Manipulating VOTables with TOPCAT and STILTS Tom McGlynn

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.

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) http://nvo-twiki.stsci.edu/twiki/pub/Main/NVOSS2008Sched/spocs.csv http://nvo-twiki.stsci.edu/twiki/pub/Main/NVOSS2008Sched/spocs.xml http://nvo-twiki.stsci.edu/twiki/pub/Main/NVOSS2008Sched/exostars.xml This URL can be used directly http://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=messier

Starting and loading a URL

Table loaded successfully

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 http://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=messier Save as CSV Portal tools may work better in handling data in non-standard formats.

Convert to a CSV file

After loading CSV convert to VOTable

The table browser

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.

Creating a subset

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

Histograms

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)

X-Y plots

Creating a subset graphically

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

3-D plots

Creating a new column

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

Cross-correlations

Viewing the correlation

Saving the correlated data.

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 …