Gaia Data Release 3 Creevey, O. L.; Sordo, R.; Pailler, F. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
674
Journal Article
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Gaia
Data Release 3 contains a wealth of new data products for the community. Astrophysical parameters are a major component of this release, and were produced by the Astrophysical parameters ...inference system (Apsis) within the
Gaia
Data Processing and Analysis Consortium (DPAC). The aim of this paper is to describe the overall content of the astrophysical parameters in
Gaia
DR3 and how they were produced. In Apsis, we use the mean BP/RP and mean RVS spectra along with astrometry and photometry, and we derive the following parameters: source classification and probabilities for 1.6 billion objects; interstellar medium characterisation and distances for up to 470 million sources, including a 2D total Galactic extinction map; 6 million redshifts of quasar candidates; 1.4 million redshifts of galaxy candidates; and an analysis of 50 million outlier sources through an unsupervised classification. The astrophysical parameters also include many stellar spectroscopic and evolutionary parameters for up to 470 million sources. These comprise
T
eff
, log
g
, and M/H (470 million using BP/RP, 6 million using RVS), radius (470 million), mass (140 million), age (120 million), chemical abundances (up to 5 million), diffuse interstellar band analysis (0.5 million), activity indices (2 million), H
α
equivalent widths (200 million), and further classification of spectral types (220 million) and emission-line stars (50 000). This paper is the first in a series of three papers, and focusses on describing the global content of the parameters in
Gaia
DR3. The accompanying Papers II and III focus on the validation and use of the stellar and non-stellar products, respectively. This catalogue is the most extensive homogeneous database of astrophysical parameters to date, and is based uniquely on
Gaia
data. It will only be superseded by
Gaia
Data Release 4, and will therefore remain a key reference over the next four years, providing astrophysical parameters independent of other ground- and space-based data.
Gaia Data Release 3 Andrae, R.; Fouesneau, M.; Sordo, R. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
674, Številka:
A27
Journal Article
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Context.
The astrophysical characterisation of sources is among the major new data products in the third
Gaia
Data Release (DR3). In particular, there are stellar parameters for 471 million sources ...estimated from low-resolution BP/RP spectra.
Aims.
We present the General Stellar Parameterizer from Photometry (GSP-Phot), which is part of the astrophysical parameters inference system (Apsis). GSP-Phot is designed to produce a homogeneous catalogue of parameters for hundreds of millions of single non-variable stars based on their astrometry, photometry, and low-resolution BP/RP spectra. These parameters are effective temperature, surface gravity, metallicity, absolute
M
G
magnitude, radius, distance, and extinction for each star.
Methods.
GSP-Phot uses a Bayesian forward-modelling approach to simultaneously fit the BP/RP spectrum, parallax, and apparent
G
magnitude. A major design feature of GSP-Phot is the use of the apparent flux levels of BP/RP spectra to derive, in combination with isochrone models, tight observational constraints on radii and distances. We carefully validate the uncertainty estimates by exploiting repeat
Gaia
observations of the same source.
Results.
The data release includes GSP-Phot results for 471 million sources with
G
< 19. Typical differences to literature values are 110 K for
T
eff
and 0.2–0.25 for log
g
, but these depend strongly on data quality. In particular, GSP-Phot results are significantly better for stars with good parallax measurements (
ϖ
/
σ
ϖ
> 20), mostly within 2 kpc. Metallicity estimates exhibit substantial biases compared to literature values and are only useful at a qualitative level. However, we provide an empirical calibration of our metallicity estimates that largely removes these biases. Extinctions
A
0
and
A
BP
show typical differences from reference values of 0.07–0.09 mag. MCMC samples of the parameters are also available for 95% of the sources.
Conclusions.
GSP-Phot provides a homogeneous catalogue of stellar parameters, distances, and extinctions that can be used for various purposes, such as sample selections (OB stars, red giants, solar analogues etc.). In the context of asteroseismology or ground-based interferometry, where targets are usually bright and have good parallax measurements, GSP-Phot results should be particularly useful for combined analysis or target selection.
Gaia Data Release 3 Fouesneau, M.; Frémat, Y.; Andrae, R. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
674
Journal Article
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Context.
The third
Gaia
data release (
Gaia
DR3) contains, beyond the astrometry and photometry, dispersed light for hundreds of millions of sources from the
Gaia
prism spectra (BP and RP) and the ...spectrograph (RVS). This data release opens a new window on the chemo-dynamical properties of stars in our Galaxy, essential knowledge for understanding the structure, formation, and evolution of the Milky Way.
Aims.
