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Abstract We use subhalo abundance and age distribution matching to create magnitude-limited mock galaxy catalogs atz∼ 0.43, 0.52, and 0.63 withz-band and 3.4μmW1-band absolute magnitudes andr−zandr−W1 colors. From these magnitude-limited mocks, we select mock luminous red galaxy (LRG) samples according to the (r−z)-based (optical) and (r−W1)-based (infrared) selection criteria for the LRG sample of the Dark Energy Spectroscopic Instrument (DESI) survey. Our models reproduce the number densities, luminosity functions, color distributions, and projected clustering of the DESI Legacy Surveys that are the basis for DESI LRG target selection. We predict the halo occupation statistics of both optical and IR DESI LRGs at fixed cosmology and assess the differences between the two LRG samples. We find that IR-based SHAM modeling represents the differences between the optical and IR LRG populations better than using thezband and that age distribution matching overpredicts the clustering of LRGs, implying that galaxy color is uncorrelated with halo age in the LRG regime. Both the optical and IR DESI LRG target selections exclude some of the most luminous galaxies that would appear to be LRGs based on their position on the red sequence in optical color–magnitude space. Both selections also yield populations with a nontrivial LRG–halo connection that does not reach unity for the most massive halos. We find that the IR selection achieves greater completeness (≳90%) than the optical selection across all redshift bins studied. 

AB In 2019, the Very Energetic Radiation Imaging Telescope Array System (VERITAS) was augmented with high-speed optical electronics in order to allow for Stellar Intensity Interferometry (SII) observational capabilities. This research shows how VERITAS-SII (VSII), which measures correlations of starlight intensity fluctuations across spatially separated telescopes, can enable the characterization of binary stellar systems. We first use VSII data collected on the binary star Spica to develop a dynamic analysis technique. We then simulate the squared visibility curve given a particular orientation of Spica's components. Because of Spica's 4.0145-day period, the binary separation and orientation, and therefore the simulated squared visibility, should vary greatly from night to night. These variations are consistent with measured variations in the observed squared visibility curves. The initial results indicate that VSII observations potentially demonstrate good sensitivity to the evolution of the Spica binary system. With further development, it may be possible to fit a multi-dimensional image to the system, opening the door to model-dependent VSII imaging. 

Iteration is pervasive in current perspectives of student reasoning, but it is also often assumed, backgrounded, or minimized in favor of other empirical interests and results, despite being foundational to reasoning processes and inquiry. This paper forefronts iterative practice while examining student reasoning in a reform-based undergraduate physics lab course. We present an instrumental case study analysis of a single student group, documenting how they engaged in micro- and macro-levels of iterative practice at the nexus of experimental activity and sensemaking throughout their experimentation. These results illustrate the nuance in students’ iterative practice at different levels and prompt new questions about how different forms of iterative practice may impact student learning.