LocalSkyModel

'''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 (attachment:LSM_functional_description.pdf) and an implementation document. The implementation document can be downloaded here: attachment:LSM_implementation.pdf

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They are based on unpublished data from Perley/Killeen, 1991.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.

}}}

attachment:ISIF.gif

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

}}}