PhoSim - Tutorial 15

PhoSim Tutorial 15: How to Redshift Sources

Sources could be redshifted by hand by adjusting the individual SEDs of each source. However, this is tedious and also creates as many SEDs as there are sources. A better way is to simply use PhoSim's redshift capabilities where individual photons are redshifted as real photons wavelengths are altered as they propagate throughout the Universe.

An example of this is by simulating the following catalogs of seven galaxies with the same SED at z=0,0.5,1.0,1.5,2.0,2.5,3.0 using three filter configurations:

rightascension 0

declination 0

filter 1

object 0 0.000 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 0 0 0 0 0 0 star none none

object 0 0.002 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 0.5 0 0 0 0 0 star none none

object 0 0.004 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 1.0 0 0 0 0 0 star none none

object 0 0.006 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 1.5 0 0 0 0 0 star none none

object 0 0.008 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 2.0 0 0 0 0 0 star none none

object 0 0.010 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 2.5 0 0 0 0 0 star none none

object 0 0.012 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 3.0 0 0 0 0 0 star none none

rightascension 0

declination 0

filter 2

object 0 0.000 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 0 0 0 0 0 0 star none none

object 0 0.002 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 0.5 0 0 0 0 0 star none none

object 0 0.004 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 1.0 0 0 0 0 0 star none none

object 0 0.006 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 1.5 0 0 0 0 0 star none none

object 0 0.008 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 2.0 0 0 0 0 0 star none none

object 0 0.010 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 2.5 0 0 0 0 0 star none none

object 0 0.012 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 3.0 0 0 0 0 0 star none none

rightascension 0

declination 0

filter 3

object 0 0.000 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 0 0 0 0 0 0 star none none

object 0 0.002 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 0.5 0 0 0 0 0 star none none

object 0 0.004 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 1.0 0 0 0 0 0 star none none

object 0 0.006 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 1.5 0 0 0 0 0 star none none

object 0 0.008 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 2.0 0 0 0 0 0 star none none

object 0 0.010 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 2.5 0 0 0 0 0 star none none

object 0 0.012 0.0 15 POPSTARKroupa/kroupa_spneb_kro_0.15_100_z0200_t9.65_total.dat.txt.gz 3.0 0 0 0 0 0 star none none

The corresponding three color image is:

The three color image is generated by:

ds9 -rgb -red output/generic_e_9999_f3_chip_E000.fits.gz -scale log -green output/generic_e_9999_f2_chip_E000.fits.gz

-scale log -blue output/generic_e_9999_f1_chip_E000.fits.gz -scale log -rgb close

The image above demonstrates the gradual reddening of the spectrum due to the redshift. Note that the overall flux is the same for each source as they are all specified with an apparent magnitude of 15. PhoSim uses the normalization at an AB magnitude at a wavelength of 500 nm/(1+z). This is so that after the photons are redshifted the photons are normalized at 500 nm.