continpars: Edit continuum subtraction parameters

Package: rv

Usage

continpars

Parameters

c_sample = "*": Lines or columns to be used in the fits. The default value ("*") selects all pixels. Type help ranges for a complete description of the syntax.

c_function = "spline3": Continuum function to be fit to the image lines or columns. The functions are "legendre" (Legendre polynomial), "chebyshev" (Chebyshev polynomial), "spline1" (linear spline), and "spline3" (cubic spline). The functions may be abbreviated.

c_interactive = "no": Interactively fit the continuum? If set to yes, each spectrum will be fit interactively as they are read into the task if the fxcor.continuum parameter requires it. The fxcor keystroke commands 'o' and 't' will automatically fit the continuum interactively.

naverage = 1: Number of sample points to combined to create a fitting point. A positive value specifies an average and a negative value specifies a median.

order = 1: The order of the polynomials or the number of spline pieces.

replace = no: Replace rejected data points with continuum fit points prior to the subtraction? If set to yes, points lying outside the low_reject or high_reject limits are replaced by the fit values prior to the continuum subtraction. This can be useful in removing emission features or cosmic ray events, but great care must be taken in setting other parameters in order to get satisfactory results. Adjusting the grow or average parameters, and using a low order function usually provide a good result.

low_reject = 2., high_reject = 2.: Rejection limits below and above the fit in units of the residual sigma.

niterate = 1: Number of rejection iterations.

grow = 1.: When a pixel is rejected, pixels within this distance of the rejected pixel are also rejected.

Description

The continpars pset is used to control the continuum subtraction from the data. When the fxcor task is run in a batch mode, the parameters are used to automatically process the data without intervention from the user. In an interactive session, the user may experiment with different parameter values by changing them with the allowed colon commands.

Continuum subtraction is done exactly as with the onedspec.continuum task. (Details of the operation are described in the continuum documentation.) The fit to the spectra is subtracted from the data, thus producing a continuum subtracted spectrum suitable for input to the correlation routines.

Users who require the full ability of the onedspec.continuum task to supply another form of output spectrum, such as the ratio of the fit, or who wish to make use of the "clean" option, should use that task and disable continuum subtraction in the rv package tasks. More functionality is planned for this pset in the future.

Task colon commands

The values of the continpars pset may be changed, displayed, or updated from within tasks that use them by means of various colon commands. Simply typing the parameter name will have the default action of printing the current value of that parameter.

:unlearn continpars: Reset the continpars pset parameters with their default values. The argument "continpars" must be present or else the command will default to the fxcor task command.

:update continpars: Update the continpars pset parameters with the current values. The argument "continpars" must be present or else the command will default to the fxcor task command.

:show continpars: Show the current values of the continpars pset parameters. The argument "continpars" must be present or else the command will default to the fxcor task command.

The following parameters will be displayed if it's name it typed, and a new value accepted if an argument is given.

:c_sample       [range_string]
:naverage       [int_value]
:c_function     [spline3|legendre|chebyshev|spline1]
:order          [int_value]
:low_reject     [int_value]
:high_reject    [int_value]
:niterate       [int_value]
:grow           [int_value]

Examples

1. List the continuum parameters.

rv> lpar continpars

2. Edit the continuum parameters

rv> continpars