J/A+A/684/A29 Radial velocities from Gaia BP/RP spectra (Verberne+, 2024)
Radial velocities from Gaia BP/RP spectra.
Verberne S., Koposov S.E., Rossi E.M., Marchetti T., Kuijken K., Penoyre Z.
<Astron. Astrophys. 684, A29 (2024)>
=2024A&A...684A..29V 2024A&A...684A..29V (SIMBAD/NED BibCode)
ADC_Keywords: Stars, high-velocity ; Radial velocities ; Optical
Keywords: techniques: radial velocities - catalogs -
stars: kinematics and dynamics - Galaxy: kinematics and dynamics
Abstract:
The Gaia mission has provided us full astrometric solutions for over
1.5B sources. However, only the brightest 34M of those have radial
velocity measurements. As a proof of concept, this paper aims to close
that gap, by obtaining radial velocity estimates from the low-
resolution BP/RP spectra that Gaia now provides. These spectra are
currently published for about 220M sources, with this number
increasing to the full ∼2B Gaia sources with Gaia Data Release 4.
To obtain the radial velocity measurements, we fit Gaia BP/RP spectra
with models based on a grid of synthetic spectra, with which we obtain
the posterior probability on the radial velocity for each object. Our
measured velocities show systematic biases that depend mainly on
colours and magnitudes of stars. We correct for these effects by using
external catalogues of radial velocity measurements.
We present in this work a catalogue of about 6.4M sources with our
most reliable radial velocity measurements and uncertainties <300 km
s^-1 obtained from the BP/RP spectra. About 23% of these have no
previous radial velocity measurement in Gaia RVS. Furthermore, we
provide an extended catalogue containing all 125M sources for which we
were able to obtain radial velocity measurements. The latter
catalogue, however, also contains a fraction of measurements for which
the reported radial velocities and uncertainties are inaccurate.
Although typical uncertainties in the catalogue are significantly
higher compared to those obtained with precision spectroscopy
instruments, the number of potential sources for which this method can
be applied is orders of magnitude higher than any previous radial
velocity catalogue. Further development of the analysis could
therefore prove extremely valuable in our understanding of Galactic
dynamics.
Description:
Radial velocity measurements for a total of ∼125M stars from Gaia
BP/RP spectra.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
main.dat 70 6367355 Main catalogue
extend.dat 178 125145490 Extended Catalogue
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: main.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Gaia DR3 source_id
21- 35 F15.11 deg RAdeg Rigth ascension (ICRS) at Ep=2016.0
37- 51 F15.11 deg DEdeg Declination (ICRS) at Ep=2016.0
53- 61 F9.3 km/s RV Radial velocity
63- 70 F8.4 km/s e_RV Radial velocity error
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Byte-by-byte Description of file: extend.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Gaia DR3 source_id
21- 35 F15.11 deg RAdeg Rigth ascension (ICRS) at Ep=2016.0
37- 51 F15.11 deg DEdeg Declination (ICRS) at Ep=2016.0
53- 61 F9.3 km/s RV Calibrated XP radial velocity
63- 74 E12.6 km/s e_RV ?=- Calibrated XP radial velocity error
76- 84 F9.3 km/s Offset ?=- Offset applied to the original radial
velocity measurement during calibration
86- 95 F10.3 --- UnderFactor ?=- Underestimation factor applied to the
measured uncertainties
97-108 E12.6 km/s NoiseFloor ?=- Noise floor applied to the measured
uncertainties
110-121 E12.6 --- CMDoutfrac ?=- CMD outlier fraction of stars in
colour-mag-extinction(-log g) range that are
considered outliers
123-127 F5.3 --- BadMeas Probability of a bad measurement based on
the Random Forest Classifier
129-130 I2 --- warning Warning flag to indicate potentially
problematic radial velocity measurements
132-136 I5 K Teff Effective temperature of the best fit model
for radial velocity
138-146 F9.6 [cm/s2] logg Surface gravity of the best fit model for
radial velocity
148-156 F9.6 [-] [Fe/H] Metallicity of the best fit model for
radial velocity
158-169 E12.6 --- rchi2 Reduced chi squared of our best fit model
171-178 F8.3 --- Skew Skewness of the radial velocity posterior
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Acknowledgements:
Sill Verbern, verberne(at)strw.leidenuniv.nl
(End) Patricia Vannier [CDS] 31-Jan-2024