Brief Description
Here's a list of the main new features of the new BUDDA version:
-
a Sérsic bar
-
a Moffat central source
-
disks that can have double exponential profiles
-
a more accurate routine for chi square minimization meaning more
reliable results
-
a much better treatment of seeing effects, modelled as
a circular Moffat PSF
-
proper modelling of edge-on galaxies (bug fixed)
-
proper use of generalized ellipses (bug fixed)
-
a much more accurate error evalution
Things you need to have:
-
a computer under Linux (Macintosh binaries coming soon!)
-
a fully reduced image of your galaxy as an ASCII file
(named ximag.pix), i.e., a table whose lines/columns' values are
the corresponding pixel values of your image (easy to do with IRAF!)
-
the GMODEL and BMODEL executables of BUDDA
-
an ASCII file (named galaxy.dat) with the input values
(1st guesses) for the structural parameters of
your galaxy
-
time to await for the BUDDA results: it can be
as short as one minute, or as long as one hour, depending on the
input values but especially on the image size
Things you need to do:
-
your ASCII image file must be named ximag.pix
-
your ASCII file with input values must be named galaxy.dat
-
run GMODEL (it is for "get model" - it will take your input
parameters and your galaxy image and get the model which best fits your
galaxy)
-
pay attention to the results BUDDA displays at the end of
each iteration to: (i) understand what it is doing to get the best fit
(e.g., is it raising the central surface brightness of the disk? Lowering
the effective radius of the bulge? Changing its ellipticity?) so that you
can give better input values if you need to run it again; and (ii) check
if for some reason something is wrong (if the effective surface brightness
of the bulge is negative, then there's something bad about your input values!)
-
when GMODEL finishes, it will generate an ASCII file called
model.dat, which contains the output parameters, i.e., the structural
parameters of the best model of your galaxy
-
run BMODEL - this one is quick (always about a minute)!
- it is for "built model",
it will take the output parameters from GMODEL (that you have put from
model.dat to galaxy.dat) and build model images
Things you'll get:
-
an ASCII file named galaxy.out which contains all
the structural parameters of your galaxy, as
determined by BUDDA, plus information about the fitting and luminosity
ratios
-
5 ASCII files named xgal.txt, xbulge.txt,
xdisk.txt, xbar.txt and xagn.txt, which are the "images"
of the model galaxy, bulge, disk, bar and central source, respectively
(these can be easily transformed to FITS images with
IRAF! Note that all model images as seeing convolved)
-
residual images (if you subtract or divide the model images
from your galaxy image) displaying sub-structures your galaxy might have