123 research outputs found
Are the ultra-high-redshift galaxies at z > 10 surprising in the context of standard galaxy formation models?
A substantial number of ultra-high redshift (8 < z < 17) galaxy candidates
have been detected with JWST, posing the question: are these observational
results surprising in the context of current galaxy formation models? We
address this question using the well-established Santa Cruz semi-analytic
models, implemented within merger trees from the new suite of cosmological
N-body simulations GUREFT, which were carefully designed for ultra-high
redshift studies. Using our fiducial models calibrated at z=0, we present
predictions for stellar mass functions, rest-frame UV luminosity functions, and
various scaling relations. We find that our (dust-free) models predict galaxy
number densities at z~11 (z~ 13) that are an order of magnitude (a factor of
~30) lower than the observational estimates. We estimate the uncertainty in the
observed number densities due to cosmic variance, and find that it leads to a
fractional error of 30-70% at z=11 (25-150% at z=13) for the available observed
fields. We explore which processes in our models are most likely to be
rate-limiting for the formation of luminous galaxies at these early epochs,
considering the halo formation rate, gas cooling, star formation, and stellar
feedback, and conclude that it is mainly efficient stellar-driven winds. We
find that a modest boost of a factor of ~4 to the UV luminosities, which could
arise from a top-heavy stellar initial mass function characteristic of Pop III
stars, would bring our current models into agreement with the observations.Comment: 20 pages, 15 figures, submitted to MNRA
Mock Galaxy Surveys for HST and JWST from the IllustrisTNG Simulations
We present and analyze a series of synthetic galaxy survey fields based on
the IllustrisTNG Simulation suite. With the Illustris public data release and
JupyterLab service, we generated a set of twelve lightcone catalogs covering
areas from 5 to 365 square arcminutes, similar to several JWST Cycle 1
programs, including JADES, CEERS, PRIMER, and NGDEEP. From these catalogs, we
queried the public API to generate simple mock images in a series of broadband
filters used by JWST-NIRCam and the Hubble Space Telescope cameras. This
procedure generates wide-area simulated mosaic images that can support
investigating the predicted evolution of galaxies alongside real data. Using
these mocks, we demonstrate a few simple science cases, including morphological
evolution and close pair selection. We publicly release the catalogs and mock
images through MAST, along with the code used to generate these projects, so
that the astrophysics community can make use of these products in their
scientific analyses of JWST deep field observations.Comment: Accepted to MNRA
Semi-analytic forecasts for JWST -- IV. Implications for cosmic reionization and LyC escape fraction
Constraining cosmology with machine learning and galaxy clustering: the CAMELS-SAM suite
As the next generation of large galaxy surveys come online, it is becoming
increasingly important to develop and understand the machine learning tools
that analyze big astronomical data. Neural networks are powerful and capable of
probing deep patterns in data, but must be trained carefully on large and
representative data sets. We developed and generated a new `hump' of the
Cosmology and Astrophysics with MachinE Learning Simulations (CAMELS) project:
CAMELS-SAM, encompassing one thousand dark-matter only simulations of (100
cMpc) with different cosmological parameters ( and
) and run through the Santa Cruz semi-analytic model for galaxy
formation over a broad range of astrophysical parameters. As a proof-of-concept
for the power of this vast suite of simulated galaxies in a large volume and
broad parameter space, we probe the power of simple clustering summary
statistics to marginalize over astrophysics and constrain cosmology using
neural networks. We use the two-point correlation function, count-in-cells, and
the Void Probability Function, and probe non-linear and linear scales across
R cMpc. Our cosmological constraints cluster around
3-8 error on and , and we explore the effect
of various galaxy selections, galaxy sampling, and choice of clustering
statistics on these constraints. We additionally explore how these clustering
statistics constrain and inform key stellar and galactic feedback parameters in
the Santa Cruz SAM. CAMELS-SAM has been publicly released alongside the rest of
CAMELS, and offers great potential to many applications of machine learning in
astrophysics: https://camels-sam.readthedocs.io.Comment: 40 pages, 22 figures (11 made of subfigures
Semi-analytic forecasts for JWST -- II. physical properties and scaling relations for galaxies at z = 4-10
The long-anticipated James Webb Space Telescope (JWST) will be able to
directly detect large samples of galaxies at very high redshift. Using the
well-established, computationally efficient Santa Cruz semi-analytic model,
with recently implemented multiphase gas partitioning and H2-based star
formation recipes, we make predictions for a wide variety of galaxy properties
for galaxy populations at = 4-10. In this work, we provide forecasts for
the physical properties of high-redshift galaxies and links to their
photometric properties. With physical parameters calibrated only to
observations, our model predictions are in good agreement with current
observational constraints on stellar mass and star formation rate distribution
functions up to . We also provide predictions representing wide,
deep, and lensed JWST survey configurations. We study the redshift evolution of
key galaxy properties and the scaling relations among them. Taking advantage of
our models' high computational efficiency, we study the impact of
systematically varying the model parameters. All distribution functions and
scaling relations presented in this work are available at
https://www.simonsfoundation.org/semi-analytic-forecasts-for-jwst/.Comment: 28 pages, 22 figures, Accepted for publication in MNRA
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