Verify the de Vaucouleurs profile of an elliptical galaxy
Thanks to Les McCommas and Brian Oldfield for these instructions!
Refer to your coursework for the underlying physics. Within IRAF, you will want to check out the following tasks:
The IRAF task ellipse creates elliptical isophotes tracing average values of surface brightness for
increasing values of surface brightness. Command:
ellipse imagename.fits -- creates a file called imagename.tab that contains
a table listing SMA, intensity, intensity error, SMA1/4, flux within isophote, etc. SMA
stands for "semi-major axis." The output is in terms of SMA in pixels and magnitude of each isophote at that
SMA in terms of magnitude per pixel2.
The output .tab file is in binary format. It can be converted to ASCII format using the task
tprint:
tprint imagename.tab > imagename.dat -- columns contain "SMA, RSMA, INTENS,
INT_ERR, TFLUX_E, NDATA" -- see phelp tprint for explanations.
Considerations:
How will you obtain an accurate estimate of the sky brightness? How will you determine the actual plate scale
for the binning you used for the observations? What are the units for the sky brightness?
Verify the exponential profile of a disk galaxy
See information under Verify the de Vaucouleurs profile of an elliptical galaxy above.
Measure the extinction in galactic dust lanes
IRAF tasks of interest: