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# stub function definition file for docstring parsing
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[docs]def uvcontsub_old(vis, field='', fitspw='', excludechans=False, combine='', solint='int', fitorder=0, spw='', want_cont=False):
r"""
Continuum fitting and subtraction in the uv plane
[`Description`_] [`Examples`_] [`Development`_] [`Details`_]
Parameters
- vis_ (path) - Name of input MS. Output goes to vis + ".contsub" (will be overwritten if already exists)
- field_ ({string, stringVec, int, intVec}='') - Select field(s) using id(s) or name(s)
- fitspw_ (string='') - Spectral window:channel selection for fitting the continuum
.. raw:: html
<details><summary><i> fitspw != '' </i></summary>
- excludechans_ (bool=False) - exclude Spectral window:channel selection in fitspw for fitting
.. raw:: html
</details>
- combine_ (string='') - Data axes to combine for the continuum estimation (none, or spw and/or scan)
- solint_ (variant='int') - Continuum fit timescale (int recommended!)
- fitorder_ (int=0) - Polynomial order for the fits
- spw_ (string='') - Spectral window selection for output
- want_cont_ (bool=False) - Create vis + ".cont" to hold the continuum estimate.
.. _Description:
Description
.. warning:: **uvcontsub_old** is deprecated and will be removed in
an upcoming release.
This task estimates the continuum emission by fitting polynomials
to the real and imaginary parts of the spectral windows and
channels selected by *fitspw*. This fit represents a model of the
continuum in all channels. The fitted continuum spectrum is
subtracted from all channels selected in *spw*, and the result
(presumably only line emission) is stored in a new MS that is
always called vis + ".contsub". If an MS with the output name
already exists, it will be overwritten. Note that because the real
and imaginary parts are fitted separately, the fitted model
amplitude has the functional form of sqrt(<*polynomial of order
fitorder* * 2>) which, in general, is not a polynomial.
**uvcontsub_old** will read from the CORRECTED_DATA column of *vis*
if it is present, or DATA if it is not. Whichever column is read is
presumed to have already been calibrated.
.. warning:: Strictly speaking, the uvcontsub model
is only a good representation of the continuum at the
phase center. Residuals may be visible for sources far
away and one may try **imcontsub** in the image domain
for improved results.
.. warning:: *fitorders* > 1 are strongly discouraged
because high order polynomials have more flexibility, may
absorb line emission, and tend to go wild at the edges
of *fitspw*, which is not what you
want. default: *0* (constant)
If *want_cont* = *True*, the continuum fit is placed in a
second new MS with the name vis + '.cont', also overwritten if
it already exists.
.. note:: Because the continuum model is necessarily a
smoothed fit, images made with it are liable to have
their field of view reduced in some strange way. Images
of the continuum should be made by simply excluding the
line channels (and probably averaging the remaining ones)
in **tclean**.
.. rubric:: Parameter descriptions
*vis*
Name of input MS. Output goes to vis + ".contsub" (will be
overwritten if already exists)
*field*
Field selection for continuum estimation and subtraction. The estimation and
subtraction is done for each selected field separately in
turn. default: '' (all fields)
*fitspw*
Selection of spectral windows and channels to use in the fit for
the continuum, using general `MS selection
syntax <../../notebooks/visibility_data_selection.ipynb>`__ for
spectral windows, e.g. in spw:chan format (spw ids are required
but '\*' can be used) or as frequencies. See the note under
*combine*. default: *fitspw=''* (all)
.. warning:: The *fitspw* selection is based on the channel
numbers in the uv-data of the input MS file, which are most
likely different from the channel numbers in the image plane
after running **tclean**.
*excludechans (fitspw subparameter)*
if *True*, it will exclude the channels (or frequency range) that
is specified in *fitspw* for the fit; this is useful to specify
the line channels to exclude rather than the continuum channels to
include in the fit. (default: *False*)
*combine*
Continuum solutions will break at scan, field, and spw boundaries
according to *solint.* To allow solutions across these boundaries,
*combine* can be set to '*spw*', '*scan*', or *'spw, scan'.
combine * must include *'spw'* if spw contains spws that are not
in *fitspw*! default: *''* which is that solutions will break at
scan, field, and spw
*solint*
Timescale for per-baseline fit (units optional) options are time
ranges, e.g. '*10s*', or '*inf*' per scan, or '*int*' per
integration. default (recommended): '*int*', i.e. no time
averaging, do a fit for each integration and let the noisy fits
average out in the image.continuum fit. If *solint* is longer
than '*int*', the continuum estimate can be
corrupted by time smearing.
*fitorder*
Polynomial order for the fits of the continuum w.r.t. frequency.
*fitorders* > 1 are strongly discouraged because high order
polynomials have more flexibility, may
absorb line emission, and tend to go wild at the edges of
*fitspw*, which is not what you want. default: *0* (constant)
*spw*
Optional per spectral window selection of channels to include in
the output. See the note under *combine*. The sub-MS output
spectral windows will be renumbered to start from 0, as in
**split**. default: *''* (all spws)
*want_cont*
Create vis + '.cont' to hold the continuum estimate.
.. _Examples:
Examples
**Example 1:**
Subtract the continuum of channels 10~100 and 300~350 in spw 0
(assuming that the line is in channels 101~299). Note that we also
exclude edge channels, e.g. the first 9 channels. We use a
fitorder of 0 (default).
::
uvcontsub_old(vis='myMS.ms',fitspw='0:10~100;300~350')
**Example 2:**
subtract continuum across all spw, assuming that the line sits at
23.694GHz with a 20 MHz width. We use fitorder 1 for the large
frequency range.
::
uvcontsub_old(vis='myMS.ms', fitspw='23.684~23.704GHz', excludechans=True, combine='spw', fitorder=1)
.. _Development:
Development
No additional development details
.. _Details:
Parameter Details
Detailed descriptions of each function parameter
.. _vis:
| ``vis (path)`` - Name of input MS. Output goes to vis + ".contsub" (will be overwritten if already exists)
.. _field:
| ``field ({string, stringVec, int, intVec}='')`` - Select field(s) using id(s) or name(s)
.. _fitspw:
| ``fitspw (string='')`` - Spectral window:channel selection for fitting the continuum
.. _excludechans:
| ``excludechans (bool=False)`` - exclude Spectral window:channel selection in fitspw for fitting
.. _combine:
| ``combine (string='')`` - Data axes to combine for the continuum estimation (none, or spw and/or scan)
.. _solint:
| ``solint (variant='int')`` - Continuum fit timescale (int recommended!)
.. _fitorder:
| ``fitorder (int=0)`` - Polynomial order for the fits
.. _spw:
| ``spw (string='')`` - Spectral window selection for output
.. _want_cont:
| ``want_cont (bool=False)`` - Create vis + ".cont" to hold the continuum estimate.
"""
pass