helplog.15: spectra, continuum

Frank Valdes wrote on Jan 31, 2005

NUMBER:	15
KEYWORDS:	spectra, continuum	
DATE:	Mon Jan 31 09:35:44 MST 2005
FROM:	valdes

Q:	I am having a strong continuum in my extracted blackbody corrected
	spectra of which I want to get rid off ( I am looking for a faint
	emission on this continuum). Can you suggest me a way to do it
	effeciently, since I am having 100 such spectra.

A:	The task CONTINUUM in the ONEDSPEC package may be used.  Defining
	the continuum can be hard if there are many lines.  Thie method in
	CONTINUUM (which is also available with the '/' key in SPLOT) is to
	fit a function with rejection of the high and low points.  It
	primarily works well with spectra that are either all absorption or
	emission so that a one sided clipping can be used.  For your
	question about emission you should use something like a 1-sigma
	threshold below and 4-sigma (or higher) above.  This will then
	approach the continuum from below removing the absorption lines
	while not removing emission lines.

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Last post on Jan 31, 2005