Gaia Data Release 3

Gaia Data Release 3 in numbers. Image credit: ESA/Gaia/DPAC. License: CC BY-SA 3.0 IGO.

Gaia Data Release 3 (Gaia DR3) was published on 13 June 2022. The data is available through the Gaia Archive. The Gaia DR3 catalogue builds upon the Early Data Release 3 (released on 3 December 2020) and combines, for the same stretch of time, these already-published data products with numerous new data products such as extended objects and non-single stars.

Contents of Gaia DR3

The set of data released as Gaia Early Data Release 3:

• The full astrometric solution (5 parameters) — positions on the sky (α, δ), parallaxes, and proper motions — for around 1.46 billion (1.46 10⁹) sources, with a limiting magnitude of about G ≈ 21 and a bright limit of about G ≈ 3. The astrometric solution is accompanied with some new quality indicators, like RUWE, and source image descriptors.
• The full astrometric solution has been done as 5-parameter solution for 585 million sources and as 6-parameter solution for 882 million sources. In the 6-parameter solution, the additional fitted quantity is the so-called pseudo-colour that had to be included for sources without high-quality colour information. 
• In addition, two-parameters solutions — positions on the sky (α, δ) — for around 344 million additional sources.
• G magnitudes for around 1.806 billion sources(with the known issue present in EDR3 corrected in Gaia DR3).
• G_BP and G_RP magnitudes for around 1.54 billion and 1.55 billion sources, respectively.

In Gaia Data Release 3 (Gaia DR3), the above set of data is complemented with new products released on 13 June 2022 (EAS presentation A. Vallenari):

• Object classifications for 1.59 billion sources and astrophysical parameters (T_eff, logg, [M/H], A_G, distance, etc.) from BP/RP spectra for 470 million objects, including MCMC samples for most sources with astrophysical parameters (EAS presentation O.Creevey). Other astrophysical parameters from the BP/RP spectra include:
  • Spectral types (217 million stars) and emission-line star classifications (57,000 stars);
  • Spectroscopic parameters for 2.3 million hot stars, 94,000 ultra-cool stars, activity index for 1.3 million cool stars, and H-alpha emission for 235 million stars;
  • Evolutionary parameters (mass and age) for 128 million stars;
  • Astrophysical parameters for 348 million objects based on the assumption of an unresolved binary in the BP/RP spectra;
  • Self-organised map (outlier) analysis based on 56 million sources with the weakest object classifications.
• Astrophysical parameters (T_eff, logg, [M/H], [X/M] for 12 elements, etc.) from RVS spectra for 5.5 million objects, including diffuse interstellar bands for 472,000 objects.
• All-sky total galactic extinction maps at 4 different spatial resolutions (HEALPix levels 6, 7, 8, and 9).
• Mean BP/RP spectra for 219 million sources, most of them with G < 17.6 mag (EAS Presentation F. De Angeli).
• Mean RVS spectra for about 1 million well-behaved objects (EAS presentation P. Sartoretti).
• Mean radial velocities for about 33 million stars and mean G_RVS magnitudes for 32 million objects with G_RVS <~ 14 mag and an effective temperature (T_eff) in the range of about 3100 to 14,500 K (EAS presentation P. Sartoretti).
• Rotational velocities for 3.5 million sources with G_RVS <~ 12 mag.
• Variability analysis, together with the underlying epoch photometry, for 10.5 million sources. Apart from classification into 24 variability classes, detailed variability results are provided in separate tables for the following candidates (EAS presentation L. Eyer):
  • Cepheids (15,021 objects);
  • Compact companions (6306 objects);
  • Eclipsing binaries (2,184,477 objects);
  • Long-period variables (1,720,588 objects);
  • Microlensing events (363 objects);
  • Planetary transits (214 objects);
  • RR Lyrae stars (271,779 objects);
  • Short-timescale variables (471,679 objects);
  • Solar-like rotational modulation variables (474,026 objects);
  • Upper-main-sequence oscillators (54,476 objects);
  • Active galactic nuclei (872,228 objects).
• Solar-system results for 158 000 sources (including 31 planetary satellites), with orbital solutions and individual epoch observations for 154,000 objects and with mean BP/RP reflectance spectra for more than 60,000 objects (EAS presentation P. Tanga).
• Some 813,000 non-single stars, including amongst others non-single-star models for sources compatible with an astrometric acceleration solution, non-single-star orbital models for spectroscopic binaries compatible with a trend, and non-single-star orbital models for sources compatible with a two-body solution (EAS presentation F. Arenou).
• Some 6.6 million quasar candidates with redshift estimates for most of them (EAS presentation L. Galluccio).
• Some 1.1 million quasars analysed with 60,000 host galaxies detected and 15,000 surface brightness profiles of the host galaxy.
• Some 4.8 million galaxy candidates with redshift estimates for more than 1 million objects (EAS presentation L. Galluccio).
• Some 900,000 galaxies analysed with two surface brightness profiles.
• The Gaia Andromeda Photometric Survey (GAPS), consisting of the photometric time series for 1.2 million sources located in a 5.5-degree radius field centred on the Andromeda galaxy.
• Selected tables from Gaia Collaboration performance verification papers published with Gaia DR3.
• All 2612 science alerts triggered in the period underlying Gaia DR3.

