J/ApJ/852/49 Properties of metal-poor stars in APOGEE DR13 (Hayes+, 2018)
Disentangling the Galactic halo with APOGEE.
I. Chemical and kinematical investigation of distinct metal-poor populations.
Hayes C.R., Majewski S.R., Shetrone M., Fernandez-Alvar E., Prieto C.A.,
Schuster W.J., Carigi L., Cunha K., Smith V.V., Sobeck J., Almeida A.,
Beers T.C., Carrera R., Fernandez-Trincado J.G., Garcia-Hernandez D.A.,
Geisler D., Lane R.R., Lucatello S., Matthews A.M., Minniti D.,
Nitschelm C., Tang B., Tissera P.B., Zamora O.
<Astrophys. J., 852, 49 (2018)>
=2018ApJ...852...49H 2018ApJ...852...49H (SIMBAD/NED BibCode)
ADC_Keywords: Abundances ; Positional data ; Photometry ; Radial velocities ;
Stars, giant ; Stars, population II
Keywords: Galaxy: disk - Galaxy: evolution - Galaxy: formation - Galaxy: halo -
stars: abundances
Abstract:
We find two chemically distinct populations separated relatively
cleanly in the [Fe/H]-[Mg/Fe] plane, but also distinguished in other
chemical planes, among metal-poor stars (primarily with metallicities
[Fe/H]←0.9) observed by the Apache Point Observatory Galactic
Evolution Experiment (APOGEE) and analyzed for Data Release 13 (DR13)
of the Sloan Digital Sky Survey. These two stellar populations show
the most significant differences in their [X/Fe] ratios for the
α-elements, C+N, Al, and Ni. In addition to these populations
having differing chemistry, the low metallicity high-Mg population
(which we denote "the HMg population") exhibits a significant net
Galactic rotation, whereas the low-Mg population (or "the LMg
population") has halo-like kinematics with little to no net rotation.
Based on its properties, the origin of the LMg population is likely an
accreted population of stars. The HMg population shows chemistry (and
to an extent kinematics) similar to the thick disk, and is likely
associated with in situ formation. The distinction between the LMg and
HMg populations mimics the differences between the populations of low-
and high-α halo stars found in previous studies, suggesting that
these are samples of the same two populations.
Description:
Table 1 contains the properties, stellar parameters, and chemical
abundances of the metal-poor stars in reported by the Apache Point
Observatory Galactic Evolution Experiment (APOGEE) in the 13th data
release of the Sloan Digital Sky survey as presented in the paper.
This table also includes population assignments for these metal-poor
stars into to the two populations that have been identified.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 559 1321 Properties, parameters, and population
identification of APOGEE DR13 metal-poor stars
--------------------------------------------------------------------------------
See also:
http://www.sdss.org/dr13/irspec/spectro_data : APOGEE Data Access Homne Page
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- APOGEE APOGEE Identifier, 2MHHMMSSss+DDMMSSs
20- 33 F14.10 deg RAdeg Right ascension (J2000)
35- 50 F16.12 deg DEdeg Declination (J2000)
