J/AJ/151/82 The 4 brightest red giants in the UFD galaxy Ret 2 (Roederer+, 2016)
Detailed chemical abundances in the r-process-rich ultra-faint dwarf galaxy
Reticulum 2.
Roederer I.U., Mateo M., Bailey III J.I., Song Y., Bell E.F., Crane J.D.,
Loebman S., Nidever D.L., Olszewski E.W., Shectman S.A., Thompson I.B.,
Valluri M., Walker M.G.
<Astron. J., 151, 82 (2016)>
=2016AJ....151...82R 2016AJ....151...82R (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Stars, giant ; Photometry, ugriz ;
Radial velocities ; Spectroscopy ; Equivalent widths ;
Effective temperatures ; Abundances
Keywords: galaxies: dwarf - galaxies: individual: Reticulum 2 -
nuclear reactions, nucleosynthesis, abundances - stars: abundances
Abstract:
The ultra-faint dwarf (UFD) galaxy Reticulum 2 (Ret 2) was recently
discovered in images obtained by the Dark Energy Survey (Diehl et al.
2014SPIE.9149E..0VD). We have observed the four brightest red giants
in Ret 2 at high spectral resolution using the Michigan/Magellan Fiber
System. We present detailed abundances for as many as 20 elements per
star, including 12 elements heavier than the Fe group. We confirm
previous detection of high levels of r-process material in Ret 2 (mean
[Eu/Fe]=+1.69±0.05) found in three of these stars (mean
[Fe/H]=-2.88±0.10). The abundances closely match the r-process
pattern found in the well-studied metal-poor halo star CS 22892-052.
Such r-process-enhanced stars have not been found in any other UFD
galaxy, though their existence has been predicted by at least one
model. The fourth star in Ret 2 ([Fe/H]=-3.42±0.20) contains only
trace amounts of Sr ([Sr/Fe]=-1.73±0.43) and no detectable heavier
elements. One r-process enhanced star is also enhanced in C (natal
[C/Fe]~+1.1). This is only the third such star known, which suggests
that the nucleosynthesis sites leading to C and r-process enhancements
are decoupled. The r-process-deficient star is enhanced in Mg
([Mg/Fe]=+0.81±0.14), and the other three stars show normal levels
of α-enhancement (mean [Mg/Fe]=+0.34±0.03). The abundances of
other α and Fe-group elements closely resemble those in UFD
galaxies and metal-poor halo stars, suggesting that the nucleosynthesis
that led to the large r-process enhancements either produced no light
elements or produced light-element abundance signatures
indistinguishable from normal supernovae.
Description:
There are only four stars brighter than the horizontal branch that are
confirmed members of Ret 2 (Simon et al. 2015, J/ApJ/808/95;
Walker et al. 2015, J/ApJ/808/108). We observed these four stars using
one arm of the Michigan/Magellan Fiber System (M2FS) and MSpec double
spectrograph (Bailey et al. 2012SPIE.8446E..5GB; Mateo et al.
2012SPIE.8446E..4YM) mounted on the Nasmyth platform at the 6.5 m
Landon Clay Telescope (Magellan II) at Las Campanas Observatory, Chile.
We observed four high-probability members of Ret 2 and one blank sky
position simultaneously on 2015 November 14 and 16, with a total
integration time of 6.67 hr. Both observations were taken in dark time.
