J/ApJ/857/74 Abundances of 7 new member stars in Tucana II (Chiti+, 2018)
Chemical abundances of new member stars in the Tucana II dwarf galaxy.
Chiti A., Frebel A., Ji A.P., Jerjen H., Kim D., Norris J.E.
<Astrophys. J., 857, 74 (2018)>
=2018ApJ...857...74C 2018ApJ...857...74C
ADC_Keywords: Abundances; Radial velocities; Equivalent widths
Keywords: galaxies: dwarf; galaxies: individual (TucII); Local Group;
stars: abundances
Abstract:
We present chemical abundance measurements for seven stars with
metallicities ranging from [Fe/H]=-3.3 to [Fe/H]=-2.4 in the TucanaII
ultra-faint dwarf galaxy (UFD), based on high-resolution spectra
obtained with the MIKE spectrograph on the 6.5m Magellan-Clay
Telescope. For three stars, we present detailed chemical abundances
for the first time. Of those, two stars are newly discovered members
of Tucana II and were selected as probable members from deep
narrowband photometry of the Tucana II UFD taken with the SkyMapper
telescope. This result demonstrates the potential for photometrically
identifying members of dwarf galaxy systems based on chemical
composition. One new star was selected from the membership catalog of
Walker+ (2016, J/ApJ/819/53). The other four stars in our sample have
been reanalyzed, following additional observations. Overall, six stars
have chemical abundances that are characteristic of the UFD stellar
population. The seventh star shows chemical abundances that are
discrepant from the other Tucana II members and an atypical, higher
strontium abundance than what is expected for typical UFD stars. While
unlikely, its strontium abundance raises the possibility that it may
be a foreground metal-poor halo star with the same systemic velocity
as Tucana II. If we were to exclude this star, Tucana II would satisfy
the criteria to be a surviving first galaxy. Otherwise, this star
implies that Tucana II has likely experienced somewhat extended
chemical evolution.
Description:
Ji+ (2016ApJ...832L...3J 2016ApJ...832L...3J) observed TucII-006, TucII-011, TucII-033,
and TucII-052 with the MIKE spectrograph (see Table 1). All four stars
were selected from the membership catalog of Walker+ (2016, J/ApJ/819/53).
They observed each star between 100min to 4.42hr in 2016 August with
the MIKE spectrograph on the Magellan-Clay telescope.
We re-observed each star in Ji+ (2016ApJ...832L...3J 2016ApJ...832L...3J) for an
additional 55min.
In addition to re-observing these stars, we observed an additional
member (TucII-078) from Walker+ (2016, J/ApJ/819/53) that had not
previously been observed with a high-resolution spectrograph.
Through a P.I. program, we obtained SkyMapper photometry of TucanaII
using the 1.3m telescope at Siding Spring Observatory.
The data in this paper were obtained with the MIKE spectrograph on the
Clay telescope at Las Campanas Observatory. The observations were
taken between 2017 August 14-17 and October 7-11 (R∼28000 on the blue
chip and R∼22000 on the red chip covering ∼3500Å to ∼9000Å).
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
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22 51 55.1 -58 34 08 Tucana II = NAME Tuc II
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 62 7 Observations
table2.dat 49 7 Stellar parameters
table3.dat 54 128 Chemical abundances
table4.dat 33 121 Uncertainties
table5.dat 47 887 Line measurements
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See also:
J/ApJ/645/613 : Abundances of HD 221170 (Ivans+, 2006)
J/ApJS/162/227 : Transition probabilities for SmII (Lawler+, 2006)
J/ApJS/182/51 : Transitions of rare earth elements (Lawler+, 2009)
J/ApJS/182/80 : Rare earth abundances (Sneden+, 2009)
J/AN/331/474 : Abundances of metal-poor stars (Frebel, 2010)
J/ApJ/708/560 : Spectroscopy of UMa II and Coma Ber (Frebel+, 2010)
J/ApJ/724/341 : Nucleosynthesis of massive metal-free stars (Heger+, 2010)
J/ApJ/711/350 : Metal-poor giant Boo-1137 abundances (Norris+, 2010)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
J/PASP/124/140 : UBVRI Hp BT and VT photonic responses (Bessell+, 2012)
J/ApJ/769/57 : Equivalent widths of metal-poor stars (Frebel+, 2013)
J/ApJ/763/61 : Abundances of 7 red giants of BootesI (Gilmore+, 2013)
J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)
J/ApJ/767/134 : Abundances of red giants in UFD galaxies (Vargas+, 2013)
J/ApJ/786/74 : EW measurements of 6 Segue 1 red giants (Frebel+, 2014)
