The following are the talks for our scientific meeting. Note that there are no Gaia talks among them. This is because there will be many Gaia talks being given during the 2 weeks at other meetings. See the Gaia web pages for more details. Also during the Division I business meeting there will be a special Gaia session. See the end of this page for more details. During the Business Meeting, van Altena will give two short presentations on SPM4 and his new astrometry book.

The talk lengths are indicted by N+2 minutes. N minutes are allocated to the talks and 2 minutes for discussion. Please keep to time.

Clicking on the title will give you access to the presentation if available.

Session 3

1. 400 Years of Astrometry: From Tycho Brahe to Hipparcos
   Erik Høg
   Niels Bohr Institute, Copenhagen
   The four centuries of techniques and results are reviewed, from the pre-telescopic era until the use of photoelectric astrometry and space technology in the first astrometry satellite, Hipparcos, launched by ESA in 1989. Galileo Galilei's use of the newly invented telescope for astronomical observation resulted immediately in epochal discoveries about the physical nature of celestial bodies, but the advantage for astrometry came much later. The quadrant and sextant were pre-telescopic instruments for measurement of large angles between stars, improved by Tycho Brahe in the years 1570-1590. Fitted with telescopic sights after 1660, such instruments were quite successful, especially in the hands of John Flamsteed. The meridian circle was a new type of astrometric instrument, already invented and used by Ole Roemer in about 1705, but it took a hundred years before it could fully take over. The centuries-long evolution of techniques is reviewed, including the use of photoelectric astrometry and space technology in the first astrometry satellite, Hipparcos, launched by ESA in 1989. Hipparcos made accurate measurement of large angles a million times more efficiently than could be done in about 1950 from the ground, and it will soon be followed by Gaia which is expected to be another one million times more efficient for optical astrometry.
   23+2 minutes

2. Series of JASMINE projects - Exploration of the Galactic Bulge
   Naoteru Gouda and JASMINE Working Group
   National Astoronomical Observatory of Japan
   At first, we briefly introduce the following series of JASMINE projects in Japan:

   1. Nano-JASMINE project: Nano-JASMINE project is planned to demonstrate the first space astrometry in Japan and to perform experiments for verifications of some technics and operation in JASMINE. Nano-JASMINE uses a nano-satellite whose size and weight are about 50 cm^3 and 25 kg, respectively. The targeted accuracy of parallaxes is about 3 mas at z=7.5 mag. Moreover we can get proper motions with high accuracies(0.1 mas/year) combining Nano-JASMINE catalogue with the Hipparcos catalogue. We have a chance that Nano-JASMINE will be launched by Cyclone-4 rocket in July 2010 with high possibility.
   2. Small-JASMINE project: Small-JASMINE is an astorometric mission that observes in an infrared band(Kw-band: central wavelength is 2.0 micron(1.5 micron - 0.5 micron)). Small-JASMINE will determine positions and parallaxes accurate to 10 micro-arcseconds for stars in the Galactic bulge, brighter than Kw=11 mag, and proper motion errors of 10 micro-arcseconds/yr. It will observe small areas of the Galactic bulge with a single beam telescope whose the diameter of the primary mirror is around 30cm. A target launch date is around 2015. The main science objective of small-JASMINE is to clarify the formation history of the Galactic bulge and also determine the moderate model of the bulge structure formation.
   3. JASMINE project: JASMINE is an extended mission of small-JASMINE mission. It is designed to perform a survey towards the whole Galactic bulge region with a single-beam telescope whose the diameter of the primary mirror is around 80cm, determining positions and parallaxes accurate to 10 micro-arc seconds for stars brighter than Kw=11 mag, and proper motion errors of 10 micro-arc seconds/yr. A target launch date is around the first half of the decades in 2020s.

