J/MNRAS/493/4677 The Pristine survey XI: the FORS2 sample (Caffau+, 2020)
The Pristine survey XI: the FORS2 sample.
Caffau E., Bonifacio P., Sbordone L., Matas Pinto A.M., Francois P.,
Jablonka P., Lardo C., Martin N.F., Starkenburg E., Aguado D.,
Gonzalez-Hernandez J.I., Venn K., Mashonkina L., Sestito F.
<Mon. Not. R. Astron. Soc., 493, 4677-4691 (2020)>
=2020MNRAS.493.4677C 2020MNRAS.493.4677C (SIMBAD/NED BibCode)
ADC_Keywords: Stars, population II ; Stars, metal-deficient ; Milky Way ;
Abundances, peculiar ; Effective temperatures ;
Radial velocities ; Stars, distances ; Optical
Keywords: stars: abundances - stars: Population II - Galaxy: abundances -
Galaxy: evolution
Abstract:
Extremely metal-poor (EMP) stars are old objects that mostly formed
very early after the big bang. They are rare and, to select them, we
have to rely on low-resolution spectroscopic or photometric surveys;
specifically the combination of narrow- and broad-band photometry
provides a powerful and time efficient way to select MP stars. The
Pristine photometric survey is using the Canada-France-Hawaii
Telescope MegaCam wide-field imager to obtain narrow-band photometry
by utilizing a filter centred at 395.2nm on the Ca II-H and -K lines.
Gaia DR2 is providing us the wide-band photometry as well as
parallaxes. Follow-up observations of MP candidates allowed us to
improve our photometric calibrations. In this paper of the series we
analyse MP stars observed with FORS2 at VLT. We demonstrate the
Pristine calibration adopted in this work to be able to provide
metallicities accurate to ±0.3dex for MP giant stars with good
parallaxes, while it performs poorly for dwarf and turn-off stars,
whatever the accuracy on the parallaxes. We find some MP and very MP
stars that are not enhanced in α elements. Such stars have
already been found in several other searches, and a higher resolution
follow-up of our sample would be useful to put our findings on a
firmer ground. This sample of stars analysed has a low fraction of
carbon-enhanced MP stars, regardless of the definition adopted. This
deficiency could indicate a small sensitivity of the Pristine filter
to carbon abundance, issue to be addressed in the future.
Description:
The purpose of these observations was to verify, and possibly improve,
the photometric calibration in the very MP regime. For the
observations in ESO periods 100 and 101 we used the catalogue of
Pristine photometry, as available up to March 2017. The CaHK
photometry was combined with SDSS gri photometry, as described in
Starkenburg et al. (2017MNRAS.471.2587S 2017MNRAS.471.2587S) and Youakim et al.
(2017MNRAS.472.2963Y 2017MNRAS.472.2963Y, Cat. J/MNRAS/472/2963), to estimate effective
temperatures and metallicities. We selected stars with g~<17 and
estimated photometric metallicity =< -2.5, no condition was set on the
temperature of the stars.
The observations were acquired in service mode at the ESO Antu 8.2m
telescope with the FORS2 instrument. We took long-slit spectra using
GRISM 600B+22 with a 0.28" wide slit that provides a resolving power
R∼2800. The spectral range covered is 330-621nm. We used a 1x1 binning
of the CCD, corresponding to 0.075nm/pixel, to avoid undersampling in
the blue spectral range. Exposure time was 2762s for each star.
