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Abstract Scaling relationships, both integrated and spatially resolved, arise owing to the physical processes that govern galaxy evolution and are frequently measured in both observed and simulated data. However, the accuracy and comparability of these measurements are hindered by various differences between studies such as spatial resolution, sample selection criteria, and fitting technique. In this Letter, we compare variations of standard least-squares techniques to the ridge line method for identifying spatially resolved scaling relations (Σ_*−Σ_SFR, Σ_*−Σ_gas, and Σ_gas−Σ_SFR) for TNG100 galaxies. We find that using the ridge line technique to fit these scaling relations with a double linear function (in logarithmic space) results in significantly better fits than fitting with ordinary least squares. We further illustrate the utility of the ridge line technique with an investigation into the dependence of resolved star formation main-sequence (rSFMS) measurements on spatial resolution and smoothing scale. Specifically, we find that the slope of the rSFMS at low Σ_*is independent (within 2σ) of spatial resolution and smoothing scale. Finally, we discuss the need for a consistent reanalysis of resolved scaling relations in the literature and physically motivate adoption of the ridge line technique over other fitting methods. 

Abstract We present radial density profiles, as traced by luminous galaxies and dark matter particles, for voids in 11 snapshots of theTNG 300simulation. The snapshots span 11.65 Gyr of cosmic time, corresponding to the redshift range 0 ≤z≤ 3. Using the comoving galaxy fields, voids were identified via a well-tested, watershed transformation-based algorithm. Voids were defined to be underdense regions that are unlikely to have arisen from Poisson noise, resulting in the selection of ∼100–200 of the largest underdense regions in each snapshot. At all redshifts, the radial density profiles as traced by both the galaxies and the dark matter resemble inverse top-hat functions. However, details of the functions (particularly the underdensities of the innermost regions and the overdensities of the ridges) evolve considerably more for the dark matter density profiles than for the galaxy density profiles. At all redshifts, a linear relationship between the galaxy and dark matter density profiles exists, and the slope of the relationship is similar to the bias estimates forTNG 300snapshots. Lastly, we identify distinct environments in which voids can exist, defining “void-in-void” and “void-in-cloud” populations (i.e., voids that reside in larger underdense or overdense regions, respectively), and we investigate ways in which the relative densities of dark matter and galaxies in the interiors and ridges of these structures vary as a function of void environment. 

Abstract We present radial profiles of luminosity-weighted age (age_L) and ΔΣ_SFRfor various populations of high- and low-mass central and satellite galaxies in the TNG100 cosmological simulation. Using these profiles, we investigate the impact of intrinsic and environmental factors on the radial distribution of star formation. For both central galaxies and satellites, we investigate the effects of black hole mass, cumulative active galactic nucleus (AGN) feedback energy, morphology, halo mass, and local galaxy overdensity on the profiles. In addition, we investigate the dependence of radial profiles of the satellite galaxies as a function of the redshifts at which they joined their hosts, as well as the net change in star-forming gas mass since the satellites joined their host. We find that high-mass (M_*> 10^10.5M_⊙) central and satellite galaxies show evidence of inside-out quenching driven by AGN feedback. Effects from environmental processes only become apparent in averaged profiles at extreme halo masses and local overdensities. We find that the dominant quenching process for low-mass galaxies (M_*< 10¹⁰M_⊙) is environmental, generally occurring at low halo mass and high local galaxy overdensity for low-mass central galaxies and at high host halo masses for low-mass satellite galaxies. Overall, we find that environmental processes generally drive quenching from the outside-in. 

Abstract We investigate the properties of voids and void galaxies in theTNG300simulation. Using a luminous galaxy catalog and a spherical void-finding algorithm, we identify 5078 voids at redshiftz= 0. The voids cover 83% of the simulation volume and have a median radius of 4.4h⁻¹Mpc. We identify two populations of field galaxies based on whether the galaxies reside within a void (“void galaxies”; 75,220 objects) or outside a void (“nonvoid galaxies”; 527,454 objects). Within the voids, mass does not directly trace light. Instead, the mean radial underdensity profile as defined by the locations of void galaxies is systematically lower than the mean radial underdensity profile as defined by the dark matter (i.e., the voids are more “devoid” of galaxies than they are of mass). Within the voids, the integrated underdensity profiles of the dark matter and the galaxies are independent of the local background density (i.e., voids-in-voids versus voids-in-clouds). Beyond the void radii, however, the integrated underdensity profiles of both the dark matter and the galaxies exhibit strong dependencies on the local background density. Compared to nonvoid galaxies, void galaxies are on average younger, less massive, bluer in color, less metal enriched, and have smaller radii. In addition, the specific star formation rates of void galaxies are ∼20% higher than nonvoid galaxies and, in the case of galaxies with central supermassive black holes withM_BH≳ 3 × 10⁶h⁻¹M_⊙, the fraction of active void galaxies is ∼25% higher than active nonvoid galaxies. 

Abstract Recent cosmological hydrodynamical simulations have produced populations of numerical galaxies whose global star-forming properties are in good agreement with those of observed galaxies. Proper modeling of energetic feedback from supernovae and active galactic nuclei is critical to the ability of simulations to reproduce observed galaxy properties, and historically, such modeling has proven to be a challenge. Here, we analyze the local properties of central and satellite galaxies in thez= 0 snapshot of the TNG100 simulation as a test of feedback models. We generate a face-on projection of stellar particles in TNG100 galaxies, from which we demonstrate the existence of a resolved star-forming main sequence (Σ_SFR–Σ_*relation) with a slope and normalization that is in reasonable agreement with previous studies. We also present radial profiles of various galaxy populations for two parameters: the distance from the resolved main-sequence line (ΔΣ_SFR) and the luminosity-weighted stellar age (Age_L). We find that, on average, high-mass central and satellite galaxies quench from the inside out, while low-mass central and satellite galaxies have similar, flatter profiles. Overall, we find that, with the exception of the starburst population, the TNG100 feedback models yield simulated galaxies whose radial distributions of Age_Land ΔΣ_SFRagree with those of observed galaxies.