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Manipulating VOTables with TOPCAT and STILTS

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1 Manipulating VOTables with TOPCAT and STILTS
Tom McGlynn

2 What are TOPCAT and STILTS?
STILTS is a powerful library that enables users to filter and convert tables in VOTable and other popular formats. TOPCAT is a user interface built on top of STILTS with extensive GUI and graphics capabilities. All written by Mark Taylor (Bristol University/UK) originally as part of the Starlink project. This demo uses TOPCAT but the underlying functionality is available through the STILTS library (in Java). There are some other standalone commands built on STILTS (e.g., votcopy). There is a TOPCAT chapter in the NVO book.

3 Starting TOPCAT In the standard distribution as command ‘topcat’
Note capabilities to download data from various VO and other data sources. Remember to run setup first! Files used in this presentation: Download these (Twiki doesn’t let TOPCAT read them directly) This URL can be used directly

4 Starting and loading a URL

5 Table loaded successfully

6 Getting to and from VOTables
Converting to VOTables from CSV Load spocs.csv (available on Twiki) Save as spocs.xml (VOTable) Can covert into many formats. Converting VOTables to CSV Load Save as CSV Portal tools may work better in handling data in non-standard formats.

7 Convert to a CSV file

8 After loading CSV convert to VOTable

9 The table browser

10 Filtering data using TOPCAT
Show SPOCS table (view/tabledata) Create a subset (view/row subsets/+) Enter name=Sunlike Enter criterion Teff>5720 && Teff<5820 && log_g>4.34 && log_g<4.54 && M_H>-0.1 && M_H <0.1 Should create subset with ~30 rows. Show with Views/Table data/Apply Subset/Sunlike We can use column names or $number. A sample can be saved in any of the supported formats.

11 Creating a subset

12 Histograms Click on histogram
Note which subsets are showing and click on all Change column to VMAG Note both all and sunlike data.

13 Histograms

14 Plots X/Y display Ensure that full sample is shown.
Change parameters to Teff/Age Zoom around sun location Create new sample from plot (third box from right) Note region selection tool (fourth from right)

15 X-Y plots

16 Creating a subset graphically

17 3-D Graphics/Synthetic columns
3-d displays (change third axis to something interesting in box) Creating new columns: column metadata/+ Name = AppMag Expr = Vmag – 5*log10(Dist/10) [note striping error] Note function browser New columns can be used anywhere and show up on output

18 3-D plots

19 Creating a new column

20 Correlations using TOPCAT
Load SPOCS table EXOStars table Click on double match Cross-correlate by position: Find all the SPOCS stars that have exoplanets

21 Cross-correlations

22 Viewing the correlation

23 Saving the correlated data.

24 Many more capabilities
Direct access to VO enabled services Density plots Column data conversions Hundreds of functions usable in creating columns PLASTIC/SAMP communication with other tasks Joining tables Stacked plots or spherical plots Table statistics

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