- ID:
- ivo://CDS.VizieR/II/360
- Title:
- Gaia DR2 x AllWISE catalogue
- Short Name:
- II/360
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The second Gaia Data Release (DR2) contains astrometric and photometric data for more than 1.6 billion objects with mean Gaia G magnitude <20.7, including many Young Stellar Objects (YSOs) in different evolutionary stages. In order to explore the YSO population of the Milky Way, we combined the Gaia DR2 database with WISE and Planck measurements and made an all-sky probabilistic catalogue of YSOs using machine learning techniques, such as Support Vector Machines, Random Forests, or Neural Networks. Our input catalogue contains 103 million objects from the DR2xAllWISE cross-match table. We classified each object into four main classes: YSOs, extragalactic objects, main-sequence stars and evolved stars. At a 90% prob- ability threshold we identified 1 129 295 YSO candidates. To demonstrate the quality and potential of our YSO catalogue, here we present two applications of it. (1) We explore the 3D structure of the Orion A star forming complex and show that the spatial distribution of the YSOs classified by our procedure is in agreement with recent results from the literature. (2) We use our catalogue to classify published Gaia Science Alerts. As Gaia measures the sources at multiple epochs, it can efficiently discover transient events, including sudden brightness changes of YSOs caused by dynamic processes of their circumstellar disk. However, in many cases the physical nature of the published alert sources are not known. A cross-check with our new catalogue shows that about 30% more of the published Gaia alerts can most likely be attributed to YSO activity. The catalogue can be also useful to identify YSOs among future Gaia alerts.
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- ID:
- ivo://CDS.VizieR/J/A+A/649/A3
- Title:
- Gaia Early Data Release 3 photometric passbands
- Short Name:
- J/A+A/649/A3
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Gaia Early Data Release 3 (Gaia EDR3) contains astrometry and photometry results for about 1.8 billion sources based on observations collected by the European Space Agency Gaia satellite during the first 34 months of its operational phase. In this paper, we focus on the photometric content, describing the input data, the algorithms, the processing, and the validation of the results. Particular attention is given to the quality of the data and to a number of features that users may need to take into account to make the best use of the Gaia EDR3 catalogue. The processing broadly followed the same procedure as for Gaia DR2, but with significant improvements in several aspects of the blue and red photometer (BP and RP) preprocessing and in the photometric calibration process. In particular, the treatment of the BP and RP background has been updated to include a better estimation of the local background, and the detection of crowding effects has been used to exclude affected data from the calibrations. The photometric calibration models have also been updated to account for flux loss over the whole magnitude range. Significant improvements in the modelling and calibration of the Gaia point and line spread functions have also helped to reduce a number of instrumental effects that were still present in DR2. Gaia EDR3 contains 1.806 billion sources with G-band photometry and 1.540 billion sources with GBP and GRP photometry. The median uncertainty in the G-band photometry, as measured from the standard deviation of the internally calibrated mean photometry for a given source, is 0.2mmag at magnitude G=10 to 14, 0.8mmag at G~17, and 2.6mmag at G~19. The significant magnitude term found in the Gaia DR2 photometry is no longer visible, and overall there are no trends larger than 1mmag/mag. Using one passband over the whole colour and magnitude range leaves no systematics above the 1% level in magnitude in any of the bands, and a larger systematic is present for a very small sample of bright and blue sources. A detailed description of the residual systematic effects is provided. Overall the quality of the calibrated mean photometry in Gaia EDR3 is superior with respect to DR2 for all bands.
