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We compare satellite quenched fractions across three cosmological simulation suites (FIREbox, the FIRE-2 zoom-ins, and IllustrisTNG50) and observational datasets from SAGA, ELVES, and the combined satellite population of the Milky Way and M31. To enable consistent comparisons, we select Milky Way-mass hosts with \\(M_{\\rm halo} = 10^{11.9}\\) - \\(10^{12.2} \\, M_{\\odot}\\) and satellites with stellar masses of \\(10^{7}\\) - \\(10^{10}\\, M_{\\odot}\\), applying uniform projected apertures and a common quenching definition. All three simulations reproduce the strong observed trend that lower-mass satellites are more likely to be quenched, closely matching the stellar-mass dependence seen in SAGA, ELVES, and the MW+M31 system. This agreement indicates that the mass dependence of satellite quenching is a robust outcome of contemporary galaxy formation models. Radial trends, however, show meaningful differences. SAGA and ELVES exhibit gently declining quenched fractions with projected distance, reflecting strong environmental quenching at small radii. TNG50 most closely matches this behavior, FIREbox, remains consistent with with a nearly flat trend within uncertainties, and the FIRE-2 zoom-ins show suppressed inner quenched fractions driven almost entirely by their paired MW-M31 hosts, which lack high-mass satellites and show strong radial segregation between star-forming and quenched systems. This environmental imprint suggests that host environment and assembly history can influence satellite quenching outcomes and may contribute to diversity across simulations. Overall, while the simulations consistently recover the stellar-mass dependence of quenching their radial trends vary, highlighting the influence of host-halo conditions and motivating deeper exploration of how host environments shape satellite quenching.

We explore how a realistic surface brightness detection limit of \\(_V 32.5\\) mag arcsec\\(^-2\\) for stars at the edges of ultra-faint galaxies affects our ability to infer their underlying properties. We use a sample of 19 galaxies with stellar masses \\( 400 - 40,000~ M_\\) simulated with FIRE-2 physics and baryonic mass resolution of \\(30~M_\\). The surface brightness cut leads to smaller sizes, lower stellar masses, and lower stellar velocity dispersions than the values inferred without the cut. However, by imposing this realistic limit, our inferred galaxy properties lie closer to observed populations in the mass-size plane, better match observed velocity dispersions as a function of stellar mass, and better reproduce derived circular velocities as a function of half-light radius. For the most massive galaxies in our sample, the surface brightness cut leads to higher mean \\( [Fe/H]\\) values, but the increase is not enough to match the observed MZR. Finally, we demonstrate that the common Wolf et al. (2010) mass estimator is less accurate when the surface brightness cut is applied. For our lowest-mass galaxies, in particular, excluding the low-surface brightness outskirts causes us to overestimate their central dark-matter densities and virial masses. This suggests that attempts to use mass estimates of ultra-faint galaxies to constrain dark-matter physics or to place constraints on the low-mass threshold of galaxy formation must take into account surface brightness limits or risk significant biases.

It is widely believed that the ultraviolet background produced during the epoch of reionization conspires against the formation of low-mass galaxies. Indeed, this mechanism is often invoked as a solution to the so-called `missing satellites problem.' In this paper we employ FIREbox, a large-volume cosmological simulation based on the Feedback In Realistic Environments (FIRE-2) physics model, to characterize the mechanisms governing galaxy ignition in the post-reionization era. By carefully matching recently-ignited halos (with stellar ages below \\(100\\) Myr at the time of selection) to halos that failed to form any stars, we conclude that the presence of cold-dense gas and halo concentration help incite the process of galaxy formation. Concretely, we find that \\(100\\%\\) of recently-ignited halos experience cold-dense gas enhancements relative to their matched failed counterparts. Likewise, approximately \\(83\\%\\) display enhancements in both cold-dense gas and Navarro-Frenk-White concentration (\\(c_{\\rm NFW}\\)), while the remaining \\(\\sim17\\%\\) exhibit enhanced cold-dense gas content and suppressed \\(c_{\\rm NFW}\\) values. Lastly, our simulation suggests that galaxy ignition can occur as late as \\(z=2\\), potentially allowing us to observationally catch this process `in the act' in the foreseeable future.