(i.e section 3) we regroup in the table1.dat photometric and
spectroscopic parameters of our selected Pristine stars sample. These
stellar atmospheric parameters are adopted in the rest of our
analysis. Hereafter, as explained in the section 3 Atmospheric
parameters and chemical abundances, from abundance analysis, we
determined some interesting element abundance ratio as Ca,Mg, Fe I, Fe
II, C, Sr and Ba via LTE and atmospheres models. More, as explicited
in the section 3.3 Uncertainties, uncertainties on measurements EW
impact atmospheric parameters errors values, for their part final
errors on elemental abundances is defined with equations 2 and 3. All
abundances results are synthesized in the table2.dat.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 101 132 Photometric and spectroscopic parameters of
our selected Pristine stars sample
table2.dat 133 128 Elemental abundances of the 128 stars kept
for the chemical analysis
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See also:
J/MNRAS/492/3241 : The Pristine survey. IX. (Venn+, 2020)
J/ApJ/797/21 : Carbon-enhanced metal-poor stars (Placco+, 2014)
J/MNRAS/493/4677 : The Pristine survey XI: the FORS2 sample (Caffau+, 2020)
J/MNRAS/487/3797 : A bright star sample observed with SOPHIE (Bonifacio+, 2019)
J/MNRAS/490/2241 : Spectroscopy of Pristine EMP star candidates (Aguado+, 2019)
J/MNRAS/472/2963 : Metallicities of Pristine stars (Youakim+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Star Star name designation Pr_DDD.dddd+DD.dddd
(Star)
21- 28 F8.4 deg RAdeg Right ascension (J2000) (RA)
30- 36 F7.4 deg DEdeg Declination (J2000) (Dec)
38- 43 F6.3 mag g0mag SDSS g0 apparent magnitude (g0)
45- 50 F6.3 mag i0mag SDSS i0 apparent magnitude (i0)
52- 57 F6.3 mag CaHK De-reddened Pristine calcium H&K lines
magnitude centered around ∼3933 Å and
∼3968 Å (CaHK0)
59- 63 F5.3 mag E(B-V) Color excess E (B-V)
65- 71 F7.2 km/s RV Radial velocity corrected (RV)
73 I1 --- o_RV The number of exposures (o_RV)
75- 78 F4.2 km/s e_RV Mean error of RV (σRV)
80- 83 I4 K Teff Effective temperature (Teff)
85- 88 F4.2 [cm/s2] logg Logarithm of the surface gravity (logg)
90- 93 F4.2 km/s Vt Micro-turbulence velocity (vt)
95- 99 F5.2 [Sun] [Fe/H] Iron to hydrogen abundance ratio ([Fe/H])
101 I1 --- n_Star ? Note for Pristine stars selection (n_Star)
(1)
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Note (1): Note on stars selections as follows:
1 = Stars rejected by the new Pristine photometric selection, 41
stars in our sample
2 = Star rejected because they are fast rotators and their
spectroscopic metallicity is poorly constrained, 3 stars in our
sample
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Star Star name designation Pr_DDD.dddd+DD.dddd
(Star)
21- 28 F8.4 --- ShortName Short name from RAdeg values in table1.dat
30- 34 F5.2 [Sun] [Fe/H] Iron to hydrogen abundance ratio ([Fe/H])
36- 39 F4.2 [-] log(FeI) Logarithm Fe I abundance relative to
log(ε) of H=12 (logFeI)
41- 44 F4.2 [-] e_log(FeI) Mean error σ of log (FeI)
(σlogFeI)
46- 48 I3 --- o_log(FeI) Number of lines used to compute log (FeI)
(NFeI)
50- 53 F4.2 [-] log(FeII) ? Logarithm Fe II abundance relative to
log(ε) of H=12 (logFeII)
55- 58 F4.2 [-] e_log(FeII) ? Mean error σ of log (FeII)
(σlogFeII)
60- 61 I2 --- o_log(FeII) ? Number of lines used to compute log (FeII)
(NFeII)
63 A1 --- l_[C/Fe] Upper limit flag of [C/Fe]
65- 69 F5.2 [Sun] [C/Fe] ? Carbon to iron abundance ratio ([C/Fe])
71- 74 F4.2 [Sun] e_[C/Fe] ? Mean error σ of [C/Fe]
(σ[C/Fe])
76- 80 F5.2 [Sun] [Mg/Fe] ? Magnesium to iron abundance ratio
([Mg/Fe])
82- 85 F4.2 [Sun] e_[Mg/Fe] ? Mean error σ of [Mg/Fe]
(σ[Mg/Fe])
87 I1 --- o_[Mg/Fe] ? Number of lines used to compute [Mg/Fe]
(N[Mg/Fe])
89 A1 --- l_[Ca/Fe] Upper limit flag of [Ca/Fe]
91- 95 F5.2 [Sun] [Ca/Fe] ? Calcium to iron abundance ratio ([Ca/Fe])
97- 100 F4.2 [Sun] e_[Ca/Fe] ? Mean error σ of [Ca/Fe]
(σ[Ca/Fe])
102- 103 I2 --- o_[Ca/Fe] ? Number of lines used to compute [Ca/Fe]
(N[Ca/Fe])
105 A1 --- l_[Sr/Fe] Upper limit flag of [Sr/Fe]
107- 111 F5.2 [Sun] [Sr/Fe] ? Strontium to iron abundance ratio
([Sr/Fe])
113- 116 F4.2 [Sun] e_[Sr/Fe] ? Mean error σ of [Sr/Fe]
(σ[Sr/Fe])
118 I1 --- o_[Sr/Fe] ? Number of lines used to compute [Sr/Fe]
(N[Sr/Fe])
120 A1 --- l_[Ba/Fe] Upper limit flag of [Ba/Fe]
122- 126 F5.2 [Sun] [Ba/Fe] ? Barium to iron abundance ratio ([Ba/Fe])
128- 131 F4.2 [Sun] e_[Ba/Fe] ? Mean error σ of [Ba/Fe]
(σ[Ba/Fe])
133 I1 --- o_[Ba/Fe] ? Number of lines used to compute [Ba/Fe]
(N[Ba/Fe])
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 20-Jan-2025