Identifier dered Purpose Dereddening of AAR or line lists Synopsis out = dered(in,ext,law,mode [,wext=wext] [,ownlaw=ownlaw] [,stat=stat]) Arguments Name I/O Type: Description: ---------------------------------------------------------- in I struct AAR or LLI to be dereddened ext I float Extinction in mag. By default, this is assumed to be a visual extinction A_V By specifying formal negative extinctions, DERED can also be used to 'redden' spectra law I string Designation of the reddening law to be used Currently implemented: 'RL85' Rieke+Lebofsky '85 0.3-13um 'M90' Mathis '90 0.35-250um 'DL84' Draine+Lee '84 0.5-250um (See description for details) 'OWN' Supply your own file specified by the `ownlaw' parameter. This has to be a two-column ASCII file of wavelengths (um) and extinctions (mag). The V band (0.55um) has to be in the range covered. DERED assumes that your file is sampled sufficiently dense so that it can interpolate linearly. mode I string Mode of dereddening. Possible options: 'SCREEN' simple foreground screen absorber I = I_0*exp(-tau) 'MIX' homogeneous 1-d mix of emission and absorption. Convention here is to specify the extinction through the whole region, i.e. front to back. I = I_0*(1-exp(-tau))/tau Taken from McLeod etal (1993), ApJ, 412, 111 wext I float Wavelength (micron) to which ext applies (supersedes default 'V' if set) ownlaw I string File with wavelengths (micron) and extinctions for own reddening law (applicable only if law = 'OWN') stat I/O int error status, 0 if ok, 1 if fatal Returns Dereddened AAR or LLI 0 if fatal error occured Description Currently, three different reddening laws are included: 'RL85': Rieke and Lebofsky (1985), ApJ, 288, 618. Expressed in terms of A_lambda/A_V, using R_V = 3.1, and based entirely on observations. It can be used to deredden spectra from 0.365 (the U band) to 13 microns. A spline was fit to the data in Table 3 of RL85, and then interpolated. The original data had to be converted to log_10-log_10 before fitting the spline so that it wouldn't go negative in the coarsely sampled parts of the data set. The law includes the 10 micron silicate feature. It is probably more valid for interstellar (diffuse cloud) extinction, where R_V is usually around 3.1, rather than dense or molecular clouds. 'M90': Mathis (1990), ARAA, 28, 37. Expressed in terms of A_lambda/A_J, using R_V=3.1, and based on both observations and grain models. It can be used to deredden spectra from 0.365 (the U band) to 250 microns. The 10 and 20 micron silicate feature profiles are taken from DL84 (see below), which are then added to a power law interpolation of an underlying continuum fitted between 7 and 250 microns. A spline was fit to the original data in Table 1 of M90, and then interpolated. The original data had to be converted to 1/lambda, log_10(A_lambda/A_J) before fitting the spline so that it wouldn't go negative in the coarsely sampled parts of the data set. A_lambda/A_J is independent of R_V above 1 micron. According to Mathis the extinction values for wavelengths greater than 15 microns are uncertain by at least a factor of two. 'DL84': Draine and Lee (1984), ApJ, 285, 89. Expressed in terms of A_lambda/A_V, and based on a model for dust grains. The law was digitised from figures 8 and 9 in DL84, after which some conversion was necessary from their units to A_lambda/A_V. This conversion required assuming R_V=3.1 and N_H=5.8*E21* E_(B-V) cm^-2 mag^-1. Also, a slight normalisation had to be applied to make A_V/A_V exactly equal to 1.0. The grain model consists of a mixture of graphite and 'astronomical silicate' grains, which obey an MRN size distribution. DL84 used Mie scattering theory for homogeneous spherical particles to compute the absorption and scattering cross sections. The extinction law here extends from 0.5 to 250 microns. A spline was fit to and interpolated from the digitised spectrum. Comment The speed of the routine is higher if data are sorted in wavelength, or in segments that are sorted, than for random wavelengths. The sampling of the implemented reddening laws has been adjusted to the smoothness of the curve to increase speed. Example outaar = dered(inaar,3.0,'DL84','screen',wext=2.20) deredden a spectrum that suffers a K band exinction of 3 mag. outlli = dered(inlli,-2.,'M90','screen') redden a linelist (visual extinction 2 mag) Dependencies CALLS: dered_getext, dered_corr, get_unit, is_struct, sap_error, sap_keyword_set, update_history CALLED FROM: GUI/IA Category ISAP Filename dered.pro Author D.Lutz/C.Wright Version 1.1 History 0.4 21-07-95 DL 0.5 24-07-95 CW Added description of RL85, M90 and DL84 laws. 0.6 12-10-95 DL standard laws moved from datafiles to code, sampling of laws optimized 0.7 18-10-95 DL use sap_error instead of error 0.8 16-11-95 ES update_history and unit check added 1.0 30-11-95 ES V1 delivery 1.1 29-01-96 ES new call to is_sruct 29-02-96 ES stat added ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; Copyright (C) 1995, Max-Planck-Institut fuer extraterrestrische Physik (MPE); Garching, Germany ; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;