sim-to-cos

Creates mock spectra for HST/COS using data from simulations

The creation of the mock spectra includes three steps:

1. Convolution with the COS-LSF according to the required setup(grating, central wavelength and lp). WARNING: this version of the code does not use the wavelength dependent LSF. Rather, it uses a single lsf that is closest to the wavelength midpoint of the simulated data.
2. Rebinning of the simulated data to the observed spectrum.
3. Adding poisson noise.

Requirements

astropy~=5.1; numpy~=1.23.3

The given versions are the tested ones. The code might work with the older versions as well.

How to use

There are two files required as input:

simulated data:

FITS file with columns z, tau_HeII and sim_id (see examples/example_sim_data.fits).

The binning of the data MUST match the dispersion of the HST/COS.

Grating	Dispersion
G130M	9.97 mA pixel^-1
G160M	12.23 mA pixel^-1
G140L	80.3 mA pixel^-1

observed data:

FITS file from FaintCOS with additional column CONT containing the fitted continuum.

WARNING:CALIB_DERED will be used instead of CALIB if present.

Arguments

The code requres six arguments:

  --sim-data PATH_TO_SIM_DATA
                        Path to the simulation data in fits format.It must have the columns "z", "tau_HeII", and "sim_id".The bin size
                        must match the COS bin size of the desired grating!
  --cos-data PATH_TO_OBS_DATA
                        Path to the observed COS spectrum reduced with FaintCOS.Additionnally, the spectrum must have the column
                        "CONT" containing fitted continuum. If data contains "CALIB_DERED" it will be used instead of "CALIB".
  --output PATH_TO_OUTPUT
                        Path to the output file. This option must end with ".fits".
  --lp LP               lifetime-poition of HST/COS
  --grating GRATING     HST/COS grating that shoud be used for mocks
  --cenwave CENWAVE     HST/COS cenwave that shoud be used for mocks

Working example

python create_mock.py --sim-data=examples/example_sim_data.fits --cos-data=examples/dummy_spec.fits --lp=4 --grating=G130M --cenwave=1291 --output=examples/mocks.fits