The new data set neither contains new astrometry nor new photometric calibrations such that the following elements are in common for and apply to both Gaia EDR3 and Gaia DR3:

• About 1.61 million celestial reference frame (Gaia-CRF3) sources.
• Cross-matches between Gaia (E)DR3 sources on the one hand and Hipparcos-2, Tycho-2 + TDSC merged, 2MASS PSC (merged with 2MASS XSC), SDSS DR13, Pan-STARRS1 DR1, SkyMapper DR2, GSC 2.3, APASS DR9, RAVE DR5, allWISE, URAT-1 and RAVE DR6 data on the other hand.
• Additionally, a Gaia DR2 to Gaia (E)DR3 match table.
• Full passband definitions for G, G_BP, G_RP, and and G_RVS. More information about the passbands. Please be aware that the photometric system for the G, GBP, and GRP bands in Gaia (E)DR3 is different from the photometric systems as used in Gaia DR2 and in Gaia DR1.
• Simulated data from the Gaia Object Generator (GOG) and the Gaia Universe Model Snapshot (GUMS).
• The commanded scan law covering the Gaia EDR3 data collection period. Also the major periods where data was not sent to the ground or could not be processed are identified.

All of the above combined makes up the full Gaia Data Release 3.

Overview of Gaia Data Release 3 in numbers:

Background of the data

Gaia DR3 data (both Gaia EDR3 and the full Gaia DR3) are based on data collected between 25 July 2014 (10:30 UTC) and 28 May 2017 (08:44 UTC), spanning a period of 34 months. As a comparison, Gaia DR2 was based on 22 months of data and Gaia DR1 was based on observations collected during the first 14 months of Gaia's routine operational phase.
The reference epoch for Gaia DR3 (both Gaia EDR3 and the full Gaia DR3) is 2016.0. Remember that the reference epoch is different for each Gaia data release (it was was J2015.5 for Gaia DR2 and J2015.0 for Gaia DR1).
Positions and proper motions are referred to the ICRS, to which the optical reference frame defined by Gaia EDR3 is aligned. The time coordinate for Gaia EDR3 is the barycentric coordinate time (TCB).

Gaia Source Identifiers

Sources in the Gaia Catalogue are uniquely identified through the Gaia Source Identifier, i.e., the source_id field in the various tables in the Gaia Archive. The construction of the source identifiers is explained in the Archive documentation (for Gaia DR1, see the data model section). In particular the source_id number contains rough information about the source position on the sky.

As explained in previous announcements, there are various reasons why the identifier of a specific source may change or disappear when going from the Gaia DR1 to the Gaia DR2 source list and on to the Gaia EDR3 source list. Users of Gaia data should thus be aware that the source list for Gaia EDR3 should be treated as independent from Gaia DR2 and from Gaia DR1.
The Gaia source names for EDR3 will all be constructed as follows:

Gaia EDR3 yyy....yy

The source list for Gaia EDR3 and Gaia DR3 is expected to be identical and a Gaia DR2 to Gaia EDR3 match table is already available from Gaia EDR3.

Limitations of Gaia DR3

Survey completeness

•     More information on the completeness of the survey will be published at https://www.cosmos.esa.int/web/gaia/dr3 .

