Catalog Column Descriptions

This document provides comprehensive descriptions of all columns found in galaxy catalogs generated by GalSBI. Note that the specific columns present in your catalog may vary depending on the configuration and models used during generation.

If the catalog is loaded using combine=True, the columns that vary across bands will have an additional suffix indicating the band, e.g., mag g parameter mag in the g-band. Parameters that are not band-dependent will not have a suffix (e.g., id).

Intrinsic Properties from UCat

Coordinate & Identification

Column	Description	Units
id	Identifier for the galaxy or star in the catalog.	—
ra	Right Ascension (J2000) of the galaxy center.	deg
dec	Declination (J2000) of the galaxy center.	deg
x	x coordinate in the image	pixel
y	y coordinate in the image	pixel
z	Redshift of the galaxy.	redshift
galaxy_type	0 for red (passive) galaxies, 1 for blue (star-forming) galaxies.	label

Photometry & SED

Column	Description	Units
mag	apparent magnitude in the corresponding band including shear.	mag
int_mag	intrinsic apparent magnitude in the corresponding band (without shear).	mag
abs_mag	Rest-frame absolute magnitude in the corresponding band. In GalSBI-SPS it refers to the galaxy component emission only (no AGN).	mag
abs_mag_lumfun	Rest-frame absolute magnitude in the band defined by the luminosity function (set by lum_fct_filter_band). Column is absent in GalSBI-SPS.	mag
excess_b_v	Color excess E(B–V) from dust reddening, used for extinction correction.	mag
template_coeffs_abs	Template coefficients for the kcorrect templates, normalized such that the generated SED corresponds to the rest-frame SED at the redshift of the galaxy. Column is absent in GalSBI-SPS.	—
template_coeffs	Template coefficients for the kcorrect templates, normalized such that the generated SED corresponds to the observed-frame SED at the redshift of the galaxy. Column is absent in GalSBI-SPS.	—
sed	Intrinsic SED of the galaxy in the observed-frame. The rest-frame wavelengths are stored in a separate file and have to be adjusted according to the redshift of the galaxy, see Saving Galaxy Spectra.	erg/s/cm2/Å

Physical properties (GalSBI-SPS only)

Column	Description	Units
log10_stellar_mass	Log10 of formed stellar mass.	Msun
log10_surviv_stellar_mass	Log10 of surviving stellar mass.	Msun
star_formation_history	Star formation history on a common observer-frame lookback time grid, see Stellar population synthesis GalSBI: Overview of the model <https://cosmo-docs.phys.ethz.ch/galsbi/galpop_sps.html>.	Msun/yr
star_formation_rate	Star formation rate averaged over last 100 Myr.	Msun/yr
mSFR	Star formation rate value at the peak of the star formation history.	Msun/yr
mpeak	Age at which the peak of the star formation history (mSFR) occurs.	Gyr
mperiod	Width of the star formation history.	Gyr
mskew	Skewness controlling the asymmetry of the star formation history. mskew=0 corresponds to a Normal distribution with standard deviation given by mperiod.	—
metallicity_history	Gas-phase metallicity history on a common observer-frame lookback time grid, see Stellar population synthesis GalSBI: Overview of the model <https://cosmo-docs.phys.ethz.ch/galsbi/galpop_sps.html>.	Absolute units of metallicity
gas_metallicity	Gas-phase metallicity at the galaxy observed redshift. It corresponds to the first time bin in the metallicity_history column. Solar value is 0.02.	Absolute units of metallicity
gas_ionization	Ionization parameter logU defined as the ratio of ionising photons to the total hydrogen density.	—
dust_attenuation	Three dimensional array containing the effective optical depths of attenuation due to dust in the diffuse ISM and in birth-clouds, and the additional attenuation at the 2175.8 Å dust bump.	—
dust_emission	Two dimensional array containing the alpha slope of the birth cloud dust and screen dust emission.	—
sigma_vel	Stellar velocity dispersion.	km/s
fagn	Ratio of AGN to galaxy bolometric luminosity.	—

Morphology

Column	Description	Units
sersic_n	Sérsic index describing the light profile shape	—
r50	Half-light radius enclosing 50% of total flux of the galaxy	pixel
int_r50	Half-light radius enclosing 50% of total flux of the galaxy (without shear).	pixel
r50_arcsec	Half-light radius enclosing 50% of total flux of the galaxy (without shear).	arcsec
int_r50_arcsec	Half-light radius enclosing 50% of total flux of the galaxy (without shear).	arcsec
r50_phys	Half-light radius enclosing 50% of total flux of the galaxy (without shear).	kpc
e1, e2	Complex ellipticity components \(e = e_1 + i e_2\).	—
int_e1, int_e2	Complex ellipticity components \(e = e_1 + i e_2\) without shear.	—
e_abs	Absolute ellipticity \(e = \sqrt{e_1^2 + e_2^2}\).	—

Shapes & Weak-Lensing Quantities

Column	Description	Units
gamma1, gamma2	Weak lensing shear components.	—
kappa	Weak lensing convergence.	—

Quantities from Image Simulation

Point Spread Function (PSF)

The PSF is modelled as a Moffat profile with distortions following Herbel+2018 and Kacprzak+2020. More details can also be found in the UFig documentation.

Column	Description	Units
psf_fwhm	PSF full width at half maximum.	pixel
psf_beta	Moffat beta parameter, if 2D, the PSF is a double Moffat profile.	—
psf_e1, psf_e2	Complex ellipticity components of the PSF \(e = e_1 + i e_2\).	—
psf_f1, psf_f2, psf_g1, psf_g2	Flexion components of the PSF.	—
psf_flux_ratio	Ratio of the flux of the two Moffat profiles in the PSF (if 2D).	—
psf_kurtosis	PSF kurtosis.	—

Other Image Properties

Column	Description	Units
nphot	Number of photons per object, estimated from the magnitude and image systemtatics (e.g., gain, exposure time).	number of photons
FLAGS_STAMP	UFig flags, using binary flags for delta weight (bit 0), bright star (1) and survey mask (2), see e.g. UFig documentation: Simulating an HSC Deep Field Image for more details.	binary bit flag
star_gal	label for star/galaxy classification, 0 for stars, 1 for galaxies. Created when intrinsic objects are matched to the measured objects in the image. Unmatched objects are set to -200.	—
bkg_noise_amp	Mean of the Gaussian noise at the position of the object	pixel counts
bkg_noise_std	Standard deviation of the Gaussian noise at the position of the object.	pixel counts

SExtractor Parameters

In the measured catalogs, the catalogs include columns from the SExtractor measurements. Depending on the configuration, different columns may be present, typical columns are:

Column	Description	Units
MAG_AUTO	SExtractor AUTO magnitude.	mag
MAGERR_AUTO	Error on the SExtractor AUTO magnitude.	mag
FLUX_AUTO	SExtractor AUTO flux.	flux
FLUXERR_AUTO	Error on the SExtractor AUTO flux.	flux
CLASS_STAR	SExtractor star/galaxy classification, 1 for stars, 0 for galaxies.	—
FLUX_RADIUS	SExtractor flux radius, the radius enclosing 50% of the total flux.	pixel

For a more comprehensive list of SExtractor parameters and their descriptions, refer to the SExtractor documentation.