J/AJ/161/100 Ages and alpha-abundances of population in K2 (Warfield+, 2021) ================================================================================ An intermediate-age Alpha-rich galactic population in K2. Warfield J.T., Zinn J.C., Pinsonneault M.H., Johnson J.A., Stello D., Elsworth Y., Garcia R.A., Kallinger T., Mathur S., Mosser B., Beaton R.L., Garcia-Hernandez D.A. =2021AJ....161..100W ================================================================================ ADC_Keywords: Surveys; Milky Way; Stars, ages; Stars, masses; Stars, giant; Abundances; Effective temperatures; Spectra, infrared Keywords: Stellar ages ; Stellar abundances ; Asteroseismology ; Galaxy evolution ; Galaxy formation ; Milky Way formation ; Galaxy stellar content ; Red giant stars ; Surveys Abstract: We explore the relationships between the chemistry, ages, and locations of stars in the Galaxy using asteroseismic data from the K2 mission and spectroscopic data from the Apache Point Galactic Evolution Experiment survey. Previous studies have used giant stars in the Kepler field to map the relationship between the chemical composition and the ages of stars at the solar circle. Consistent with prior work, we find that stars with high [{alpha}/Fe] have distinct, older ages in comparison to stars with low [{alpha}/Fe]. We provide age estimates for red giant branch (RGB) stars in the Kepler field, which support and build upon previous age estimates by taking into account the effect of {alpha}-enrichment on opacity. Including this effect for [{alpha}/Fe]-rich stars results in up to 10% older ages for low- mass stars relative to corrected solar mixture calculations. This is a significant effect that Galactic archeology studies should take into account. Looking beyond the Kepler field, we estimate ages for 735 RGB stars from the K2 mission, mapping age trends as a function of the line of sight. We find that the age distributions for low- and high-[{alpha}/Fe] stars converge with increasing distance from the Galactic plane, in agreement with suggestions from earlier work. We find that K2 stars with high [{alpha}/Fe] appear to be younger than their counterparts in the Kepler field, overlapping more significantly with a similarly aged low-[{alpha}/Fe] population. This observation may suggest that star formation or radial migration proceeds unevenly in the Galaxy. Description: The spectroscopic data for this work is from the sixteenth data release of the APOGEE survey. This survey has been collecting high-resolution infrared spectra for hundreds of thousand of stars throughout the Milky Way. The spectroscopic data in APOGEE DR16 was collected with the 2.5m Sloan Foundation Telescope at the Apache Point Observatory in New Mexico, USA and the 2.5m du Pont Telescope at Las Campanas Observatory in Chile as a part of SDSS-IV. APOGEE uses twin R~22500 H-band spectrographs. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table3.dat 450 805 Data for K2 campaigns 4, 6, and 7, including our ages table4.dat 190 2407 RGB stars in the Kepler field, including our ages -------------------------------------------------------------------------------- See also: V/133 : Kepler Input Catalog (Kepler Mission Team, 2009) I/337 : Gaia DR1 (Gaia Collaboration, 2016) I/345 : Gaia DR2 (Gaia Collaboration, 2018) III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020) J/A+A/410/527 : Abundances in the Galactic disk (Bensby+, 2003) J/ApJ/746/16 : Modelling the convection zone (van Saders+, 2012) J/ApJS/215/19 : APOKASC catalog of Kepler red giants (Pinsonneault+, 2014) J/MNRAS/445/2758 : KIC giants Bayesian dist. & extinctions (Rodrigues+, 2014) J/MNRAS/452/2127 : Fundamental parameters of Kepler stars (Silva Aguirre+,2015) J/AJ/151/144 : ASPCAP weights for 15 APOGEE chemic. elements (Garcia+,2016) J/A+A/597/A30 : Seismology & spectroscopy of CoRoGEE red giants (Anders+,2017) J/ApJ/844/102 : KIC star plxs from asteroseismology vs Gaia (Huber+, 2017) J/ApJ/835/173 : Kepler asteroseismic LEGACY sample. II. (Silva Aguirre+, 2017) J/ApJ/835/83 : K2 GAP data release. I. Campaign 1 (Stello+, 2017) J/ApJS/239/32 : APOKASC-2 catalog of Kepler evolved stars (Pinsonneault+,2018) J/AJ/156/18 : APOGEE DR14:Binary comp. of evolved stars (Price-Whelan+,2018) J/A+A/627/A173 : Abundances for 4 metal-poor stars (Valentini+, 2019) J/ApJS/251/23 : K2 GAP DR2: campaigns 4, 6 & 7 (Zinn+, 2020) J/A+A/645/A85 : Age dissection of the Milky Way discs (Miglio+, 2021) Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 11 F11.1 --- K2 K2 object ID 13- 13 I1 --- K2camp [4/7] K2 campaign field 15- 32 A18 --- APOGEE APOGEE object ID 34- 39 F6.2 Gyr Age [0.14/652] Median calculated stellar age 41- 46 F6.2 Gyr e_Age [0/457] Lower 1-sigma deviation on stellar age 48- 54 F7.2 Gyr E_Age [0/4998] Upper 1-sigma deviation on stellar age 56- 74 F19.15 deg RAdeg [51.6/291] Right Ascension (J2000) 76- 94 F19.15 deg DEdeg [-29.6/26.2] Declination (J2000) 96-123 A28 --- GAIA Object GAIA designation 125-133 F9.4 K Teff [3732/5304] Corrected effective temperature from APOGEE DR16 135-144 F10.6 K e_Teff [60/158] Uncertainty on Teff 146-153 F8.6 [cm/s2] logg [0.67/3.19] Corrected log surface gravity from APOGEE DR16 155-162 F8.6 [cm/s2] e_logg [0.03/0.12] Uncertainty on corrected logg 164-171 F8.6 [Sun] [alpha/M] [0.0002/0.39] Alpha abundance from APOGEE DR16 173-180 F8.6 [Sun] e_[alpha/M] [0.004/0.04] Uncertainty on [alpha/M] 182-190 F9.6 [Sun] [Fe/H] [-1.9/0.43] Metallicity from APOGEE DR16 192-199 F8.6 [Sun] e_[Fe/H] [0.005/0.04] Uncertainty on [Fe/H] 201-207 F7.3 uHz numax [6.57/207] Mean value of numax from all pipelines that returned a value from K2GAP 209-213 F5.3 uHz e_numax [0.024/2.66] Uncertainty on numax 215-220 F6.3 uHz dnu [1.07/16.6]? Mean value of dnu from all pipelines that returned a value from K2GAP 222-226 F5.3 uHz e_dnu [0/0.32]? Uncertainty on dnu 228-234 F7.3 uHz numax.COR [6.47/207]? Corrected numax from the COR pipeline from K2GAP 236-240 F5.3 uHz e_numax.COR [0.23/3.39]? Uncertainty on numax.COR 242-248 F7.3 uHz numax.A2Z [6.16/183]? Corrected numax from the A2Z pipeline from K2GAP 250-255 F6.3 uHz e_numax.A2Z [0.34/23]? Uncertainty on numax.A2Z 257-263 F7.3 uHz numax.BAM [7.07/185]? Corrected numax from the BAM pipeline from K2GAP 265-269 F5.3 uHz e_numax.BAM [0.18/3.8]? Uncertainty on numax.BAM 271-277 F7.3 uHz numax.CAN [7.78/176]? Corrected numax from the CAN pipeline from K2GAP 279-283 F5.3 uHz e_numax.CAN [0.25/3.4]? Uncertainty on numax.CAN 285-291 F7.3 uHz numax.BHM [9.94/181]? Corrected numax from the BHM pipeline from K2GAP 293-297 F5.3 uHz e_numax.BHM [0.19/3.3]? Uncertainty on numax.BHM 299-305 F7.3 uHz numax.SYD [7.44/207]? Corrected numax from the SYD pipeline from K2GAP 307-312 F6.3 uHz e_numax.SYD [0.12/36]? Uncertainty on numax.SYD 314-319 F6.3 uHz dnu.COR [1.05/16.4]? Corrected dnu from the COR pipeline from K2GAP 321-325 F5.3 uHz