J/ApJ/823/114 The Cannon: a new approach to determine masses (Ness+, 2016)
Spectroscopic determination of masses (and implied ages) for red giants.
Ness M., Hogg D.W., Rix H.-W., Martig M., Pinsonneault M.H., Ho A.Y.Q.
<Astrophys. J., 823, 114 (2016)>
=2016ApJ...823..114N 2016ApJ...823..114N (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Stars, masses ; Stars, ages ; Abundances ;
Spectra, infrared
Keywords: Galaxy: stellar content; methods: data analysis;
methods: statistical; stars: evolution;
stars: fundamental parameters; techniques: spectroscopic
Abstract:
The mass of a star is arguably its most fundamental parameter. For red
giant stars, tracers luminous enough to be observed across the Galaxy,
mass implies a stellar evolution age. It has proven to be extremely
difficult to infer ages and masses directly from red giant spectra
using existing methods. From the Kepler and APOGEE surveys, samples of
several thousand stars exist with high-quality spectra and
asteroseismic masses. Here we show that from these data we can build a
data-driven spectral model using The Cannon, which can determine
stellar masses to ∼0.07dex from APOGEE DR12 spectra of red giants;
these imply age estimates accurate to ∼0.2dex (40%). We show that The
Cannon constrains these ages foremost from spectral regions with CN
absorption lines, elements whose surface abundances reflect
mass-dependent dredge-up. We deliver an unprecedented catalog of 70000
giants (including 20000 red clump stars) with mass and age estimates,
spanning the entire disk (from the Galactic center to R∼20kpc). We
show that the age information in the spectra is not simply a corollary
of the birth-material abundances [Fe/H] and [α/Fe], and that,
even within a monoabundance population of stars, there are age
variations that vary sensibly with Galactic position. Such stellar age
constraints across the Milky Way open up new avenues in Galactic
archeology.
Description:
We make use of The Cannon (Ness et al. 2015, J/ApJ/808/16), which is a
data-driven method for determining stellar parameters and abundances
(see section 2.1 for further explanations).
APOGEE is a Sloan Digital Sky Survey (SDSS) (Eisenstein et al.
2011AJ....142...72E 2011AJ....142...72E) infrared survey of the Milky Way disk, bulge, and
halo and has provided H-band spectra (1500-1700nm) of about 150000
stars in the public data release DR12. The three labels of Teff, logg,
and [Fe/H] delivered with The Cannon were demonstrated in Ness et al.
(2015, J/ApJ/808/16). In this work we train on and then determine two
additional labels: [α/Fe] and mass.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 124 73180 Stellar parameters, masses and ages as determined
by The Cannon for APOGEE giants
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See also:
J/ApJ/819/2 : APOGEE kinematics. I. Galactic bulge overview (Ness+, 2016)
J/ApJS/221/24 : SDSS-III APOGEE H-band spectral line lists (Shetrone+, 2015)
J/MNRAS/452/2127 : Fundamental param. of Kepler stars (Silva Aguirre+, 2015)
J/ApJ/808/16 : The Cannon: new approach to determine abundances (Ness+, 2015)
J/A+A/577/A9 : Sc, V, Mn, and Co in Milky Way stars (Battistini+, 2015)
J/ApJS/215/19 : APOKASC catalog of Kepler red giants (Pinsonneault+, 2014)
J/ApJ/794/125 : IN-SYNC. I. APOGEE stellar parameters (Cottaar+, 2014)
J/AJ/146/133 : Stellar parameters from SDSS-III APOGEE DR10 (Meszaros+, 2013)
J/A+A/549/A147 : Abundances of microlensed Bulge dwarf stars V. (Bensby+, 2013)
J/A+A/530/A138 : Geneva-Copenhagen survey re-analysis (Casagrande+, 2011)
http://www.sdss3.org/ : SDSS-III home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- Type Red giant type (1)
4- 5 A2 --- --- [2M]
6- 21 A16 --- 2MASS 2MASS identifier (HHMMSSss+DDMMSSs; J2000)
23- 29 F7.2 K Teff [4054/5120] Effective temperature
31- 35 F5.3 [cm/s2] log(g) [1.3/3.4] log surface gravity
37- 42 F6.3 [Sun] [Fe/H] [-0.9/0.4] log Fe/H number abundance (2)
44- 49 F6.3 [Sun] [a/Fe] [-0.03/0.3] log α/Fe number abundance (2)
51- 61 E11.4 [Msun] lnM [-1.1/1.9] ln stellar mass (3)
63- 73 E11.4 [Gyr] lnAge [-2.8/5.3] ln stellar age (4)
75- 79 F5.2 --- chi2 [0.1/24.3] The χ2 statistic (5)
81- 87 F7.3 kpc Rgal [-13.25/21.77] Galactocentric radius
89- 94 F6.3 K e_Teff [0.7/73] Uncertainty in Teff (6)
96-100 F5.3 [cm/s2] e_log(g) [0.004/0.2] Uncertainty in log(g) (6)
102-106 F5.3 [Sun] e_[Fe/H] [0.001/0.06] Uncertainty in [Fe/H] (6)
108-112 F5.3 [Sun] e_[a/Fe] [0.001/0.03] Uncertainty in [a/Fe] (6)
114-118 F5.3 [Msun] e_lnM [0.006/0.3] Uncertainty in lnM (6)
120-124 F5.3 [Gyr] e_lnAge [0.01/0.6] Uncertainty in lnAge (6)
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Note (1): Star type as follows:
I = Part I: red giant (54174 sources).
II = Part II: red clump (19906 sources).
The Cannon for 54174 red giant stars and 19906 red clump stars
(identified by Bovy et al. (2014ApJ...790..127B 2014ApJ...790..127B)) in APOGEE's data
release DR12.
Note (2): Relative to solar.
Note (3): Derived from training on mass derived from seismic scaling
relations (see text).
Note (4): Derived from training on age from Martig et al. (2016MNRAS.456.3655M 2016MNRAS.456.3655M).
Note (5): An indicator of the fidelity of the stellar labels.
Note (6): The errors quoted are the formal errors from The Cannon for
the uncertainties on the labels (see Figures 1 and 11).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 08-Aug-2016