32 research outputs found
Gaia Data Release 3
CONTEXT:
Gaia Data Release 3 (Gaia DR3) contains the second release of the combined radial velocities. It is based on the spectra collected during the first 34 months of the nominal mission. The longer time baseline and the improvements of the pipeline made it possible to push the processing limit from GRVSâ=â12 in Gaia DR2 to GRVSâ=â14 mag.
AIMS:
We describe the new functionalities implemented for Gaia DR3, the quality filters applied during processing and post-processing, and the properties and performance of the published velocities.
METHODS:
For Gaia DR3, several functionalities were upgraded or added to the spectroscopic pipeline. The calibrations were improved in order to better model the temporal evolution of the straylight and of the instrumental point spread function (PSF). The overlapped spectra, which were mostly discarded in Gaia DR2, are now handled by a dedicated module. The hot star template mismatch, which prevented publication of hot stars in Gaia DR2, is largely mitigated now, down to GRVSâ=â12 mag. The combined radial velocity of stars brighter than or equal to GRVSâ=â12 mag is calculated in the same way as in Gaia DR2, that is, as the median of the epoch radial velocity time series. The combined radial velocity of the fainter stars is measured from the average of the cross-correlation functions.
RESULTS:
Gaia DR3 contains the combined radial velocities of 33 812 183 stars. With respect to Gaia DR2, the temperature interval has been expanded from Teffâââ[3600,â6750] K to Teffâââ[3100,â14â500] K for the bright stars (GRVSââ€â12 mag) and [3100,â6750] K for the fainter stars. The radial velocities sample a significant part of the Milky Way: they reach a few kiloparsecs beyond the Galactic centre in the disc and up to about 10â15 kpc vertically into the inner halo. The median formal precision of the velocities is 1.3 km sâ1 at GRVSâ=â12 and 6.4 km sâ1 at GRVSâ=â14 mag. The velocity zeropoint exhibits a small systematic trend with magnitude that starts around GRVSâ=â11 mag and reaches about 400 m sâ1 at GRVSâ=â14 mag. A correction formula is provided that can be applied to the published data. The Gaia DR3 velocity scale agrees satisfactorily with APOGEE, GALAH, GES, and RAVE; the systematic differences mostly remain below a few hundred m sâ1. The properties of the radial velocities are also illustrated with specific objects: open clusters, globular clusters, and the Large Magellanic Cloud. For example, the precision of the data allows mapping the line-of-sight rotational velocities of the globular cluster 47 Tuc and of the Large Magellanic Cloud
Gaia Focused Product Release: A catalogue of sources around quasars to search for strongly lensed quasars
Context. Strongly lensed quasars are fundamental sources for cosmology. The
Gaia space mission covers the entire sky with the unprecedented resolution of
" 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. 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.Comment: 35 pages, 60 figures, accepted for publication by Astronomy and
Astrophysic
Gaia Focused Product Release: Radial velocity time series of long-period variables
The third Gaia Data Release (DR3) provided photometric time series of more
than 2 million long-period variable (LPV) candidates. Anticipating the
publication of full radial-velocity (RV) in DR4, this Focused Product Release
(FPR) provides RV time series for a selection of LPVs with high-quality
observations. We describe the production and content of the Gaia catalog of LPV
RV time series, and the methods used to compute variability parameters
published in the Gaia FPR. Starting from the DR3 LPVs catalog, we applied
filters to construct a sample of sources with high-quality RV measurements. We
modeled their RV and photometric time series to derive their periods and
amplitudes, and further refined the sample by requiring compatibility between
the RV period and at least one of the , , or
photometric periods. The catalog includes RV time series and variability
parameters for 9\,614 sources in the magnitude range , including a flagged top-quality subsample of 6\,093 stars
whose RV periods are fully compatible with the values derived from the ,
, and photometric time series. The RV time series
contain a mean of 24 measurements per source taken unevenly over a duration of
about three years. We identify the great most sources (88%) as genuine LPVs,
with about half of them showing a pulsation period and the other half
displaying a long secondary period. The remaining 12% consists of candidate
ellipsoidal binaries. Quality checks against RVs available in the literature
show excellent agreement. We provide illustrative examples and cautionary
remarks. The publication of RV time series for almost 10\,000 LPVs constitutes,
by far, the largest such database available to date in the literature. The