J/A+A/562/A146 : Chemical abundances of 8 metal-poor stars (Ishigaki+, 2014)
J/A+A/571/A47 : Linelist of CH in stellar atmospheres (Masseron+, 2014)
J/ApJ/797/21 : Carbon-enhanced metal-poor stars (Placco+, 2014)
J/MNRAS/440/2665 : SDSS J021933.13+200830.2 spectroscopy (Roederer+, 2014)
J/AJ/147/136 : Stars of very low metal abundance. VI. (Roederer+, 2014)
J/ApJ/801/125 : Carbon in red giants in GCs and dSph galaxies (Kirby+, 2015)
J/ApJ/830/93 : Abundances of Ret II brightest red giant members (Ji+, 2016)
J/ApJ/817/41 : Abundances of 4 metal-poor red giants in BooII (Ji+, 2016)
J/ApJ/819/53 : Magellan/M2FS spectroscopy of Tuc 2 & Grus 1 (Walker+, 2016)
J/ApJ/838/44 : Abundances of Tuc III brightest members (Hansen+, 2017)
J/ApJ/838/83 : RVs, abundances & membership in TriII (Kirby+, 2017)
J/ApJ/838/11 : Member stars in the MW satellite Tucana III (Simon+, 2017)
J/ApJ/856/142 : Abundances of metal-poor stars in Sculptor (Chiti+, 2018)
J/ApJ/852/99 : Abundances of 3 metal-poor stars in Hor I (Nagasawa+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Star name
11- 12 I2 h RAh Hour of right ascension (J2000)
14- 15 I2 min RAm Minute of right ascension (J2000)
17- 21 F5.2 s RAs Second of right ascension (J2000)
23 A1 --- DE- Sign of declination (J2000)
24- 25 I2 deg DEd Degree of declination (J2000)
27- 28 I2 arcmin DEm Arcminute of declination (J2000)
30- 33 F4.1 arcsec DEs Arcsecond of declination (J2000)
35- 37 F3.1 arcsec Slit [1] Slit size
39- 43 F5.2 mag gmag [18.2/18.9] SkyMapper g-band magnitude
45- 47 I3 min Exp [155/385] Exposure time
49 A1 --- f_Exp Flag on Exp (1)
51- 52 I2 --- S/N4500 [15/17] Signal-to-noise (S/N) per pixel
for 4500Å
54- 55 I2 --- S/N6500 [30/37] Signal-to-noise (S/N) per pixel
for 6500Å
57- 62 F6.1 --- HRV [-127/-119] Heliocentric radial velocity
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Note (1):
b = Combined exposure time from Ji+ (2016ApJ...832L...3J 2016ApJ...832L...3J) and this work.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Star name
11- 14 I4 K Teff [4693/5017] Effective temperature
16- 18 I3 K e_Teff [153/227] Teff uncertainty
20- 23 F4.2 [cm/s2] logg [1.2/1.9] log of surface gravity
25- 28 F4.2 [cm/s2] e_logg [0.3/0.9] logg uncertainty
30- 33 F4.2 km/s Vt [1.8/2.2] Microturbulent velocity
35- 38 F4.2 km/s e_Vt [0.2/0.3] Vt uncertainty
40- 44 F5.2 [-] [Fe/H] [-3.4/-2.4] Metallicity
46- 49 F4.2 [-] e_[Fe/H] [0.1/0.3] [Fe/H] uncertainty
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Tucana II star name
11- 15 A5 --- Sp Atomic species of absorption feature
17- 17 A1 --- f_Sp Species corrected (1)
19- 20 I2 --- Nl [1/99] Number of lines fit
22- 25 F4.2 [-] loge [0.5/8.5] Log number abundance
27- 27 A1 --- l_[X/H] Limit flag on [X/H]
29- 33 F5.2 [-] [X/H] [-4.9/-1.6] Log abundance relative to hydrogen
35- 35 A1 --- u_[X/H] Uncertainty flag on [X/H]
39- 39 A1 --- l_[X/Fe] Limit flag on [X/Fe]
41- 45 F5.2 [-] [X/Fe] [-2.0/1.3] Log abundance relative to iron
47- 47 A1 --- u_[X/Fe] Uncertainty flag on [X/Fe]; see text
51- 54 F4.2 --- sigma [0.1/0.7]? Random uncertainties; See Table 4
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Note (1): Species corrected for evolutionary status of the star following
Placco+ (2014, J/ApJ/797/21).
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Tucana II star name
11- 15 A5 --- Sp Atomic species of absorption feature
17- 18 I2 --- Nl [1/99] Number of lines fit
20- 23 F4.2 --- Rand [0.12/0.66]? Random uncertainty
25- 28 F4.2 --- Sys [0.13/0.64]? Systematic uncertainty
30- 33 F4.2 --- Tot [0.18/0.8]? Total uncertainty
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Tucana II star name
11- 17 F7.2 0.1nm lambda [3783.5/6678] Rest wavelength of
absorption feature
19- 23 A5 --- Sp Atomic species of absorption feature
25- 28 F4.2 eV chi [0/4.4]? Excitation potential of
absorption line (1)
30- 34 F5.2 [-] loggf [-5.7/0.7]? Oscillator strength of
absorption line (1)
36- 40 F5.1 0.1pm EW [15.7/253]? Measured equivalent width
of absorption line (1)
42- 42 A1 --- l_loge Limit flag on logepsilon
43- 47 F5.2 [-] loge [-2.7/6.5] Measured chemical abundance
from absorption feature
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Note (1): Chemical abundances listed for entries with blank (null) values for
chi, loggf, and EW were derived from spectrum syntheses.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 25-Feb-2019