Gaia Data Release 2 Hambly, N. C.; Cropper, M.; Boudreault, S. ...
Astronomy and astrophysics (Berlin),
08/2018, Letnik:
616
Journal Article
Recenzirano
Odprti dostop
Context.
The European Space Agency’s
Gaia
satellite was launched into orbit around L2 in December 2013. This ambitious mission has strict requirements on residual systematic errors resulting from ...instrumental corrections in order to meet a design goal of sub-10 microarcsecond astrometry. During the design and build phase of the science instruments, various critical calibrations were studied in detail to ensure that this goal could be met in orbit. In particular, it was determined that the video-chain offsets on the analogue side of the analogue-to-digital conversion electronics exhibited instabilities that could not be mitigated fully by modifications to the flight hardware.
Aims.
We provide a detailed description of the behaviour of the electronic offset levels on short (<1 ms) timescales, identifying various systematic effects that are known collectively as “offset non-uniformities”. The effects manifest themselves as transient perturbations on the gross zero-point electronic offset level that is routinely monitored as part of the overall calibration process.
Methods.
Using in-orbit special calibration sequences along with simple parametric models, we show how the effects can be calibrated, and how these calibrations are applied to the science data. While the calibration part of the process is relatively straightforward, the application of the calibrations during science data processing requires a detailed on-ground reconstruction of the readout timing of each charge-coupled device (CCD) sample on each device in order to predict correctly the highly time-dependent nature of the corrections.
Results.
We demonstrate the effectiveness of our offset non-uniformity models in mitigating the effects in
Gaia
data.
Conclusions.
We demonstrate for all CCDs and operating instrument/modes on board
Gaia
that the video-chain noise-limited performance is recovered in the vast majority of science samples.
Gaia observations of naked-eye stars: status update Sahlmann, J.; Mora, A.; Martín-Fleitas, J. M. ...
Proceedings of the International Astronomical Union,
04/2017, Letnik:
12, Številka:
S330
Journal Article
Recenzirano
ESA's Gaia space astrometry mission is performing an all-sky survey of stellar objects. At the beginning of the nominal mission in July 2014, an operation scheme was adopted that enabled Gaia to ...routinely acquire observations of all stars brighter than the original limit of G~6, i.e. the naked-eye stars. We present the current status and extent of those observations.
Gaia Data Release 2 Hambly, N. C.; Cropper, M.; Boudreault, S. ...
Astronomy and astrophysics (Berlin),
08/2018, Letnik:
616
Journal Article
Recenzirano
Odprti dostop
Context. The European Space Agency’s Gaia satellite was launched into orbit around L2 in December 2013. This ambitious mission has strict requirements on residual systematic errors resulting from ...instrumental corrections in order to meet a design goal of sub-10 microarcsecond astrometry. During the design and build phase of the science instruments, various critical calibrations were studied in detail to ensure that this goal could be met in orbit. In particular, it was determined that the video-chain offsets on the analogue side of the analogue-to-digital conversion electronics exhibited instabilities that could not be mitigated fully by modifications to the flight hardware. Aims. We provide a detailed description of the behaviour of the electronic offset levels on short (<1 ms) timescales, identifying various systematic effects that are known collectively as “offset non-uniformities”. The effects manifest themselves as transient perturbations on the gross zero-point electronic offset level that is routinely monitored as part of the overall calibration process. Methods. Using in-orbit special calibration sequences along with simple parametric models, we show how the effects can be calibrated, and how these calibrations are applied to the science data. While the calibration part of the process is relatively straightforward, the application of the calibrations during science data processing requires a detailed on-ground reconstruction of the readout timing of each charge-coupled device (CCD) sample on each device in order to predict correctly the highly time-dependent nature of the corrections. Results. We demonstrate the effectiveness of our offset non-uniformity models in mitigating the effects in Gaia data. Conclusions. We demonstrate for all CCDs and operating instrument/modes on board Gaia that the video-chain noise-limited performance is recovered in the vast majority of science samples.
Gaia Data Release 3 Arenou, F.; Lammers, U. L.; Mignard, F. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
674, Številka:
A1
Journal Article, Web Resource
Recenzirano
Odprti dostop
Context.
We present the third data release of the European Space Agency’s
Gaia
mission,
Gaia
DR3. This release includes a large variety of new data products, notably a much expanded radial velocity ...survey and a very extensive astrophysical characterisation of
Gaia
sources.
Aims.
We outline the content and the properties of
Gaia
DR3, providing an overview of the main improvements in the data processing in comparison with previous data releases (where applicable) and a brief discussion of the limitations of the data in this release.
Methods.
The
Gaia
DR3 catalogue is the outcome of the processing of raw data collected with the
Gaia
instruments during the first 34 months of the mission by the
Gaia
Data Processing and Analysis Consortium.
Results.