availability of simultaneous photometric measurements gives a unique added
value to the Gaia catalog (abridged)Comment: 36 pages, 38 figure
Gaia Focused Product Release: Asteroid orbital solution: Properties and assessment
Context. We report the exploitation of a sample of Solar System observations based on data from the third Gaia Data Release (Gaia DR3) of nearly 157 000 asteroids. It extends the epoch astrometric solution over the time coverage planned for the Gaia DR4, which is not expected before the end of 2025. This data set covers more than one full orbital period for the vast majority of these asteroids. The orbital solutions are derived from the Gaia data alone over a relatively short arc compared to the observation history of many of these asteroids. Aims. The work aims to produce orbital elements for a large set of asteroids based on 66 months of accurate astrometry provided by Gaia and to assess the accuracy of these orbital solutions with a comparison to the best available orbits derived from independent observations. A second validation is performed with accurate occultation timings. Methods. We processed the raw astrometric measurements of Gaia to obtain astrometric positions of moving objects with 1D sub-mas accuracy at the bright end. For each asteroid that we matched to the data, an orbit fitting was attempted in the form of the best fit of the initial conditions at the median epoch. The force model included Newtonian and relativistic accelerations to derive the observation equations, which were solved with a linear least-squares fit. Results. Orbits are provided in the form of state vectors in the International Celestial Reference Frame for 156 764 asteroids, including near-Earth objects, main-belt asteroids, and Trojans. For the asteroids with the best observations, the (formal) relative uncertainty Ïa/a is better than 10â10. Results are compared to orbits available from the Jet Propulsion Laboratory and MPC. Their orbits are based on much longer data arcs, but from positions of lower quality. The relative differences in semi-major axes have a mean of 5 Ă 10â10 and a scatter of 5 Ă 10â9
Gaia Focused Product Release: Radial velocity time series of long-period variables
Context. The third Gaia Data Release (DR3) provided photometric time series of more than 2 million long-period variable (LPV) candidates. Anticipating the publication of full radial-velocity data planned with Data Release 4, this Focused Product Release (FPR) provides radial-velocity time series for a selection of LPV candidates with high-quality observations. Aims. We describe the production and content of the Gaia catalog of LPV radial-velocity time series, and the methods used to compute the variability parameters published as part of the Gaia FPR. Methods. Starting from the DR3 catalog of LPV candidates, we applied several filters to construct a sample of sources with high-quality radial-velocity measurements. We modeled their radial-velocity and photometric time series to derive their periods and amplitudes, and further refined the sample by requiring compatibility between the radial-velocity period and at least one of the G, GBP, or GRP photometric periods. Results. The catalog includes radial-velocity time series and variability parameters for 9614 sources in the magnitude range 6 âČ G/mag âČ 14, including a flagged top-quality subsample of 6093 stars whose radial-velocity periods are fully compatible with the values derived from the G, GBP, and GRP photometric time series. The radial-velocity time series contain a mean of 24 measurements per source taken unevenly over a duration of about three years. We identify the great majority of the sources (88%) as genuine LPV candidates, with about half of them showing a pulsation period and the other half displaying a long secondary period. The remaining 12% of the catalog consists of candidate ellipsoidal binaries. Quality checks against radial velocities available in the literature show excellent agreement. We provide some illustrative examples and cautionary remarks. Conclusions. The publication of radial-velocity time series for almost ten thousand LPV candidates constitutes, by far, the largest such database available to date in the literature. The availability of simultaneous photometric measurements gives a unique added value to the Gaia catalog
FEDReD
Aims. We aim to map the 3D distribution of the interstellar extinction of the Milky Way disc up to distances larger than those probed with the Gaia parallax alone.
Methods. We applied the FEDReD (Field Extinction-Distance Relation Deconvolver) algorithm to the 2MASS near-infrared photometry together with the Gaia DR2 astrometry and photometry. This algorithm uses a Bayesian deconvolution approach, based on an empirical HR-diagram representative of the local thin disc, in order to map the extinction as a function of distance of various fields of view.
