J/MNRAS/485/5153 Spectroscopy of extremely metal-poor stars (Marino+, 2019)
Keck HIRES spectroscopy of SkyMapper commissioning survey candidate extremely
metal-poor stars.
Marino A.F., Da Costa G.S., Casey A.R., Asplund M., Bessell M.S.,
Frebel A., Keller S.C., Lind K., Mackey A.D., Murphy S.J., Nordlander T.,
Norris J.E., Schmidt B.P., Yong D.
<Mon. Not. R. Astron. Soc., 485, 5153-5167 (2019)>
=2019MNRAS.485.5153M 2019MNRAS.485.5153M (SIMBAD/NED BibCode)
ADC_Keywords: Abundances ; Stars, population II ; Stars, metal-deficient ;
Spectroscopy ; Optical
Keywords: stars: abundances - stars: Population II - Galaxy: halo -
Galaxy: stellar content
Abstract:
We present results from the analysis of high-resolution spectra
obtained with the Keck HIRES spectrograph for a sample of 17 candidate
extremely metal-poor (EMP) stars originally selected from
commissioning data obtained with the SkyMapper telescope. Fourteen of
the stars have not been observed previously at high dispersion. Three
have [Fe/H]=←3.0, while the remainder, with two more metal-rich
exceptions, have -3.0=<[Fe/H]=←2.0dex. Apart from Fe, we also derive
abundances for the elements C, N, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn,
Co, Ni, and Zn, and for n-capture elements Sr, Ba, and Eu. None of the
current sample of stars is found to be carbon-rich. In general, our
chemical abundances follow previous trends found in the literature,
although we note that two of the most metal-poor stars show very low
[Ba/Fe] (~-1.7) coupled with low [Sr/Ba] (~-0.3). Such stars are
relatively rare in the Galactic halo. One further star, and possibly
two others, meet the criteria for classification as a r-I star. This
study, together with that of Jacobson et al. (2015ApJ...807..171J 2015ApJ...807..171J,
Cat. J/ApJ/807/171), completes the outcomes of the SkyMapper
commissioning data survey for EMP stars.
Description:
The candidates observed with the HIRES spectrograph (Vogt et al.
1994SPIE.2198..362V 1994SPIE.2198..362V) at the Keck-I telescope were those in the
commissioning survey EMP candidate sample that had not been previously
observed at high dispersion (cf. Jacobson et al. 2015ApJ...807..171J 2015ApJ...807..171J,
Cat. J/ApJ/807/171), which were accessible from the Keck Observatory
on the scheduled date and which had low-resolution spectroscopic
abundance estimates [Fe/H]2.3m=←2.5dex, as determined from the 2.3m
spectra. In all, HIRES spectra were obtained for 15 candidate EMP
stars on the ANU-allocated night of 2013 September 21 (UT), together
with spectra of two stars that had also been observed at Magellan with
the MIKE spectrograph in the Jacobson et al. (2015ApJ...807..171J 2015ApJ...807..171J,
Cat. J/ApJ/807/171) study. One further star, SMSS J221334.13-072604.1,
was subsequently found to be included in the sample analysed by Aoki
et al. (2013AJ....145...13A 2013AJ....145...13A, Cat. J/AJ/145/13) under the designation
SDSS J2213-0726.
Observing conditions were good with the seeing slowly rising from 0.6
to 1arcsec by the end of the night. The spectrograph was configured
with the HIRESb cross-disperser and the C1 decker that has a slit
width of 0.86arcsec yielding a resolution R∼50000. Detector binning
was 2(spatial)x1(spectral) and the low-gain setting (∼2e-/DN) was
used for the three CCDs in the detector mosaic. Details of the
observations are given in Table 1. The table lists the SkyMapper
survey designations, the positions, and the SkyMapper g, (g-i)0 and
mi photometry taken from the SkyMapper DR1.1 data release (Wolf et
al. 2018PASA...35...10W 2018PASA...35...10W, Cat. II/358), which supersede the original
commissioning-era photometry.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 88 17 Details of the target stars and the Keck HIRES
observations
table2.dat 51 17 Adopted atmospheric parameters
table3.dat 57 1083 Atomic data and EWs for program stars
table4.dat 92 17 Chemical abundance ratios for the light elements
C, N, Na, and Al
table5.dat 90 17 Chemical abundances for α elements, Mg,
Si, Ca, and Ti
table6.dat 136 17 Chemical abundances for FeI and FeII, and
Fe-peak elements Sc (ScII), Cr, Mn, Co, Ni, and
Zn
table7.dat 67 17 Chemical abundances for the n-capture elements,
Sr, Ba, and Eu
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See also:
J/ApJ/807/171 : SkyMapper Survey metal-poor star spectroscopy
(Jacobson+, 2015)
