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Start Over Subject astrometry Validation Level 2
231. Gaia GraL. II. Known multiply imaged quasars
ID:
ivo://CDS.VizieR/J/A+A/618/A56
Title:
Gaia GraL. II. Known multiply imaged quasars
Short Name:
J/A+A/618/A56
Date:
21 Oct 2021
Publisher:
CDS
Description:
Thanks to its spatial resolution the ESA/Gaia space mission offers a unique opportunity to discover new multiply-imaged quasars and to study the already known lensed systems at sub-milliarcsecond astrometric precisions. Aims : In this paper, we address the detection of the known multiply-imaged quasars from the Gaia Data Release 2 and determine the astrometric and photometric properties of the individually detected images found in the Gaia DR2 catalogue. We have compiled an exhaustive list of quasar gravitational lenses from the literature to search for counterparts in the Gaia Data Release 2. We then analyze the astrometric and photometric properties of these Gaia's detections. To highlight the tremendous potential of Gaia at the sub-milliarcsecond level we finally perform a simple Bayesian modeling of the well-known gravitational lens system HE0435-1223, using Gaia Data Release 2 and HST astrometry. From 478 known multiply imaged quasars, 200 have at least one image found in the Gaia Data Release 2. Among the 41 known quadruply-imaged quasars of the list, 26 have at least one image in the Gaia Data Release 2, 12 of which are fully detected (2MASX J01471020+4630433, HE 0435-1223, SDSS1004+4112, PG1115+080, RXJ1131-1231, 2MASS J11344050-2103230, 2MASS J13102005-1714579, B1422+231, J1606-2333, J1721+8842, WFI2033-4723, WGD2038-4008), 6 have three counterparts, 7 have two and 1 has only one. As expected, the modeling of HE0435-1223 shows that the model parameters are significantly better constrained when using Gaia astrometry compared to HST astrometry, in particular the relative positions of the background quasar source and the centroid of the deflector. The Gaia sub-milliarcsecond astrometry also significantly reduces the parameter correlations. Besides providing an up-to-date list of multiply imaged quasars and their detection in the Gaia DR2, this paper shows that more complex modeling scenarios will certainly benefit from Gaia sub-milliarcsecond astrometry.
232. Gaia-IPHAS/KIS Value-Added Catalogues
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.
233. Gaia-PS1-SDSS (GPS1) proper motion catalog
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.
234. GaiaSimu Universe Model Snapshot
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.
235. Galactic Center secondary IR astrometric standards
ID:
ivo://CDS.VizieR/J/ApJ/830/17
Title:
Galactic Center secondary IR astrometric standards
Short Name:
J/ApJ/830/17
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new, more precise measurements of the mass and distance of our Galaxy's central supermassive black hole, Sgr A*. These results stem from a new analysis that more than doubles the time baseline for astrometry of faint stars orbiting Sgr A*, combining 2 decades of speckle imaging and adaptive optics data. Specifically, we improve our analysis of the speckle images by using information about a star's orbit from the deep adaptive optics data (2005-2013) to inform the search for the star in the speckle years (1995-2005). When this new analysis technique is combined with the first complete re-reduction of Keck Galactic Center speckle images using speckle holography, we are able to track the short-period star S0-38 (K-band magnitude=17, orbital period=19yr) through the speckle years. We use the kinematic measurements from speckle holography and adaptive optics to estimate the orbits of S0-38 and S0-2 and thereby improve our constraints of the mass (M_bh_) and distance (R_o_) of SgrA*: M_bh_=(4.02+/-0.16+/-0.04)x10^6^M_{sun}_ and 7.86+/-0.14+/-0.04kpc. The uncertainties in M_bh_ and R_o_ as determined by the combined orbital fit of S0-2 and S0-38 are improved by a factor of 2 and 2.5, respectively, compared to an orbital fit of S0-2 alone and a factor of ~2.5 compared to previous results from stellar orbits. This analysis also limits the extended dark mass within 0.01 pc to less than 0.13x10^6^M_{sun}_ at 99.7% confidence, a factor of 3 lower compared to prior work.
236. Galaxies in the Tycho-2 catalogue
ID:
ivo://CDS.VizieR/J/A+A/413/771
Title:
Galaxies in the Tycho-2 catalogue
Short Name:
J/A+A/413/771
Date:
21 Oct 2021
Publisher:
CDS
Description:
The accuracy of the link of the proper motion system of astrometric satellite missions like AMEX and GAIA is discussed. Monte-Carlo methods were used to simulate catalogues of positions and proper motions of quasars and galaxies to test the link. The main conclusion is, that future satellite missions like GAIA may be "self-calibrated" by their measurements of QSOs, while additional measurements from radio stars or HST-data are needed to calibrate the less deep reaching astrometric satellite missions of AMEX type.