Results. We analysed more than 5.6 million stars to obtain an extinction map of the entire Galactic disc within |b| < 0.24°. This map provides information up to 5 kpc in the direction of the Galactic centre and more than 7 kpc in the direction of the anticentre. This map reveals the complete shape of structures that are known locally, such as the Vela complex and the split of the local arm. Furthermore, our extinction map shows many large âclean bubblesâ, especially the one in the Sagittarius-Carina complex, and four others, which define a structure that we nickname the butterfly
Hétérogénéités de déformation au cours du forgeage d'aubes de turbine en alliage de titane TA6V
National audienc
FEDReD: I. 3D extinction and stellar maps by Bayesian deconvolution
International audienceContext. While Gaia enables us to probe the extended local neighbourhood in great detail, the thin disc structure at larger distances remains sparsely explored.Aims. We aim here to build a non-parametric 3D model of the thin disc structures handling both the extinction and the stellar density simultaneously.Methods. We developed a Bayesian deconvolution method in two dimensions: extinction and distance. It uses a reference catalogue whose completeness information defines the selection function. It is designed so that any complementary information from other catalogues can be added. It has also been designed to be robust to outliers, which are frequent in crowded fields, and differential extinction. The prior information is designed to be minimal: only a reference H-R diagram. We derived for this an empirical H-R diagram of the thin disc using Gaia DR2 data, but synthetic isochrone-based H-R diagrams can also be used.Results. We validated the method on simulations and real fields using 2MASS and UKIDSS data complemented by Gaia DR2 photometry and parallaxes. We detail the results of two test fields: a 2MASS field centred around the NGC 4815 open cluster, which shows an over-density of both extinction and stellar density at the cluster distance, and a UKIDSS field at lâ=â10° where we recover the position of the Galactic bar
Toward a 3D kinetic tomography of Taurus clouds: I. Linking neutral potassium and dust
International audienceContext: Gaia parallaxes and photometric measurements open a three-dimensional (3D) era for the Milky Way, including its interstellar (IS) matter. Three-dimensional Galactic dust distributions are constructed in various ways, based on Gaia data and photometric or spectroscopic surveys.Aims: The assignment of radial motions to IS dust structures seen in 3D, or 3D kinetic tomography, would be a valuable tool allowing one to connect the structures to emission lines of the associated gas, which are now measured at increasingly higher spectral and angular resolutions, and rich in information on physical and chemical processes. To this end, one of the potential techniques is to establish a link between dust clouds and Doppler velocities of absorption lines imprinted in stellar spectra by the gas associated with the dust. This requires a relatively close correlation between the absorber column and the dust opacity. We have investigated the link between the strength of interstellar KâŻI absorption and the opacity of the dust in front of stars in the Taurus area, and we have tested the feasibility of assigning velocities to 3D dust clouds on the basis of KâŻI absorption data.Methods: We have obtained high spectral resolution and high signal-to-noise spectra of 58 early-type stars in the direction of the Taurus, Perseus, and California molecular clouds. We have developed a new, dual interstellar and telluric profile-fitting technique to extract the interstellar KâŻI λλ 7665, 7699 â« absorption lines from stellar spectra and applied it to the new data and to archived spectra of 58 additional targets. In parallel, we have updated 3D dust maps reconstructed through the inversion of individual stellar light extinctions. To do so, we supplemented the catalog of extinction estimates based on Gaia and 2MASS photometry with recently published extinction catalogs based on stellar spectroscopic surveys. We used the 3D map and the set of velocity components seen in absorption to assign radial velocities to the dust clouds distributed along their paths in the most consistent way.Results: We illustrate our profile-fitting technique and present the KâŻI velocity structure of the dense ISM along the paths to all targets. As a validation test of the dust map, we show comparisons between distances to several reconstructed clouds with recent distance assignments based on different techniques. Target star extinctions estimated by integration in the 3D map are compared with their KâŻI 7699 â« absorptions and the degree of correlation is found comparable to the one between the same KâŻI line and the total hydrogen column for stars distributed over the sky that are part of a published high resolution survey. We show images of the updated dust distribution in a series of vertical planes in the Galactic longitude interval 150â182.5° and our estimated assignments of radial velocities to the opaque regions. Most clearly defined KâŻI absorptions may be assigned to a dense dust cloud between the Sun and the target star. It appeared relatively straightforward to find a velocity pattern consistent will all absorptions and ensuring coherence between adjacent lines of sight, at the exception of a few weak lines. We compare our results with recent determinations of the velocities of several clouds and find good agreement. These results demonstrate that the extinction-KâŻI relationship is tight enough to allow one to link the radial velocity of the KâŻI lines to the dust clouds seen in 3D and that their combination may be a valuable tool in building a 3D kinetic structure of the dense ISM. We discuss limitations and perspectives for this technique