J/AJ/162/229 13 Magellanic Clouds metal-poor stars (Reggiani+, 2021)
The most metal-poor stars in the Magellanic Clouds are r-process enhanced.
Reggiani H., Schlaufman K.C., Casey A.R., Simon J.D., Ji A.P.
<Astron. J., 162, 229-229 (2021)>
=2021AJ....162..229R 2021AJ....162..229R (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds; Abundances; Stars, metal-deficient;
Spectra, optical
Keywords: Galaxy accretion; Galaxy chemical evolution; Galaxy environments
Magellanic Clouds; Population II stars; Stellar abundances
Abstract:
The chemical abundances of a galaxy's metal-poor stellar population
can be used to investigate the earliest stages of its formation and
chemical evolution. The Magellanic Clouds are the most massive of the
Milky Way's satellite galaxies and are thought to have evolved in
isolation until their recent accretion by the Milky Way. Unlike the
Milky Way's less massive satellites, little is known about the
Magellanic Clouds' metal-poor stars. We have used the mid-infrared
metal-poor star selection of Schlaufman & Casey and archival data to
target nine LMC and four SMC giants for high-resolution Magellan/MIKE
spectroscopy. These nine LMC giants with -2.4≲[Fe/H]≲-1.5 and four
SMC giants with -2.6≲[Fe/H]≲-2.0 are the most metal-poor stars in
the Magellanic Clouds yet subject to a comprehensive abundance
analysis. While we find that at constant metallicity these stars are
similar to Milky Way stars in their α, light, and iron-peak
elemental abundances, both the LMC and SMC are enhanced relative to
the Milky Way in the r-process element europium. These abundance
offsets are highly significant, equivalent to 3.9σ for the LMC,
2.7σ for the SMC, and 5.0σ for the complete Magellanic
Cloud sample. We propose that the r-process enhancement of the
Magellanic Clouds' metal-poor stellar population is a result of the
Magellanic Clouds' isolated chemical evolution and long history of
accretion from the cosmic web combined with r-process nucleosynthesis
on a timescale longer than the core-collapse supernova timescale but
shorter than or comparable to the thermonuclear (i.e., Type Ia)
supernova timescale.
Description:
We followed up 13 stars with the Magellan Inamori Kyocera Echelle
(MIKE) spectrograph on the Magellan Clay Telescope at Las Campanas
Observatory. We used either the 0.7" or 1.0" slits and the standard
blue and red grating azimuths, yielding spectra between 335 and 950nm
with resolution R∼40000/28000 in the blue and R∼31000/22000 in the red
for the 0.7"/1.0" slits.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 94 13 Log of Magellan/MIKE observations
table2.dat 63 2574 Atomic data, equivalent-width, &
individual-line abundance inferences
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020)
V/154 : Sloan Digital Sky Surveys (SDSS), Release 16 (DR16) (Ahumada+, 2020)
J/ApJ/743/156 : NEOWISE observations NEOs: preliminary results (Mainzer+, 2011)
J/A+A/560/A44 : Abundances of LMC bar and disk stars (Van der Swaelmen+, 2013)
J/AJ/145/107 : Zr, Ba, La, & Eu abundances 19 open clusters (Jacobson+, 2013)
J/ApJ/767/134 : Abundances of red giant stars in UFD galaxies (Vargas+, 2013)
J/AJ/147/136 : Stars very low metal abundance. VI. Abundances (Roederer+, 2014)
J/ApJ/769/57 : Equivalent widths of metal-poor stars (Frebel+, 2013)
J/ApJ/780/59 : Araucaria project: eclipsing binaries in SMC (Graczyk+, 2014)
J/ApJ/789/147 : Star formation histories of LG dwarf galaxies (Weisz+, 2014)
J/ApJ/797/13 : Abundances of bright metal-poor stars (Schlaufman+, 2014)
J/MNRAS/442/1680 : Red giants in SMC. Abundances (Dobbie+, 2014)