The
Gaia
DR3 catalogue contains the same source list, celestial positions, proper motions, parallaxes, and broad band photometry in the
G
,
G
BP
, and
G
RP
pass-bands already present in the Early Third Data Release,
Gaia
EDR3.
Gaia
DR3 introduces an impressive wealth of new data products. More than 33 million objects in the ranges
G
RVS
< 14 and 3100 <
T
eff
< 14 500, have new determinations of their mean radial velocities based on data collected by
Gaia
. We provide
G
RVS
magnitudes for most sources with radial velocities, and a line broadening parameter is listed for a subset of these. Mean
Gaia
spectra are made available to the community. The
Gaia
DR3 catalogue includes about 1 million mean spectra from the radial velocity spectrometer, and about 220 million low-resolution blue and red prism photometer BP/RP mean spectra. The results of the analysis of epoch photometry are provided for some 10 million sources across 24 variability types.
Gaia
DR3 includes astrophysical parameters and source class probabilities for about 470 million and 1500 million sources, respectively, including stars, galaxies, and quasars. Orbital elements and trend parameters are provided for some 800 000 astrometric, spectroscopic and eclipsing binaries. More than 150 000 Solar System objects, including new discoveries, with preliminary orbital solutions and individual epoch observations are part of this release. Reflectance spectra derived from the epoch BP/RP spectral data are published for about 60 000 asteroids. Finally, an additional data set is provided, namely the
Gaia
Andromeda Photometric Survey, consisting of the photometric time series for all sources located in a 5.5 degree radius field centred on the Andromeda galaxy.
Conclusions.
This data release represents a major advance with respect to
Gaia
DR2 and
Gaia
EDR3 because of the unprecedented quantity, quality, and variety of source astrophysical data. To date this is the largest collection of all-sky spectrophotometry, radial velocities, variables, and astrophysical parameters derived from both low- and high-resolution spectra and includes a spectrophotometric and dynamical survey of SSOs of the highest accuracy. The non-single star content surpasses the existing data by orders of magnitude. The quasar host and galaxy light profile collection is the first such survey that is all sky and space based. The astrophysical information provided in
Gaia
DR3 will unleash the full potential of
Gaia
’s exquisite astrometric, photometric, and radial velocity surveys.
Gaia Data Release 2 Lindegren, L.; Hernández, J.; Bombrun, A. ...
Astronomy and astrophysics (Berlin),
08/2018, Letnik:
616
Journal Article
Recenzirano
Odprti dostop
Context. Gaia
Data Release 2 (
Gaia
DR2) contains results for 1693 million sources in the magnitude range 3 to 21 based on observations collected by the European Space Agency
Gaia
satellite during ...the first 22 months of its operational phase.
Aims.
We describe the input data, models, and processing used for the astrometric content of
Gaia
DR2, and the validation of these resultsperformed within the astrometry task.
Methods.
Some 320 billion centroid positions from the pre-processed astrometric CCD observations were used to estimate the five astrometric parameters (positions, parallaxes, and proper motions) for 1332 million sources, and approximate positions at the reference epoch J2015.5 for an additional 361 million mostly faint sources. These data were calculated in two steps. First, the satellite attitude and the astrometric calibration parameters of the CCDs were obtained in an astrometric global iterative solution for 16 million selected sources, using about 1% of the input data. This primary solution was tied to the extragalactic International Celestial Reference System (ICRS) by means of quasars. The resulting attitude and calibration were then used to calculate the astrometric parameters of all the sources. Special validation solutions were used to characterise the random and systematic errors in parallax and proper motion.
Results.
For the sources with five-parameter astrometric solutions, the median uncertainty in parallax and position at the reference epoch J2015.5 is about 0.04 mas for bright (
G
< 14 mag) sources, 0.1 mas at
G
= 17 mag, and 0.7 masat
G
= 20 mag. In the proper motion components the corresponding uncertainties are 0.05, 0.2, and 1.2 mas yr
−1
, respectively.The optical reference frame defined by
Gaia
DR2 is aligned with ICRS and is non-rotating with respect to the quasars to within 0.15 mas yr
−1
. From the quasars and validation solutions we estimate that systematics in the parallaxes depending on position, magnitude, and colour are generally below 0.1 mas, but the parallaxes are on the whole too small by about 0.03 mas. Significant spatial correlations of up to 0.04 mas in parallax and 0.07 mas yr
−1
in proper motion are seen on small (< 1 deg) and intermediate (20 deg) angular scales. Important statistics and information for the users of the
Gaia
DR2 astrometry are given in the appendices.
Gaia Early Data Release 3 Brown, A. G. A.; Prusti, T.; Eyer, L. ...
Astronomy and astrophysics (Berlin),
05/2021, Letnik:
649
Journal Article, Web Resource
Recenzirano
Odprti dostop
Context.
