TOPCAT basics. Modern Astrophysics Techniques. Contact: Mladen Novak,

Transcription

1 TOPCAT basics Modern Astrophysics Techniques Contact: Mladen Novak,

2 What is TOPCAT? TOPCAT= Tool for OPeraBons on Catalogues And Tables hep:// 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

3 Installa3on Download topcat- full.jar and put it somewhere in your home folder hep:// 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:// hep://andromeda.star.bris.ac.uk/topcat/tutorial/

4 The face of TOPCAT Main tools for opening, saving, plozng, matching,... Opened tables (currently none) Some useful info and opbons when a table is opened memory usage SAMP hub status - used for program intercommunicabon (for example, sending data to ds9)

5 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_ fits radio at 3 GHz zphot_cosmos2015_v1.1_ zgal.fits opbcal+photometric redshi_ not yet in public domain so do not share outside Zagreb group (ZGAL)

6 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

7 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,...

8 Crea3ng sub- selec3ons Use expression to pick a sample that sabsfies some criteria All enbre catalog with about 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++)

9 PloAng sources in the sky All sources in the catalog posiboned on the sky use mouse and scroll to move around Sexagesimal coordinates (COSMOS is equatorial - small declinabon) Color different subsets (if they exist) Pick columns with coordinates (automabc if ra/dec)

10 Histograms Easy histograms flux density distribubon of all sources Display subsets also Flux densibes in μjy More fainter sources (unbl detecbon limit) Logarithmic axis PosiBon legend Fill this

11 ScaFer plots Used for plozng X- Y pairs, one point for each pair Save the plot Brighter sources are visible across more pixels in the radio map (they stand high above the background noise variabons) Signal- to- noise rabo of the source Size of the source in pixels (in the radio map)

12 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

13 Catalog cross- matching 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. Many opbcal sources Find sources separated no more than 0.4 (on the sky) between the two catalogs radio Few radio sources opbcal coords (deg) Match! OpBcal catalog ~1,200,000 sources Radio catalog ~10,000 sources

14 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

15 Interop using DS9 In DS9: File SAMP Connect Open some COSMOS map Send a table directly to opened DS9 (be pabent as 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: To show text (some column value, ID for example): Symbol advanced text =$ID_1