583. Gaia EDR3
- ID:
- ivo://CDS.VizieR/I/350
- Title:
- Gaia EDR3
- Short Name:
- I/350
- Date:
- 18 Jan 2022 09:31:17
- Publisher:
- CDS
- Description:
- Gaia DR3 data (both Gaia EDR3 and the full Gaia DR3) are based on data collected between 25 July 2014 (10:30 UTC) and 28 May 2017 (08:44 UTC), spanning a period of 34 months. As a comparison, Gaia DR2 was based on 22 months of data and Gaia DR1 was based on observations collected during the first 14 months of Gaia's routine operational phase. Survey completeness: The Gaia EDR3 catalogue is essentially complete between G=12 and G=17. The source list for the release is incomplete at the bright end and has an ill-defined faint magnitude limit, which depends on celestial position. The combination of the Gaia scan law coverage and the filtering on data quality which will be done prior to the publication of Gaia EDR3, does lead to some regions of the sky displaying source density fluctuations that reflect the scan law pattern. In addition, small gaps exist in the source distribution, for instance close to bright stars. Astrometry: The parallax improvement is typically 20% with respect to Gaia DR2. The proper motions are typically a factor two better than in Gaia DR2. An overall reduction of systematics has been achieved. E.g., the parallax zero point deduced from the extragalactic sources is about -20{mu}as. A tentative correction formula for the parallax zero point will be provided. Closer to the release date of Gaia Early Data Release 3, an update will be given on the astrometry. Photometry: The G-band photometric uncertainties are ~0.25mmag for G<13, 1mmag at G=17, and 5mmag at G=20mag. The GBP-band photometric uncertainties are ~1mmag for G<13, 10mmag at G=17, and 100mmag at G=20mag. The GRP-band photometric uncertainties are ~1mmag for G<13, 5mmag at G=17, and 50mmag at G=20mag. Closer to the release date of Gaia Early Data Release 3, an update will be given on the photometry. Gaia EDR3 does not contain new radial velocities. The radial velocities of Gaia Data Release 2 have been added to Gaia EDR3 in order to ease the combination of spectrosopic and astrometric data. Radial velocities: Gaia EDR3 hence contains Gaia DR2 median radial velocities for about 7.21 million stars with a mean G magnitude between ~4 and ~13 and an effective temperature (Teff) in the range ~3550 to 6900K. The overall precision of the radial velocities at the bright end is of the order of ~200-300m/s while at the faint end, the overall precision is ~1.2km/s for a Teff of 4750K and ~3.5km/s for a Teff of 6500K. Before publication in Gaia EDR3, an additional filtering has been performed onto the Gaia DR2 radial velocities to remove some 4000 sources that had wrong radial velocities. Please be aware that the Gaia DR2 values are assigned to the Gaia EDR3 sources through an internal cross-match operation. In total, ~10000 Gaia DR2 radial velocities could not be associated to a Gaia EDR3 source. Astrophysical parameters: Gaia EDR3 does not contain new astrophysical parameters. Astrophysical parameters have been published in Gaia DR2 and a new set is expected to be released with the full Gaia DR3 release. Variable stars: Gaia EDR3 does not contain newly classified variable stars. For the overview of the currently available variable stars from Gaia DR2, have a look here. Classifications for a larger set of variable stars are expected with the full Gaia DR3 release. Solar system objects: A large set of solar system objects with orbits will become available with the full Gaia DR3 release. Information on the currently available asteroids in Gaia DR2 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. The various chapters of the documentation have been indexed at ADS allowing them to be cited. Please visit the Gaia Archive (https://gea.esac.esa.int/archive) to access this documentation, and make sure to check out all relevant information given through the documentation overview page (https://www.cosmos.esa.int/web/gaia-users/archive).
- ID:
- ivo://CDS.VizieR/J/A+A/598/A5
- Title:
- Gaia-ESO Survey iDR4 calibrators
- Short Name:
- J/A+A/598/A5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Gaia-ESO survey (GES) is now in its fifth and last year of observations and has produced tens of thousands of high-quality spectra of stars in all Milky Way components. This paper presents the strategy behind the selection of astrophysical calibration targets, ensuring that all GES results on radial velocities, atmospheric parameters, and chemical abundance ratios will be both internally consistent and easily comparable with other literature results, especially from other large spectroscopic surveys and from Gaia. The calibration of GES is particularly delicate because of (i) the large space of parameters covered by its targets, ranging from dwarfs to giants, from O to M stars; these targets have a large wide of metallicities and also include fast rotators, emission line objects, and stars affected by veiling; (ii) the variety of observing setups, with different wavelength ranges and resolution; and (iii) the choice of analyzing the data with many different state-of-the-art methods, each stronger in a different region of the parameter space, which ensures a better understanding of systematic uncertainties. An overview of the GES calibration and homogenization strategy is also given, along with some examples of the usage and results of calibrators in GES iDR4, which is the fourth internal GES data release and will form the basis of the next GES public data release. The agreement between GES iDR4 recommended values and reference values for the calibrating objects are very satisfactory. The average offsets and spreads are generally compatible with the GES measurement errors, which in iDR4 data already meet the requirements set by the main GES scientific goals.
