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From page 264... ... This fact enables large-scale structure surveys to probe fundamental physics of neutrinos, such as their mass and possibly even their self-interaction cross section. Further, this characterization of neutrino properties will also be necessary to model the cosmological observables that feed into the dark energy measurements described above. Read the entire page →
From page 265... ... In the intervening decade, Laser Interferometer Gravitational-Wave Observatory (LIGO) has observed the merger of tens of binary black holes, and its discovery of a binary neutron star merger has heralded the era of multi-messenger astronomy. Read the entire page →
From page 266... ... To list some cosmological examples: (1) Gravitational wave emission from rapidly spinning black holes may reveal light bosonic particles whose Compton wavelength matches the horizon size. Read the entire page →
From page 267... ... delay the formation of the first luminous objects, while theories that enhance small-scale power (e.g., primordial black holes, dark sector interactions that boost early black hole formation, or models that create compositional fluctuations on small scales) advance this timing. Read the entire page →
From page 268... ... Advances in theory and scientific computing (the latter enhanced by advances from the data science and machine learning communities) directly enable analyses from current experiments and help to guide the design of future ones. Read the entire page →
From page 269... ... C-Q1a: Primordial gravitational waves C-Q1b: Non-Gaussianity of the large-scale structure of the universe C-Q1c: The initial power spectrum of density fluctuations C-Q2: What are the properties of dark matter and the dark sector? C-Q2a: Dark sector signatures in small-scale structure C-Q2b: Dark sector imprints on Big Bang nucleosynthesis and recombination C-Q2c: Annihilation by-products C-Q3: What physics drives the cosmic expansion and large-scale C-Q3a: The physics of cosmic acceleration evolution of the universe? Read the entire page →
From page 270... ... Primordial gravitational waves delensing; (C-1b) non-Gaussian Approach cosmic variance limit of mapping LSS using kinematic SZ field; (C-1c) Read the entire page →
From page 271... ... These newly established paradigms point to critical, and addressable, paths forward. We must observe and understand the sources that caused cosmic reionization, and we must isolate the individual physical processes that drive the evolution of the ecosystem and govern the connection between gas, stars, black holes, galaxies, and their dark matter halos. Read the entire page →
From page 272... ... and by accreting supermassive black holes (SMBHs) Read the entire page →
From page 273... ... Stellar feedback, which has been shown to correlate with the surface density of star formation, is considered the dominant mechanism for driving outflows in low- and intermediate-mass galaxies, and, by driving ISM turbulence, it regulates the efficiency of star formation on scales from individual molecular clouds to entire galaxies. For massive galaxies and halos, there is broad consensus that radiation and jets powered Read the entire page →
From page 274... ... Dynamical measurements of these galaxies show many orders of magnitude range in stellar mass over a narrow range of halo mass, Mhalo ~108–1010 M⊙, suggesting that the final stellar masses are sensitive to intersections between star formation histories, feedback processes, dark matter assembly, and, possibly, dark matter physics, in ways that are still not fully understood. Large populations of "ultra-diffuse galaxies," with low central surface brightness and large sizes, have been discovered and characterized in galaxy groups and clusters. Read the entire page →
From page 275... ... Wide-field imaging surveys (e.g., with the Roman Space Telescope) will observe >105 galaxies out to z ~10–12, down to KAB ~26, suitable for cross-correlation with the HI signal. Read the entire page →
From page 276... ... D-Q1c. Properties of the First Stars, Galaxies, and Black Holes in the LambdaCDM model, and are expected to form until z ≲6 in isolated regions. Read the entire page →
From page 277... ... D-Q2a. The Acquisition of the Gas Necessary to Fuel Star Formation As galaxies grow, their reservoirs of fuel for star formation are expected to be replenished. Read the entire page →
From page 278... ... Such simulations will have sufficient overlap in spatial and temporal scales and in modeled physics with simulations of star formation and ISM to establish self-consistent physical models for different astrophysical phenomena over vast dynamical scales. Within the disk, the gas is transformed into stars. Read the entire page →
From page 279... ... Cosmological simulations require feedback from stellar winds/supernovae and from SMBHs at the low and high galaxy mass ends, respectively, to regulate the baryonic accretion onto dark matter halos and reduce star formation efficiency. Models predict that, depending on the halo mass, a catastrophic loss of cool ISM from the galaxy's disk can occur, after which the galaxy remains quiescent until a new gas supply is accreted. Read the entire page →
From page 280... ... D-Q3a. The Seeds of Supermassive Black Holes The existence of luminous quasars at z >7 requires SMBHs to grow to M ~109 M⊙ in the challengingly short period, <1 Gyr, available since the Big Bang. Read the entire page →
From page 281... ... D-Q3c. Comprehensive Census of Supermassive Black Hole Growth Recent National Aeronautics And Space Administration (NASA) Read the entire page →
From page 282... ... D-Q3d. The Physics of Black Hole Feedback The energy released by accreting SMBHs contributes feedback that helps regulate the growth of galaxies, although the magnitude and importance of that feedback is currently highly uncertain and likely varies for galaxies of different masses, environments, and evolutionary stage. Read the entire page →
From page 283... ... The goal of observational and theoretical studies of the Milky Way is to understand the assembly, star formation, and chemical enrichment histories of the thin disk, thick disk, bulge, bar, and stellar halo; the origin of the striking bimodality of element abundance ratios across the disk; the importance of gas accretion, radial gas flows, fountains, and outflows through time and at present; the impact of dynamical perturbations on kinematic structure; the baryon content and temperature-density structure of the gaseous halo; and the mass, density profile, shape, and substructure of the dark matter halo. The final data releases from ongoing spectroscopic surveys and from the Rubin Observatory and Roman in the coming decade will greatly advance our knowledge of the structure and substructure of the Milky Way's stellar components. Read the entire page →

From page 264...

... This fact enables large-scale structure surveys to probe fundamental physics of neutrinos, such as their mass and possibly even their self-interaction cross section. Further, this characterization of neutrino properties will also be necessary to model the cosmological observables that feed into the dark energy measurements described above.