Magellanic Clouds Exploration
Motivation
• VO tools enable quick comparison of catalogs: position, photometry, proper motion, when available
• Cross match of Photometric Catalogs with NVO-compatible surveys
• Assess astrometric and photometric quality when cross-matching databases with different qualities– Good astrometry but bad photometry matched to
not so good astrometry but good photometry
Concept
• Cross correlate published catalogs (TABULARSKYSERVICE) with USNOB, GSC, 2MASS in the Magellanic Clouds
• By comparison of data, evaluate the reliability of cross matching for proper motion studies of selected stellar populations– Is XMATCH sufficient to safely cross-match
extended databases, or is more sophisticated analysis needed?
Demers Photometry
US
NO
Pho
tom
etry
Right Ascension
Dec
linat
ion
Demers IC catalog USNOB
Demers IC catalog USNOB
• USNOB: lots of stars with null p.m. in the south– Quantization of p.m.:
• 2,4,6,8,… mas/yr
• No p.m. data should be blank or p.m.>>0
P.M. RA
P.M
. D
EC
Demers IC 2MASS
J
J - H
2dF + Rebeirot <=> USNOB
2dF + Rebeirot <=> USNOB
We want more … but
Demers IC GSC2.2 : failed– Query area too large, too many stars
• 5K rows limitation in Simple Query:
Right Ascension
Dec
linat
ion
Dec
linat
ion
Right Ascension
5000 Rows Limit in XMatch
2dF <=> USNOB, rad=240’
Conclusions
• Promising Idea• Ability to draw conclusions limited by statistics and
available catalogs• Difficulties : importing MyData + 5K rows• Richer Catalogs Needed
– UCAC2, Tycho-2, SPM3, etc.– Catalogs of the future
• More Functionality needed– 5k row limit is restrictive
• Good news: this limit to be lifted