Abstract Over the past decade, rest-frame color–color diagrams have become popular tools for selecting quiescent galaxies at high redshift, breaking the color degeneracy between quiescent and dust-reddened star-forming galaxies. In this work, we study one such color–color selection tool—the rest-frame U − V versus V − J diagram—by employing mock observations of cosmological galaxy formation simulations. In particular, we conduct numerical experiments assessing both trends in galaxy properties in UVJ space and the color–color evolution of massive galaxies as they quench at redshifts z ∼ 1–2. We find that our models broadly reproduce the observed UVJ diagram at z = 1–2, including (for the first time in a cosmological simulation) reproducing the population of extremely dust-reddened galaxies in the top right of the UVJ diagram. However, our models primarily populate this region with low-mass galaxies and do not produce as clear a bimodality between star-forming and quiescent galaxies as is seen in observations. The former issue is due to an excess of dust in low-mass galaxies and relatively gray attenuation curves in high-mass galaxies, while the latter is due to the overpopulation of the green valley in simba . When investigating the time evolution of galaxies on the UVJ diagram, we find that the quenching pathway on the UVJ diagram is independent of the quenching timescale, and instead dependent primarily on the average specific star formation rate in the 1 Gyr prior to the onset of quenching. Our results support the interpretation of different quenching pathways as corresponding to the divergent evolution of post-starburst and green valley galaxies.
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IQ Collaboratory. III. The Empirical Dust Attenuation Framework—Taking Hydrodynamical Simulations with a Grain of Dust
Abstract We present the empirical dust attenuation (EDA) framework—a flexible prescription for assigning realistic dust attenuation to simulated galaxies based on their physical properties. We use the EDA to forward model synthetic observations for three state-of-the-art large-scale cosmological hydrodynamical simulations: SIMBA, IllustrisTNG, and EAGLE. We then compare the optical and UV color–magnitude relations, ( g − r ) − M r and (far-UV −near-UV) − M r , of the simulations to a M r < − 20 and UV complete Sloan Digital Sky Survey galaxy sample using likelihood-free inference. Without dust, none of the simulations match observations, as expected. With the EDA, however, we can reproduce the observed color–magnitude with all three simulations. Furthermore, the attenuation curves predicted by our dust prescription are in good agreement with the observed attenuation–slope relations and attenuation curves of star-forming galaxies. However, the EDA does not predict star-forming galaxies with low A V since simulated star-forming galaxies are intrinsically much brighter than observations. Additionally, the EDA provides, for the first time, predictions on the attenuation curves of quiescent galaxies, which are challenging to measure observationally. Simulated quiescent galaxies require shallower attenuation curves with lower amplitude than star-forming galaxies. The EDA, combined with forward modeling, provides an effective approach for shedding light on dust in galaxies and probing hydrodynamical simulations. This work also illustrates a major limitation in comparing galaxy formation models: by adjusting dust attenuation, simulations that predict significantly different galaxy populations can reproduce the same UV and optical observations.
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- Award ID(s):
- 1831412
- NSF-PAR ID:
- 10333842
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 926
- Issue:
- 2
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 122
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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ABSTRACT We present predictions for high redshift (z = 2−10) galaxy populations based on the IllustrisTNG simulation suite and a full Monte Carlo dust radiative transfer post-processing. Specifically, we discuss the H α and H β + $[\rm O \,{\small III}]$ luminosity functions up to z = 8. The predicted H β + $[\rm O \,{\small III}]$ luminosity functions are consistent with present observations at z ≲ 3 with ${\lesssim} 0.1\, {\rm dex}$ differences in luminosities. However, the predicted H α luminosity function is ${\sim }0.3\, {\rm dex}$ dimmer than the observed one at z ≃ 2. Furthermore, we explore continuum spectral indices, the Balmer break at 4000 Å; (D4000) and the UV continuum slope β. The median D4000 versus specific star formation rate relation predicted at z = 2 is in agreement with the local calibration despite a different distribution pattern of galaxies in this plane. In addition, we reproduce the observed AUV versus β relation and explore its dependence on galaxy stellar mass, providing an explanation for the observed complexity of this relation. We also find a deficiency in heavily attenuated, UV red galaxies in the simulations. Finally, we provide predictions for the dust attenuation curves of galaxies at z = 2−6 and investigate their dependence on galaxy colours and stellar masses. The attenuation curves are steeper in galaxies at higher redshifts, with bluer colours, or with lower stellar masses. We attribute these predicted trends to dust geometry. Overall, our results are consistent with present observations of high-redshift galaxies. Future James Webb Space Telecope observations will further test these predictions.more » « less
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3847/1538-4357/ac4253