237. Galaxy coordinates. II
ID:
ivo://CDS.VizieR/J/A+AS/140/89
Title:
Galaxy coordinates. II
Short Name:
J/A+AS/140/89
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using images of the Digitized Sky Survey we measured coodinates for 17298 galaxies having poorly defined coordinates. As a control, we measured with the same method 1522 galaxies having accurate coordinates. The comparison with our own measurements shows that the accuracy of the method is about 6 arcsec on each axis (RA and DEC).
238. Galilean moons & Jupiter positions
ID:
ivo://CDS.VizieR/J/other/SoSyR/50.344
Title:
Galilean moons & Jupiter positions
Short Name:
J/other/SoSyR/50
Date:
21 Oct 2021
Publisher:
CDS
Description:
Observational results are presented for Jupiter and its Galilean moons from the Normal Astrograph at Pulkovo Observatory in 2013-2015. The following data are obtained: 154 positions of the Galilean satellites and 47 calculated positions of Jupiter in the system of the UCAC4 (ICRS, J2000.0) catalogue; the differential coordinates of the satellites relative to one another are determined. The mean errors of the satellites normal places in right ascension and declination over the entire observational period are, respectively: (eps)RA=0.0065" and (eps)DE=0.0068", and their standard deviations are (sigm)RA=0.0804" and (sigm)DE=0.0845". The equatorial coordinates are compared with planetary and satellite motion theories. The average (O-C) residuals in the two coordinates relative to the motion theories are 0.05" or less. The best agreement with the observations is achieved by a combination of the EPM2011m and V. Lainey-V.2.0|V1.1 motion theories; the average (O-C) residuals are 0.03" or less. The (O-C) residuals for the features of the positions of Io and Ganymede are comparable with measurement errors. Jupiter's positions calculated from the observations of the satellites and their theoretical jovicentric coordinates are in good agreement with the motion theories. The (O-C) residuals for Jupiter's coordinates are, on average, 0.027" and -0.025" in the two coordinates.
239. Galilean moons positions
ID:
ivo://CDS.VizieR/J/other/SoSyR/52.312
Title:
Galilean moons positions
Short Name:
J/other/SoSyR/52
Date:
21 Oct 2021
Publisher:
CDS
Description:
Results of the Galilean moons observationals taken with Normal Astrograph of the Pulkovo Observatory in 2016-2017 are presented. 761 positions of the Galilean moons of Jupiter in the system of the Gaia DR1 catalog (ICRF, J2000.0) and 854 differential coordinates of the satellites relative to each other were obtained. The mean errors in the satellites' normal places and the corresponding root-mean-square deviations are (eps)RA=0.0020", (eps)DE=0.0027", (sigm)RA=0.0546", and (sigm)DE=0.0757". The equatorial coordinates of the moons are compared to the motion theories of planets and satellites. On average, the (O-C) residuals in the both coordinates relative to the motion theories are less than 0.031". The best agreement with observations is achieved by a combination of the EPM2015 and V. Lainey-V.2.0|V1.1 motion theories, which yields the average (O-C) residuals of approximately 0.02". Peculiarities in the behavior of the (O-C) residuals and error values in Ganymede have been noticed.
240. Galilean satellites & Jupiter positions
ID:
ivo://CDS.VizieR/J/other/SoSyR/49.383
Title:
Galilean satellites & Jupiter positions
Short Name:
J/other/SoSyR/49
Date:
21 Oct 2021
Publisher:
CDS
Description:
For observational period of 2009-2011 we have obtained 140 positions of Galilean satellites and 42 calculated positions of Jupiter in the system of UCAC4 catalogue (ICRS, J2000.0). Accuracy estimation gives error of mean position as 0.02-0.04". The resulting equatorial coordinates satellites were compared with the eight contemporary theories of the motion of planets and satellites. On average, the (O-C) residuals in both coordinates do not exceed 0.08" relative to all theories of motion. Comparison of the calculated equatorial coordinates of Jupiter (were obtained from observations of galilean satellites) with the INPOP10 theory of planetary motion has shown satisfactory results. The average deviations were obtained respectively (O-C)RA=0.040" and (O-C)DE=-0.053". This work was supported by the Program 22 of the Presidium of RAS and RFBR grant (12-02-00675-a).

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