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Journees 2014
List of abstracts
Session 1: Celestial reference system and frame
Session 2: Relativity and time scales
Session 3: Solar and extrasolar systems dynamics
Session 4: Earth's rotation and geodynamics
Session 5: Astronomical almanacs and software
Session 1:
Celestial reference system and frame
Some preliminary photometric results of QSOs useful for the link between future Gaia CRF and ICRF

Goran Damljanovic, Taris F. (SYRTE, Observatoire de Paris, France) and Boeva S. (Institute of Astronomy with NAO, BAS, Bulgaria)

Submitted for Session 1 (oral)

Institution of the first author:
Astronomical Observatory
Serbia

Gaia was launched in December 2013 as cornerstone mission of ESA. Its main goal is to map the entire Galaxy (over one billion stars) and more than 500000 quasars (QSOs); all objects with apparent V band magnitudes in the range 5.6<V<20. During its 5-year lifetime it will produce a unique time-domain space survey. It will be made a dense optical QSO-based Gaia CRF, and the link between future Gaia CRF and International CRF with the highest accuracy will be of importance. About 90% of the ICRF sources are not suitable for the link (they are not bright enough in optical domain, they have significant extended radio emission, etc.), but there are other (candidate) sources (weak extragalactic radio sources - ERS with bright optical counterparts) which we need to investigate. Some candidate sources were imaging by VLBI. And some sources were detected as useful ones on VLBI scales. The astrophysical processes could produce displacements of the optical photocenter of these objects, and because of it the variations of their light curves are important information to establish the link of reference systems. Our observations of 47 objects were carried out more than one year in the B, V and R bands using new telescope D(cm)/F(cm)=60/600 at the Astronomical Station Vidojevica - ASV of Astronomical Observatory in Belgrade (Serbia), and TJO (Telescopi Juan Oro) 0.8 m telescope in Observatori Astronomic del Montsec (Spain). Some photometric results are presented as a part of astrophotometric and astrophysical investigations of ERS in the framework of the reference systems.
The Galactic coordinate system based on multi-wavelength catalogues

Ping-Jie Ding, Jia-cheng Liu, Zi Zhu

Submitted for Session 1 (oral)

Institution of the first author:
Nanjing University
China

The Galactic coordinate system (GalCS) is important for studying structure, kinematics and dynamics of our Galaxy. The current GalCS, transformed from the FK4 system at B1950.0 to the FK5 system at J2000.0, was adopted by the Hipparcos Team. Since it is not connected directly to the International Celestial Reference System (ICRS), establishing a new GalCS based on recent observations is essential. We have carried out a series of work to find the Galactic plane and directions of three axes of the GalCS using data from four all-sky surveys 2MASS, SPECFIND, AKARI, and WISE. The wavelengths for these observations are no shorter than the near infrared wave, therefore the effect of extinction is not significant. By analyzing different methods employed in calculating three GalCs parameters, used for computing the transformation matrix from the equatorial system to the new GalCS, we have determined a most proper way to find an optimal GalCS, which means that the x-axis pointing to the observed Galactic center, and the x-y plane coincide with the best determined Galactic plane. After calculating the GalCS parameters in eight wavelengths, we synthesized these parameters with various wavelengths and the resulting parameters for defining the new GalCS in the ICRS are summarized as: alpha^p =192.777 deg, delta^p=26.9298 deg, for the equatorial coordinates of the north Galactic pole and theta =122.95017 deg for the position angle of the Galactic center.
First results of S/X and X/Ka-band catalogue combinations with full covariance information

Andreas Iddink, Christopher Jacobs, Thomas Artz, Axel Nothnagel

Submitted for Session 1 (oral)

Institution of the first author:
IGG, University of Bonn
Germany

The currently existing realizations of the International Celestial Reference System (ICRS), the ICRF1 and ICRF2, are based on solutions estimated by a single VLBI group. All sessions used were dual frequency S/X-band (2.3/8.4 GHz) VLBI sessions. In addition to an improved precision one of the main goals for the upcoming realization of the ICRF3 is an enhanced frequency coverage compared to the ICRF2. By including solutions with full variance-covariance information based on X/Ka-band (8.4/32GHz) observations in the rigorous VLBI intra-technique combination, an improved frequency coverage can be realized. In this paper, we present a method to mix the combination on the level of datum free NEQ and on the solution level with full covariance information. We show preliminary results of a combined S/X- and X/Ka-band catalogue and discuss the prerequisites and the limitations of this approach. Furthermore, we show the benefits for the upcoming ICRF3.
The stability of the ICRS axes