   After the introduction of the series of JASMINE projects, we will focus on the small-JASMINE mission and its science objectives in our presentation.
   18+2 minutes

3. A Very Small Satellite for Space Astrometry: Nano-JASMINE
   Yoichi Hatsutori, Naoteru Gouda, Yukiyasu Kobayashi, Taihei Yano,Yoshiyuki Yamada, and Nano-JASMINE team
   National Astoronomical Observatory of Japan
   The outline and the current status of the Nano-JASMINE project is presented. The objective of this project is a scientific astrometry, technical demonstration for JASMINE and a first experience of space astrometry in Japan. Nano-JASMINE is a very small satellite for space astrometry. It has only 25 kg and aims to carry out astrometry measurement of nearby bright stars (z<7.5mag) with an accuracy of 3 milli- arcseconds. This satellite adopts the same observation technique used by HIPPARCOS satellite. In this technique, two different fields of view are observed by beam-combiner simultaneously. Nano-JASMINE telescope is based on a standard Ritchey-Chretien type optical system and has a beam-combiner, a 5 cm effective aperture, a 167 cm focal length and a field of view of 0.5x0.5 degree. The major technical difference between Nano-JASMINE and HIPPARCOS is a CCD sensor. A full depletion CCD will be used in the time delay integration (TDI) mode in order to efficiently survey the whole sky in wavelengths including the near infrared. By using TDI mode, Nano-JASMINE will achieve astrometry accuracy comparable to that achieved by HIPPARCOS with such a small satellite. From a scientific viewpoint, Nano-JASMINE measure the same stars that were observed by HIPPARCOS with the same accuracy, then we can significantly improve the accuracy of proper motion and correct the degradation of the HIPPARCOS catalogs. The current status of Nano-JASMINE is in the process of production as engineering model. Thermal tests and vibration tests were already conducted with Structure-Thermal Model (STM) in last summer, the design validation of satellite was confirmed. Moreover, it is confirmed that the telescope can achieved diffraction limit by the performance test. We have a plan to launch Nano-JASMINE in 2010. National Astronomical Observatory of Japan, The University of Tokyo, Alcantara Cyclone Space and SDO Yuzhnoye reached a consensus to launch Nano-JASMINE by Cyclone-4 rocket in the Federal Republic of Brazil.
   13+2 minutes

4. The Second Realization of the International Celestial Reference Frame: ICRF-2
   Alan L. Fey
   USNO
   Construction of a second realization of the International Celestial Reference Frame, ICRF-2, has been underway for the last several years. The work was carried out by two working groups: the ICRF-2 Working Group of the International Earth Rotation and Reference System Service (IERS) in cooperation with the International VLBI Service for Geodesy and Astrometry (IVS) and the ICRF-2 Working Group of the International Astronomical Union. The task of the IERS/IVS Working Group was to generate ICRF-2 from Very Long Baseline Interferometry observations of extragalactic radio sources consistent with the current realization of the International Terrestrial Reference Frame and Earth Orientation Parameter data products with oversight from the IAU Working Group. A brief summary of the results are presented.
   18+2 minutes

5. Strengthening the ICRS optical link in the northern hemisphere
   P. Popescu, A. Nedelcu, O. Badescu, P. Paraschiv,
   Astronomical Institute of Romanian Academy
   In 2005 Astronomical Institute of Romanian Academy has started an observational program, using Belogradchik Zeiss Telescope (Bulgaria), to investigate the link between the International Celestial Reference Frame (ICRF) and its representation at optical wave-lengths. 59 astrometric positions of ICRF optical counterparts were obtained with average values of the optical-radio offsets of +6 mas and +7 mas in R.A. and Declination and standard deviation of 51 mas and 57 mas respectively. The radio-stars astrometry program is in work and it will be extended to include sources from VLBA Calibrator Survey - the largest high resolution radio survey available.
   12+2 minutes

   Session 4

6. UCAC, NOMAD, URAT - star catalogs for astrometry
   Norbert Zacharias
   USNO
   Properties of the final release of the USNO CCD Astrograph Catalog are presented. This all-sky astrometric catalog supersedes UCAC2. The USNO Robotic Astrometric Telescope is a new observing program which will begin in late 2009. Plans for updates of the Naval Observatory Merged Astrometric Dataset (NOMAD) are discussed and recommendations given about the "best" star catalog to be used for astrometric reference stars for the general astronomer.
   18+2 minutes

