Just over a decade ago, astronomers detected the first examples of brown dwarfs, low-mass objects that bridge the gap between hydrogen-burning stars and giant gas planets. Since then, hundreds of these intrinsically cold and dim sources have been identified in the vicinity of the Sun, in young clusters and associations and as companions to nearby stars.

Brown dwarf astrophysics is progressing from an era of discovery to one focused on fundamental investigations into the nature of low-temperature atmospheres, the processes of stellar and planetary formation, and the structure and evolution of the Galaxy. In this talk I will discuss how the salient properties of brown dwarfs - their complex atmospheres and spectral energy distributions, and their steady thermal evolution - make them ideal standard candles for such investigations. Brown dwarfs can serve as both rulers and clocks at the intersection of planetary and Galactic astrophysics.

Lya Emitters (LAEs) at high redshifts are useful probes of low-mass galaxy formation and cosmic reionization. I present the recent results from our Subaru deep wide-field surveys for LAEs at z=3-7 in a total area of 1.2 deg². I show statistical properties of LAEs with luminosity functions, correlation functions, and composite spectra which are obtained from our large photometric and spectroscopic samples of 1301 and 178 LAEs, respectively. I discuss galaxy formation and evolution based on these measurements including errors of statistics and field variance robustly estimated from our large samples. Cosmic reionization at z=6-7 are characterized by the evolution of luminosity function and clustering amplitudes. At the last part of my talk, I introduce our on-going z=8.8 LAE search to study galaxy formation and reionization at z=7-9.

Andrea Ghez, a professor of physics and astronomy at UCLA, was named one of the "20 Young Scientists to Watch" in Discover magazine's 20th anniversary issue (October 2000). Her research focuses on the origin and early life of stars and planets. She has demonstrated the existence of a supermassive black hole at the center of our galaxy, with a mass 4 million times that of our sun. More than a quarter century ago, scientists suggested that galaxies such as our own Milky Way might harbor massive, though possibly dormant, central black holes. Based on 10 years of high resolution imaging, Ghez's team has moved the case for a supermassive black hole at the galactic center from a possibility to a certainty. The lecture is part of an annual series on astrophysics -- the Las Cumbres Observatory Lectures -- presented jointly by the Department of Physics at UC Santa Barbara and the Santa Barbara Museum of Natural History.

Quasar host galaxies are some of the most extreme environments in which star formation is known to occur. Molecular gas may both feed the central supermassive black hole and fuel the star formation in these systems, and thus holds the key to understanding the buildup of active galaxies throughout cosmic times. Recent studies of the molecular gas phase in quasar host galaxies out to the highest redshifts at 1 kpc (0.15" at z>4) resolution with the VLA and PdBI show that the molecular reservoirs are resolved both spatially and dynamically in all studied cases. These observations allow us to constrain both the total gas masses and the dynamical masses. Together with black hole mass estimates from optical observations, these observations indicate that 1) most of the dynamical mass is molecular in the high-z systems, while the gas mass is only a small fraction of the dynamical mass in a control sample of nearby quasars, and 2) the high-z sources have significantly less massive stellar bulges (as constrained by the dynamical masses) than predicted by the local M_BH-sigma_bulge relation, while the nearby quasars appear to follow this relation. These observations thus uniquely constrain the properties of the molecular environments in and dynamical properties of host galaxies in key targets out to the most distant galaxies currently observable, and thus pave the way for future studies with ALMA.

The earliest generations of stars are thought to have transformed the universe from darkness to light and to have reionized and heated the intergalactic medium. I will explore the ability of measurements of the 21-cm power spectrum to enable the simultaneous reconstruction of the reionization history and the properties of the ionizing sources. I will show that our ignorance about the properties of the galaxies does affect strongly the accuracy of the reconstruction, but the expected accuracy is still rather high. I will also consider the early stages of cosmic hydrogen or helium reionization, when ionizing sources were still rare. I will show that Poisson fluctuations in the galaxy distribution substantially affected the early bubble size distribution, but galaxy clustering was also an important factor even at early times. Even at very high redshifts, a significant fraction of the ionized volume resided in bubbles containing multiple sources.