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LocalSkyModel
Gijs Molenaar edited this page Feb 13, 2014
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The Local Sky Model
For now we will work with a LSM containing apparent fluxes. This postpones the problem of the unknown beam shape. Note that each telescope / station has its own beam shape. In general these beams will slightly differ from one another.
Initial Implementation
A prototype Local Sky Model is under construction. It is connected to an existing ParmTable (a mep-table). It is not yet available from cvs, but if you want to play with it ask RJN.
Two documents describing the LSM have been produced: a functional description document () and an implementation document. The implementation document can be downloaded here:
The ParmTable consists of data for some Calibrator sources.
# A MEPTable with CPS parameters using the Baars flux scale (Baars et al., A&A 61, 99-106, 1977)
#
# Available sources:
#
# The A-team: CasA, CygA, VirA, TauA
#
# WSRT Calibrator Sources: 3C48, 3C147, 3C286, 3C295
#
# ATCA Calibrator Source: 1934-638
#
# Intensity (given as ISIF=Log(I)) is a PolcLog with l_scale 10^6 (1 MHz).
#
# For 3C286 coefficients for StokesQ and StokesU are given. These are taken from the MYRIAD routine 'calstoke'.
# They are based on unpublished data from Perley/Killeen, 1991.
# StokesQ and StokesU (given as QSIF=Q, USIF=V) are PolcLogs with l_scale 10^9 (1 GHz).
#
# StokesV is zero for all sources.
#
Below is some preliminary decription of the protolsm object.
# the protolsm always contains
#
# self.mep : A meptable object that is linked to an AIPS++ Table containing LSM parameters.
# self.tablename : Name of the meptable. Needed for creating MeqParms.
#
# and may additionally contain the following objects:
#
# self.LSM_Trees[q=xyz][RA_Tree = defrec1,
# Dec_Tree = defrec2,
# StokesI_Tree = defrec3,
# StokesQ_Tree = defrec4,
# StokesU_Tree = defrec5,
# StokesV_Tree = defrec6
# ]
#
# defrec1.name = 'RA[q=xyz]'
# defrec1.default = meq_polc
# defrec1.groups = 'Parm'
#
# defrec2.name = 'Dec[q=xyz]'
# defrec2.default = meq_polc
# defrec2.groups = 'Parm'
#
# defrec3.class = 'MeqPow'
# defrec3.name = 'StokesI[q=xyz]'
# defrec3.children = meq.list()
#
# defrec4.name = 'StokesQ[q=xyz]'
# defrec4.default = meq_polclog
# defrec4.groups = 'Parm'
#
# defrecs 5,6 just like defrec4
#
# Furthermore, the protolsm contains the following public functions:
#
# public.done()
# public.show() : browse the LSM mep-table
# public.plot(...) : plot one of the Stokes parameters as function of frequency for all sources in the LSM
# public.qnames() : returns a list of source names
# public.defrec('treename'): returning the defrec of the Tree asked for, e.g. 'StokesI[q=RJN1]'
# public.go() : build and execute all 6 LSM trees for all sources