1. Global Sky Model for LOFAR and
MSSS catalog
A. Mints
Hamburger Sternwarte
September 21, 2012
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2. Global Sky Model Data Flow
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3. GSM components
Database
Storage only (all logic in the pipeline);
MonetDB or PostgreSQL support;
Pipeline
Python code with unified database binding.
Front-ends (planned)
Web-interface;
Python API;
Direct DB access;
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4. Data
Observations (pyBDSM output)
Time, frequency, Stokes parameter, position
(+size/orientation), peak/total flux, errors.
Catalog
runningcatalog Position, spectral parameters,
classification, errors, (+Frequency, Stokes
parameter, size/orientation).
runningcatalog fluxes Frequency, Stokes
parameter, peak/total flux, errors
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5. Point and extended sources
Point sources
1 record in positions table and N records in fluxes
table.
Extended sources
N+1 record in positions table and N records in
fluxes table.
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6. Matching
Matching criteria for point sources is based on de
Ruiter distance:
2 (α1 cos δ1 − α2 cos δ2 )2 (δ1 − δ2 )2
RdeRuiter = +
(∆α1 )2 + (∆α2 )2 (∆δ1 )2 + (∆δ2 )2
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7. Extended source matching
1. Search for a match in the same band;
2. If 1. failed – search for a cross-band match.
∗2 (α1 cos δ1 − α2 cos δ2 )2 + (δ1 − δ2 )2
RdeRuiter = 2 2
gmajor ,1 + gmajor ,2
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8. First snapshot
6
5
4
3
2
1
0
-1
-1 0 1 2 3 4 5 6
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9. Second snapshot
6
2
5
4
3
2
4 3
1
1
0
-1
-1 0 1 2 3 4 5 6
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10. Resolved source
For point sources a “flux splitting” technique is
applied.
For extended sources flux splitting is applied only
at per-band level.
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11. Merged source
In this case the nearest source is chosen.
Exception: extended sources are merged if possible:
A1, 2, 3 + B5, 6, 7 + X 4 = A1, 2, 3, 4, 5, 6, 7 (1)
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12. Groups
Assigned a unique group ID
(all detections in the group).
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13. Code features
Coding style: Python PEP8 style rules;
In-code documentation (docstrings);
Unit testing (34 tests unified for
MonetDB/PostgreSQL);
SQL mini-preprocessor:
1. Queries stored in SQL-file, called by unique Id;
2. Parameters can be passed;
3. Global parameters can be set;
4. Arbitrary Python-code can be called and result
substituted:
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