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ABSTRACT We introduce a suite of cosmological volume simulations to study the evolution of galaxies as part of the Feedback in Realistic Environments project. FIREbox, the principal simulation of the present suite, provides a representative sample of galaxies (∼1000 galaxies with $$M_{\rm star}\gt 10^8\, M_\odot$$ at z = 0) at a resolution ($$\Delta {}x\sim {}20\, {\rm pc}$$ , $$m_{\rm b}\sim {}6\times {}10^4\, M_\odot$$ ) comparable to state-of-the-art galaxy zoom-in simulations. FIREbox captures the multiphase nature of the interstellar medium in a fully cosmological setting (L = 22.1 Mpc) thanks to its exceptionally high dynamic range (≳106) and the inclusion of multichannel stellar feedback. Here, we focus on validating the simulation predictions by comparing to observational data. We find that star formation rates, gas masses, and metallicities of simulated galaxies with $$M_{\rm star}\lt 10^{10.5-11}\, M_\odot$$ broadly agree with observations. These galaxy scaling relations extend to low masses ($$M_{\rm star}\sim {}10^7\, M_\odot$$ ) and follow a (broken) power-law relationship. Also reproduced are the evolution of the cosmic HI density and the HI column density distribution at z ∼ 0–5. At low z , FIREbox predicts a peak in the stellar-mass–halo-mass relation but also a higher abundance of massive galaxies and a higher cosmic star formation rate density than observed, showing that stellar feedback alone is insufficient to reproduce the properties of massive galaxies at late times. Given its high resolution and sample size, FIREbox offers a baseline prediction of galaxy formation theory in a ΛCDM Universe while also highlighting modelling challenges to be addressed in next-generation galaxy simulations.
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Realistic mock observations of the sizes and stellar mass surface densities of massive galaxies in FIRE-2 zoom-in simulations
ABSTRACT The galaxy size–stellar mass and central surface density–stellar mass relationships are fundamental observational constraints on galaxy formation models. However, inferring the physical size of a galaxy from observed stellar emission is non-trivial due to various observational effects, such as the mass-to-light ratio variations that can be caused by non-uniform stellar ages, metallicities, and dust attenuation. Consequently, forward-modelling light-based sizes from simulations is desirable. In this work, we use the skirt dust radiative transfer code to generate synthetic observations of massive galaxies ($$M_{*}\sim 10^{11}\, \rm {M_{\odot }}$$ at z = 2, hosted by haloes of mass $$M_{\rm {halo}}\sim 10^{12.5}\, \rm {M_{\odot }}$$) from high-resolution cosmological zoom-in simulations that form part of the Feedback In Realistic Environments project. The simulations used in this paper include explicit stellar feedback but no active galactic nucleus (AGN) feedback. From each mock observation, we infer the effective radius (Re), as well as the stellar mass surface density within this radius and within $$1\, \rm {kpc}$$ (Σe and Σ1, respectively). We first investigate how well the intrinsic half-mass radius and stellar mass surface density can be inferred from observables. The majority of predicted sizes and surface densities are within a factor of 2 of the intrinsic values. We then compare our predictions to the observed size–mass relationship and the Σ1−M⋆ and Σe−M⋆ relationships. At z ≳ 2, the simulated massive galaxies are in general agreement with observational scaling relations. At z ≲ 2, they evolve to become too compact but still star forming, in the stellar mass and redshift regime where many of them should be quenched. Our results suggest that some additional source of feedback, such as AGN-driven outflows, is necessary in order to decrease the central densities of the simulated massive galaxies to bring them into agreement with observations at z ≲ 2.
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- PAR ID:
- 10237289
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 501
- Issue:
- 2
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- 1591 to 1602
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/mnras/staa3765
