Provided by: alfa_1.0-2build3_amd64 bug

NAME

       alfa - automated line fitting algorithm

SYNOPSIS

       alfa [OPTION] [VALUE]... [FILE]

DESCRIPTION

       alfa  rapidly  fits  emission  line spectra, using a genetic algorithm to optimise fitting
       parameters.  It is intended to be entirely automated, but while the default values  should
       work  well  in  many  situations,  a  good  fit to your observed spectrum may require some
       adjustments to the input parameters.  It is optimised for  optical  spectra,  but  can  be
       applied to any wavelength range if a suitable line catalogue is provided.

       alfa  reads one dimensional spectra in either plain text or FITS format.  Plain text input
       should consist of two columns, giving wavelength and flux.  It can also  read  data  cubes
       and  row-stacked  spectra in FITS format.  Results are written out in plain text, to files
       containing the fit (total fit, continuum-subtracted original,  continuum,  sky  lines  and
       residuals), and the line flux measurements.

OPTIONS

       -b, --bad-data [REAL]
              If  all  values  in a spectrum are below the value specified, alfa will not fit it.
              Most useful for avoiding wasting time on low signal regions of data cubes.

       --citation
              Prints out the bibliographic details of the paper to cite if you use alfa  in  your
              research.

       -g, --generations [INTEGER]
              The number of generations used in the genetic algorithm. Default: 500

       -n, --normalise [VALUE]
              Normalise  to Hb=100 assuming that F(Hb)=VALUE.  If VALUE is zero, no normalisation
              is applied.  If this option is not  specified,  fluxes  are  normalised  using  the
              measured value of Hb if it is detected, and not normalised otherwise.

       -o, --output-dir [DIRECTORY]
              The directory in which to put the output files. Default: current working directory.

       -pr, --pressure [REAL]
              The  fraction  of  the population retained from each generation. The product of the
              pressure and the population size should be an integer.  Default: 0.3

       -ps, --populationsize [INTEGER]
              The size of the population used in the genetic algorithm. Default: 30

       -rg, --resolution-guess [VALUE]
              Initial guess for the resolution [lambda/delta lambda].  Default:  estimated  using
              the sampling of the input spectrum, assuming that it is Nyquist sampled.

       -rtol1, --resolution-tolerance-1 [VALUE]
              Variation  allowed  in resolution in first pass. Default: equal to 0.9 x resolution
              guess.

       -rtol2, --resolution-tolerance-2 [VALUE]
              Variation allowed in resolution in second pass. Default: 500.

       -skycat, -strongcat, -deepcat [FILENAME]
              The files containing the line catalogues to be used for the removal of  sky  lines,
              the  estimation of velocity and resolution, and the full line fitting.  The default
              catalogues are stored in  /usr/share/alfa  .   If  you  wish  to  create  your  own
              catalogue, the required format is that each line should be 85 characters wide, with
              a wavelength in the first column, and the rest of the characters are  not  used  by
              the code but are transferred to the output files.  They can thus be used, as in the
              supplied catalogues, for line transition data.

       -ss, --subtract-sky
              Fit and subtract night sky emission lines before fitting nebular emission lines.

       -ul, --upper-limits
              Write out upper limits for all lines searched for and not detected.

       -vg, --velocity-guess [VALUE]
              Initial guess for the velocity of the object [km/s]. Default: 0.

       -vtol1, --velocity-tolerance-1 [VALUE]
              Variation allowed in velocity in first pass of the fitting. Default: 900km/s

       -vtol2, --velocity-tolerance-2 [VALUE]
              Variation allowed in velocity in second pass of the fitting. Default: 60km/s

SEE ALSO

       neat

BUGS

       No known bugs.

AUTHOR

       Roger Wesson