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What is TOPCAT?
• TOPCAT= Tool for OPeraBons on Catalogues And Tables • hEp://www.star.bris.ac.uk/~mbt/topcat/
Useful, because with few clicks it: • handles large astrophysics data catalogs -‐ opens millions of
rows without trouble • plots the data: histogram, X-‐Y scaEer, density, sky • creates subsets of data • cross-‐correlates different catalogs based on source posiBons
on the sky • can send table directly to opened ds9 program to visualize
sources on the observed sky map • runs on all plaPorms (Java) + free
Installa3on
• Download topcat-‐full.jar and put it somewhere in your home folder – hEp://www.star.bris.ac.uk/~mbt/topcat/#install
• To run it, write in terminal: java -‐jar topcat-‐full.jar
• Or put in your .bashrc something like this
alias topcat='java -‐jar /home/studentX/topcat-‐full.jar’ • And then just write topcat in the terminal
• Detailed help, reference manual and some tutorials: – hEp://www.star.bris.ac.uk/~mbt/topcat/#docs – hEp://andromeda.star.bris.ac.uk/topcat/tutorial/
The face of TOPCAT
memory usage SAMP hub status -‐ used for program intercommunicaBon (for example, sending data to ds9)
Main tools for opening, saving, ploZng, matching,...
Opened tables (currently none) Some useful info and opBons
when a table is opened
COSMOS catalogs
• Catalogs are lists of sources containing their coordinates and properBes that are specific to each survey or analysis – types: stars, galaxies, AGNs; fluxes at different wavelengths, detecBon
quality, error esBmates, redshi_, computed properBes: mass,...
• PanchromaBc COSMOS survey – hEp://cosmos.astro.caltech.edu/ – 2 square degrees (10 full moons) – X-‐ray to radio with ground&space telescopes
• On krampus machine catalogs can be found here: – /home/mladen/cosmos/catalogs/ – vla3_msmf_blobs_5sig_cat_20150724.fits – radio at 3 GHz – zphot_cosmos2015_v1.1_150601.zgal.fits – opBcal+photometric redshi_ – not yet in public domain so do not share outside Zagreb group (ZGAL)
Opening files • Two types of data files commonly used for catalogs:
– ASCII – plain text readable by eyes (*.txt for example) – FITS – binary file with specific structure (also used for sky maps)
• Use correct one when opening a table (“auto” will recognize fits file but not ASCII file) – also when saving the table
pick correct one
find your file
Viewing the table Look/change cell values Look/change column names
ID of the source
Right ascension
DeclinaBon Coordinates in degrees
Note: when opening an ASCII file, TOPCAT will automaBcally try to parse the last commented line (starBng with # ) before the actual data as column names, if it fails for some reason, column names will be col1, col2,...
Crea3ng sub-‐selec3ons • Use expression to pick a sample that saBsfies some criteria
– All – enBre catalog with about 10000 components – Bright – pick sources with flux density higher than 1mJy (10-‐3 Jansky) – Stripe cut – do a selecBon in coordinates, between 150<RA<150.1 deg
• Note: && is logical AND, || is logical OR (same as C/C++)
PloAng sources in the sky
All 10375 sources in the catalog posiBoned on the sky – use mouse and scroll to move around
Color different subsets (if they exist)
Pick columns with coordinates (automaBc if ra/dec)
Sexagesimal coordinates (COSMOS is equatorial -‐small declinaBon)
Histograms Easy histograms – flux density distribuBon of all sources
Display subsets also
Logarithmic axis
PosiBon legend
Flux densiBes in μJy More fainter sources (unBl detecBon limit)
Fill this
ScaFer plots Used for ploZng X-‐Y pairs, one point for each pair
Signal-‐to-‐noise raBo of the source
Size of the source in pixels (in the radio map)
Brighter sources are visible across more pixels in the radio map (they stand high above the background noise variaBons)
Save the plot
Panchroma3c observa3ons
• COSMOS field is observed with mulBple telescopes – hEp://cosmos.astro.caltech.edu/page/telescopes – at different wavelengths (radio, IR, opBcal, UV, X-‐ray) – at different Bmes (past 20 years) – each have a different sensiBvity (deep, shallow) and resoluBon (arcsec) – physical processes producing those emissions are different
(thermal, synchrotron, young stars, dusty torus, relaBvisBc jets,...) – emission is redshi_ed between bands depending on the distance
• Each survey produces a catalog, or mulBple versions meaning many sources, many posiBons, many different fluxes,...
• There is only one sky with physical sources above us • Main goal is to accumulate different observaBons and connect them
to a specific source (galaxy) in the sky
Catalog cross-‐matching
radio
opBcal
coords (deg)
Suppose if two sources in two surveys are close enough on the sky (depending on the resoluBon), that they are the same physical source. Finding such pairs = cross-‐matching.
Find sources separated no more than 0.4” (on the sky) between the two catalogs
Many opBcal sources
Few radio sources
Match!
OpBcal catalog ~1,200,000 sources Radio catalog ~10,000 sources
Catalog cross-‐matching 3ps
• Max error should not be more than one resoluBon element (0.75” for the 3 GHz radio data) – Half of that value is usually a good choice – Lower resoluBon dataset imposes this constraint – Chance of false match increases for fainter sources and lower resoluBon – If many sources (at high resoluBon) can fit into one (at low resoluBon),
then coordinate based matching is mostly useless = “confusion” – When sources exhibit complex morphology, manual inspecBon is needed
• Match algorithm = exact value is useful when matching ID or index • Join type = All from 1 will append columns from the second catalog to
the first one where match was successful • If there are mulBple choices only the closest match is used • Simultaneously matching more then 2 catalogs is also possible
(Triple, Quadruple match) • SeparaBon column (in arcsec) is added to the created match table
Interop – using DS9
To show text (some column value, ID for example): Symbol – advanced – text =$ID_1
In DS9: File – SAMP – Connect Open some COSMOS map
Send a table directly to opened DS9 (be paBent as 5000+ large catalogs can be slooow)
This should open a catalog window in DS9 Set α, δ and Max Rows and circles should appear
Result = map + catalog:
