Gaia Data Release 3 (Gaia DR3)

 

Gaia Data Release 3 (Gaia DR3) will be released on 13 June 2022. The data will become available through the Gaia Archive (and through the partner data centres). The Gaia DR3 catalogue builds upon the Early Data Release 3 (released on 3 December 2020) and combines, for the same stretch of time and the same set of observations, 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 (Gaia EDR3) on 3 December 2020 comprises:

  • The full astrometric solution — 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).
  • GBP and GRP 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 (Teff, logg, [M/H], AG, 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 (Teff, 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 1 million well-behaved objects (EAS presentation P. Sartoretti).
  • Mean radial velocities for 33 million stars and mean GRVS magnitudes for 32 million objects with GRVS <~ 14 mag with effective temperatures (Teff) in the range of ~3100 to 14,500 K (EAS presentation P. Sartoretti).
  • Rotational velocities for 3.5 million sources with GRVS <~ 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 all 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 photometric passband definitions for G, GBP, GRP, and GRVS. More information is available here. 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 (E)DR3 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.

 

This is 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 full astrometry 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 2191
   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 in Gaia Data Release 3 Gaia DR2 Gaia DR1
   Sources with radial velocities 33,812,183 7,224,631 -
   Sources with mean GRVS-band magnitudes 32,232,187 - -
   Sources with rotational velocities 3,524,677 - -
   Mean BP/RP spectra 219,197,643 - -
   Mean RVS spectra 999,645 - -
   Variable-source analysis 10,509,536 550,737 3,194
   Variability types (supervised machine learning) 24 6 2
   Supervised machine-learning classification for variables 9,976,881 390,449 3,194
   Specific Object Studies – Cepheids 15,021 9,575 599
   Specific Object Studies – Compact companions 6,306 - -
   Specific Object Studies – Eclipsing binaries 2,184,477 - -
   Specific Object Studies – Long-period variables 1,720,588 89,617 -
   Specific Object Studies – Microlensing events 363 - -
   Specific Object Studies – Planetary transits 214 - -
   Specific Object Studies – RR Lyrae stars 271,779 140,784 2,595
   Specific Object Studies – Short-timescale variables 471,679 3,018 -
   Specific Object Studies – Solar-like rotational modulation variables 474,026 147,535 -
   Specific Object Studies – Upper-main-sequence oscillators 54,476 - -
   Specific Object Studies – Active galactic nuclei 872,228 - -
   Photometrically-variable sources with radial-velocity time series 1,898 - -
   Sources with object classifications 1,590,760,469 - -
   Stars with emission-line classifications 57,511 - -
   Sources with astrophysical parameters from BP/RP spectra 470,759,263 161,497,595 -
   Sources with astrophysical parameters assuming an unresolved binary 348,711,151 - -
   Sources with spectral types 217,982,837 - -
   Sources with evolutionary parameters (mass and age) 128,611,111 - -
   Hot stars with spectroscopic parameters 2,382,015 - -
   Ultra-cool stars 94,158 - -
   Cool stars with activity index 1,349,499 - -
   Sources with H-alpha emission measurements 235,384,119 - -
   Sources with astrophysical parameters from RVS spectra 5,591,594 - -
   Sources with chemical abundances from RVS spectra (up to 13 species) 2,513,593 - -
   Sources with a diffuse interstellar band (DIB) in their RVS spectrum 472,584 - -
   Non-single stars (astrometric, spectroscopic, eclipsing, orbits, trends) 813,687 - -
   Non-single stars - orbital astrometric solutions 169,227 - -
   Non-single stars - orbital spectroscopic solutions (SB1 / SB2) 186,905 - -
   Non-single stars - eclipsing binaries 87,073 - -
   QSO candidates 6,649,162 - -
   QSO candidates - redshifts 6,375,063 - -
   QSO candidates - host galaxy detected 64,498 - -
   QSO candidates - host galaxy surface brightness profiles 15,867 - -
   Galaxy candidates 4,842,342 - -
   Galaxy candidates - redshifts 1,367,153 - -
   Galaxy candidates - surface brightness profiles 914,837 - -
   Solar system objects 158,152 14,099 -
   Solar system objects - epoch astrometry (CCD transits) 23,336,467 - -
   Solar system objects - orbits 154,787 - -
   Solar system objects - average BP/RP reflectance spectra 60,518 - -
   Solar system objects - planetary satellites 31 - -
   All-sky total galactic extinction maps at different spatial resolutions HEALPix levels 6, 7, 8, and 9 - -
   Gaia Andromeda Photometric Survey (GAPS) with lightcurves for all objects 1,257,319 - -

 

 

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.

 

More details on Gaia DR3 data products

More details on some of the Gaia DR3 data products will be provided here soon.

 

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.

The full Gaia DR3 data set is downloadable from the Gaia Archive as a set of compressed ECSV files. The total size will be about 10 TB (or about 9 TiB)

 

Please be aware that to allow for the publication of Gaia's data release 3, the Gaia Archive will be down right before the release from:

Monday 6 June 09:00 CEST to Monday 13 June at 12:00 CEST

 

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 for G, GBP and GRP and can be found here. An additional set of passbands will be published for GRVS.

 

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 is available for download below to help you get your code ready. This is a draft version, meaning small changes to the actual contents can be expected.

The tables related to the Gaia-ESO survey will not be released on 13 June but are expected to be published in the months after the Gaia DR3 release.

 

Download the draft data model for Gaia's data release 3

 

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.

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