7. Determination of L Dwarf Distances and Objects in the L/T Transition
   Richard Smart (1), Jucira Lousada Penna (2) , Alexandre H. Andrei (2,3), Ramachrisna Teixeira (4), Beatrice Bucciarelli (1), Victor A. d'vila (2), Julio Ignácio Bueno de Camargo (2), Dario N. da Silva Neto (5), Mario Lattanzi (1), Kátia M.L. da Cunha (2,6)
   1. INAF/Osservatorio Astronomico di Torino, Italy
   2. Observatorio Nacional/MCT, Brasil
   3. Observatorio do Valongo/UFRJ, Brasil
   4. Instituto Astronômico e Geofísico/USP, Brasil
   5. Centro Universitario Estadual da Zona Oeste, Brasil
   6. National Optical Astronomy Observatory, USAA PROGRAM FOR THE SYSTEMATIC
   L and T dwarfs are ultracool objects, cooler than M dwarfs, which are fundamental to the understanding of the star/planet transition. They have spectra dominated by molecular absorption due to water, methane and pressure-induced molecular hydrogen. Since the first defining L dwarfs GD165B known in 1997 there have been nearly 500 discovered. These come primarily from the Sloan Digital Sky Survey and from 2MASS. Model atmosphere analyses indicate temperatures of 2500 to 750 K. To understand the intrinsic properties of ultra cool dwarfs and ultimately massive Jupiter-like exoplanets, it is essential to determine their absolute luminosities. The only direct method to achieve this is with astrometric parallaxes, yet to date less than 40 have measured parallaxes. In this project it is undertaken a systematic determination of L and T dwarf parallaxes. While the sequence of subdwarf luminosities is already reasonably defined by the objects with known parallaxes, this program allows a substantial improvement on that calibration and allow for direct confrontation with the structure models for sub-stellar objects. The observations are being made at the WFI ESO2.2m, La Silla. The program started in April 2007 and has secured time at least to the end of 2009. It contains 140 objects, all of which already with four or more observations. Typically the observations are made every other month, and so far there are at least four observations for each object, up to ten observations. This has enabled a first determination of parallaxes to some objects and a comprehensive study of the 2MASS referred proper motion field. The astrometric repeatability is at 10mas. At this level there is a significant reduction on the length and number of observations usually required for this type of program.
   18+2 minutes

8. The LQRF - An Optical Representation of the ICRS
   A.H. Andrei(1,2,3), J. Souchay(3), N. Zacharias(4),R.L. Smart(5), R. Vieira Martins(1,2), D.N. da Silva Neto(2,6), J.I.B. Camargo(2), M. Assafin(2), C. Barache(3), S. Bouquillon(3), J.L. Penna(1)
   1. Observatorio Nacional/MCT, Brasil
   2. Observatorio do Valongo/UFRJ, Brasil
   3. Observatoire de Paris/SYRTE, France
   4. US Naval Observatory, USA
   5. INAF/Osservatorio Astronomico di Torino, Italy
   6. Centro Universitario Estadual da Zona Oeste, Brasil
   The large number, and all sky repartition of quasars from different surveys combined with their presence in large, deep astrometric catalogues, enables to build an optical materialization of the ICRS following its defining principles - namely, kinematically non-rotating with respect to the ensemble of distant extragalactic objects, aligned to the mean equator and dynamical equinox of J2000, and realized by a list of adopted coordinates of extragalatic sources. The LQRF (Large Quasar Reference Frame) was build with the care of avoiding misrepresentation of its constituents quasars, of homogenizing the astrometry from the different catalogues and lists from which the constituent quasars are gathered, and of attaining the milli-arcsecond global alignment to the ICRF, as well as typical individual source position accuracies even to better than 100 milli-arcsecond. Starting from the updated and presumably complete LQAC (Large Quasar Astrometric Catalog) list of QSOs, initial optical positions for those quasars are found in the USNO B1.0 and GSC2.3 catalogues, and from the SDSS Data Release 5. The initial positions are next placed onto UCAC2 based reference frames, following by an alignment to the ICRF, as well as of the most precise sources from the VLBA calibrator list and from the VLA calibrator list - in the three cases under the proviso that also reliable optical counterparts exist. Finally the LQRF axis are surveyed through spherical harmonics, contemplating right ascension, declination and magnitude terms. The LQRF contains 100,165 quasars, well represented on all-sky basis, from -83.5 to +88.5 degrees of declination, and with 10 arcmin as the average distance between adjacent elements. The global alignment to the ICRF is of 1.5 mas, and the individual position accuracies are represented by a Poisson distribution peaking at 139 mas on right ascension and at 130 mas on declination. As a by product, significant equatorial corrections appear for all the used catalogues (but the SDSS DR5), an empirical magnitude correction can be discussed for the GSC2.3 intermediate and faint regimens, both the 2MASS and the preliminary northernmost UCAC2 positions show consistent astrometric accuracy, and the harmonic terms come out small always. The LQRF contains J2000 referred equatorial coordinates, and is completed by redshift and photometry information from the LQAC. It is aimed to be an astrometric frame, but it is also the basis for the GAIA mission initial quasars' list, and can be used as a test bench for quasars' space distribution and luminosity function studies. The LQRF is meant to be updated when of the release of new quasar identifications and newer versions of the used astrometric frames. In the later case it can itself be used to examine the interrelations between those frames.
   18+2 minutes