S Lambert

Submitted for Session 1 (oral)

Institution of the first author:
Observatoire de Paris - SYRTE
France

The ICRS axes are defined by the coordinates of distant radio sources observed by the VLBI. The stability of the axes is primarily depending on the apparent variations of sources' coordinates which are due to intrinsic phenomenon like, e.g., jets and flux variations, or to global effects like the galactic aberration. The mismodeling of the Earth's nutation and precession also affects the position of the celestial pole as defined by the TRF-to-CRF coordinate transformation. In this talk, I will review the various points above and comment the accuracy of the current quasar catalogs and nutation series.
Binary black hole systems and the ICRF

S Lambert, J. Roland

Submitted for Session 1 (poster)

Institution of the first author:
Observatoire de Paris - SYRTE
France

Last two decades of VLBI observations bring strong evidences that quasars host black hole systems. Studies of VLBA maps at 15GHz of some well-observed radiosources suggest binary black hole (BBH) systems of apparent radius of few hundreds of microarcseconds, i.e., several times larger than the current accuracy of the ICRF source positions. In this study, we compare the results of fitting BBH system parameters to VLBI data against geodetic VLBI results. We also address the possible consequences of BBH systems for high precision astrometry in the current geodetic VLBI program as well as for higher frequency observations and the future link to Gaia.
Using positional observations of numbered minor planets for determination of star catalog errors

Yurii Medvedev, Kuznetsov V.B.

Submitted for Session 1 (oral)

Institution of the first author:
Institute of Applied Astronomy RAS
Russia

The systematic errors of star catalogs have been defined by the O-C ("observed-calculated" residuals) for the asteroid positional observations. Improvement of asteroid orbits was carried out by differential method which was conducted in two steps. At the first step the orbital elements of Ceres, Pallas and Vesta were improved, taking into account the perturbations from the major planets, the Moon, Pluto using DE405 and their mutual perturbations. Then we calculated ephemerides of these three planets. To calculate the orbital elements of other numbered asteroids we used obtained ephemerides and all available positional observations. The mean value of O-C was calculated for each of 10212 equal areas on the celestial sphere and interpreted as a star catalog systematic bias for the corresponding area. Error of this value depends on number of O-C and number of planets which observations were used for calculation in this area. We calculated the systematic errors of USNO A2.0 and UCAC-2 and 3. The estimations of variation of systematic errors for the USNO A2.0 catalog have been defined also. Our calculation shows considerable variation of systematic errors of USNO A2.0, especially in declination. This allows us to conclude, that values of systematic errors for this catalog are changed not only from area to area, but also with time. It means that the observations based on this catalog must be corrected not only depending on various areas, but various epochs as well.
Some common problems in geodesy and astrometry after establishing ICRF

Victor Popadyov, Tolchelnikova S. A.

Submitted for Session 1 (oral)

Institution of the first author:
Centre de geodesie et cartographie (CNIIGAiK)
Russie

Revolution in astrometry on the border of XX - XXI centuries was a result of technical progress in equipment and methods of observations. Since that time radio system ICRF was established as the main reference frame for astrometry and sciences connected to it, e. g. geodesy and gravimetry. During previous years stars were used as reference points and unity of the sciences based on observations, was achieved by means using the plumb lines as terrestrial reference at observatories. The expansion of this terrestrial frame to vertical lines in many places has been one of the purposes of geodetic measurements. We consider this very useful empirical unity of three branches of the one indivisible science should be preserved. Up to now some parameters geodesists get or use in common with astronomy, therefore we consider a comparison of different views will be helpful. We suppose Journees "System de Reference Spatio-Temporale" is the most important place for discussion of fundamental problems of modern astronomy.
On the systematics in apparent proper motions of radio sources observed by VLBI

Virginia Raposo-Pulido, Sebastien Lambert, Nicole Capitaine, Tobias Nilsson, Robert Heinkelmann, and Harald Schuh

Submitted for Session 1 (oral)

