Templates

Lazy.jl fits photometric data by finding the best linear combination of spectral energy distribution (SED) templates at each redshift. The choice of template set determines what types of galaxies the fitter can model.

Built-in Template Sets

Use lazy list-templates to see available sets. Select a set in your parameter file with:

[fitting]
    template_set = 'sfhz'

Base Sets

Template Set	Templates	Attribution	Description
fsps_full	12	eazy, FSPS	Standard FSPS templates from eazy
sfhz	13	eazy, FSPS, Gabe Brammer	Star-formation-history templates with redshift-dependent SEDs
jades	16	Hainline+, Brammer+08, Coe+06, Erb+10	JADES survey template set

Extended Sets

The base sets can be extended with additional template components:

• Larson22: High-redshift galaxy templates from Larson et al. (2022), designed for z > 6 candidates with young stellar populations and nebular emission

• Schrodinger (_schr): Model constructed to match the extreme z=4.9 "schrodinger's galaxy" (Naidu+22, Arrabal-Haro+23) with red continuum and strong emission lines.

• LRD (_lrd): Little red dot template constructed from the best-fit model to CAPERS-LRD-z9 (Taylor+25).

Template Set	Templates	Components
fsps_Larson22	15	FSPS + Larson22
fsps_Larson22_schr	16	FSPS + Larson22 + Schrodinger
fsps_Larson22_lrd	16	FSPS + Larson22 + LRD
fsps_Larson22_schr_lrd	17	FSPS + Larson22 + Schrodinger + LRD
sfhz_Larson22	19	SFHZ + Larson22
sfhz_Larson22_schr	20	SFHZ + Larson22 + Schrodinger
sfhz_schr	14	SFHZ + Schrodinger
sfhz_lrd	14	SFHZ + LRD
sfhz_schr_lrd	15	SFHZ + Schrodinger + LRD
sfhz_Larson22_lrd	19	SFHZ + Larson22 + LRD
sfhz_Larson22_schr_lrd	20	SFHZ + Larson22 + Schrodinger + LRD
jades_Larson22	19	JADES + Larson22

Custom Template Sets

Instead of a named set, you can provide a list of template file paths:

[fitting]
    template_set = [
        'sfhz/corr_sfhz_13_bin3_av0.50.fits',
        'sfhz/corr_sfhz_13_bin3_av0.01.fits',
        'custom/my_template.dat',
    ]

Paths are relative to the src/templates/ directory.

Template File Formats

Lazy.jl supports two template formats:

ASCII (.dat, .sed): Two-column files with wavelength (Angstroms) and flux. These are redshift-independent – the same SED is used at all redshifts.

FITS: Contains a 2D flux array that varies with redshift. These are redshift-dependent templates where the SED shape changes across the fitting grid. The SFHZ templates use this format.

Adding Custom Templates

1. Place your template files in a subdirectory of src/templates/:

src/templates/my_set/template1.dat
src/templates/my_set/template2.dat

2. Add an entry to src/templates/template_directory.toml:

[my_set]
    files = [
        'my_set/template1.dat',
        'my_set/template2.dat',
    ]
    attribution = "Your citation"

3. Verify with lazy list-templates.

Contributions of new template sets are very welcome! If you've added templates that may be useful to others, please open a pull request to include them in the package. See Development for the contributing workflow.