- ID:
- ivo://CDS.VizieR/IV/36
- Title:
- Gaia-IPHAS/KIS Value-Added Catalogues
- Short Name:
- IV/36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sub-arcsecond cross-match of Gaia DR2 (Cat. I/345) against the INT Photometric H-alpha Survey of the Northern Galactic Plane Data Release 2 (IPHAS DR2, Cat. II/321) and the Kepler-INT Survey (KIS, Cat. J/AJ/144/24). The resulting value-added catalogues (VACs) provide additional precise photometry to the Gaia photometry (r, i and H-alpha for IPHAS, with additional U and g for KIS). In building the catalogue, proper motions given in Gaia DR2 are wound back to match the epochs of IPHAS DR2, thus ensuring high proper motion objects are appropriately cross-matched. The catalogues contain 7927224 and 791071 sources for IPHAS and KIS, respectively. The requirement of >5 sigma parallax detection for every included source means that distances out to 1-1.5kpc are well covered. We define two additional parameters for each catalogued object: (i) fc, a magnitude-dependent tracer of the quality of the Gaia astrometric fit; (ii) fFP, the false-positive rate for parallax measurements determined from astrometric fits of a given quality at a given magnitude. Selection cuts based on these parameters can be used to clean colour-magnitude and colour-colour diagrams in a controlled and justified manner. We provide both full and light versions of the VAC, with VAC-light containing only objects that represent our recommended trade-off between purity and completeness. Uses of the catalogues include the identification of new variable stars in the matched data sets, and more complete identification of H-alpha-excess emission objects thanks to separation of high-luminosity stars from the main sequence.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A92
- Title:
- Gaia LMC eclipsing binary and multiple systems
- Short Name:
- J/A+A/606/A92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The advent of large scale multi-epoch surveys raises the need for automated light curve (LC) processing. This is particularly true for eclipsing binaries (EBs), which form one of the most populated types of variable objects. The Gaia mission, launched at the end of 2013, is expected to detect of the order of few million EBs over a 5-year mission. We present an automated procedure to characterize EBs based on the geometric morphology of their LCs with two aims: first to study an ensemble of EBs on a statistical ground without the need to model the binary system, and second to enable the automated identification of EBs that display atypical LCs. We model the folded LC geometry of EBs using up to two Gaussian functions for the eclipses and a cosine function for any ellipsoidal-like variability that may be present between the eclipses. The procedure is applied to the OGLE-III data set of EBs in the Large Magellanic Cloud (LMC) as a proof of concept. The bayesian information criterion is used to select the best model among models containing various combinations of those components, as well as to estimate the significance of the components. Based on the two-Gaussian models, EBs with atypical LC geometries are successfully identified in two diagrams, using the Abbe values of the original and residual folded LCs, and the reduced chi^2^. Cleaning the data set from the atypical cases and further filtering out LCs that contain non-significant eclipse candidates, the ensemble of EBs can be studied on a statistical ground using the two-Gaussian model parameters. For illustration purposes, we present the distribution of projected eccentricities as a function of orbital period for the OGLE-III set of EBs in the LMC, as well as the distribution of their primary versus secondary eclipse widths.
- ID:
- ivo://CDS.VizieR/J/MNRAS/481/307
- Title:
- Gaia Nuclear Transient (GNT) cand.
- Short Name:
- J/MNRAS/481/307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The high spatial resolution and precise astrometry and photometry of the Gaia mission should make it particularly apt at discovering and resolving transients occurring in, or near, the centres of galaxies. Indeed, some nuclear transients are reported by the Gaia Science Alerts (GSA) team, but not a single confirmed tidal disruption event (TDE) has been published. In order to explore the sensitivity of GSA, we performed an independent and systematic search for nuclear transients using Gaia observations. Our transient search is driven from an input galaxy catalogue (derived from the Sloan Digital Sky Survey Release 12). We present a candidate detection metric that is independent from the existing GSA methodology, to see if Gaia Alerts are biased against the discovery of nuclear transients, and in particular which steps may have an impact. Our technique does require significant manual vetting of candidates, making implementation in the GSA system impractical for daily operations, although it could be run weekly, which for month-to-year long transients would make a scientifically valuable addition. Our search yielded 480 nuclear transients, 5 of which were alerted and published by GSA. The list of (in some cases ongoing) transients includes candidates for events related to enhanced accretion on to a super-massive black hole and TDEs. An implementation of the detection methodology and criteria used in this paper as an extension of GSA could open up the possibility for Gaia to fulfil the role as a main tool to find transient nuclear activity as predicted in the literature.
