Gaia Data Release 3 (Gaia DR3)

 

Gaia Data Release 3 (Gaia DR3) is expected in Q2 2022. The data will become 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. The full contents of Gaia DR3 is described below.

 

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.
  • GBP and GRP magnitudes for around 1.54 billion and 1.55 billion sources, respectively.
  • Please be aware that the photometric system for the G, GBP, and GRP bands in Gaia EDR3 is different from the photometric system as used in Gaia DR2 and Gaia DR1.
  • Full passband definitions for G, GBP, and GRP. More information is available here.
  • About 1.61 million celestial reference frame (Gaia-CRF3) sources.
  • Cross-matches between Gaia EDR3 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, and URAT-1 data on the other hand.
  • Additionally, a Gaia DR2 to Gaia EDR3 match table.
  • 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.

complemented with new data (a more detailed description with all new data products will follow soon) (EAS presentation A. Vallenari):

  • Object classification for nearly all objects and astrophysical parameters for about 500 million objects (EAS presentation O.Creevey)
  • BP/RP spectra for at least 100 million sources with G < 17.6 mag (EAS Presentation F. De Angeli)
  • RVS spectra for about 1 million well-behaved objects (EAS presentation P. Sartoretti)
  • Mean radial velocities for about 33 million stars with GRVS <~ 14 mag and an effective temperature (Teff) in the range of about 3100 to 14,500 K (EAS presentation P. Sartoretti)
  • Variable-star classifications, together with the epoch photometry used for the stars, for about 13 million sources and approximately 25 different variability types (EAS presentation L. Eyer)
  • Solar-system results with preliminary orbital solutions and individual epoch observations for about 150,000 sources, with reflectance spectra for about 50,000 of these sources (EAS presentation P. Tanga)
  • A few 100,000 non-single stars (EAS presentation F. Arenou)
  • Results for a few million Quasars and Galaxies (EAS presentation L. Galluccio) and a few 100,000 Extended Objects
  • The Gaia Andromeda Photometric Survey (GAPS), consisting of the photometric time series for all sources located in a 5.5-degree radius field centred on the Andromeda galaxy (about 1 million sources)

which together make up the full Gaia Data Release 3. Exact numbers will only be available after the detailed validation process, which is currently ongoing.

 

Below an overview of Gaia Data Release 3 in numbers:

 

  # sources in Gaia DR3 # sources in Gaia DR2 # sources in Gaia DR1
Total number of sources 1,811,709,771 1,692,919,135 1,142,679,769
  Gaia Early Data Release 3    
Number of sources with minimally 5 astrometric parameters 1,467,744,818 1,331,909,727 2,057,050
Number of 5-parameter sources 585,416,709    
Number of 6-parameter sources 882,328,109    
Number of 2-parameter sources 343,964,953 361,009,408 1,140,622,719
Gaia-CRF sources 1,614,173 556,869 2,191
Sources with mean G magnitude 1,806,254,432 1,692,919,135 1,142,679,769
Sources with mean GBP-band photometry 1,542,033,472 1,381,964,755 -
Sources with mean GRP-band photometry 1,554,997,939 1,383,551,713 -
  New data in Gaia Data Release 3 (pending validation)    
Sources with radial velocities ≈ 33,000,000 7,224,631 -
BP/RP spectra > 100,000,000 - -
RVS spectra ≈ 1,000,000 - -
Variable source classifications ≈ 13,000,000 550,737 3,194
Object classifications ≈ 1,000,000,000 - -
Sources with astrophysical parameters ≈ 500,000,000 161,497,595 -
Non-single stars ≈ a few 100,000 - -
QSO host and galaxy morphological characterisation ≈ a few 1,000,000 - -
Extended Objects ≈ a few 100,000 - -
Solar system objects ≈ 150,000 14,099 -
Reflectance spectra for solar system objects ≈ 50,000 - -
Average BP/RP reflectance spectra of asteroids ≈ 10,000 - -
Gaia Andromeda Photometric Survey (GAPS) ≈ 1,000,000 - -

 

 

Background of the data

 

Gaia DR3 data (both Gaia EDR3 and the full Gaia DR3) is based on data collected between 25 July 2014 (10:30 UTC) and 28 May 2017 (08:44 UTC) spanning a period of 34 months of data collection. As a comparison, Gaia DR2 was based on 22 months of data and Gaia DR1 was based on observations collected in 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, and that the reference epoch for Gaia DR2 was J2015.5 and for Gaia DR1 was J2015.0.

Positions and proper motions are referred to the ICRS, to which the optical reference frame defined by Gaia DR3 (Gaia-CRF3) is aligned. The time coordinate for Gaia DR3 results is the barycentric coordinate time (TCB).

 

Gaia Source Identifiers

 

Sources in the Gaia Catalogue are all 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 DR3 source list. Users of Gaia data should thus be aware that the source list for Gaia DR3 should be treated as independent from Gaia DR2 and from Gaia DR1. With each new Gaia data release, the source list is becoming progressively more stable.

The Gaia source names ('designations') for Gaia DR3 are all constructed as follows:

Gaia DR3 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 closer to the release of 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. E.g., 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, GBP, and GRP 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 GBP-band photometric uncertainties are ~0.9 mmag for G<13, 12 mmag at G=17, and 108 mmag at G=20 mag.
  • The GRP-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 closer to the release of Gaia DR3.

Radial velocities

  • More information on the properties and limitations of the radial velocities and RVS spectra will be published closer to the release of Gaia DR3.

Astrophysical parameters

  • More information on the properties and limitations of the astrophysical parameters will be published closer to the release of Gaia DR3.

Variable stars

  • More information on the properties and limitations of the variable star information will be published closer to the release of Gaia DR3.

Solar system objects

  • More information on the properties and limitations of the solar system objects will be published closer to the release of Gaia DR3.

Non Single sources

  • More information on the properties and limitations of the non single sources will be published closer to the release of Gaia DR3.

Galaxies and extended objects

  • More information on the properties and limitations of the galaxies and extended objects will be published closer to the release of Gaia DR3.

 

Accessing the DATA

 

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

 

Passbands

 

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 and can be found here.

 

Documentation

 

Data release documentation is provided along with each data release in the form of a downloadable PDF and a webpage. Please visit the Gaia Archive to access this documentation, and make sure to go through all relevant information given from the documentation overview page.

 

Known issues with Gaia Data Release 3

 

We will inform you of any issues with the data or info given along with the data that is discovered after the official release. A link to this information will be provided here.

 

Data model

 

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.

 

Data Release 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 announced closer to the release of Gaia DR3.

​​​​​​​​​​​​​​