1. Searching for Tidal Streams in SDSS Chinese Virtual Observatory 刘 超 中国科学院国家天文台

2. 11/29-12/03China-VO 2006, Guilin2 Why search for Tidal Stream Galactic Structure –Shape, Kinematics, chemical properties, etc. Galactic Halo Origin –Two models debate Cold Dark Matter Model –More dwarf galaxies disrupted

3. 11/29-12/03China-VO 2006, Guilin3 Currently Known Tidal Stream Sgr dSph Tidal Streams (Majewski03;Belokurov06b) Virgo Stream (Juric05 ) Monoceros Ring (Newberg02) Orphan Stream (GD06b) GD-1 (GD06b) NGC5466 Tidal Tail (Belokurov06a) Pal 5 Tidal Stream (GD06a) NGC5053 (Lauchner06) NGC4147??

4. 11/29-12/03China-VO 2006, Guilin4 UMa I CVn I Boo Com CVn II Segue 1 Her Leo IV UMa II Will 1 References: Willman05a Willman05b Zucker06 Belokurov 06c Belokurov06d

5. 11/29-12/03China-VO 2006, Guilin5 Why Use SDSS Study methods –Star count analysis –Kinematics –Chemical composition –Comparison with other galaxies Star count analysis is a prompt way Large sky area survey –DSS –2MASS –SDSS SDSS –Deep space and mass dataset –Precise photometry –Cover Galactic North Pole

6. 11/29-12/03China-VO 2006, Guilin6 Our Approach Binning a wide area sky –RA=120~270deg, DEC=25~70deg –i=19~22mag, g-i=0~1mag –Step=0.05deg Pick out all over-densities –2sigma higher above background Color-Magnitude feature analysis –Isochrone line matching

7. 11/29-12/03China-VO 2006, Guilin7 Results

8. 11/29-12/03China-VO 2006, Guilin8

9. 11/29-12/03China-VO 2006, Guilin9 GNP Our Result GD-1 Orphan Monoceros NGC5466

10. 11/29-12/03China-VO 2006, Guilin10 Conclusion Ten over-densities are most likely dwarf spheroidal galaxies or star clumps on tidal streams Nine over-densities and Four known satellites compose a remarkable arc –Possibly a tidal stream Distances are likely related to metalicity for the over-densities and known dSphs

11. 11/29-12/03China-VO 2006, Guilin11 China-VO Data Access Service (DAS) 刘 超 中国科学院国家天文台 Chinese Virtual Observatory

12. 11/29-12/03China-VO 2006, Guilin12 Goals Access mass data –Query data from all over the world –You need a BIG hard disk when study SDSS data –database knowledge is necessary –Furthermore, a lot of time are spent on data r/w: download data, save temp data, format transformation –Manage your data by yourself DAS goals are simply do all above for you –Let you focus on science and algorithms –Save your query time and disk space –Simplify data transferring and format transformation –Manage your data on line

13. 11/29-12/03China-VO 2006, Guilin13 Functions Multiple ways to access data –By a client application –By a web page –By web service interface Image, Spectroscopy data as well as Catalog data Data query result transfer –FTP, GridFTP, etc. Data query result format transformation –ASCII, VOTable, FITS, etc. Cross match among distributed catalogs Function scalability –Add new databases –Add data mining tools –As a atomic service in a workflow

14. 11/29-12/03China-VO 2006, Guilin14 Architecture DAS Server –A grid service provider complies with WSRF Data Node –An OGSA-DAI server provides multiple data resources to community Client –A stand alone java application –A series of web page –A program coded by users

15. 11/29-12/03China-VO 2006, Guilin15 Features ADQL for all –Catalogs, Images and Spectroscopies Asynchronous query for mass data Not a system but a community –Anybody can publish their database as a Data Node and share them to all users Users can combine data query into their programs by Grid Service Interface so that data need not to be downloaded to local disk and data format will not be a problem An unified entrance for all kinds of astronomical data Basis of data mining tools –Send computation to data server in future

16. 11/29-12/03China-VO 2006, Guilin16 More details DAS server: Tian Haijun Cross match & ADQL execute planning: Gao Dan Discover Data Node & Multi-type data support: Lu Yong Client & Data Node: Yang Yang

17. 11/29-12/03China-VO 2006, Guilin17 Actions Submit a query Asynchronous execution Data federation in distributed environment Data format transformation Data transportation Job tracking

18. 11/29-12/03China-VO 2006, Guilin18 Status & Future work Status –DAS server can run a simple job without Data Node –A java application Client is in developing –A Data Node test server is established –Data Node Discovery is in developing Future work –The system query data in next spring –Multiple data format support –Distributed cross match –Connect with MySpace? –Data mining tools integration (e.g. JDL) –Visualization Integration –LAMOST data server?

19. Thanks!