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8.2.1.3 sdbaseline
infile -- name of input SD dataset
antenna -- antenna name or id (only effective for MS input).
fluxunit -- units for line flux
options: ’K’,’Jy’,’’
default: ’’ (keep current fluxunit)
WARNING: For GBT data, see description below.
>>> fluxunit expandable parameter
telescopeparm -- the telescope characteristics
options: (str) name or (list) list of gain info
default: ’’ (none set)
example: if telescopeparm=’’, it tries to get the telescope
name from the data.
Full antenna parameters (diameter,ap.eff.) known
to ASAP are
’ATPKSMB’, ’ATPKSHOH’, ’ATMOPRA’, ’DSS-43’,
’CEDUNA’,’HOBART’. For GBT, it fixes default fluxunit
to ’K’ first then convert to a new fluxunit.
telescopeparm=[104.9,0.43] diameter(m), ap.eff.
telescopeparm=[0.743] gain in Jy/K
telescopeparm=’FIX’ to change default fluxunit
see description below
specunit -- units for spectral axis
options: (str) ’channel’,’km/s’,’GHz’,’MHz’,’kHz’,’Hz’
default: ’’ (=current)
example: this will be the units for masklist
frame -- frequency frame for spectral axis
options: (str) ’LSRK’,’REST’,’TOPO’,’LSRD’,’BARY’,
’GEO’,’GALACTO’,’LGROUP’,’CMB’
default: currently set frame in scantable
WARNING: frame=’REST’ not yet implemented
doppler -- doppler mode
options: (str) ’RADIO’,’OPTICAL’,’Z’,’BETA’,’GAMMA’
default: currently set doppler in scantable
scanlist -- list of scan numbers to process
default: [] (use all scans)
example: [21,22,23,24]
this selection is in addition to field, iflist, and pollist
field -- selection string for selecting scans by name
default: ’’ (no name selection)
example: ’FLS3a*’
this selection is in addition to scanlist, iflist, and pollist
iflist -- list of IF id numbers to select
default: [] (use all IFs)
example: [15]
this selection is in addition to scanlist, field, and pollist
pollist -- list of polarization id numbers to select
default: [] (use all polarizations)
example: [1]
this selection is in addition to scanlist, field, and iflist
tau -- atmospheric optical depth
default: 0.0 (no correction)
masklist -- list or string of mask regions to INCLUDE in BASELINE fit
a string masklist allows per IF selection of channels.
default: [] (entire spectrum)
example: [[1000,3000],[5000,7000]]
’0:1000~3000;5000~7000, 1:200~350;450~600’
when maskmode is ’auto’ or ’interact’, this mask
will be applied first before fitting as base mask
maskmode -- mode of setting additional channel masks
options: (str) ’auto’,’list’,’interact’
default: ’auto’
example: maskmode=’auto’ runs linefinder to detect line regions
to be excluded from fitting. this mode requires three
expandable parameters: thresh, avg_limit, and edge.
USE WITH CARE! May need to tweak the expandable parameters.
maskmode=’list’ uses the given masklist only: no additional
masks applied.
maskmode=’interact’ allows users to manually modify the
mask regions by dragging mouse on the spectrum plotter GUI.
use LEFT or RIGHT button to add or delete regions,
respectively.
>>> maskmode expandable parameters
thresh -- S/N threshold for linefinder
default: 5
example: a single channel S/N ratio above which the channel is
considered to be a detection
avg_limit -- channel averaging for broad lines
default: 4
example: a number of consecutive channels not greater than
this parameter can be averaged to search for broad lines
edge -- channels to drop at beginning and end of spectrum
default: 0
example: [1000] drops 1000 channels at beginning AND end
[1000,500] drops 1000 from beginning and 500 from end
Note: For bad baselines threshold should be increased,
and avg_limit decreased (or even switched off completely by
setting this parameter to 1) to avoid detecting baseline
undulations instead of real lines.
blfunc -- baseline model function
options: (str) ’poly’,’cspline’,’sinusoid’
default: ’poly’
example: blfunc=’poly’ uses a single polynomial line of
any order which should be given as an expandable
parameter ’order’ to fit baseline.
blfunc=’cspline’ uses a cubic spline function, a piecewise
cubic polynomial having C2-continuity (i.e., the second
derivative is continuous at the joining points).
blfunc=’sinusoid’ uses a combination of sinusoidal curves.