To provide insight into the physical properties of Milky Way stars, we used these data to produce a uniformly derived all-sky catalogue of stellar astrophysical parameters: atmospheric properties (
T
eff
, log
g
, M/H,
α
/Fe, activity index, emission lines, and rotation), 13 chemical abundance estimates, evolution characteristics (radius, age, mass, and bolometric luminosity), distance, and dust extinction.
Methods.
We developed the astrophysical parameter inference system (Apsis) pipeline to infer astrophysical parameters of
Gaia
objects by analysing their astrometry, photometry, BP/RP, and RVS spectra. We validate our results against those from other works in the literature, including benchmark stars, interferometry, and asteroseismology. Here we assess the stellar analysis performance from Apsis statistically.
Results.
We describe the quantities we obtained, including the underlying assumptions and the limitations of our results. We provide guidance and identify regimes in which our parameters should and should not be used.
Conclusions.
Despite some limitations, this is the most extensive catalogue of uniformly inferred stellar parameters to date. They comprise
T
eff
, log
g
, and M/H (470 million using BP/RP, 6 million using RVS), radius (470 million), mass (140 million), age (120 million), chemical abundances (5 million), diffuse interstellar band analysis (half a million), activity indices (2 million), H
α
equivalent widths (200 million), and further classifications of spectral types (220 million) and emission-line stars (50 thousand). More precise and detailed astrophysical parameters based on epoch BP, RP, and RVS spectrophotometry are planned for the next
Gaia
data release.
Gaia Data Release 3 Lanzafame, A. C.; Brugaletta, E.; Frémat, Y. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
674
Journal Article
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Context.
The
Gaia
Radial Velocity Spectrometer (RVS) provides the unique opportunity of a spectroscopic analysis of millions of stars at medium resolution (
λ
/Δ
λ
∼ 11 500) in the near-infrared ...(845−872 nm). This wavelength range includes the Ca
II
infrared triplet (IRT) at 850.03, 854.44, and 866.45 nm, which is a good indicator of magnetic activity in the chromosphere of late–type stars.
Aims.
Here we present the method devised for inferring the
Gaia
stellar activity index from the analysis of the Ca
II
IRT in the RVS spectrum, together with its scientific validation.
Methods.
The
Gaia
stellar activity index is derived from the Ca
II
IRT excess equivalent width with respect to a reference spectrum, taking the projected rotational velocity (
v
sin
i
) into account. We performed scientific validation of the
Gaia
stellar activity index by deriving a
R
′
IRT
index, which is largely independent of the photospheric parameters, and considering the correlation with the
R
′
HK
index for a sample of stars. A sample of well-studied pre-main-sequence (PMS) stars is considered to identify the regime in which the
Gaia
stellar activity index may be affected by mass accretion. The position of these stars in the colour–magnitude diagram and the correlation with the amplitude of the photometric rotational modulation is also scrutinised.
Results.Gaia
DR3 contains a stellar activity index derived from the Ca
II
IRT for some 2 × 10
6
stars in the Galaxy. This represents a ‘gold mine’ for studies on stellar magnetic activity and mass accretion in the solar vicinity. Three regimes of the chromospheric stellar activity are identified, confirming suggestions made by previous authors based on much smaller
R
′
HK
datasets. The highest stellar activity regime is associated with PMS stars and RS CVn systems, in which activity is enhanced by tidal interaction. Some evidence of a bimodal distribution in main sequence (MS) stars with
T
eff
≳ 5000 K is also found, which defines the two other regimes, without a clear gap in between. Stars with 3500 K ≲
T
eff
≲ 5000 K are found to be either very active PMS stars or active MS stars with a unimodal distribution in chromospheric activity. A dramatic change in the activity distribution is found for
T
eff
≲ 3500 K, with a dominance of low activity stars close to the transition between partially- and fully convective stars and a rise in activity down into the fully convective regime.
Gaia Data Release 3 Recio-Blanco, A.; de Laverny, P.; Palicio, P. A. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
674
Journal Article
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Context.
The chemo-physical parametrisation of stellar spectra is essential for understanding the nature and evolution of stars and of Galactic stellar populations. A worldwide observational effort ...from the ground has provided, in one century, an extremely heterogeneous collection of chemical abundances for about two million stars in total, with fragmentary sky coverage.
Aims.
This situation is revolutionised by the
Gaia
third data release (DR3), which contains the parametrisation of Radial Velocity Spectrometer (RVS) data performed by the General Stellar Parametriser-spectroscopy, GSP-Spec, module. Here we describe the parametrisation of the first 34 months of
Gaia
RVS observations.
Methods.