Institution of the first author:
IGN / GFZ
Germany

Since about twenty years, several authors have investigated the systematics in the apparent proper motions of radio source positions. In some cases, the theoretical work developed (Pyne et al., 1996) could not be assessed due to the few number of VLBI observations. In other cases, the effects attributed to apparent proper motion could not be related successfully because of there were not significant evidences from a statistical point of view (MacMillan, 2005). In this work we provide preliminary results about the estimation of the coefficients of spherical harmonics, based on a Three-step procedure: (i) Radio source time series from VLBI analysis (VieVS software), (ii) Apparent proper motions fitted to their coordinate time series, (iii) Spherical harmonics fitted to the proper motion field. The early stage of this work has been to compare step by step the computations and estimation process between the CALC and VieVs software. To do that, the results were analyzed and compared with the previous study done by Titov and Lambert in 2013. With the improvement of the VLBI system and the increase of number of VLBI observations, we aim to provide useful information regarding the current situation of the radio sources observed with VLBI.
Comparison of astrometric catalogues UCAC4, XPM, PPMXL

Alexander Tsvetkov, V.V.Vityazev

Submitted for Session 1 (oral)

Institution of the first author:
St. Petersburg State University
Russia

The fast procedure to represent the systematic differences of proper motions of stars in UCAC4, XPM and PPMXL catalogues by means of vector spherical harmonics in galactic coordinate system is suggested. The representation of the differences UCAC4-PPMXL, XPM-UCAC4 and XPM-PPMXL by vector spherical harmonics is made in the 10 to 16 J mag range. It was found that the absolute proper motion XPM catalogue has the least systematic deviation from the ICRS proper motion catalogue UCAC4 in the 12-16 J mag range. The magnitude equation in the differences was found. The influence of systematic differences of proper motions on the determination of kinematical parameters is discussed.
Morphology of QSO Host Galaxies - a look at the SED

Alexandre Humberto Andrei, Bruno Coelho (O.V./UFRJ-BR), Sonia Anton (1-CICGE/FCUP-PO; 2-SIM/FCUL-PO)

Submitted for Session 1 (oral)

Institution of the first author:
(1) ON/MCTI-BR; (2) OV/UFRJ-BR; (3) SYRTE/OP-FR; (4) OATo/INAF-IT
Brasil

We develop a program to study the host galaxies of QSOs present in the SDSS up to its 8th release. The main observational data thus comprises a large retrieved data bank of images in the ugriz colors for the 105,783 objects spectroscopically found as QSOs, within frames containing tens of comparison stars and several field galaxies. Complementary, images of nearly 200 bright quasars that will be used to link the future GCRF to the ICRF were taken using 2m class telescopes, over the entire sky. The first scope of this program is to select QSOs for which the isophotes of the host galaxy are not pronounced so that the centroid determination is not affected over those fundamental grid-points of the GCRF. Ancillary we prepare templates upon which the Gaia observations of the ensemble QSO plus host galaxy can be interpreted. This program in itself aims to discuss the characteristics of the host galaxy on basis of this large, statistically complete sample of images. Since the target images come from relatively short exposures, our approach is to access disturbances of the target PSF relatively to the nearby stars, as well as the photometric ratio between the central and the peripherical portions, and the interpretation of best morphological fit. We present the first results for absolute magnitude of QSOs combining the SDSS colors and the SED library from Gaia. Finally we discuss the findings of the signature of the presence of host galaxies at redshifts larger than one in terms of the population of young stars in the host galaxy, fostered up by the presence of the central QSO.
Core sources set selection

Sergey Kurdubov, Elena Skurikhina

Submitted for Session 1 (poster)

Institution of the first author:
Institute of Applied Astronomy RAS
Russia

Ranking method for sources sets in order to select the list of sources that better define the orientation parameters of rigid rotation transformation from one system to another suggested in earliest works is applied. The transformation parameters formal errors were selected as characteristic of sources set. For all catalogues IVS WG2 was selected special order in the sources list and obtained transformation parameters accuracy as function of the number of sources. For all catalogues that function has a minimum between 300 and 400 sources, adding the sources after the minimum leads to increasing formal errors of orientation parameters. After that we selected the common sources which placed before minimum of functions and obtained the "optimal set". Source position time series were obtained and analyzed for the optimal set of sources. It was shown that some of the core sources have unstable positions and need to be excluded from optimal set. Nevertheless time series shows that mainly optimal source set consists from stable sources.
On the transition to the radio system coordinates ICRF

Anton Lipovka, Lipovka N.M.