e_dnu.COR [0.05/0.23]? Uncertainty on dnu.COR 327-332 F6.3 uHz dnu.A2Z [1.23/15.5]? Corrected dnu from the A2Z pipeline from K2GAP 334-338 F5.3 uHz e_dnu.A2Z [0.01/0.87]? Uncertainty on dnu.A2Z 340-345 F6.3 uHz dnu.BAM [1.24/14.4]? Corrected dnu from the BAM pipeline from K2GAP 347-351 F5.3 uHz e_dnu.BAM [0.005/1.4]? Uncertainty on dnu.BAM 353-358 F6.3 uHz dnu.CAN [1.09/14]? Corrected dnu from the CAN pipeline from K2GAP 360-364 F5.3 uHz e_dnu.CAN [0.009/0.36]? Uncertainty on dnu.CAN 366-371 F6.3 uHz dnu.BHM [1.48/14.9]? Corrected dnu from the BHM pipeline from K2GAP 373-377 F5.3 uHz e_dnu.BHM [0.05/0.95]? Uncertainty on dnu.BHM 379-384 F6.3 uHz dnu.SYD [1.47/14.4]? Corrected dnu from the SYD pipeline from K2GAP 386-390 F5.3 uHz e_dnu.SYD [0.02/0.84]? Uncertainty on dnu.SYD 392-396 F5.3 [cm/s2] logg.SEIS [1.71/3.23] Asteroseismic log surface gravity 398-402 F5.3 [cm/s2] e_logg.SEIS [0.004/0.04] Uncertainty on logg.SEIS 404-408 F5.3 solMass Mass [0.3/3.67] Asteroseismic mass 410-414 F5.3 solMass e_Mass [0.03/1.1]? Uncertainty on Mass 416-420 F5.2 kpc Dist [0.33/11.4] Distance calculated from GAIA parallax from Bailer-Jones 2015 422-425 F4.2 kpc e_Dist [0.01/7.4] Uncertainty on Dist 427-432 F6.2 kpc X [-12.3/-1.04] Galactocentric X coordinate calculated with astropy 434-438 F5.2 kpc Y [-4.26/1.4] Galactocentric Y coordinate calculated with astropy 440-444 F5.2 kpc Z [-2.37/8.66] Galactocentric Z coordinate calculated with astropy 446-450 F5.2 kpc R [1.59/12.31] Galactocentric R coordinate calculated with astropy -------------------------------------------------------------------------------- Byte-by-byte Description of file: table4.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 8 I8 --- KIC MAST Kepler Input Catalog ID 10- 27 A18 --- APOGEE APOGEE object ID 29- 34 F6.2 Gyr Age [0.28/150] Median calculated stellar age 36- 40 F5.2 Gyr e_Age [0.02/88] Lower 1-sigma deviation on Age 42- 47 F6.2 Gyr E_Age [0.03/400] Upper 1-sigma deviation on Age 49- 53 F5.2 Gyr Age.APO [0.4/17.7] Calculated stellar age from Pinsonneault et al. 2018 55- 63 F9.4 K Teff [3942/5239] Corrected effective temperature from APOGEE DR16 65- 74 F10.6 K e_Teff [65/130] Uncertainty on Teff 76- 83 F8.6 [cm/s2] logg [1.41/3.35] Corrected log surface gravity from APOGEE DR16 85- 92 F8.6 [cm/s2] e_logg [0.02/0.12] Uncertainty on logg 94-101 F8.6 [Sun] [alpha/M] [6e-06/0.39] Alpha abundance from APOGEE DR16 103-110 F8.6 [Sun] e_[alpha/M] [0.004/0.03] Uncertainty on [alpha/M] 112-120 F9.6 [Sun] [Fe/H] [-2.15/0.45] Metallicity from APOGEE DR16 122-129 F8.6 [Sun] e_[Fe/H] [0.005/0.03] Uncertainty on [Fe/H] 131-137 F7.3 uHz numax [4.78/249] Mean value of numax from all pipelines from APOKASC2 139-143 F5.3 uHz e_numax [0.05/7.01] Uncertainty on numax 145-150 F6.3 uHz dnu [0.74/19.2] Mean value of dnu from all pipelines from APOKASC2, with our f_dnu_ correction 152-156 F5.3 uHz e_dnu [0.004/0.5] Uncertainty on dnu 158-162 F5.3 solMass Mass [0.53/3.4] Asteroseismic mass 164-168 F5.3 solMass e_Mass [0.03/1.1] Uncertainty on Mass 170-174 F5.2 kpc X [-8.26/-5.69] Galactocentric X coordinate calculated with astropy 176-179 F4.2 kpc Y [0.19/9.18] Galactocentric Y coordinate calculated with astropy 181-184 F4.2 kpc Z [0.06/2.58] Galactocentric Z coordinate calculated with astropy 186-190 F5.2 kpc R [7.73/11.09] Galactocentric R coordinate calculated with astropy -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS], Coralie Fix [CDS], 13-Apr-2021