GSP-Spec estimates the chemo-physical parameters from combined RVS spectra of single stars, without additional inputs from astrometric, photometric, or spectro-photometric BP/RP data. The main analysis workflow described here, MatisseGauguin, is based on projection and optimisation methods and provides the stellar atmospheric parameters; the individual chemical abundances of N, Mg, Si, S, Ca, Ti, Cr, Fe
I
, Fe
II
, Ni, Zr, Ce and Nd; the differential equivalent width of a cyanogen line; and the parameters of a diffuse interstellar band (DIB) feature. Another workflow, based on an artificial neural network (ANN) and referred to with the same acronym, provides a second set of atmospheric parameters that are useful for classification control. For both workflows, we implement a detailed quality flag chain considering different error sources.
Results.
With about 5.6 million stars, the
Gaia
DR3 GSP-Spec all-sky catalogue is the largest compilation of stellar chemo-physical parameters ever published and the first one from space data. Internal and external biases have been studied taking into account the implemented flags. In some cases, simple calibrations with low degree polynomials are suggested. The homogeneity and quality of the estimated parameters enables chemo-dynamical studies of Galactic stellar populations, interstellar extinction studies from individual spectra, and clear constraints on stellar evolution models. We highly recommend that users adopt the provided quality flags for scientific exploitation.
Conclusions.
The
Gaia
DR3 GSP-Spec catalogue is a major step in the scientific exploration of Milky Way stellar populations. It will be followed by increasingly large and higher quality catalogues in future data releases, confirming the
Gaia
promise of a new Galactic vision.
Context: As part of the third Gaia Data Release, we present the contributions of the non-stellar and classification modules from the eighth coordination unit (CU8) of the Data Processing and Analysis ...Consortium, which is responsible for the determination of source astrophysical parameters using Gaia data. This is the third in a series of three papers describing the work done within CU8 for this release.
Aims: For each of the five relevant modules from CU8, we summarise their objectives, the methods they employ, their performance, and the results they produce for Gaia DR3. We further advise how to use these data products and highlight some limitations.
Methods: The Discrete Source Classifier (DSC) module provides classification probabilities associated with five types of sources: quasars, galaxies, stars, white dwarfs, and physical binary stars. A subset of these sources are processed by the Outlier Analysis (OA) module, which performs an unsupervised clustering analysis, and then associates labels with the clusters to complement the DSC classification. The Quasi Stellar Object Classifier (QSOC) and the Unresolved Galaxy Classifier (UGC) determine the redshifts of the sources classified as quasar and galaxy by the DSC module. Finally, the Total Galactic Extinction (TGE) module uses the extinctions of individual stars determined by another CU8 module to determine the asymptotic extinction along all lines of sight for Galactic latitudes |b| > 5 degrees.
Results: Gaia DR3 includes 1591 million sources with DSC classifications; 56 million sources to which the OA clustering is applied; 1.4 million sources with redshift estimates from UGC; 6.4 million sources with QSOC redshift; and 3.1 million level 9 HEALPixes of size 0 :013 deg(2) where the extinction is evaluated by TGE.
Conclusions: Validation shows that results are in good agreement with values from external catalogues; for example 90% of the QSOC redshifts have absolute error lower than 0:1 for sources with empty warning flags, while UGC redshifts have a mean error of 0:008 +/- 0:037 if evaluated on a clean set of spectra. An internal validation of the OA results further shows that 30 million sources are located in high confidence regions of the clustering map.
Gaia Data Release 3 Babusiaux, C.; Fabricius, C.; Khanna, S. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
674
Journal Article
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Context.
The third
Gaia
data release (DR3) provides a wealth of new data products. The early part of the release,
Gaia
EDR3, already provided the astrometric and photometric data for nearly two ...billion sources. The full release now adds improved parameters compared to
Gaia
DR2 for radial velocities, astrophysical parameters, variability information, light curves, and orbits for Solar System objects. The improvements are in terms of the number of sources, the variety of parameter information, precision, and accuracy. For the first time,
Gaia
DR3 also provides a sample of spectrophotometry and spectra obtained with the Radial Velocity Spectrometer, binary star solutions, and a characterisation of extragalactic object candidates.
Aims.
Before the publication of the catalogue, these data have undergone a dedicated transversal validation process. The aim of this paper is to highlight limitations of the data that were found during this process and to provide recommendations for the usage of the catalogue.
Methods.
The validation was obtained through a statistical analysis of the data, a confirmation of the internal consistency of different products, and a comparison of the values to external data or models.
Results.
Gaia
DR3 is a new major step forward in terms of the number, diversity, precision, and accuracy of the
Gaia
products. As always in such a large and complex catalogue, however, issues and limitations have also been found. Detailed examples of the scientific quality of the
Gaia
DR3 release can be found in the accompanying data-processing papers as well as in the performance verification papers. Here we focus only on the caveats that the user should be aware of to scientifically exploit the data.