We present the early installment of the third
Gaia
data release,
Gaia
EDR3, consisting of astrometry and photometry for 1.8 billion sources brighter than magnitude 21, complemented with the ...list of radial velocities from
Gaia
DR2.
Aims.
A summary of the contents of
Gaia
EDR3 is presented, accompanied by a discussion on the differences with respect to
Gaia
DR2 and an overview of the main limitations which are present in the survey. Recommendations are made on the responsible use of
Gaia
EDR3 results.
Methods.
The raw data collected with the
Gaia
instruments during the first 34 months of the mission have been processed by the
Gaia
Data Processing and Analysis Consortium and turned into this early third data release, which represents a major advance with respect to
Gaia
DR2 in terms of astrometric and photometric precision, accuracy, and homogeneity.
Results. Gaia
EDR3 contains celestial positions and the apparent brightness in
G
for approximately 1.8 billion sources. For 1.5 billion of those sources, parallaxes, proper motions, and the (
G
BP
−
G
RP
) colour are also available. The passbands for
G
,
G
BP
, and
G
RP
are provided as part of the release. For ease of use, the 7 million radial velocities from
Gaia
DR2 are included in this release, after the removal of a small number of spurious values. New radial velocities will appear as part of
Gaia
DR3. Finally,
Gaia
EDR3 represents an updated materialisation of the celestial reference frame (CRF) in the optical, the
Gaia
-CRF3, which is based solely on extragalactic sources. The creation of the source list for
Gaia
EDR3 includes enhancements that make it more robust with respect to high proper motion stars, and the disturbing effects of spurious and partially resolved sources. The source list is largely the same as that for
Gaia
DR2, but it does feature new sources and there are some notable changes. The source list will not change for
Gaia
DR3.
Conclusions. Gaia
EDR3 represents a significant advance over
Gaia
DR2, with parallax precisions increased by 30 per cent, proper motion precisions increased by a factor of 2, and the systematic errors in the astrometry suppressed by 30–40% for the parallaxes and by a factor ~2.5 for the proper motions. The photometry also features increased precision, but above all much better homogeneity across colour, magnitude, and celestial position. A single passband for
G
,
G
BP
, and
G
RP
is valid over the entire magnitude and colour range, with no systematics above the 1% level
Gaia Data Release 2 Prusti, T.; Evans, D. W.; Eyer, L. ...
Astronomy and astrophysics (Berlin),
08/2018, Letnik:
616
Journal Article, Web Resource
Recenzirano
Odprti dostop
Context.
We present the second
Gaia
data release,
Gaia
DR2, consisting of astrometry, photometry, radial velocities, and information on astrophysical parameters and variability, for sources brighter ...than magnitude 21. In addition epoch astrometry and photometry are provided for a modest sample of minor planets in the solar system.
Aims.
A summary of the contents of
Gaia
DR2 is presented, accompanied by a discussion on the differences with respect to
Gaia
DR1 and an overview of the main limitations which are still present in the survey. Recommendations are made on the responsible use of
Gaia
DR2 results.
Methods.
The raw data collected with the
Gaia
instruments during the first 22 months of the mission have been processed by the
Gaia
Data Processing and Analysis Consortium (DPAC) and turned into this second data release, which represents a major advance with respect to
Gaia
DR1 in terms of completeness, performance, and richness of the data products.
Results. Gaia
DR2 contains celestial positions and the apparent brightness in
G
for approximately 1.7 billion sources. For 1.3 billion of those sources, parallaxes and proper motions are in addition available. The sample of sources for which variability information is provided is expanded to 0.5 million stars. This data release contains four new elements: broad-band colour information in the form of the apparent brightness in the
G
BP
(330–680 nm) and
G
RP
(630–1050 nm) bands is available for 1.4 billion sources; median radial velocities for some 7 million sources are presented; for between 77 and 161 million sources estimates are provided of the stellar effective temperature, extinction, reddening, and radius and luminosity; and for a pre-selected list of 14 000 minor planets in the solar system epoch astrometry and photometry are presented. Finally,
Gaia
DR2 also represents a new materialisation of the celestial reference frame in the optical, the
Gaia
-CRF2, which is the first optical reference frame based solely on extragalactic sources. There are notable changes in the photometric system and the catalogue source list with respect to
Gaia
DR1, and we stress the need to consider the two data releases as independent.
Conclusions. Gaia
DR2 represents a major achievement for the
Gaia
mission, delivering on the long standing promise to provide parallaxes and proper motions for over 1 billion stars, and representing a first step in the availability of complementary radial velocity and source astrophysical information for a sample of stars in the
Gaia
survey which covers a very substantial fraction of the volume of our galaxy.
Gaia Data Release 3 de Laverny, P.; Spagna, A.; Vallenari, A. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
674
Journal Article, Web Resource
Recenzirano
Odprti dostop
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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