II/358 : SkyMapper Southern Sky Survey. DR1.1 (Wolf+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- Name SkyMapper identifier (SMSS JHHMMSS.ss+DDMMSS.s)
26- 27 I2 h RAh Right ascension (J2000)
29- 30 I2 min RAm Right ascension (J2000)
32- 36 F5.2 s RAs Right ascension (J2000)
38 A1 --- DE- Declination sign (J2000)
39- 40 I2 deg DEd Declination (J2000)
42- 43 I2 arcmin DEm Declination (J2000)
45- 48 F4.1 arcsec DEs Declination (J2000)
50- 55 F6.3 mag gmag SkyMapper g-band magnitude
57- 61 F5.3 mag g-i g-i colour index
63- 68 F6.3 --- mi Metallicity index (1)
70- 73 I4 s Texp Integration time
75- 76 I2 pix-1 S/N450 Signal to noise ratio per pixel at 450nm
78- 79 I2 pix-1 S/N600 Signal to noise ratio per pixel at 600nm
81- 86 F6.1 km/s RV Radial velocity
88 I1 --- Notes ? Previous observations (2)
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Note (1): The metallicity index is defined as mi=(v-g)0-1.5(g-i)0, for
which more negative values at fixed colour indicate potentially lower
metallicity (see Keller et al. 2007PASA...24....1K 2007PASA...24....1K)
Note (2): Notes as follows:
1 = In Aoki et al. (2013AJ....145...13A 2013AJ....145...13A, Cat. J/AJ/145/13) as
SDSS J2213-0726
2 = In Jacobson et al. (2015ApJ...807..171J 2015ApJ...807..171J, Cat. J/ApJ/807/171)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- Name SkyMapper identifier
(SMSS JHHMMSS.ss+DDMMSS.s)
26- 29 I4 K Teff Effective temperature
31- 34 F4.2 [cm/s2] logg Surface gravity
36- 40 F5.2 [-] [Fe/H]LTE LTE Iron to hydrogen abundance ratio
42- 46 F5.2 [-] [Fe/H]nLTE Iron to hydrogen abundance ratio obtained by
applying non-LTE corrections to FeI lines
48- 51 F4.2 km/s vt Microturbulence velocity
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- Name SkyMapper identifier (SMSS JHHMMSS.ss+DDMMSS.s)
26- 33 F8.3 0.1nm lambda Wavelenght of the spectral line used in the
abundance analysis
35- 38 F4.1 --- Species Chemical species analysed
40- 44 F5.3 eV EP Excitational potential
46- 51 F6.3 [-] loggf Total oscillator strength employed
53- 57 F5.1 10-4nm EW Measured equivalent width
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- Name SkyMapper identifier
(SMSS JHHMMSS.ss+DDMMSS.s)
26- 30 F5.2 [-] [C/Fe] C to iron abundance ratio
32- 35 F4.2 [-] e_[C/Fe] Error on [C/Fe]
37 I1 --- o_[C/Fe] Number of spectral features analysed for
[C/Fe]
39- 43 F5.2 [-] [C/Fe]evol Evolutionary corrected [C/Fe] abundance (1)
45- 48 F4.2 [-] [N/Fe] ? N to iron abundance ratio
50- 53 F4.2 [-] e_[N/Fe] ? Error on [N/Fe]
55 I1 --- o_[N/Fe] ? Number of spectral features analysed for
[N/Fe]
57- 61 F5.2 [-] [Na/Fe]LTE LTE [Na/Fe] abundance
63- 66 F4.2 [-] e_[Na/Fe]LTE Error on [Na/Fe]LTE
68- 72 F5.2 [-] [Na/Fe]nLTE non-LTE [Na/Fe] abundance
74- 77 F4.2 [-] e_[Na/Fe]nLTE Error on [Na/Fe]nLTE
79 I1 --- o_[Na/Fe]LTE Number of spectral features analysed for
[Na/Fe]LTE
81- 85 F5.2 [-] [Al/Fe] ? Al to iron abundance ratio
87- 90 F4.2 [-] e_[Al/Fe] ? Error on [Al/Fe]
92 I1 --- o_[Al/Fe] ? Number of spectral features analysed for
[Al/Fe]
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Note (1): The evolutionary corrected abundances were derived by applying
corrections from V. Placco (private communication); the estimated
natal [C/Fe] corresponds to [C/Fe]evol.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- Name SkyMapper identifier (SMSS JHHMMSS.ss+DDMMSS.s)
26- 30 F5.2 [-] [Mg/Fe] Mg to iron abundance ratio
32- 35 F4.2 [-] e_[Mg/Fe] Error on [Mg/Fe]
37 I1 --- o_[Mg/Fe] Number of spectral features analysed for
[Mg/Fe]
39- 42 F4.2 [-] [Si/Fe] Si to iron abundance ratio
44- 47 F4.2 [-] e_[Si/Fe] ? Error on [Si/Fe]
49 I1 --- o_[Si/Fe] Number of spectral features analysed for
[Si/Fe]
51- 55 F5.2 [-] [Ca/Fe] ? Ca to iron abundance ratio
57- 60 F4.2 [-] e_[Ca/Fe] ? Error on [Ca/Fe]
62 I1 --- o_[Ca/Fe] ? Number of spectral features analysed for
[Ca/Fe]
64- 68 F5.2 [-] [TiI/Fe] ? TiI to iron abundance ratio
70- 73 F4.2 [-] e_[TiI/Fe] ? Error on [TiI/Fe]
75 I1 --- o_[TiI/Fe] ? Number of spectral features analysed for
[TiI/Fe]
77- 81 F5.2 [-] [TiII/Fe] TiII to iron abundance ratio
83 I1 --- f_[TiII/Fe] ? Flag on [TiII/Fe] (1)
85- 88 F4.2 [-] e_[TiII/Fe] Error on [TiII/Fe]
90 I1 --- o_[TiII/Fe] Number of spectral features analysed for
[TiII/Fe]
--------------------------------------------------------------------------------
Note (1): Flag as follows:
1 = Given the lack of FeII abundances, FeI has been used for the TiII
abundances relative to Fe.
