Models and Parameters

This document describes the galaxy parameters and models that are implemented in the generate.py program. For more detailed information take a look into analysis.models and the galsim documentation.

Galaxy Models

Name	Description
gaussian	Gaussian galaxy profile, galsim.Gaussian.
exponential	Exponential galaxy profile, galsim.Exponential.
deVaucouleurs	DeVaucouleurs galaxy profile, galsim.DeVaucouleurs.
bulgeDisk	Combined exponential (disk) and deVaucouleurs (bulge) profile.

Galaxy Parameters

Name	Type	Description
Program Parameters
project	string	Pixel offset of left edge of bounding box relative to left edge of survey image.
gal	int32	Pixel offset of right edge of bounding box relative to left edge of survey image.
ymin	int32	Pixel offset of bottom edge of bounding box relative to bottom edge of survey image.
ymax	int32	Pixel offset of top edge of bounding box relative to bottom edge of survey image.
Source Properties
f_disk	float32	Fraction of total galaxy flux to due a Sersic n=1 disk component.
f_bulge	float32	Fraction of total galaxy flux to due a Sersic n=4 bulge component.
flux	float32	Total detected flux in electrons.
x	float32	Source centroid in x relative to image center in arcseconds.
y	float32	Source centroid in y relative to image center in arcseconds.
e1	float32	Real part (+) of galaxy ellipticity spinor (Q11-Q22+2*Q12)/(Q11+Q22).
e2	float32	Imaginary part (x) of galaxy ellipticity spinor 2*Q12/(Q11+Q22).
g1	float32	Real part (+) of galaxy ellipticity spinor (Q11-Q22)/(Q11+Q22+2|Q|**0.5).
g2	float32	Imaginary part (x) of galaxy ellipticity spinor (2*Q12)/(Q11+Q22+2|Q|**0.5).
eta1	float32	Conformal shear with a/b = exp(eta).
eta2	float32	Conformal shear with a/b = exp(eta).
sigma	float32	Galaxy size arcseconds calculated as |Q|**0.25.
sigma_p	float32	Galaxy size in arcseconds calculated as (0.5*trQ)**0.5.
hlr	float32	The half-light-radius of the profile.
beta	float32	Position angle of second-moment ellipse in radians, or zero when a = b.
q	float32	b/a ratio of semi-minor axis to semi-major axis.
fwhm	float32	Full-width-half-max of the profile, defined as radius at half the max peak…
snr	float32	Signal to noise ration as defined in…
hlr_b	float32	hlr for the bulge component of the analysis.models.bulgeDisk model.
flux_d	float32	flux for the disk component of the analysis.models.bulgeDisk model.
flux_b	float32	flux for the bulge component of the analysis.models.bulgeDisk model.
R_r	float32	hlr for the bulge component of the analysis.models.bulgeDisk model.

PSF Models

Name	Description
psf_gaussian	Gaussian galaxy profile, galsim.Gaussian.
psf_moffat	Moffat galaxy profile, galsim.Moffat.

PSF Parameters

For the PSF, the parameters have the same significance as in the table of parameters as above.