Objects:
-------------------------------------------------------------
RA (ICRS) DE Designation(s)
-------------------------------------------------------------
03 35 42.1 -54 02 57 Reticulum 2 = NAME Reticulum II
-------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 64 4 Basic Stellar Data
table3.dat 59 207 Equivalent Widths and Atomic Data
table4.dat 43 4 Stellar Parameters
table5.dat 32 428 Abundances Derived from Individual Lines
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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/167/292 : Laboratory transition probabilities for Gd II
(Den Hartog+, 2006)
J/ApJ/667/1267 : CrI transition probabilities (Sobeck+, 2007)
J/ApJS/182/51 : Transition probabilities of rare earth elements
(Lawler+, 2009)
J/ApJS/182/80 : Rare earth abundances (Sneden+, 2009)
J/ApJS/194/35 : Atomic transition probabilities of Mn (Den Hartog+, 2011)
J/ApJ/750/76 : r-process peaks elements in HD 160617 (Roederer+, 2012)
J/ApJ/767/134 : Abundances of red giant stars in UFD galaxies
(Vargas+, 2013)
J/ApJS/208/27 : Sun and HD 84937 TiII log(gf) and abundances (Wood+, 2013)
J/ApJS/211/20 : NiI transition probability measurements (Wood+, 2014)
J/ApJS/215/20 : Vanadium log(gf) and transition probabilities
(Lawler+, 2014)
J/MNRAS/441/3127 : FeI oscillator strengths for Gaia-ESO (Ruffoni+, 2014)
J/ApJ/808/95 : Spectroscopy of Reticulum II (Simon+, 2015)
J/ApJ/808/108 : M2FS stellar spectroscopy of Reticulum 2 (Walker+, 2015)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [Star]
6 I1 --- Star [1/4] Star name from this work (Star N)
8- 10 A3 --- --- [DES]
12- 30 A19 --- DES Dark Energy Survey (DES, Diehl et al.
2014SPIE.9149E..0VD) star name from Simon et al.
(2015, J/ApJ/808/95) (DES JHHMMSS.ss+DDMMSS.s)
32- 36 A5 --- --- [Ret2-]
37- 39 I3 --- Ret2- [80/178]? Star name from Walker et al.
(2015, J/ApJ/808/108) (Ret2-NNN)
41- 45 F5.2 mag gmag [16.47/17.57] Star g-band magnitude, adopted from
Koposov et al. (2015ApJ...805..130K 2015ApJ...805..130K)
47- 50 F4.2 mag g-r [0.56/0.80] Star g-r color, adopted from
Koposov et al. (2015ApJ...805..130K 2015ApJ...805..130K)
52- 55 F4.1 km/s [59.7/65.5] Mean calculated heliocentric radial
velocity
57- 58 I2 --- S/N4300 [15/26] Spectral signal-to-noise ratio at 4300Å
60- 61 I2 --- S/N4800 [26/45] Spectral signal-to-noise ratio at 4800Å
63- 64 I2 --- S/N5200 [33/59] Spectral signal-to-noise ratio at 5200Å
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Ion Species
7- 13 F7.2 0.1nm Wave [4149.20/5429.70] Wavelength λ (Å)
15- 18 F4.2 eV ExPot [0.00/4.47] Excitation potential
20- 24 F5.2 [-] log(gf) [-5.62/0.65] Log of degeneracy times oscillator
strength
26- 27 I2 --- r_log(gf) [1/29] Literature reference for log(gf) value
(1)
29 A1 --- f_EW-1 [ls] Flag on EW-1 (2)
31- 35 F5.1 0.1pm EW-1 [17.7/144.7]? Equivalent width for Star 1
(mÅ)
37 A1 --- f_EW-2 [ls] Flag on EW-2 (2)
39- 43 F5.1 0.1pm EW-2 [21.3/238.1]? Equivalent width for Star 2
(mÅ)
45 A1 --- f_EW-3 [ls] Flag on EW-3 (2)
47- 51 F5.1 0.1pm EW-3 [6.4/190.3]? Equivalent width for Star 3
(mÅ)
53 A1 --- f_EW-4 [ls] Flag on EW-4 (2)
55- 59 F5.1 0.1pm EW-4 [8.4/220.3]? Equivalent width for Star 4
(mÅ)
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Note (1): Reference as follows:
1 = NIST, Kramida et al. (2015, NIST Atomic Spectra Database (v. 5.3) online:
http://physics.nist.gov/asd);
2 = Aldenius et al. (2007A&A...461..767A 2007A&A...461..767A);
3 = Lawler & Dakin (1989JOSAB...6.1457L 1989JOSAB...6.1457L), using hyperfine splitting (HFS)