J/ApJ/807/171 : SkyMapper Survey metal-poor star spectroscopy (Jacobson+, 2015)
J/A+A/586/A120 : Grid of 1D models for Mg line formation (Osorio+, 2016)
J/AJ/151/82 : 4 brightest red giants in the UFD galaxy Ret 2 (Roederer+, 2016)
J/AJ/151/144 : ASPCAP weights for 15 APOGEE chemical elements (Garcia+, 2016)
J/ApJ/816/49 : Spitzer/IRAC observations of SMC Cepheids (Scowcroft+, 2016)
J/ApJ/830/93 : Abundances of the Ret II brightest red giant members (Ji+, 2016)
J/A+A/608/A46 : Constraining cosmic scatter (Reggiani+, 2017)
J/AcA/67/297 : OGLE Galactic center Cepheids and RR Lyrae (Soszynski+, 2017)
J/ApJ/838/44 : Abundances of the brightest member of Tuc III (Hansen+, 2017)
J/ApJ/850/179 : 2MASSJ15111324-2130030 metal-poor star abund. (Casey+, 2017)
J/A+A/616/A12 : Gaia DR2 sources in GC and dSph (Gaia Collaboration+, 2018)
J/AcA/68/89 : VI light curves of MC type II Cepheids (Soszynski+, 2018)
J/AJ/156/18 : APOGEE DR14:Binary companions evolved stars (Price-Whelan+, 2018)
J/ApJ/858/92 : RPA Southern Pilot Search of 107 Stars (Hansen+, 2018)
J/ApJ/863/89 : Gaia DR2 PMs of stars in ultra-faint MW satellites (Simon, 2018)
J/ApJ/868/110 : R-Process Alliance 1st release in Galactic halo (Sakari+, 2018)
J/A+A/627/A177 : Non-LTE analysis of K I in late-type stars (Reggiani+, 2019)
J/ApJ/882/177 : Abundances of 4 member stars of Tucana III (Marshall+, 2019)
J/AJ/160/173 : Abundances of metal-poor stars in Inner Bulge (Reggiani+, 2020)
J/AJ/160/181 : Chemical abundances in red giants with Magellan (Ji+, 2020)
J/ApJ/889/177 : RGB abundances in disk, stream & halo of M31 (Escala+, 2020)
J/ApJ/895/78 : [Fe/H] and [α/Fe] in M31 dwarf galaxies (Wojno+, 2020)
J/ApJ/898/150 : High-res. MIKE obs. of metal-poor stars (Ezzeddine+, 2020)
J/ApJS/249/30 : R-Process Alliance: metal-poor star spectro. (Holmbeck+, 2020)
J/ApJS/252/23 : E(V-I) reddening map MCs from OGLE-IV RC stars (Skowron+, 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- 2MASS 2MASS identifier
19- 21 A3 --- Gal Galaxy identifier; Small/Large Magellanic Cloud
23- 24 I2 h RAh [0/6] Hour of right ascension (J2000)
26- 27 I2 min RAm Minute of right ascension (J2000)
29- 33 F5.2 s RAs Second of right ascension (J2000)
35 A1 --- DE- [-] Sign of declination (J200)
37- 38 I2 deg DEd Degree of declination
40- 41 I2 arcmin DEm Arcminute of declination
43- 47 F5.2 arcsec DEs Arcsecond of declination
49- 52 I4 yr Obs.Y [2016/2020] Year of observation
54- 56 A3 "month" Obs.M Month of observation
58- 59 I2 d Obs.D Day of observation
61- 62 I2 h Obs.h Hour of observation
64- 65 I2 min Obs.m Minute of observation
67- 68 I2 s Obs.s Second of observation
70- 72 F3.1 arcsec Slit [0.7/1] Slit width
74- 78 I5 s Texp [3584/25200] Exposure time
80- 84 F5.1 km/s RVel [100/357] Radial velocity
86- 88 F3.1 km/s e_RVel [0.9/4] Error on RVel
90- 91 I2 --- S/N4500 [14/30] Signal to noise ratio at 4500Å
93- 94 I2 --- S/N6500 [31/76] Signal to noise ratio at 6500Å
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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- 17 A17 --- 2MASS 2MASS designation
19- 21 A3 --- Gal Galaxy identifier; Small/Large Magellanic Cloud
23- 30 F8.3 0.1nm Wave [3999/7789] Wavelength; Angstroms
32- 35 A4 --- Species Species identifier
37- 41 F5.3 eV ExPot [0/5.09] Excitation potential
43- 48 F6.3 [-] loggf [-5.63/0.55] log oscillator strength
50- 56 F7.2 10-13m EW [1.9/3149]? Equivalent width; milli-Angstroms
58- 63 F6.3 [-] loge [-1.47/7.04] log Abundance
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 18-Feb-2022