functions in doppler.i -
airvac
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vacwl=airvac(airwl) Compute vacuum wavelength from air wavelength in Angstroms. Information found in; http://www-obs.univ-lyon1.fr/hypercat/pleinpot/imdwaxisc1.html "The IAU standard for conversion from air to vacuum wavelengths is given in Morton (1991, ApJS, 77, 119). For vacuum wavelengths (VAC) in Angstroms, convert to air wavelength (AIR) via: AIR = VAC / (1.0 + 2.735182E-4 + 131.4182 / VAC^2 + 2.76249E8 / VAC^4)" |
lambdaofv
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lambdaofv(v,lambda0) Returns observed wavelength corresponding to lambda0 Doppler-shifted with velocity v. Wavelength are in vacuum unless AIR is set to non void and non null. If AIR is specified, wavelengths must be in angstroms, or MICRONS or COEF must be specified too (see airvac and vacair). Velocities are in m/s. If VLSR keyword is set to the real velocity in the local standard of rest of an object which radial velocity relative to the earth is zero at the time of observations, V is considered a velocities in the local standard of rest and apparent wavelengths at the time of observations are computed. If not, V should not be in the local standard of rest but at the time of observations for the return wavelengths to be accurate. Example: say you have a spectrum of an object, which velocity in the local standard of rest is 0 but at the time of observations, an observed velocity of 0m/s would indeed correspond to a velocity in the local standard of rest of VLSR(m/s). AXIS contains the observed wavelength in micron for this spectrum. Then, lambdaofv(voflambda(AXIS,vlsr=VLSR),vlsr=0) would return the axis, corrected for the earth's motion. Now, if radial velocity of the object in the LSR is not 0, but Vobj, then the axis corrected for both the earth's and object's motions is given by lambdaofv(voflambda(AXIS,vlsr=VLSR),vlsr=-Vobj). (Note: don't trust me, at the time I'm writing these lines, I'm quite tired...) | |
SEE ALSO: | voflambda |
LightSpeed
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LightSpeed The velocity of light in vacuum and in m/s. |
vacair
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airwl=vacair(vacwl) Compute air wavelength from vacuum wavelength in Angstroms. Information found in; http://www-obs.univ-lyon1.fr/hypercat/pleinpot/imdwaxisc1.html "The IAU standard for conversion from air to vacuum wavelengths is given in Morton (1991, ApJS, 77, 119). For vacuum wavelengths (VAC) in Angstroms, convert to air wavelength (AIR) via: AIR = VAC / (1.0 + 2.735182E-4 + 131.4182 / VAC^2 + 2.76249E8 / VAC^4)" |
voflambda
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voflambda(lambda,lambda0) Attention: ALL velocities, including VLSR, are in m/s (NOT in km/s). Returns radial velocity necessary to Doppler-shift lambda0 to lambda. Wavelengths are in vacuum unless AIR is set to non void and non null. If AIR is specified, wavelengths must be in angstroms, or MICRONS or COEF must be specified too (see airvac and vacair). Velocities are in m/s. VLSR keyword can be used to shift the returned value: VLSR must be set to the real velocity in the local standard of rest of an object which radial velocity relative to the earth is zero at the time of observations. In that case, VOFLAMBDA returns velocities in the local standard of rest. If not, it returns velocities relative to the observer. | |
SEE ALSO: | lambdaofv |