sumspec is an IRAF task in the rvsao package which combines spectra, shifting them to a common redshift. The VELOCITY header parameter of each of these spectra is assumed to be a solar-system-barycenter-corrected velocity, and a barycentric correction (computed by sumtemp or extracted from the BCV or HCV header parameter) is subracted to get the redshift of the spectrum. Each spectrum is shifted and rebinned to the desired wavelength range and bin size, which may be linear in wavelength or in log-wavelength, then added to the summed template. Input may be multispec or twodspec format, but output is always a one-dimensional file. Continuum may be removed from input spectra or the resulting spectrum using the parameters set by contsum.

The resulting spectrum can then be used as a template by xcsao to find redshifts from spectra by cross-correlating them against it following the method of Tonry and Davis 1979, A.J., 84, 1511).



Cursor Commands


Last updated October 6, 2000 by Doug Mink dmink@cfa.harvard.edu

Telescope Data Center [rvsao] [xcsao] [emsao] [sumspec] [contsum] [linespec]