UFig Simulations and Input Catalogues of low S/N sources for the PAUS Collaboration

Summary

Using Ultra Fast Image Generator (UFig; Bergé et al., 2013), we simulated the 8 bluest filters of 25 PAUS fields in the COSMOS area.

We simulated both the images with realistic noise and low S/N sources, and the images with low S/N sources but without noise. We also generated the catalogues of input properties.

See the section conditions of use for the conditions of use.

Image simulations

The images are simulated with UFig. UFig uses a hybrid simulation approach, simulating stars directly on the pixel grid, and the galaxies by sampling the distributions photon-by-photon. This approach and the numerical optimizations makes the image simulation process ultra-fast. Its performance (~3min for a 0.5 sq. deg image) in simulating one image is comparable to running Source Extractor on this image.

At a given fixed field (e.g., centered on RA:09h 59m DEC:+02 05’), we simulate the 8 bluest filters which belong to the filter tray FT_NB455_NB545.

Exposure times, gains, saturation levels, magnitude zero-points, seeings, background noise amplitudes and sigmas and astrometric properties for each simulated image are taken from the corresponding PAUS real one. The PSF is modeled as a circular Moffat profile.

Galaxy properties (e.g., magnitudes, sizes, Sersic indices etc.) are drawn from the galaxy population model calibrated in Tortorelli et al. 2020.

We simulated two sets of images:

The galaxy magnitude range is set to be between 25 and 30. The noise is drawn from a Gaussian distribution with mean and sigma given by the "bkg_mean", "bkg_std" key for each image from the production_id 813. The correlated noise is given by a Lanczos resampling. No stars are simulated. These images have suffix "*seed_number.sim.fits", where "seed_number" is the noise seed.
The galaxy magnitude range is set to be between 25 and 30. No noise is simulated on the image. No stars are simulated. These images have suffix "*seed_number.nonoise.sim.fits", where "seed_number" is the noise seed.

More details on the image simulation can be found in Tortorelli et al. 2020, Tortorelli et al. 2018, Herbel et al. 2017 and Bergé et al. 2013.

Catalogues of input properties

The catalogues containing galaxy input properties from UFig are in FITS format. Catalogue filenames have the same structure of the simulated images filenames: "*seed_number.gal.cat" for images with noise and sources, "*seed_number.nonoise.gal.cat" for images with sources but without noise. The following are the catalogue parameters:

ID #UFig ID object

x #x pixel coordinate

y #y pixel coordinate

mag #apparent magnitude

r50 #half-light radius

e1 #galaxy ellipticity e1

e2 #galaxy ellipticity e2

sersic_n #sersic index

z #redshift of the object

n_phot #number of photons rendered for each object

int_r50 #input half-light radius from size distribution

int_mag #input apparent magnitude from luminosity function

int_e1 #input ellipticity e1 from ellipticity distribution

int_e2 #input ellipticity e1 from ellipticity distribution

abs_mag #absolute magnitude from B-band luminosity function

template_coeffs #linear combination coefficients of template spectra

blue_red #blue(1), red(0) galaxy separation

excess_b_v #B-V Milky-Way extinction

psf_beta #Moffat profile beta

psf_fwhm #PSF fwhm at galaxy position

psf_r50 #PSF half-light radius at galaxy position

psf_e1 #PSF e1 at galaxy position

psf_e2 #PSF e2 at galaxy position

psf_g1 #not used, set to 0.001

psf_g2 #not used, set to 0.001

psf_f1 #not used, set to 0.001

psf_f2 #not used, set to 0.001

psf_kurtosis #not used

psf_flux_ratio #not used

kappa #not used

gamma1 #not used

gamma2 #not used

How to download data

We provide the line of code to download all files:


        wget --wait=0.1 -r -v -nH --cut-dirs=3 --no-parent -nc --show-progress --reject=“index.html*” -o [LOGFILENAME].log https://people.phys.ethz.ch/~ipa/cosmo/paus_low_sn_sims/data

For individual file download, go to https://people.phys.ethz.ch/~ipa/cosmo/paus_low_sn_sims/data

Conditions of Use

For internal use of the PAUS collaboration only. For permission to use in publication please contact:

Luca Tortorelli: torluca@phys.ethz.ch
Alexandre Refregier: alexandre.refregier@phys.ethz.ch

If used in publication, please cite papers in References.

Credits: Luca Tortorelli, Claudio Bruderer, Alexandre Refregier

Contact

For further information on data products and image simulations, please contact:

Luca Tortorelli: torluca@phys.ethz.ch