from Kurucz & Bell (1995KurCD..23.....K 1995KurCD..23.....K);
4 = Lawler et al. (2013ApJS..205...11L 2013ApJS..205...11L);
5 = Wood et al. (2013, J/ApJS/208/27);
6 = Lawler et al. (2014, J/ApJS/215/20);
7 = Sobeck et al. (2007, J/ApJ/667/1267);
8 = Nilsson et al. (2006A&A...445.1165N 2006A&A...445.1165N);
9 = Booth et al. (1984MNRAS.208..147B 1984MNRAS.208..147B);
10 = Den Hartog et al. (2011, J/ApJS/194/35) for both log(gf) value and HFS;
11 = Ruffoni et al. (2014, J/MNRAS/441/3127);
12 = Wood et al. (2014, J/ApJS/211/20);
13 = NIST, Kramida et al. (2015, NIST Atomic Spectra Database (v. 5.3) online:
http://physics.nist.gov/asd), using HFS from Kurucz & Bell
(1995KurCD..23.....K 1995KurCD..23.....K);
14 = Roederer & Lawler (2012, J/ApJ/750/76);
15 = Biemont et al. (2011MNRAS.414.3350B 2011MNRAS.414.3350B);
16 = Ljung et al. (2006A&A...456.1181L 2006A&A...456.1181L);
17 = Palmeri et al. (2005MNRAS.363..452P 2005MNRAS.363..452P);
18 = Wickliffe et al. (1994JQSRT..51..545W 1994JQSRT..51..545W);
19 = NIST, Kramida et al. (2015, NIST Atomic Spectra Database (v. 5.3) online:
http://physics.nist.gov/asd), using HFS/isotope shifts (IS) from
McWilliam (1998AJ....115.1640M 1998AJ....115.1640M) when available;
20 = Lawler et al. (2001ApJ...556..452L 2001ApJ...556..452L), using HFS from Ivans et al.
(2006, J/ApJ/645/613);
21 = Lawler et al. (2009, J/ApJS/182/51);
22 = Li et al. (2007PhyS...76..577L 2007PhyS...76..577L), using HFS from Sneden et al.
(2009, J/ApJS/182/80);
23 = Ivarsson et al. (2001PhyS...64..455I 2001PhyS...64..455I), using HFS from Sneden et al.
(2009, J/ApJS/182/80);
24 = Den Hartog et al. (2003ApJS..148..543D 2003ApJS..148..543D), using HFS/IS from
Roederer et al. (2008ApJ...675..723R 2008ApJ...675..723R) when available;
25 = Lawler et al. (2006, J/ApJS/162/227), using HFS/IS from Roederer et al.
(2008ApJ...675..723R 2008ApJ...675..723R) when available;
26 = Lawler et al. (2001ApJ...563.1075L 2001ApJ...563.1075L), using HFS/IS from Ivans et al.
(2006, J/ApJ/645/613);
27 = Den Hartog et al. (2006, J/ApJS/167/292);
28 = Lawler et al. (2001ApJS..137..341L 2001ApJS..137..341L), using HFS from Lawler et al.
(2001ApJS..137..351L 2001ApJS..137..351L) when available;
29 = Wickliffe et al. (2000JQSRT..66..363W 2000JQSRT..66..363W).
Note (2): Flag as follows:
s = Indicates that abundances were derived by spectral synthesis matching;
l = Indicates that an upper limit was derived from a non-detection.
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [Star]
6 I1 --- Star [1/4] Star name from this work (Star N)
8- 11 I4 K Teff [4710/5020] Derived stellar effective
temperature
13- 15 I3 K e_Teff [140] Uncertainty in Teff
17- 20 F4.2 [cm/s2] logg [1.22/2.09] Derived log of surface gravity
22- 25 F4.2 [cm/s2] e_logg [0.38/0.40] Uncertainty in logg
27- 30 F4.2 km/s Vt [2.00/2.85] Derived microturbulence velocity
32- 34 F3.1 km/s e_Vt [0.2/0.3] Uncertainty in Vt
36- 39 F4.1 [Sun] [M/H] [-3.3/-2.7] Model derived metallicity
41- 43 F3.1 [Sun] e_[M/H] [0.2] Uncertainty in [M/H]
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [Star]
6 I1 --- Star [1/4] Star name from this work (Star N)
8- 12 A5 --- Ion Species
14- 20 F7.2 0.1nm Wave [4149.20/5429.70] Wavelength λ (Å)
22 A1 --- l_logeps [<] Limit flag on logeps
23- 27 F5.2 [-] logeps [-2.59/5.35] Log ε abundance
29- 32 F4.2 [-] e_logeps [0.15/0.57]? Error on logeps
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 21-Mar-2018