9. Astrometry of ICRF Sources: The Influence of Radio Extended Structures on Offsets between the Optical and VLBI Positions
   Camargo, J.I.B., Assafin, M., Andrei, A.H., Vieira-Martins, R., Da Silva Neto, D.N.
   The International Celestial Reference Frame - ICRF - is the currently adopted IAU celestial reference frame. Its coordinate axes are materialized by the positions of 212 extragalactic radio sources unevenly distributed over the entire sky. Such positions are determined by VLBI techniques and have median uncertainty better than 0.5 milliarcsecond. In addition to these so called defining sources, other 505 extragalactic radio sources are also listed in the ICRF. Their VLBI positions are consistent with the ICRF and serve to densify the frame. All of them, no matter whether defining or not, are in practice used to directly access the ICRF and may present spatially extended structures as seen from their high resolution S/X-band images. In this work, we obtained optical positions of 14 compact and extended ICRF sources with the ESO/MPG 2.2m telescope and compared them to their VLBI counterparts. The intrinsic radio structure of the extragalactic sources is one of the limiting factors in defining the ICRF. It may also lead to the noncoincidence between the VLBI and optical positions. This question of noncoincidence, already addressed and verified by da Silva Neto et al. 2002 (AJ, 124, 612), is revisited here. In particular, we identified two sources for which this noncoincidence may have been motivated by the presence of the extended radio structure. As given by the Bordeaux VLBI Image Database, the structure indices of these sources in the X band are 3 and 4, indicating that they are probably not very good reference frame objects. From their high resolution images, as given by the USNO Radio Reference Frame Image Database, one may infer a possible correlation between the VLBI/optical offset and the plane of the sky orientation of the extended radio structures. One implication is that the relationship between the radio and optical frames should take into consideration structure effects in the future.
   8+2 minutes

10. The Joint Milli-Arcsecond Pathfinder Survey (J-MAPS) Mission: Introduction and Science Goals
    Ralph Gaume
    USNO
    J-MAPS is a small, US-funded, space-based, all-sky visible wavelength astrometric and photometric survey mission for 0th through 14th V-band magnitude stars with a 2012 launch. The primary objective of the J-MAPS mission is the generation of an astrometric star catalog with better than 1 milliarcsecond positional accuracy and photometry to the 1% accuracy level, or better at 1st to 12th mag. A 1-mas all-sky survey will have a significant impact on our current understanding of galactic and stellar astrophysics. J-MAPS will improve our understanding of the origins of nearby young stars, provide insight into the dynamics of star formation regions and associations, investigate the dynamics and membership of nearby open clusters, and discover the smallest brown dwarfs at distances up to 5 pc after a 2- year mission, and Jupiter-like planets out to 3 pc after 4 years. J-MAPS will provide critical milliarcsecond-level parallaxes of tens of millions of stars in the difficult 8-14th magnitude range, which when combined with stellar spectroscopy and relative radii determined from exoplanet transit surveys, allows a determination of stellar radii and exoplanet densities. In addition, the 20-year baseline between the groundbreaking Hipparcos mission and the J-MAPS mission allows a combination of the J-MAPS and Hipparcos catalogs to produce common proper motions on the order of 50-100 microarcseconds per year.
    18+2 minutes

11. The Wavelet Search for Stellar Clusters in NOMAD
    Veniamin Vitayzev, Alex Tsvwtkov and Irina Kumkova
    We present the wavelet technique for searching the heterogeneities of stellar density in the data of the NOMAD (Naval Observatory Merged Astrometric Dataset) catalogue which contains more than a billion stars. The known and unknown globular and open clusters have been detected in various photometric bands up to V=18. A lot of artifacts in NOMAD data were found in addition. This technique can be used for future catalogues including the products of the Gaia mission.
    13+2 minutes

Commission 8 posters at GA27

The Gaia Session during the Division I meeting