Astrometry (published as part of Gaia EDR3)

• The uncertainties for the 6-parameter solutions are on average slightly worse than for the 5-parameter solutions that are presented below. The median 2-parameter solution (position only) uncertainties are 1-3 mas.
• The median position uncertainties are 0.01-0.02 mas for G<15, 0.05 mas at G=17, 0.4 mas at G=20, and 1.0 mas at G=21 mag.
• The median parallax uncertainties are 0.02-0.03 mas for G<15, 0.07 mas at G=17, 0.5 mas at G=20, and 1.3 mas at G=21 mag.
• The median proper motion uncertainties are 0.02-0.03 mas/yr for G<15, 0.07 mas/yr at G=17, 0.5 mas/yr at G=20, and 1.4 mas/yr at G=21 mag.
• An overall reduction of systematics has been achieved compared to Gaia DR2. For example, the parallax zero point deduced from the extragalactic sources is about -17 μas. A tentative correction formula for the parallax zero point is provided.

Photometry (G, G_BP, and G_RP published as part of Gaia EDR3, OTHER DATA ARE NEW IN GAIA DR3)

• The G-band photometric uncertainties are ~0.3 mmag for G<13, 1 mmag at G=17, and 6 mmag at G=20 mag.
• The G_BP-band photometric uncertainties are ~0.9 mmag for G<13, 12 mmag at G=17, and 108 mmag at G=20 mag.
• The G_RP-band photometric uncertainties are ~0.6 mmag for G<13, 6 mmag at G=17, and 52 mmag at G=20 mag.
• More information on the properties and limitations of the BP/RP spectra will be published at https://www.cosmos.esa.int/web/gaia/dr3 .

Radial velocities

• More information on the properties and limitations of the radial velocities and RVS spectra will be published at https://www.cosmos.esa.int/web/gaia/dr3 .

Astrophysical parameters

• More information on the properties and limitations of the radial velocities and RVS spectra will be published at https://www.cosmos.esa.int/web/gaia/dr3 .

Variable stars

• More information on the properties and limitations of the radial velocities and RVS spectra will be published at https://www.cosmos.esa.int/web/gaia/dr3 .

Solar system objects

• More information on the properties and limitations of the radial velocities and RVS spectra will be published at https://www.cosmos.esa.int/web/gaia/dr3 .

Non Single sources

• More information on the properties and limitations of the non single sources will be published at https://www.cosmos.esa.int/web/gaia/dr3 .

Galaxies and extended objects

• More information on the properties and limitations of the galaxies and extended objects will be published at https://www.cosmos.esa.int/web/gaia/dr3 .

Gaia DR3 passbands, data model and additional information

Gaia DR3 passbands are offered to users as a record to understand how the Gaia DR3 magnitudes are computed, and to eventually reproduce analysis of data made by other DPAC Coordination Units. The Gaia DR3 passbands are identical to the Gaia EDR3 passbands. Information about Gaia EDR3 passbands is available from Gaia EDR3 passbands page on ESA website.

The Gaia DR3 data model describes all tables together with the names and contents of the columns inside each table. This information will become available from the Gaia Archive along with the release of the data. A draft version of the data model will be made public some time before the release of the data to help you get your code ready. A link will be provided here once available.

More information about Gaia DR3 can be found in Gaia DR3 overview section of ESA's website.

Gaia DR3 documentation

Data release documentation is provided along with each data release in the form of a downloadable PDF and a website. Please visit the Gaia Archive to access this documentation; additional  information is given on the documentation overview page.

Gaia DR3 data

The Gaia Archive is the main point of access for the Gaia Early DR3 data, but the data is also served from Gaia partner data centres (CDS, ASDC, ARI, and AIP). Data can be extracted from the Gaia Archive by performing ADQL queries and subsequently downloading the corresponding results tables.

Gaia DR3 papers

Along with the Gaia DR3 data release documentation, several data processing papers will be published describing the specifics of the data processing and validation performed by the different coordination units in the Gaia Data Processing and Analysis Consortium (DPAC). There will also be some papers on the performance verification of Gaia, providing basic demonstrations of the scientific potential of the Gaia DR3 catalogue.

Please be aware that the Gaia DR3 papers are complemented with the Gaia EDR3 papers which were published with the Gaia Early Data Release 3.

The titles of the Gaia DR3 performance verification papers will be published on Gaia Data Release 3 papers page on ESA's website.