J/ApJ/889/63 Properties of Sgr Stars (Hayes+, 2020)
Metallicity and α-element abundance gradients along the
Sagittarius stream as seen by APOGEE.
Hayes C.R., Majewski S.R., Hasselquist S., Anguiano B., Shetrone M.,
Law D.R., Schiavon R.P., Cunha K., Smith V.V., Beaton R.L.,
Price-whelan A.M., Allende Prieto C., Battaglia G., Bizyaev D.,
Brownstein J.R., Cohen R.E., Frinchaboy P.M., Garcia-hernandez D.A.,
Lacerna I., Lane R.R., Meszaros S., Moni Bidin C., Munoz R.R.,
Nidever D.L., Oravetz A., Oravetz D., Pan K., Roman-lopes A., Sobeck J.,
Stringfellow G.
<Astrophys. J., 889, 63-63 (2020)>
=2020ApJ...889...63H 2020ApJ...889...63H (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Stars, population II ; Abundances ;
Photometry ; Radial velocities
Keywords: Sagittarius dwarf spheroidal galaxy - Milky Way stellar halo -
chemical abundances - Galaxy evolution - tidal tails -
Galaxy chemical evolution - Galaxy abundances - Stellar kinematics -
Stellar abundances - Dwarf galaxies
Abstract:
Using 3D positions and kinematics of stars relative to the Sagittarius
(Sgr) orbital plane and angular momentum, we identify 166 Sgr stream
members observed by the Apache Point Observatory Galactic Evolution
Experiment (APOGEE) that also have Gaia DR2 astrometry. This sample of
63/103 stars in the Sgr trailing/leading arm is combined with an
APOGEE sample of 710 members of the Sgr dwarf spheroidal core (385 of
them newly presented here) to establish differences of 0.6dex in
median metallicity and 0.1dex in [α/Fe] between our Sgr core
and dynamically older stream samples. Mild chemical gradients are
found internally along each arm, but these steepen when anchored by
core stars. With a model of Sgr tidal disruption providing estimated
dynamical ages (i.e., stripping times) for each stream star, we find a
mean metallicity gradient of 0.12±0.03dex/Gyr for stars
stripped from Sgr over time. For the first time, an [α/Fe]
gradient is also measured within the stream, at 0.02_/-0.01dex/Gyr
using magnesium abundances and at 0.04±0.01dex/Gyr^ using silicon,
which imply that the Sgr progenitor had significant radial abundance
gradients. We discuss the magnitude of those inferred gradients and
their implication for the nature of the Sgr progenitor within the
context of the current family of Milky Way satellite galaxies, and we
suggest that more sophisticated Sgr models are needed to properly
interpret the growing chemodynamical detail we have on the Sgr system.
Description:
The table contains the properties, stellar parameters, and chemical
abundances of the Sagittarius (Sgr) and Sgr stream stars reported by
the Apache Point Observatory Galactic Evolution Experiment (APOGEE) in
the 16th data release of the Sloan Digital Sky Survey as presented in
Table 1. This table also includes spectrophotometric distances from
the StarHorse code presented in Queiroz et al. (2018MNRAS.476.2556Q 2018MNRAS.476.2556Q),
Galactocentric positions and velocities of these stars with respect to
the Sgr coordinate system, and estimated dynamical ages of the Sgr
stream stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 463 876 Properties of Sgr Stars
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Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- APOGEE APOGEE identifier