Context . Strongly lensed quasars are fundamental sources for cosmology. The Gaia space mission covers the entire sky with the unprecedented resolution of 0.18″ in the optical, making it an ideal ...instrument to search for gravitational lenses down to the limiting magnitude of 21. Nevertheless, the previous Gaia Data Releases are known to be incomplete for small angular separations such as those expected for most lenses. Aims . We present the Data Processing and Analysis Consortium GravLens pipeline, which was built to analyse all Gaia detections around quasars and to cluster them into sources, thus producing a catalogue of secondary sources around each quasar. We analysed the resulting catalogue to produce scores that indicate source configurations that are compatible with strongly lensed quasars. Methods . GravLens uses the DBSCAN unsupervised clustering algorithm to detect sources around quasars. The resulting catalogue of multiplets is then analysed with several methods to identify potential gravitational lenses. We developed and applied an outlier scoring method, a comparison between the average BP and RP spectra of the components, and we also used an extremely randomised tree algorithm. These methods produce scores to identify the most probable configurations and to establish a list of lens candidates. Results . We analysed the environment of 3 760 032 quasars. A total of 4 760 920 sources, including the quasars, were found within 6″ of the quasar positions. This list is given in the Gaia archive. In 87% of cases, the quasar remains a single source, and in 501 385 cases neighbouring sources were detected. We propose a list of 381 lensed candidates, of which we identified 49 as the most promising ones. Beyond these candidates, the associate tables in this Focused Product Release allow the entire community to explore the unique Gaia data for strong lensing studies further.
Ultrahigh energy cosmic ray air showers probe particle physics at energies beyond the reach of accelerators. Here we introduce a new method to test hadronic interaction models without relying on the ...absolute energy calibration, and apply it to events with primary energy 6-16 EeV (E_{CM}=110-170 TeV), whose longitudinal development and lateral distribution were simultaneously measured by the Pierre Auger Observatory. The average hadronic shower is 1.33±0.16 (1.61±0.21) times larger than predicted using the leading LHC-tuned models EPOS-LHC (QGSJetII-04), with a corresponding excess of muons.
Gaia Data Release 3 de Laverny, P.; Spagna, A.; Vallenari, A. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
674
Journal Article, Web Resource
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Context.
The motion of stars has been used to reveal details of the complex history of the Milky Way, in constant interaction with its environment. Nevertheless, to reconstruct the Galactic history ...puzzle in its entirety, the chemo-physical characterisation of stars is essential. Previous
Gaia
data releases were supported by a smaller, heterogeneous, and spatially biased mixture of chemical data from ground-based observations.
Aims.
Gaia
Data Release 3 opens a new era of all-sky spectral analysis of stellar populations thanks to the nearly 5.6 million stars observed by the Radial Velocity Spectrometer (RVS) and parametrised by the GSP-Spec module. In this work, we aim to demonstrate the scientific quality of
Gaia
’s Milky Way chemical cartography through a chemo-dynamical analysis of disc and halo populations.
Methods.
Stellar atmospheric parameters and chemical abundances provided by
Gaia
DR3 spectroscopy are combined with DR3 radial velocities and EDR3 astrometry to analyse the relationships between chemistry and Milky Way structure, stellar kinematics, and orbital parameters.
Results.
The all-sky
Gaia
chemical cartography allows a powerful and precise chemo-dynamical view of the Milky Way with unprecedented spatial coverage and statistical robustness. First, it reveals the strong vertical symmetry of the Galaxy and the flared structure of the disc. Second, the observed kinematic disturbances of the disc – seen as phase space correlations – and kinematic or orbital substructures are associated with chemical patterns that favour stars with enhanced metallicities and lower
α
/Fe abundance ratios compared to the median values in the radial distributions. This is detected both for young objects that trace the spiral arms and older populations. Several
α
, iron-peak elements and at least one heavy element trace the thin and thick disc properties in the solar cylinder. Third, young disc stars show a recent chemical impoverishment in several elements. Fourth, the largest chemo-dynamical sample of open clusters analysed so far shows a steepening of the radial metallicity gradient with age, which is also observed in the young field population. Finally, the
Gaia
chemical data have the required coverage and precision to unveil galaxy accretion debris and heated disc stars on halo orbits through their
α
/Fe ratio, and to allow the study of the chemo-dynamical properties of globular clusters.
Conclusions.
Gaia
DR3 chemo-dynamical diagnostics open new horizons before the era of ground-based wide-field spectroscopic surveys. They unveil a complex Milky Way that is the outcome of an eventful evolution, shaping it to the present day.
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