2021A&A...649A..13M


Query : 2021A&A...649A..13M

2021A&A...649A..13M - Astronomy and Astrophysics, volume 649A, 13-13 (2021/5-1)

Validation of the accuracy and precision of Gaia EDR3 parallaxes with globular clusters.

MAIZ APELLANIZ J., PANTALEONI GONZALEZ M. and BARBA R.H.

Abstract (from CDS):


Context. The recent early third data release (EDR3) from the Gaia mission has produced parallaxes for 1.468 x 109 sources with better quality than those reported in the previous data release. Nevertheless, there are calibration issues with the data that require corrections to the published values and uncertainties.
Aims. We want to properly characterize the behavior of the random and systematic uncertainties of the Gaia EDR3 parallaxes in order to maximize the precision of the derived distances without compromising their accuracy. We also aim to provide a step-by-step procedure for the calculation of distances to stars and stellar clusters when using these parallaxes.
Methods. We reanalyzed some of the data presented in the calibration papers for quasar and Large Magellanic Cloud (LMC) parallaxes and combine these results with measurements for six bright globular clusters. We calculated the angular covariance of EDR3 parallaxes at small separations (up to a few degrees) based on the LMC results and combined it with the results for larger angles using quasars to obtain an approximate analytical formula for the angular covariance over the whole sky. The results for the six globular clusters were used to validate the parallax bias correction as a function of magnitude, color, and ecliptic latitude and to determine the multiplicative constant k used to convert internal uncertainties to external ones.
Results. The angular covariance at zero separation is estimated to be 106µas2, yielding a minimum (systematic) uncertainty for EDR3 parallaxes of 10.3µas for individual stars or compact stellar clusters. This value can be slightly reduced for globular clusters that span ≥30' after considering the behavior of the angular covariance of the parallaxes for small separations. A recent parallax bias correction is found to work quite well, except perhaps for the brighter magnitudes, where improvements may be possible. The value of k is found to be 1.1-1.7 and to depend on G. We find that stars with moderately large values of the renormalized unit weight error can still provide useful parallaxes, albeit with larger values of k. We give accurate and precise Gaia EDR3 distances to the six globular clusters, and for the specific case of 47 Tuc we are able to beat the angular covariance limit through the use of the background Small Magellanic Cloud as a reference and derive a high-precision distance of 4.53±0.06kpc. Finally, a recipe for the derivation of distances to stars and stellar clusters using Gaia EDR3 parallaxes is given.

Abstract Copyright: © ESO 2021

Journal keyword(s): astrometry - globular clusters: general - methods: data analysis - parallaxes - stars: distances - surveys

Simbad objects: 14

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Number of rows : 14
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 NGC 104 GlC 00 24 05.359 -72 04 53.20   5.78 4.09     ~ 3736 0
2 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 11880 1
3 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 10314 1
4 M 33 GiG 01 33 50.8965749232 +30 39 36.630403128 6.17 6.27 5.72     ~ 5524 1
5 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 16153 1
6 NGC 2264 OpC 06 40 52 +09 52.6           ~ 1693 0
7 NGC 5139 GlC 13 26 47.28 -47 28 46.1   6.12 5.33     ~ 3252 0
8 M 5 GlC 15 18 33.22 +02 04 51.7   7.34 5.95     ~ 1879 0
9 M 13 GlC 16 41 41.634 +36 27 40.75     5.8     ~ 2107 0
10 NGC 6397 GlC 17 40 42.09 -53 40 27.6   7.39 5.17     ~ 1885 1
11 NGC 6752 GlC 19 10 52.11 -59 59 04.4   6.96 6.28     ~ 1902 0
12 Cl Collinder 419 OpC 20 18 08 +40 43.9           ~ 37 0
13 NAME Galactic Bulge reg ~ ~           ~ 3895 0
14 NAME Local Group GrG ~ ~           ~ 7717 0

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2022.08.10-06:59:30

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