Evolution of Stellar-To-Halo Mass Ratio at Z = 0-7 Identified by Clustering Analysis with the Hubble Legacy Imaging and Early Subaru/Hyper Suprime-Cam Survey Data

We present clustering analysis results from 10,381 Lyman break galaxies (LBGs) at z ∼ 4-7, identified in the Hubble legacy deep imaging and new complimentary large-area Subaru/Hyper Suprime-Cam data. We measure the angular correlation functions of these LBGs at z ∼ 4, 5, 6, and 7 and fit these measurements using halo occupation distribution (HOD) models that provide an estimate of halo masses, Mh ~ (1 - 20 ) x 1011 M⊙. Our Mh estimates agree with those obtained by previous clustering studies in a UV-magnitude versus Mh plane and allow us to calculate stellar-to-halo mass ratios (SHMRs) of LBGs. By comparison with the Z ~ 0 SHMR, we identify evolution of the SHMR from z ~ 0 to z ~ 4 and from z ~ 4 to z ~ 7 at the \u3e 98% confidence levels. The SHMR decreases by a factor of ∼2 from z ~ 0 to 4 and increases by a factor of ∼4 from z ~ 4 to 7 at the dark matter halo mass of Mh ~ 1011 M⊙. We compare our SHMRs with results of a hydrodynamic simulation and a semianalytic model and find that these theoretical studies do not predict the SHMR increase from to 7. We obtain the baryon conversion efficiency (BCE) of LBGs at z ~ 4 and find that the BCE increases with increasing dark matter halo mass. Finally, we compare our clustering+HOD estimates with results from abundance matching techniques and conclude that the Mh estimates of the clustering+HOD analyses agree with those of the simple abundance matching within a factor of 3, and that the agreement improves when using more sophisticated abundance matching techniques that include subhalos, incompleteness, and/or evolution in the star formation and stellar mass functions

Crowdsourcing Controls: A Review and Research Agenda for Crowdsourcing Controls Used for Macro-tasks

Crowdsourcing—the employment of ad hoc online labor to perform various tasks—has become a popular outsourcing vehicle. Our current approach to crowdsourcing—focusing on micro-tasks—fails to leverage the potential of crowds to tackle more complex problems. To leverage crowds to tackle more complex macro tasks requires a better comprehension of crowdsourcing controls. Crowdsourcing controls are mechanisms used to align crowd workers’ actions with predefined standards to achieve a set of goals and objectives. Unfortunately, we know very little about the topic of crowdsourcing controls directed at accomplishing complex macro tasks. To address issues associated with crowdsourcing controls formacro-tasks, this chapter has several objectives. First, it presents and discusses the literature on control theory. Second, this chapter presents a scoping literature review of crowdsourcing controls. Finally, the chapter identifies gaps and puts forth a research agenda to address these shortcomings. The research agenda focuses on understanding how to employ the controls needed to perform macro-tasking in crowds and the implications for crowdsourcing system designers.National Science Foundation grant CHS-1617820Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150493/1/Robert 2019 Preprint Chapter 3.pdfDescription of Robert 2019 Preprint Chapter 3.pdf : PrePrint Versio

GOLDRUSH. II. Clustering of Galaxies at z ∼ 4-6 Revealed with the Half-Million Dropouts over the 100 Deg² Area Corresponding to 1 Gpc³

We present clustering properties from 579492 Lyman-break galaxies (LBGs) at z ∼ 4-6 over the 100 deg2 sky (corresponding to a 1.4 Gpc3 volume) identified in early data of the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey.We derive angular correlation functions (ACFs) for the HSC LBGs with unprecedentedly high statistical accuracies at z ∼ 4-6, and compare them with the halo occupation distribution (HOD) models. We clearly identify significant ACF excesses in 10 \u3c θ \u3c 90 , the transition scale between one- and two-halo terms, suggestive of the existence of the non-linear halo bias effect. Combining the HOD models and previous clustering measurements of faint LBGs at z ∼ 4-7, we investigate the dark matter halo mass (Mh) of the z ∼ 4-7 LBGs and its correlation with various physical properties including the star formation rate (SFR), the stellar-to-halo mass ratio (SHMR), and the dark matter accretion rate (Mh) over a wide mass range of Mh/M⊙ = 4 x 1010-4 x 1012. We find that the SHMR increases from z ∼ 4 to 7 by a factor of ∼4 at Mh ≃ 1 x 1011M, while the SHMR shows no strong evolution in the similar redshift range at Mh ≃ 1 x 1012 M⊙. Interestingly, we identify a tight relation of SFR/Mh-Mh showing no significant evolution beyond 0.15 dex in this wide mass range over z ∼ 4-7. This weak evolution suggests that the SFR/Mh-Mh relation is a fundamental relation in high-redshift galaxy formation whose star formation activities are regulated by the dark matter mass assembly. Assuming this fundamental relation, we calculate the cosmic star formation rate densities (SFRDs) over z = 0-10 (a.k.a. the Madau-Lilly plot). The cosmic SFRD evolution based on the fundamental relation agrees with the one obtained by observations, suggesting that the cosmic SFRD increase from z ∼ 10 to 4 - 2 (decrease from z ∼ 4-2 to 0) is mainly driven by the increase of the halo abundance (the decrease of the accretion rate)