>>> blfunc expandable parameters
order -- order of baseline polynomial
options: (int) (<0 turns off baseline fitting)
default: 5
example: typically in range 2-9 (higher values
seem to be needed for GBT)
npiece -- number of the element polynomials of cubic spline curve
options: (int) (<0 turns off baseline fitting)
default: 2
applyfft -- automatically set wave numbers of sinusoidal functions
for fitting by applying some method like FFT.
options: (bool) True, False
default: True
fftmethod -- method to be used when applyfft=True. Now only
’fft’ is available and it is the default.
fftthresh -- threshold to select wave numbers to be used for
sinusoidal fitting. both (float) and (str) accepted.
given a float value, the unit is set to sigma.
for string values, allowed formats include:
’xsigma’ or ’x’ (= x-sigma level. e.g., ’3sigma’), or
’topx’ (= the x strongest ones, e.g. ’top5’).
default is 3.0 (unit: sigma).
addwn -- additional wave number(s) of sinusoids to be used
for fitting.
(list) and (int) are accepted to specify every
wave numbers. also (str) can be used in case
you need to specify wave numbers in a certain range,
e.g., ’a-b’ (= a, a+1, a+2, ..., b-1, b),
’<a’ (= 0,1,...,a-2,a-1),
’>=a’ (= a, a+1, ... up to the maximum wave
number corresponding to the Nyquist
frequency for the case of FFT).
default: []
rejwn -- wave number(s) of sinusoid NOT to be used for fitting.
can be set just as addwn but has higher priority:
wave numbers which are specified both in addwn
and rejwn will NOT be used.
default: []
clipthresh -- clipping threshold for iterative fitting
default: 3
clipniter -- maximum iteration number
default: 0 (no iteration, i.e., no clipping)
verify -- verify the results of baseline fitting
options: (bool) True,False
default: False
NOTE: Currently available only when blfunc=’poly’
WARNING: Currently this just asks whether you accept
the displayed fit and if not, continues
without doing any baseline fit.
verbose -- output fitting results to logger and a file as well
default: True
example: If False, the fitting results including coefficients,
residual rms, etc., are not output to either the CASA
logger or a text file (<outfile>_blparam.txt), while
the processing speed gets faster by a factor of about 20
percent
showprogress -- show progress status for large data
default: True
minnrow -- minimum number of input spectra to show progress status
default: 1000
outfile -- Name of output file
default: ’’ (<infile>_bs)
outform -- format of output file
options: ’ASCII’,’SDFITS’,’MS’,’ASAP’
default: ’ASAP’
example: the ASAP format is easiest for further sd
processing; use MS for CASA imaging.
If ASCII, then will append some stuff to
the outfile name
overwrite -- overwrite the output file if already exists
options: (bool) True,False
default: False
WARNING: if outform=’ASCII’, this parameter is ignored
plotlevel -- control for plotting of results
options: (int) 0=none, 1=some, 2=more, <0=hardcopy
default: 0 (no plotting)
example: plotlevel<0 as abs(plotlevel), e.g.
-1 => hardcopy of final plot (will be named
<outfile>_bspec.eps)
WARNING: be careful plotting in fsotf mode!
DESCRIPTION:
Task sdbaseline performs baseline fitting/removal for single-dish spectra. The fit parameters, terms and rms of baseline are saved to an ASCII file, <outfile>_blparam.txt.
See the sdcal description for information on fluxunit conversion and the telescopeparm parameter. Also, see the sdcal description for note on GBT raw SDFITS format data.
By setting maskmode=’interact’, you can set/unset mask regions interactively using mouse buttons. Current mask regions will be shown with yellow shading. Baseline fit parameters and rms of fitted spectra are saved to an ASCII file, <outfile>_blparam.txt, when verbose=True.
The parameter masklist accepts per IF selection of mask regions. See § 2.3.3.1 for details. Note, the mask regions should be specified in unit of specunit in this task.
Available functions for baseline subtraction are polynomial, cubic spline, and sinusoid. Also, iterative n-σ clipping becomes available with cubic spline and sinusoid.
More information about CASA may be found at the
CASA web page
Copyright © 2010 Associated Universities Inc., Washington, D.C.
This code is available under the terms of the GNU General Public Lincense
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