Synthetic Emission Line Catalog and High-Resolution SEDs for SPHEREx Galaxy Simulations

Overview:

This repository contains the synthetic galaxy models derived from multi-wavelength photometry in the COSMOS field (166k galaxies over 1.27 sq. deg., 18 < i < 25) and from the GAMA survey (44k galaxies over 217 sq. deg., i < 18). These encompass a representative sample of galaxies SPHEREx will observe, and should be applicable for other surveys as well.

• Synthetic emission line strengths in the rest-frame optical/near-infrared (H-alpha, H-beta, Paschen-alpha, [OIII], [OII], [NII], [SII])
• High-resolution SEDs (0.1 - 8 micron), which are produced by 1) fitting a library of 160 galaxy templates to multi-band photometry and 2) inserting emission lines with strengths predicted by an empirical model that depends on galaxy type, redshift and stellar mass.

These products were made using the modeling framework Conditional LIne Painting on Synthetic Spectra (CLIPonSS), the details of which are summarized in Feder+2023b (arXiv link here). The synthetic emission line catalog is validated against a variety of LF measurements, line ratio trends and direct line comparisons. 

Data description:

High-resolution SEDs: The SEDs are stored in .FITS files, for which each galaxy SED has its own Header Data Unit (HDU). This format was chosen due to the fact that the wavelength sampling for the 160 galaxy empirical and model-based templates varies, i.e., we do not perform any interpolation onto a homogenized wavelength grid. In cases where emission lines are added but the continuum template resolution is coarse, the resolution is increased in the vicinity of the emission line(s) to adequately sample the line profiles. Each galaxy's HDU is indexed by its Farmer ID (for COSMOS) or alternatively its uberID (GAMA). The COSMOS SEDs are split into three files for relative ease of access, while the GAMA sources are all in one file.

Emission line catalogs: The emission line catalogs are stored in .csv format with the following information:

Tractor_ID (or uberID) [integer]: Unique identifier for each source

RA/DEC [float, in degrees]: Celestial coordinates

imag [AB]: i-band magnitude

mass_best [float]: log-stellar masses estimated through SED fitting process

ebv [float]: Galaxy intrinsic dust extinction (ranging from ebv=0 to 1)

redshift [float]: Best-fit redshift from COSMOS2020 (GAMA) catalogs

bfit_tid [integer]: Best fit template ID from library of templates

dustlaw [integer]: Best fit dust law (1=Prevot, 2=Calzetti, 3=Seaton, 4=Allen, 5=Fitzpatrick)

L_{line} [float, erg s-1]: Line luminosities from empirical model

F_{line} [float, erg cm-2 s-1]: Line fluxes from empirical model

ew_ha [float, Angstrom]: Equivalent width of H-alpha from empirical model

Fitting templates: We include the 31 model-based templates and 129 empirical templates from Brown+2014. In the Brown templates we have removed any relevant lines that were directly measured in the initial spectra, however we do not fit for/remove PAH features. These can serve as the basis for other empirically based galaxy simulations with different emission line prescriptions.

Any questions regarding the use of these data products or related issues can be directed to Richard Feder (link to personal website).