Semi-analytic forecasts for the Universe

Semi-analytic forecasts for the Universe is an ongoing project that provides physically motivated predictions for the properties and demographics of galaxies and quasars forming across cosmic time in the universe. We provide a wide variety of scientific predictions and simulated data products that are designed to be useful for optimizing observing strategies, physically interpreting observational results, and ultimately maximizing the scientific output of galaxy surveys.

These predictions are made with the well-established Santa Cruz semi-analytic model (SAM) for galaxy formation. Taking advantage of the physically motivated and yet computationally efficient model, we provide predictions for tens of millions of galaxies across wide ranges of mass and redshift. Over the course of seven publications, we compared the model outputs with a wide variety of observational constraints available to date, including distribution functions for rest-frame UV magnitude, stellar mass, star formation rate and a variety of scaling relations. We showed that the model reproduces constraints well up to z ~ 10. We use NASA’s flagship observatories James Webb Space Telescope (JWST) and Nancy Grace Roman Space Telescope (Roman) as practical examples to demonstrate how these predictions can be used. These results are presented in a series of publications entitled “Semi-analytic forecasts for JWST” and “Semi-analytic forecasts for Roman”.


Side-view of the simulated universe as presented in the final publication of the Semi-analytic forecasts for JWST series (Yung, Somerville et al. 2022, MNRAS in press). Each data point represents a galaxy. Larger and darker data points represent galaxies with more mass, and vice versa.

We provide three sets of simulated lightcones: 1) a set of 40 wide-field lightcones, each spanning ~1,000 sq. arcmin with footprints overlapping the five CANDELS legacy fields, resolving galaxies down to M*~10^7 Msun; 2) a set of 8 deep-field lightcones, each spanning 132 sq. arcmin with footprints overlapping the HUDF, resolving galaxies down to M*~5.7×10^7 Msun; and 3) a set of 5 ultra-wide lightcones, each spanning 2 sq degrees, with resolution matching the wide-field lightcones. For all three sets of catalogs, we provide observed-frame photometry for JWST (NIRCam), Roman (WFI), Hubble (WFC3/ACS), Spitzer, Euclid, Rubin, GALEX, SDSS, UKIRT, VISTA and DECam, as well as rest-frame luminosity for NUV, FUV and Johnson/Bessel/Cousins bands, and a wide variety of predicted physical properties for halos and galaxies.


Data Access

1. Simulated lightcones access through interactive portal Flathub
• select galaxy samples and create simple diagnostic plots

2. Simulated lightcones access direct download in this directory
• include full object catalogs, SEDs, and star formation histories

3. Tabulated data are available in this directory
• include distribution functions and scaling relations


JWST I Yung et al. 2019a MNRAS 483, 2983
JWST II Yung et al. 2019b MNRAS 490, 2879
JWST III Yung et al. 2020a MNRAS 494, 1002
JWST IV Yung et al. 2020b MNRAS 496, 4574
JWST V Yung et al. 2021 MNRAS 508, 2706
JWST VI Yung et al. 2022a MNRAS 515, 5416
Roman Yung et al. 2022b Coming in October

Team Members

Aaron Yung (NASA/GSFC) Rachel Somerville (Flatiron/CCA)
Steve Finkelstein (UT Austin) Jon Gardner (NASA/GSFC)
Gergö Popping (ESO) Romeel Dave (Edinburgh)
Harry Ferguson (STScI) Peter Behroozi (Arizona)
Aparna Venkatesan (USF) Michaela Hirschmann (EPFL)
Micaela Bagley (UT Austin)



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