J/A+A/695/A75 Mapping the Milky Way with Gaia Bp/Rp spectra (Ye+, 2025)
Mapping the Milky Way with Gaia Bp/Rp spectra.
I. Systematic flux corrections and atmospheric parameters for 68 million stars.
Ye X., Wu W., Allende Prieto C., Aguado D.S., Zhao J.,
Gonzalez Hernandez J.I., Rebolo R., Zhao G., Li Z., del Burgo C., Chen Y.
<Astron. Astrophys. 695, A75 (2025)>
=2025A&A...695A..75Y 2025A&A...695A..75Y (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Effective temperatures ; Abundances, [Fe/H] ; Optical
Keywords: catalogs - stars: fundamental parameters - Galaxy: stellar content
Abstract:
Gaia Bp/Rp spectrophotometry for over two hundred million stars has
been publicly released as part of Gaia Data Release 3 (DR3). These
data have great potential for mapping metallicity across the Milky
Way. Several recent studies have analyzed this data set to derive
atmospheric parameters and identify new metal-poor stars. In addition,
systematics in the fluxes of the Bp/Rp spectra have also been
identified and characterized.
We aim to construct an alternative catalog of atmospheric parameters
from Gaia Bp/Rp spectra by fitting them with synthetic spectra based
on model atmospheres, and provide corrections to the Bp/Rp fluxes
according to stellar colors, magnitudes, and interstellar extinction.
We use GaiaXPy to obtain calibrated spectra and apply FERR to match
the corrected Bp/Rp spectra with models and infer atmospheric
parameters. We train a neural network (NN) using stars in the Apache
Point Observatory Galactic Evolution Experiment (APOGEE) to predict
flux corrections as a function of wavelength for each target.
Based on the comparison with APOGEE parameters, we conclude that our
estimated parameters have systematic errors and uncertainties in Teff,
logg, and [M/H] about -38±167K, 0.05±0.40dex, and -0.12±0.19dex,
respectively, for stars in the range 4000≤Teff≤7000K. The corrected
Bp/Rp spectra show improved agreement with both models and Hubble
Space Telescope (HST) CALSPEC data. Our correction increases the
precision of the relative spectrophotometry of the Bp/Rp data from
3.2-3.7% to 1.2-2.4%. We also compare our results with other similar
catalogs from the literature and validate them using star clusters.
Finally, we have built a catalog of atmospheric parameters for stars
within 4000≤Teff≤7000K, comprising 68394431 sources, along with a
subset of 124 188 stars with [M/H]≤-2.5. Our catalogs and flux
correction code are publicly available.
Our results confirm that the Gaia Bp/Rp flux calibrated spectra show
systematic patterns as a function of wavelength that are tightly
related to colors, magnitudes, and extinction. Our optimization
algorithm can give us accurate atmospheric parameters of stars with a
clear and direct link to models of stellar atmospheres, and can be
used to efficiently search for extremely metal-poor (EMP) stars.
Description:
Gaia Data Release 3 provides over two hundred million stars with Gaia
Bp/Rp spectrophotometry, and systematics in the fluxes of Bp/Rp
spectra have also been characterized. We use GaiaXPy to calibrate
Bp/Rp spectra and apply Neural Network to correct the Bp/Rp fluxes
according to stellar colors, magnitudes, and interstellar extinction.
Then we use FERRE to fit Bp/Rp spectra with model spectra to derive
the atmospheric parameters. Our correction increases the precision of
the relative spectrophotometry of the Bp/Rp data and the estimation of
derived atmospheric parameters. Based on the comparison with APOGEE
parameters, we conclude that our estimated parameters have systematic
errors and uncertainties in Teff, logg, and [M/H] about -38±167K,
0.05±0.40dex, and -0.12±0.19dex, respectively, for stars in the
range 4000≤Teff≤7000K. A catalog of atmospheric parameters within
this effective temperature range has been built, comprising 68394431
sources, along with a subset of 124188 stars with [M/H]≤-2.5. More
details can be found in our corresponding paper.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
catalog.dat 68 68394431 General catalog containing atmospheric parameters
met-poor.dat 298 124188 Metal-poor subset of the general catalog
--------------------------------------------------------------------------------
See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: catalog.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaDR3 Name of each source, Gaia DR3 source_id
21- 28 F8.3 K Teff Effective temperature derived from the
corrected Bp/Rp spectra
30- 34 F5.3 [cm/s2] logg Surface gravity derived from the
corrected Bp/Rp spectra
36- 41 F6.3 [-] [Fe/H] Metallicity derived from the
corrected Bp/Rp spectra
43- 48 F6.3 [-] logchi2 log10 of the reduced chi^2%
50- 67 F18.16 % dfluxper Percentage of data points from
ΔFlux∼FluxXP-Fluxmodel
exceeding ±0.05
--------------------------------------------------------------------------------
Byte-by-byte Description of file: met-poor.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaDR3 Name of each source, Gaia DR3 source_id
21- 28 F8.3 K Teff Effective temperature derived from the
corrected Bp/Rp spectra
30- 34 F5.3 [cm/s2] logg Surface gravity derived from the corrected
Bp/Rp spectra
36- 41 F6.3 [-] [Fe/H] Metallicity derived from the corrected
Bp/Rp spectra
43- 48 F6.3 [-] logchi2 log10 of the reduced chi2
50- 67 F18.16 % dfluxper Percentage of data points from
ΔFlux∼FluxXP-Fluxmodel
exceeding ±0.05
69- 80 F12.10 mag AV V-band extinction AV calculated from the
two-dimensional SFD dust map
(Schlegel et al. 1998ApJ...500..525S 1998ApJ...500..525S,
Schlafly & Finkbeiner 2011ApJ...737..103S 2011ApJ...737..103S)
82-104 F23.19 deg RAdeg Right ascension (ICRS) at Ep=2016.0
from Gaia DR3
106-129 F24.20 deg DEdeg Declination (ICRS) at Ep=2016.0
from Gaia DR3
131-154 E24.17 mas/yr pmRA ? Proper motion in right ascension direction,
pmRA*cos(DE) from Gaia DR3
156-168 F13.10 mas/yr e_pmRA ? Standard error of pmRA from Gaia DR3
170-193 E24.17 mas/yr pmDE ? Proper motion in declination direction
from Gaia DR3
195-207 F13.10 mas/yr e_pmDE ? Standard error of pmDE from Gaia DR3
209-232 E24.17 mas plx ? Parallax from Gaia DR3
234-246 F13.10 mas e_plx ? Standard error of parallax from Gaia DR3
248-261 F14.9 km/s RV ? Radial velocity from Gaia DR3
263-275 F13.9 km/s e_RV ? Radial velocity error from Gaia DR3
277-286 F10.7 mag Gmag Gaia G-band mean magnitude from Gaia DR3
288-297 F10.8 mag BP-RP Gaia DR3 color BP-BP,
photbpmeanmag-photrpmeanmag
--------------------------------------------------------------------------------
Acknowledgements:
Xianhao Ye, yexianhao(at)nao.cas.cn
(End) Patricia Vannier [CDS] 05-Feb-2025