J/MNRAS/489/2079 Calibration of distances with deep learning (Leung+, 2019)
Simultaneous calibration of spectro-photometric distances and the Gaia DR2
parallax zero-point offset with deep learning.
Leung H.W., Bovy J.
<Mon. Not. R. Astron. Soc., 489, 2079-2096 (2019)>
=2019MNRAS.489.2079L 2019MNRAS.489.2079L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, distances ; Stars, fundamental ; Spectra, infrared ;
Models
Keywords: methods: data analysis - techniques: spectroscopic - astrometry -
stars: distances - stars: fundamental parameters - Galaxy: structure
Abstract:
Gaia measures the five astrometric parameters for stars in the Milky
Way, but only four of them (positions and proper motion, but not
distance) are well measured beyond a few kpc from the Sun. Modern
spectroscopic surveys such as APOGEE cover a large area of the Milky
Way disc and we can use the relation between spectra and luminosity to
determine distances to stars beyond Gaia's parallax reach. Here, we
design a deep neural network trained on stars in common between Gaia
and APOGEE that determines spectro-photometric distances to APOGEE
stars, while including a flexible model to calibrate parallax
zero-point biases in Gaia DR2. We determine the zero-point offset to
be -52.3±2.0µas when modelling it as a global constant, but also
train a multivariate zero-point offset model that depends on G,
GBP-GRP colour, and Teff and that can be applied to all ∼58
million stars in Gaia DR2 within APOGEE's colour-magnitude range and
within APOGEE's sky footprint. Our spectro-photometric distances are
more precise than Gaia at distances ≳2kpc from the Sun. We release a
catalogue of spectro-photometric distances for the entire APOGEE DR14
data set which covers Galactocentric radii 2kpc~<R~<19kpc; ∼150000
stars have <10 per cent uncertainty, making this a powerful sample to
study the chemo-dynamical structure of the disc. We use this sample to
map the mean [Fe/H] and 15 abundance ratios [X/Fe] from the Galactic
Centre to the edge of the disc. Among many interesting trends, we find
that the bulge and bar region at R~<5kpc clearly stands out in [Fe/H]
and most abundance ratios.
Description:
The spectroscopic data in this work come from Data Release 14 (DR14;
Abolfathi et al. 2018ApJS..235...42A 2018ApJS..235...42A; Holtzman et al.
2018AJ....156..125H 2018AJ....156..125H; Jonsson et al. 2018AJ....156..126J 2018AJ....156..126J, Cat.
J/AJ/156/126) of the APO Galactic Evolution Experiment (APOGEE;
Majewski et al. 2017AJ....154...94M 2017AJ....154...94M, Cat. III/284).
We use data from the second data release (DR2; Gaia Collaboration
2018A&A...616A...1G 2018A&A...616A...1G, Cat. I/345) to train the model and calibrate the
Gaia DR2 zero-point offset. Gaia DR2 contains 1.3 billion source with
5 astrometric parameters (positions, proper motions, parallaxes). We
match Gaia sources to APOGEE stars using a celestial position
cross-match with a tolerance of 2arcsec. Out of 277371 stars in APOGEE
DR14, 265761 have both a Gaia DR2 parallax and a 2MASS Ks band
apparent magnitude.
We create one training set and one test set from the APOGEE DR14
spectra. Both data sets consist of continuum-normalized APOGEE spectra
and Gaia DR2 parallaxes. The training set contains 35112 stars, while
the test set has 33468 stars. The main difference between the training
and test set is in the SNR. The training is constructed using only
high-SNR spectra with SNR>200, whereas the test set consists only of
low-SNR spectra with SNR<200.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 309 277371 astroNN Apogee DR14 Distance data
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See also:
J/AJ/156/126 : Stellar parameters & abund. from BACCHUS analysis
(Jonsson+, 2018)
III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Name APOGEE star name (2MHHMMSSss+DDMMSSs or
APHHMMSSss+DDMMSSs)
20- 23 I4 --- Loc [1/5203] Field location identifier
25- 34 F10.6 deg RA2deg ?=0 Right ascension (J2000) from APOGEE DR14
36- 45 F10.6 deg DE2deg ?=0 Declination (J2000) from APOGEE DR14
47- 59 F13.6 pc dist ?=-9999 NN inverse parallax
61 A1 --- f_dist [*] Flag on dist (1)
63- 76 F14.7 pc medist ?=-9999 NN inverse parallax model uncertainty
78 A1 --- f_medist [*] Flag on dist (1)
80- 93 F14.7 pc e_dist ?=-9999 NN inverse parallax total uncertainty
95 A1 --- fedist [*] Flag on dist (1)
97-108 F12.6 mas plx ?=-9999 NN parallax
110-122 F13.7 mas meplx ?=-9999 NN parallax model uncertainty
124-137 F14.7 mas e_plx ?=-9999 NN parallax total uncertainty
139 A1 --- feplx [*] Flag on dist (1)
141-153 F13.6 mag fakemag NN pseudo-luminosity Lpseudo
155-168 F14.7 mag e_fakemag ?=-9999 Error on fakemag
170 A1 --- fefakemag [*] Flag on dist (1)
172-184 F13.6 pc wdist ?=-9999 Inverse variance weighted combined
distance from NN and Gaia (2)
186 A1 --- f_wdist [*] Flag on dist (1)
188-201 F14.7 pc e_wdist ?=-9999 Error on wdist
203 A1 --- fewdist [*] Flag on dist (1)
205-216 F12.6 deg RAdeg ?=-9999 Right ascension (ICRS) at
Ep=2015.5 (3)
218-229 F12.6 deg DEdeg ?=-9999 Declination (ICRS) at Ep=2015.5 (3)
231-242 F12.6 mas/yr pmRA ?=-9999 Proper motion in right ascension (3)
244-256 F13.7 mas/yr e_pmRA ?=-9999 Error on pmRA
258-269 F12.6 mas/yr pmDE ?=-9999 Proper motion in declination (3)
271-283 F13.7 mas/yr e_pmDE ?=-9999 Error on pmDE
285-296 F12.6 mag Gmag ?=-9999 Gaia DR2 G-band magnitude (3)
298-309 F12.6 mag BP-RP ?=-9999 Gaia DR2 BP-RP colour (3)
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Note (1): Flag as follows:
* = Values >1000000 were truncated to 999999
Note (2): Calculated based on the NN distance and ϖGaia+52µas
Note (3): Values taken from Gaia DR2 (Gaia collaboration, 2018A&A...616A...1G 2018A&A...616A...1G,
Cat. I/345)
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 09-Jan-2023