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Title: Simultaneous calibration of spectro-photometric distances and the Gaia DR2 parallax zero-point offset with deep learning

Abstract

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 $$-52.3 \pm 2.0\, \mu \mathrm{as}$$ 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 $${\gtrsim} 2\, \mathrm{kpc}$$ from the Sun. We release a catalogue of spectro-photometric distances for the entire APOGEE DR14 data set which covers Galactocentric radii $$2\, \mathrm{kpc} \lesssim R \lesssim 19\, \mathrm{kpc}$$; $${\approx} 150\, 000$$ stars have $${\lt} 10{{\ \rm per\ cent}}$$ 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 $$R \lesssim 5\, \mathrm{kpc}$$ clearly stands out in [Fe/H] and most abundance ratios.

Authors:
ORCiD logo [1]; ORCiD logo [2]
  1. Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario M5S 3H4, Canada
  2. Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario M5S 3H4, Canada, Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario M5S 3H4, Canada
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1560687
Resource Type:
Published Article
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Name: Monthly Notices of the Royal Astronomical Society Journal Volume: 489 Journal Issue: 2; Journal ID: ISSN 0035-8711
Publisher:
Oxford University Press
Country of Publication:
United Kingdom
Language:
English

Citation Formats

Leung, Henry W., and Bovy, Jo. Simultaneous calibration of spectro-photometric distances and the Gaia DR2 parallax zero-point offset with deep learning. United Kingdom: N. p., 2019. Web. doi:10.1093/mnras/stz2245.
Leung, Henry W., & Bovy, Jo. Simultaneous calibration of spectro-photometric distances and the Gaia DR2 parallax zero-point offset with deep learning. United Kingdom. doi:10.1093/mnras/stz2245.
Leung, Henry W., and Bovy, Jo. Tue . "Simultaneous calibration of spectro-photometric distances and the Gaia DR2 parallax zero-point offset with deep learning". United Kingdom. doi:10.1093/mnras/stz2245.
@article{osti_1560687,
title = {Simultaneous calibration of spectro-photometric distances and the Gaia DR2 parallax zero-point offset with deep learning},
author = {Leung, Henry W. and Bovy, Jo},
abstractNote = {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 $-52.3 \pm 2.0\, \mu \mathrm{as}$ 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 ${\gtrsim} 2\, \mathrm{kpc}$ from the Sun. We release a catalogue of spectro-photometric distances for the entire APOGEE DR14 data set which covers Galactocentric radii $2\, \mathrm{kpc} \lesssim R \lesssim 19\, \mathrm{kpc}$; ${\approx} 150\, 000$ stars have ${\lt} 10{{\ \rm per\ cent}}$ 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 $R \lesssim 5\, \mathrm{kpc}$ clearly stands out in [Fe/H] and most abundance ratios.},
doi = {10.1093/mnras/stz2245},
journal = {Monthly Notices of the Royal Astronomical Society},
number = 2,
volume = 489,
place = {United Kingdom},
year = {2019},
month = {8}
}

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