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- Name SkyMapper identifier
(SMSS JHHMMSS.ss+DDMMSS.s)
26- 30 F5.2 [-] [FeI/H] FeI to hydrogen abundance ratio
32- 35 F4.2 [-] e_[FeI/H] Error on [FeI/H]
37- 38 I2 --- o_[FeI/H] Number of spectral features analysed for
[FeI/H]
40- 44 F5.2 [-] [FeII/H] ? FeII to iron abundance ratio
46- 49 F4.2 [-] e_[FeII/H] ? Error on [FeII/H]
51 I1 --- o_[FeII/H] ? Number of spectral features analysed for
[FeII/H]
53- 57 F5.2 [-] [Sc/Fe] ? Sc to iron abundance ratio
59- 62 F4.2 [-] e_[Sc/Fe] ? Error on [Sc/Fe]
64 I1 --- o_[Sc/Fe] ? Number of spectral features analysed for
[Sc/Fe]
66- 70 F5.2 [-] [CrI/Fe] ? CrI to iron abundance ratio
72- 75 F4.2 [-] e_[CrI/Fe] ? Error on [CrI/Fe]
77 I1 --- o_[CrI/Fe] ? Number of spectral features analysed for
[CrI/Fe]
79- 83 F5.2 [-] [CrII/Fe] ? CrII to iron abundance ratio
85 I1 --- o_[CrII/Fe] ? Number of spectral features analysed for
[CrII/Fe]
87- 91 F5.2 [-] [Mn/Fe] Mn to iron abundance ratio
93- 96 F4.2 [-] e_[Mn/Fe] Error on [Mn/Fe]
98 I1 --- o_[Mn/Fe] Number of spectral features analysed for
[Mn/Fe]
100-104 F5.2 [-] [Co/Fe] ? Co to iron abundance ratio
106-109 F4.2 [-] e_[Co/Fe] ? Error on [Co/Fe]
111 I1 --- o_[Co/Fe] ? Number of spectral features analysed for
[Co/Fe]
113-117 F5.2 [-] [Ni/Fe] ? Ni to iron abundance ratio
119-122 F4.2 [-] e_[Ni/Fe] ? Error on [Ni/Fe]
124 I1 --- o_[Ni/Fe] ? Number of spectral features analysed for
[Ni/Fe]
126-129 F4.2 [-] [Zn/Fe] ? Zn to iron abundance ratio
131-134 F4.2 [-] e_[Zn/Fe] ? Error on [Zn/Fe]
136 I1 --- o_[Zn/Fe] ? Number of spectral features analysed for
[Zn/Fe]
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 24 A24 --- Name SkyMapper identifier
(SMSS JHHMMSS.ss+DDMMSS.s)
26- 30 F5.2 [-] [Sr/Fe] Sr to iron abundance ratio
32- 35 F4.2 [-] e_[Sr/Fe] Error on [Sr/Fe]
37 I1 --- o_[Sr/Fe] Number of spectral features analysed for
[Sr/Fe]
39 A1 --- l_[Ba/Fe] Limit flag on [Ba/Fe]
41- 45 F5.2 [-] [Ba/Fe] Ba to iron abundance ratio
47- 50 F4.2 [-] e_[Ba/Fe] Error on [Ba/Fe]
52 I1 --- o_[Ba/Fe] Number of spectral features analysed for
[Ba/Fe]
54 A1 --- l_[Eu/Fe] Limit flag on [Eu/Fe]
56- 60 F5.2 [-] [Eu/Fe] Eu to iron abundance ratio
62- 65 F4.2 [-] e_[Eu/Fe] ? Error on [Eu/Fe]
67 I1 --- o_[Eu/Fe] ? Number of spectral features analysed for
[Eu/Fe]
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 10-Oct-2022