- ID:
- ivo://CDS.VizieR/I/343
- Title:
- Gaia-PS1-SDSS (GPS1) proper motion catalog
- Short Name:
- I/343
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine Gaia DR1, PS1, Sloan Digital Sky Survey (SDSS), and 2MASS astrometry to measure proper motions for 350 million sources across three-fourths of the sky down to a magnitude of m_r_~20. Using positions of galaxies from PS1, we build a common reference frame for the multi-epoch PS1, single-epoch SDSS and 2MASS data, and calibrate the data in small angular patches to this frame. As the Gaia DR1 excludes resolved galaxy images, we choose a different approach to calibrate its positions to this reference frame: we exploit the fact that the proper motions of stars in these patches are linear. By simultaneously fitting the positions of stars at different epochs of-Gaia DR1, PS1, SDSS, and 2MASS-we construct an extensive catalog of proper motions dubbed GPS1. GPS1 has a characteristic systematic error of less than 0.3mas/yr and a typical precision of 1.5-2.0mas/yr. The proper motions have been validated using galaxies, open clusters, distant giant stars, and QSOs. In comparison with other published faint proper motion catalogs, GPS1's systematic error (<0.3mas/yr) should be nearly an order of magnitude better than that of PPMXL and UCAC4 (>2.0mas/yr). Similarly, its precision (~1.5mas/yr) is a four-fold improvement relative to PPMXL and UCAC4 (~6.0mas/yr). For QSOs, the precision of GPS1 is found to be worse (~2.0-3.0mas/yr), possibly due to their particular differential chromatic refraction.
- ID:
- ivo://CDS.VizieR/J/MNRAS/501/1116
- Title:
- GAIA pulsars and where to find them
- Short Name:
- J/MNRAS/501/1116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- While the majority of massive stars have a stellar companion, most pulsars appear to be isolated. Taken at face value, this suggests that most massive binaries break apart due to strong natal kicks received in supernova explosions. However, the observed binary fraction can still be subject to strong selection effects, as monitoring of newly discovered pulsars is rarely carried out for long enough to conclusively rule out multiplicity. Here, we use the second Gaia data release to search for companions to 1534 rotation-powered pulsars with positions known to better than 0.5arcsec. We find 22 matches to known pulsars, including 1 not reported elsewhere, and 8 new possible companions to young pulsars. We examine the photometric and kinematic properties of these systems and provide empirical relations for identifying Gaia sources with potential millisecond pulsar companions. Our results confirm that the observed multiplicity fraction is small. However, we show that the number of binaries below the sensitivity of Gaia and radio timing in our sample could still be significantly higher. We constrain the binary fraction of young pulsars to be f^true^_young_<5.3(8.3) per cent under realistic (conservative) assumptions for the binary properties and current sensitivity thresholds. For massive stars (>10M_{sun}_) in particular, we find f^true^_OB_<3.7 per cent, which sets a firm independent upper limit on the Galactic neutron star merger rate, <=7.2x10^-4^/yr. Ongoing and future projects, such as the CHIME/pulsar program, MeerTime, HIRAX, and ultimately the SKA, will significantly improve these constraints in the future.
- ID:
- ivo://CDS.VizieR/VI/137
- Title:
- GaiaSimu Universe Model Snapshot
- Short Name:
- VI/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Context: This study has been developed in the framework of the computational simulations that are executed for the preparation of the ESA Gaia astrometric mission. Aims: We focus on describing the objects and characteristics that Gaia will potentially observe without taking into consideration instrumental effects (detection efficiency, observing errors). Methods: The theoretical Universe Model prepared for the Gaia simulation has been statistically analysed at a given time. Ingredients of the model are described, with the greatest emphasis on the stellar content, the double and multiple stars, and variability. Results: In this simulation the errors have not yet been included. Hence we estimated the number of objects and their theoretical photometric, astrometric and spectroscopic characteristics if they are perfectly detected.We show that Gaia will be able to potentially observe 1.1 billion of stars (single or part of multiple star systems) of which about 2% are variable stars and 3% have one or two exoplanets. At the extragalactic level, observations will be potentially composed of several millions of galaxies, half a million to 1 million quasars and about 50,000 supernovae that will occur during the five years of the mission.
