GaiaEarly Data Release 3

Abstract

Context. Gaia Early Data Release 3 (Gaia EDR3) provides accurate astrometry for about 1.6 million compact (QSO-like) extragalactic sources, 1.2 million of which have the best-quality five-parameter astrometric solutions. Aims. The proper motions of QSO-like sources are used to reveal a systematic pattern due to the acceleration of the solar systembarycentre with respect to the rest frame of the Universe. Apart from being an important scientific result by itself, the acceleration measured in this way is a good quality indicator of the Gaia astrometric solution. Methods. Theeffect of the acceleration was obtained as a part of the general expansion of the vector field of proper motions in vector spherical harmonics (VSH). Various versions of the VSH fit and various subsets of the sources were tried and compared to get the most consistent result and a realistic estimate of its uncertainty. Additional tests with the Gaia astrometric solution were used to get a better idea of the possible systematic errors in the estimate. Results. Our best estimate of the acceleration based on Gaia EDR3 is (2.32 ± 0.16) × 10−10 m s−2 (or 7.33 ±0.51 km s−1 Myr−1) towards α = 269.1° ± 5.4°, δ = −31.6° ± 4.1°, corresponding to a proper motion amplitude of 5.05 ±0.35 μas yr−1. This is in good agreement with the acceleration expected from current models of the Galactic gravitational potential. We expect that future Gaia data releases will provide estimates of the acceleration with uncertainties substantially below 0.1 μas yr−1.

A Dynamical Mass Estimate from the Magellanic Stream

“…with pulsar timing (Chakrabarti et al 2021), and in the future with extreme precision radial velocity measurements (Chakrabarti et al 2020), as the LMC is expected to produce the largest contributor to the measurement of the solar system acceleration (Gaia Collaboration et al 2020). Our fiducial LMC mass is consistent with the measured solar system acceleration from Gaia EDR3 data (Klioner et al 2021). Ultimately, by using pulsar timing observations of pulsars within the Magellanic Clouds, we could directly constrain the potential of the Milky Way out to large distances, e.g., with the planned MeerKAT survey (Titus et al 2020).…”

“…This yields a somewhat larger mass than what is used in our fiducial model. The mass selected here is consistent with the estimated solar system acceleration from Gaia EDR3 data (Klioner et al 2021), and our masses are consistent with the selections made there. The LMC is one of the largest contributors to the acceleration of our solar system, and the selected LMC mass produces accelerations that are consistent with measurements of this acceleration.…”

Chandra revisits WR48a: testing colliding wind models in massive binaries

“…We have to keep in mind that the Gaia DR2 (Data Release 2) distance to this object is not tightly constrained: 2.70 +1.23 −0.67 kpc (Bailer-Jones et al 2018); 2.27 +0.92 −0.57 kpc (Rate & Crowther 2020). Also, we might expect some appreciable changes in the distance estimates of WR 48a based on the parallax values of 0.3451 ± 0.1082 mas (DR2; Gaia Collaboration et al 2018) and 0.1933 ± 0.0462 mas (Gaia EDR3, Early Data Release 3; Gaia Collaboration et al 2021).…”

Measuring the Streaming motion in the Milky Way disc with Gaia EDR3 +

“…As demonstration of the high quality astrometry from Gaia EDR3, Gaia Collaboration et al (2021c) used the apparent proper motion of about 1.6 million quasar-like objects, to directly determine that the centripetal acceleration at the Solar System is 𝛼 = 5.05 ± 0.35𝜇as 𝑦𝑟 −1 . Right after, Bovy (2020) neatly combined this result, with typical values for 𝑅 and Ω Sgr (proper motion of Sgr A*), to derive 𝑉 = 8.0 ± 8.4 km s −1 .…”