52- 68 F17.13 deg GLON Galactic Longitude
70- 85 F16.12 deg GLAT Galactic Latitude
87- 92 F6.3 mag Jmag 2MASS J magnitude
94- 99 F6.3 mag Hmag 2MASS H magnitude
101-106 F6.3 mag Kmag 2MASS Ks magnitude
108-118 F11.6 km/s HRV Heliocentric radial velocity
120-129 F10.8 km/s e_HRV Uncertainty in HRV
131-137 F7.2 K Teff Effective surface temperature (1)
139-146 F8.6 [cm/s2] logg Surface gravity (1)
148-155 F8.6 km/s Vturb Microturbulent velocity
157-164 F8.5 km/s Vmacro Macroturbulent velocity
166-174 F9.6 [-] [Fe/H] ?=-9999.0 Log abundance, [Fe/H]
176-184 F9.7 [-] e_[Fe/H] ?=-9999.0 Uncertainty in [Fe_H]
186-196 F11.8 [-] [a/Fe] ?=-9999.0 Log abundance, [a/Fe]
198-206 F9.7 [-] e_[a/Fe] ?=-9999.0 Uncertainty in [a/Fe]
208-218 E11.7 [-] [C/Fe] ?=-9999.0 Log abundance, [C/Fe]
220-233 F14.8 [-] e_[C/Fe] ?=-9999.0 Uncertainty in [C/Fe]
235-245 E11.7 [-] [N/Fe] ?=-9999.0 Log abundance, [N/Fe]
247-260 F14.8 [-] e_[N/Fe] ?=-9999.0 Uncertainty in [N/Fe]
262-275 F14.8 [-] [O/Fe] ?=-9999.0 Log abundance, [O/Fe]
277-290 F14.8 [-] e_[O/Fe] ?=-9999.0 Uncertainty in [O/Fe]
292-302 E11.7 [-] [Mg/Fe] ?=-9999.0 Log abundance, [Mg/Fe]
304-313 F10.8 [-] e_[Mg/Fe] ?=-9999.0 Uncertainty in [Mg/Fe]
315-325 E11.7 [-] [Al/Fe] ?=-9999.0 Log abundance, [Al/Fe]
327-340 F14.8 [-] e_[Al/Fe] ?=-9999.0 Uncertainty in [Al/Fe]
342-352 E11.7 [-] [Si/Fe] ?=-9999.0 Log abundance, [Si/Fe]
354-367 F14.8 [-] e_[Si/Fe] ?=-9999.0 Uncertainty in [Si/Fe]
369-379 E11.7 [-] [K/Fe] ?=-9999.0 Log abundance, [K/Fe]
381-393 F13.7 [-] e_[K/Fe] ?=-9999.0 Uncertainty in [K/Fe]
395-408 F14.8 [-] [CA/Fe] ?=-9999.0 Log abundance, [Ca/Fe]
410-423 F14.8 [-] e_[CA/Fe] ?=-9999.0 Uncertainty in [Ca/Fe]
425-435 E11.7 [-] [CR/Fe] ?=-9999.0 Log abundance, [Cr/Fe]
437-450 F14.8 [-] e_[CR/Fe] ?=-9999.0 Uncertainty in [Cr/Fe]
452-465 F14.8 [-] [Mn/Fe] ?=-9999.0 Log abundance, [Mn/Fe]
467-480 F14.8 [-] e_[Mn/Fe] ?=-9999.0 Uncertainty in [Mn/Fe]
482-492 E11.7 [-] [Ni/Fe] ?=-9999.0 Log abundance, [Ni/Fe]
494-503 F10.8 [-] e_[Ni/Fe] ?=-9999.0 Uncertainty in [Ni/Fe]
505-515 E11.7 [-] [CN/Fe] ?=-9999.0 Log abundance, [CN/Fe]
517-529 E13.9 [-] e_[CN/Fe] ?=-9999.0 Uncertainty in [CN/Fe]
531-541 E11.7 [-] [CNO/Fe] ?=-9999.0 Log abundance, [CNO/Fe]
543-555 F13.7 [-] e_[CNO/Fe] ?=-9999.0 Uncertainty in [CNO/Fe]
557-559 A3 --- Pop [LMg HMg] Assigned Population (2)
--------------------------------------------------------------------------------
Note (1): Corrected according to the recommendations in the APOGEE DR13
documentation (http://www.sdss.org/dr13/irspec/parameters/) to remove
surface temperature and gravity trends found post-calibration.
Note (2): Assigned Population as follows:
LMg = low-[Mg/Fe] population
HMg = high-[Mg/Fe] population
--------------------------------------------------------------------------------
Acknowledgements:
Christian R. Hayes, crh7gs(at)virginia.edu
References:
Fernandez-Alvar et al. Paper II. 2018ApJ...852...50F 2018ApJ...852...50F Cat. J/ApJ/852/50
(End) Christian R. Hayes [Univ. Virginia], Patricia Vannier [CDS] 24-Jan-2018