Source Finder Testing Overview & Status

Dario Carbone

Transcript

1. LOFAR TKP meeting
   Amsterdam, December 4th 2012
   Source Finder Testing
   Overview & Status
   Dario Carbone
   

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2. LOFAR Source Finders WG
   Lead by Chiara Ferrari
   R. Breton, D. Carbone, P. Carroll, A. Dabbech, H. Garsden, A. van der Horst, A.
   Mints, R. Paladino, D. Rafferty, A. Rowlinson, A. Shulevski, J. Swinbank, S. van
   Velzen.
   http://www.lofar.org/wiki/doku.php?id=commissioning:source_finders
   

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3. LOFAR Source Finders WG
   Lead by Chiara Ferrari
   R. Breton, D. Carbone, P. Carroll, A. Dabbech, H. Garsden, A. van der Horst, A.
   Mints, R. Paladino, D. Rafferty, A. Rowlinson, A. Shulevski, J. Swinbank, S. van
   Velzen.
   http://www.lofar.org/wiki/doku.php?id=commissioning:source_finders
   Main aims
   ●
   Identify the best settings for automatically running source finders in
   LOFAR/MSSS/TRAP pipelines
   ●
   Report bugs and needs to developers and provide support to LOFAR
   users
   ●
   LOFAR representative in the international radio source finding
   discussion
   

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4. Work done & to be done
   DONE
   ●
   Tests on real LOFAR data
   ●
   Presence of both testers and developers
   ●
   Finding & fixing bugs
   ●
   Evaluate the performance of the SF tools
   

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5. Work done & to be done
   DONE
   ●
   Tests on real LOFAR data
   ●
   Presence of both testers and developers
   ●
   Finding & fixing bugs
   ●
   Evaluate the performance of the SF tools
   TO BE DONE
   ●
   Test SF tools on reliable simulated LOFAR maps
   ●
   Participate to the international campaign on SF by
   Hancock et al.
   

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6. Tests & users assistance
   WENSS map by R. Pizzo
   

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7. Tests & users assistance
   Test and development by D. Rafferty and C. Ferrari
   

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8. Tests & users assistance
   LOFAR map of GRS1915 by D. Carbone
   Source extraction by D. Rafferty
   

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9. Systematic position errors
   ●
   Very important for the transient pipeline
   ●
   Source could not to be associated
   ●
   Tests on 70 images of 10 fields, with a pixel
   size of 45 arcsec.
   

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10. Systematic position errors
    ●
    ●
    PyBDSM loses 13.3% PySE 3.4%
    R
    DR
    = 5.68
    Credits to A. Van der Horst
    

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11. Systematic position errors
    ●
    Systematic position error of 20 arcsec
    ●
    PyBDSM loses 2.0% PySE 1.0%
    Credits to A. Van der Horst
    

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12. Flux errors
    Circles: objects both in the VLSS and the
    LOFAR catalogs (extracted with PyBDSM
    and/or PySE)
    Differences :
    < 40%
    < 70%
    < 80%
    > 80%
    Credits to C. Ferrari
    

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13. Statistics on source detection
    

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14. Diagnostic of non detection
    

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15. Questions at SF WG meeting
    i. Which source finders should we keep testing?
    We should focus our tests on PySE and PyBDSM.
    

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16. Questions at SF WG meeting
    ii. Which are the parameters that are important to set for optimizing source finders?
    Detection threshold, Analysis threshold, False Detection Rate, RMS box and Adaptive
    RMS box, Margins or radius, Beam infos, De-blending and Extended sources detection
    i. Which source finders should we keep testing?
    We should focus our tests on PySE and PyBDSM.
    

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17. Questions at SF WG meeting
    iii. Which corrections should we introduce in theoretical error bars given by the source
    finder tools?
    The position errors are underestimated by PyBDSM and systematics errors have to be
    introduced. Better constrains will be put using simulated maps.
    ii. Which are the parameters that are important to set for optimizing source finders?
    Detection threshold, Analysis threshold, False Detection Rate, RMS box and Adaptive
    RMS box, Margins or radius, Beam infos, De-blending and Extended sources detection
    i. Which source finders should we keep testing?
    We should focus our tests on PySE and PyBDSM.
    

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18. Questions at SF WG meeting
    iv. Which source association tools and strategy should we use in order to combine
    different catalogs?
    B. Scheers's method: the De Ruiter radius, taking into account position errors and thus
    preventing spurious source associations.
    CAVEAT: without appropriate systematic position errors very bright sources could be NOT
    associated.
    

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19. Questions at SF WG meeting
    iv. Which source association tools and strategy should we use in order to combine
    different catalogs?
    B. Scheers's method: the De Ruiter radius, taking into account position errors and thus
    preventing spurious source associations.
    CAVEAT: without appropriate systematic position errors very bright sources could be NOT
    associated.
    v. Which source extraction and association strategy should we use for multi-band LOFAR
    catalogs?
    MSSS scripts and spectral module of PyBDSM being tested to make multi-band LOFAR
    catalogs. Could be implemented in PYSE if desirable.
    

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20. Simulated maps
    ●
    Procedure:
    – input Gaussian noise in the visibilities of a true
    LOFAR MS to have the directional dependent gains
    already in place.
    – input simulated sources in the visibilities, centered
    on the pointing center of the original LOFAR MS,
    keeping the instrument table untouched. The
    simulated source must be in BBS format.
    – calibrate and image the obtained MS as a normal
    observation.
    

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21. Simulated maps
    Simulated LOFAR map by A. Rowlinson
    

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22. Simulated maps
    Simulated LOFAR map by A. Rowlinson
    A very bright source has been added
    

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23. Conclusion
    Main aims of LOFAR SF WG:
    ●
    Identify the best settings for automatically running source finders
    ●
    Report bugs to developers and provide support to LOFAR users
    Work done:
    ●
    Tests on real LOFAR data
    ●
    Evaluate the performance of the SF tools
    Work to be done:
    ●
    Test SF tools on reliable simulated LOFAR maps
    

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24. SF WG wikipage
    http://www.lofar.org/wiki/doku.php?id=commissioning:source_finders
    

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