Submitted for Session 1 (poster)

Institution of the first author:
Sonora state university
Mexico

ICRF Radio Catalogue was recommended by IAU in 2009 as a main reference coordinate system, to which all results of observations in optical wavelength range should be agreed. In this paper we show that the binding of the optical and radio sky must be proved and confirmed by the coincidence of several objects in radio and optic in the investigated field, within the first lobe of the radio interferometer. Paradox of mismatching (non-coincidence) of most part of radio objects with the optical ones, should be resolved by using the correct method of the identification of the radio sources with the optical ones.
On the selection of the common VLBI/Gaia sources

Zinovy Malkin

Submitted for Session 1 (poster)

Institution of the first author:
Pulkovo Observatory
Russia

IAU-approved International Celestial Reference Frame (ICRF) is based on the source position catalog obtained from VLBI observations. It is expected that by the end of this decade, the new highly accurate Gaia Celestial Reference Frame (GCRF) will be available. Comparison and merging of these frames is one of the actual tasks of modern astrometry. The accuracy of the ICRF-GCRF link would benefit of larger number of extragalactic objects, primarily quasars, which have precise VLBI-derived position and are bright enough to be reliably observed with Gaia. An extended list of optically bright radio sources suitable for the alignment of GCRF to ICRF is discussed in this presentation.
The ICRF-3: Status, Plans, and Progress on the next generation Celestial Reference Frame

Zinovy Malkin, Christopher S. Jacobs, ICRF-3 IAU Working Group

Submitted for Session 1 (oral)

Institution of the first author:
Pulkovo Observatory
Russia

ICRF-3 seeks to improve upon the highly successful ICRF-2. Our goals are to improve the precision, spatial and frequency coverage relative to the ICRF-2 by 2018. This date is driven by the desire to create radio frames that are ready for comparison with the Gaia optical frame. Several specific actions are underway. A collaboration has started to improve at S/X-band precision of the VLBA Calibrator Survey' 2000+ sources which are typically 5 times less precise than the rest of the ICRF-2. S/X-band southern precision improvements are planned from observations with southern antennas such as the AuScope and HartRAO, S. Africa. We seek to improve radio frequency coverage with X/Ka and K-band work. An X/Ka frame of 640 sources now has full sky coverage from the addition of a 2nd southern station in Argentina which should strengthen the southern hemisphere in general. A K-band collaboration has formed with similar coverage and southern precision goals. On the analysis front, special attention will be given to combination techniques both of VLBI catalogs and of multiple data types. Consistency of the CRF with the TRF and EOP is another area of concern. Finally, work is underway to identify and pinpoint sources bright enough in both radio and optical to allow for a robust frame tie between VLBI and Gaia optical frames.
Optical monitoring of QSOs in the framework of the Gaia space mission

Francois Taris, G. Damljanovic , A. Andrei

Submitted for Session 1 (poster)

Institution of the first author:
Observatoire de Paris - SyRTE
France

The Gaia astrometric mission of the European Space Agency has been launched the 19th December 2013. It will provide an astrometric catalogue of 500.000 extragalactic sources that could be the basis of a new optical reference frame after the Hipparcos satellite one. On the other hand, the current International Celestial Reference Frame (ICRF) is based on the observations of extragalactic sources at radio wavelength. The astrometric coordinates of sources in these two reference systems will have roughly the same uncertainty. It is then mandatory to observe a set of common targets at both optical and radio wavelength to link the ICRF with what could be called the GCRF (Gaia Celestial Reference Frame). This poster presents the set of optical telescopes used to observe the targets chosen for the link of the two reference systems. More precisely we will focus on results obtained with the TJO, Telescopi Juan Oro, from Observatori Astronomic del Montsec in Spain. It also presents some results obtained with the Lomb-Scargle method applied to optical magnitude monitoring of extragalactic sources suitable for the GCRF-ICRF link. A morphological index is defined and applied to the 5000 images obtained during a first observation campaign.
Kinematics derived from Northern and Southern Galactic hemispheres of huge ICRS optical catalogues

Veniamin Vityazev, A.S.Tsvetkov