PhoSim Tutorial 4: How to Generate a Field of Stars and Galaxies

To simulate a field of astronomical objects you can do the following command:

phosim examples/small_catalog -c examples/nobackground

It should look like this (log scale and zoomed in):

PhoSim Shallow Star Galaxy Simulation

The small catalog file has the following commands:

rightascension 0

declination 0

moonalt -90.0

stars 18.0 30.0 0.1

galaxies 18.0 30.0 0.1

This specifies a set of stars and galaxies in the 18th through 30th magnitude range covering a circle with diameter of 0.1 degrees. The stars and galaxies have a range of realistic spectral energy distribution and sky densities. The galaxies have a detailed set of morphologies.

If you increase the exposure time in the small_catalog to obtain a much deeper image as:

vistime 150000.0

Then the following image will be obtained:

PhoSim Deep Star Galaxy Simulation

The angular size of the image can be chosen to be larger than the focal plane and PhoSim will correctly trim away objects that do not contribute photons.