A total of 135 spectra were analysed. Seven were discarded due to poor
quality, 30 were used to determine metallicity only, and 98 were used
for a full chemical analysis where abundances were determined for
several elements.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 110 135 Stellar parameters
abund.dat 185 98 Detailed chemical composition of 98 stars
orbit.dat 152 55 Orbital parameters of 55 stars with
[Fe/H]=< -2.5
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 25 A25 --- Name Star name (Pristine_DDD.dddd+DD.dddd)
27 A1 --- f_Name [a] Flag on Name (1)
29- 30 I2 h RAh Right ascension (J2000)
32- 33 I2 min RAm Right ascension (J2000)
35- 39 F5.2 s RAs Right ascension (J2000)
41 A1 --- DE- Declination sign (J2000)
42- 43 I2 deg DEd Declination (J2000)
45- 46 I2 arcmin DEm Declination (J2000)
48- 51 F4.1 arcsec DEs Declination (J2000)
53- 56 I4 K Teff Effective temperature
58- 61 F4.2 [cm/s2] logg Surface gravity
63- 66 F4.2 [cm/s2] e_logg Error on logg
68- 71 F4.2 km/s vt Microturbulence velocity
73- 77 F5.2 [-] [Fe/H]ph ? Photometric Fe/H abundance ratio
79- 83 F5.2 [-] [Fe/H] ? Fe/H abundance ratio
85- 88 F4.2 [-] e_[Fe/H] ? Error on [Fe/H]
90- 94 F5.2 [-] [Ca/H] ? Lain cols 85-88
96- 99 F4.2 [-] e_[Ca/H] ? Lain cols 96-99
101- 104 I4 km/s RV ? Radial velocity
106- 107 I2 km/s e_RV ? Statistical error on the radial velocity
(2)
109- 110 I2 km/s dRV ? Maximum radial velocity shift for the
zenith angle at which the star was observed
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Note (1): Flag as follows:
a = Weak H-line EWs
Note (2): The statistical error on the radial velocity reflects the S/N ratio
of the spectrum and is estimated from the χ2 of the
spectrum-template match
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Byte-by-byte Description of file: abund.dat
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Bytes Format Units Label Explanations
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1- 25 A25 --- Name Star name (Pristine_DDD.dddd+DD.dddd)
27- 30 I4 K Teff Effective temperature
32- 35 F4.2 [cm/s2] logg Surface gravity
37- 40 F4.2 km/s vt Microturbulence velocity
42- 46 F5.2 [-] [M/H] ? Photometric metallicity
48- 52 F5.2 [-] [Fe/H] Spectroscopic Fe/H abundance ratio
54- 57 F4.2 --- A(Fe) Iron abundance
59- 62 F4.2 --- s(Fe) Line-to-line scatter on the Fe abundance
64- 65 I2 --- o_A(Fe) Number of FeI lines
67 A1 --- l_A(C) Limit flag on A (C)
69- 72 F4.2 --- A(C) Carbon abundance
74 A1 --- u_A(C) Uncertainty flag on A (C)
76 A1 --- l_A(N) Limit flag on A (N)
78- 81 F4.2 --- A(N) ? Nitrogen abundance
83 A1 --- u_A(N) Uncertainty flag on A (N)
85- 88 F4.2 --- A(CaK) ? Calcium abundance from the CaII-K line
90- 93 F4.2 --- A(Fe2) ? Iron abundance from one FeII line
95- 98 F4.2 --- A(Mg) Magnesium abundance
100- 103 F4.2 --- s(Mg) ? Line-to-line scatter on the Mg abundance
105 I1 --- o_A(Mg) Number of Mg lines
107- 110 F4.2 --- A(Ca1) ? Calcium abundance from CaI lines
112- 115 F4.2 --- s(Ca1) ? Line-to-line scatter on the Ca abundance
from CaI lines
117 I1 --- o_A(Ca1) ? Number of CaI lines
119- 122 F4.2 --- A(Ti1) ? Titanium abundance from one TiI line
124- 127 F4.2 --- s(Ti1) ? Line-to-line scatter on the Ti abundance
from TiI lines
129 I1 --- o_A(Ti1) ? Number of TiI lines
131- 134 F4.2 --- A(Ti2) ? Titanium abundance from one TiII line
136- 139 F4.2 --- s(Ti2) ? Line-to-line scatter on the Ti abundance
from TiII lines
141 I1 --- o_A(Ti2) ? Number of TiII lines
143- 146 F4.2 --- A(Cr) ? Chromium abundance
148- 151 F4.2 --- A(Mn) ? Manganese abundance
153- 156 F4.2 --- s(Mn) ? Line-to-line scatter on the Mn abundance
158 I1 --- o_A(Mn) ? Number of Mn lines
160- 163 F4.2 --- A(Ni) ? Nickel abundance
165- 169 F5.2 --- A(Sr) ? Strontium abundance
171- 175 F5.2 --- A(Ba) ? Barium abundance
177- 180 F4.2 --- A(Na) ? Sodium abundance
182- 185 F4.2 --- s(Na) ? Line-to-line scatter on the Na abundance
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Byte-by-byte Description of file: orbit.dat
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Bytes Format Units Label Explanations
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1- 25 A25 --- Name Star name (Pristine_DDD.dddd+DD.dddd)
27- 31 F5.2 kpc Dist Heliocentric distance
33- 36 F4.2 kpc e_Dist Error on Dist
38- 43 F6.2 kpc rapo Apocentre distance
45- 50 F6.2 kpc E_rapo Upper error on rapo
52- 57 F6.2 kpc e_rapo Lower error on rapo
59- 63 F5.2 kpc rperi Pericentre distance
65- 68 F4.2 kpc E_rperi Upper error on rperi
70- 73 F4.2 kpc e_rperi Lower error on rperi
75- 78 F4.2 --- e Eccentricity
80- 83 F4.2 --- E_e Upper error on e
85- 88 F4.2 --- e_e Lower error on e
90- 96 F7.1 kpc.km/s Jphi Azimuthal component of the action
98- 103 F6.1 kpc.km/s E_Jphi Upper error on Jphi
105- 110 F6.1 kpc.km/s e_Jphi Lower error on Jphi
112- 118 F7.1 kpc.km/s Jz Vertical component of the action
120- 125 F6.1 kpc.km/s E_Jz Upper error on Jz
127- 132 F6.1 kpc.km/s e_Jz Lower error on Jz
134- 139 F6.2 kpc Zmax Maximum excursion from the Milky Way plane
141- 146 F6.2 kpc E_Zmax Upper error on Zmax
148- 152 F5.2 kpc e_Zmax Lower error on Zmax
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History:
From electronic version of the journal
References:
Starkenburg et al., Paper I 2017MNRAS.471.2587S 2017MNRAS.471.2587S
Caffau et al., Paper II 2017AN....338..686C 2017AN....338..686C, Cat. J/AN/338/686
Youakim et al., Paper III 2017MNRAS.472.2963Y 2017MNRAS.472.2963Y, Cat. J/MNRAS/472/2963
Starkenburg et al., Paper IV 2018MNRAS.481.3838S 2018MNRAS.481.3838S
Bonifacio et al., Paper V 2019MNRAS.487.3797B 2019MNRAS.487.3797B, Cat. J/MNRAS/487/3797
Aguado et al., Paper VI 2019MNRAS.490.2241A 2019MNRAS.490.2241A, Cat. J/MNRAS/490/2241
Starkenburg et al., Paper VII 2019MNRAS.490.5757S 2019MNRAS.490.5757S
Youakim et al., Paper VIII 2020MNRAS.492.4986Y 2020MNRAS.492.4986Y
Venn et al., Paper IX 2020MNRAS.492.3241V 2020MNRAS.492.3241V
Sestito et al., Paper X 2020MNRAS.497L...7S 2020MNRAS.497L...7S
Kielty et al., Paper XII 2021MNRAS.506.1438K 2021MNRAS.506.1438K
Fernandez-Alvar et al., Paper XIII 2021MNRAS.508.1509F 2021MNRAS.508.1509F
Lardo et al., Paper XIV 2021MNRAS.508.3068L 2021MNRAS.508.3068L
Lucchesi et al., Paper XV 2022MNRAS.511.1004L 2022MNRAS.511.1004L
Martin et al., Paper XVI 2022MNRAS.516.5331M 2022MNRAS.516.5331M
Yuan et al., Paper XVII 2022MNRAS.514.1664Y 2022MNRAS.514.1664Y
Errani et al., Paper XVIII 2022MNRAS.514.3532E 2022MNRAS.514.3532E
Caffau et al., Paper XIX 2023MNRAS.518.3796C 2023MNRAS.518.3796C
Arentsen et al., Paper XX 2023MNRAS.519.5554A 2023MNRAS.519.5554A, Cat. J/MNRAS/519/5554
(End) Ana Fiallos [CDS] 04-May-2023