20- 29 F10.6 deg RAdeg Right Ascension (J2000)
31- 40 F10.6 deg DEdeg Declination (J2000)
42- 59 F18.14 deg GLON Galactic longitude
61- 75 F15.11 deg GLAT Galactic latitude
77- 90 F14.10 deg lambdaSun Heliocentric Sagitarius longitude
92-104 F13.9 deg betaSun Heliocentric Sagitarius latitude
106-116 F11.7 deg lambdaGC Galactocentric Sagitarius longitude
118-130 F13.9 deg betaGC Galactocentric Sagitarius latitude
132-137 F6.3 mag Jmag 2MASS J band magnitude
139-144 F6.3 mag Hmag 2MASS H band magnitude
146-151 F6.3 mag Ksmag 2MASS Ks band magnitude
153-158 F6.2 kpc Dist Heliocentric distance
160-164 F5.2 kpc e_Dist Uncertainty in Dist
166-176 F11.6 km/s HRV DR16 Heliocentric radial velocity (1)
178-187 F10.8 km/s e_HRV Uncertainty in HRV (1)
189-194 F6.3 mas/yr pmRA Proper motion in RA, pmRA*cosDE
196-200 F5.3 mas/yr e_pmRA Uncertainty in pmRA
202-207 F6.3 mas/yr pmDE Proper motion in DE
209-213 F5.3 mas/yr e_pmDE Uncertainty in pmDE
215-220 F6.2 kpc Xs Sgr galactocentric cartesian Xs position
222-227 F6.2 kpc Ys Sgr galactocentric cartesian Ys position
229-234 F6.2 kpc Zs Sgr galactocentric cartesian Zs position
236-241 F6.2 kpc Rcys Gsr galactocentric cylindrical radius
243-249 F7.2 km/s Vxs Sgr galactocentric cartesian Xs velocity
251-258 F8.2 km/s Vys Sgr galactocentric cartesian Ys velocity
260-266 F7.2 km/s Vzs Sgr galactocentric cartesian Zs velocity
268-274 F7.2 km/s Vrs Sgr galactocentric cylindrical radial
velocity
276-282 F7.2 km/s Vphis Sgr galactocentric cylindrical rotational
velocity
284-291 F8.4 --- SNR Signal-to-Noise Ratio (2)
293-301 F9.4 K Teff DR16 effective surface temperature (1)
303-312 F10.6 K e_Teff Uncertainty in Teff (1)
314-325 F12.9 [cm/s2] log(g) DR16 surface gravity (1)
327-337 F11.9 [cm/s2] e_log(g) Uncertainty in log(g) (1)
339-348 F10.8 km/s Vturb DR16 microturbulent velocity (1)
350-359 F10.7 km/s Vmacro DR16 macroturbulent velocity (1)
361-371 F11.8 [Sun] [Fe/H] DR16 Metallicity (1)
373-384 F12.10 [Sun] e_[Fe/H] Uncertainty in [Fe/H] (1)
386-399 F14.11 [Sun] [Mg/Fe] log Mg/Fe abundance (1)
401-411 F11.9 [Sun] e_[Mg/Fe] Uncertainty in [Mg/Fe] (1)
413-425 F13.10 [Sun] [Si/Fe] log Si/Fe abundance (1)
427-438 F12.10 [Sun] e_[Si/Fe] Uncertainty in [Si/Fe] (1)
440-450 F11.5 Gyr Age Dynamical age; -9999 = Null (3)
452-457 A6 --- Mem Stream or core membership identifier (4)
459-463 A5 --- Study Source of membership with Sgr system (5)
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Note (1): Publicly released in SDSS-IV DR16.
Note (2): Of spectrum per pixel in APOGEE DR16.
Note (3): An Age of "-1" indicates the star is still bound to the Sgr dSph core.
Note (4): Stars are listed with a membership of "dsph" or "stream" depending on
if they are members of the Sgr dSph core, or the Sgr stream, respectively.
Note (5): Source of membership with Sgr system as follows:
Has17 = Hasselquist et al., 2017ApJ...845..162H 2017ApJ...845..162H
Has19 = Hasselquist et al., 2019ApJ...872...58H 2019ApJ...872...58H
Hay20 = This work.
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Acknowledgements:
Christian R. Hayes, crh7gs(at)virginia.edu
(End) Christian Hayes [Univ. Virginia], Patricia Vannier [CDS] 02-Jul-2020