Comprising over 70% of the Solar Neighborhood, the vast majority of the nearest stars are M-dwarfs. Given their large number and relative ease of planet detection, M-dwarfs form the target samples for large upcoming ground- and space-based exoplanet searches. Together with the lower mass brown dwarf population, the lowest mass stars are prime systems for detailed study with high-contrast adaptive optics imaging and submillimeter interferometry. In this talk, I will describe the companion properties and environments of low-mass systems from The M-dwarfs in Multiples (MinMs) Survey, a volume-limited survey of 245 M-dwarfs within 15 pc, and the Taurus Boundary of Stellar/Substellar (TBOSS) Survey, an ongoing study of disk properties for low-mass members within the Taurus star-forming region. Direct imaging of M-dwarfs is a sensitive technique to identify low-mass companions over a wide range of orbital separation, and the high proper motion of nearby M-dwarfs enables rapid confirmation of new multiple stars. The new and archival observations of low-mass stars from the MinMs survey demonstrate lower binary frequency and closer orbital separations in comparison to those of solar-mass stars. From the TBOSS project, 885µm ALMA continuum observations of Taurus disks enable measurements of submillimeter emission from dust grains around hosts spanning the stellar/substellar boundary. The TBOSS results show a decrease in disk dust mass over the span of ~1 to ~10 Myr, and decreasing disk dust mass for lower host star mass, consistent with low incidence of giant planet detections around M-dwarfs.

The most highly magnified, strongly lensed sources will forever constitute a unique and finite number of opportunities for probing the astrophysics of galaxy evolution and star formation in the distant universe. Wide-field surveys reveal on the order of a hundred strongly lensed galaxies that are magnified to have AB magnitude ~<21; these exceptional sources reveal the complexity of star formation on sub-galaxy scales. I will summarize several recent results of strong lensing-assisted studies from the Sloan Giant Arcs Survey (SGAS), with an emphasis on measurements that are uniquely enabled by the highest-magnification systems. I will also discuss the first results from a new deep spectroscopic follow-up program targeting highly magnified galaxies. The Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas (MEGaSaURA) is comprised of high signal-to-noise, moderate resolution rest-frame UV spectra of 15 of the brightest known lensed galaxies, at redshifts of 1.7<z<3.6. The individual MEGaSaURA spectra reveal a wealth of spectral diagnostics: absorption from the outflowing wind; photospheric absorption lines and P Cygni profiles from the massive stars that power the outflow; and faint nebular emission lines from the HII regions produced by those stars. The stacked MEGaSaURA data form the best spectrum yet obtained for star-forming galaxies at these redshifts, surpassing previous data in both wavelength coverage and spectral resolution. This stack reveals numerous rest-UV spectral diagnostics, is ideal for refining our toolkit for deducing the properties of the first galaxies and stars in the Universe with the next generation of observational facilities (e.g., JWST, 30m-class telescopes).

Massive stars play an essential role in the Universe. They are rare, yet the energy and momentum they inject into the interstellar medium with their intense radiation fields dwarfs the contribution by their vastly more numerous low-mass cousins. During their formation, the radiation pressure exerted by massive stars on the gas and dust around them can become stronger than their gravitational attraction, thereby inhibiting their growth by accretion. Therefore, detailed simulation of the formation of massive stars requires an accurate treatment of radiation. For this purpose, I will present a new, highly accurate radiation algorithm that properly treats the absorption of the direct radiation field from stars and the re-emission and processing by interstellar dust. With this new tool, we performed a set of three-dimensional radiation- hydrodynamic simulations of the collapse of massive pre-stellar cores with laminar and turbulent initial conditions. We find that mass is channeled to the stellar system via gravitational and Rayleigh-Taylor (RT) instabilities through nonaxisymmetric disks and filaments that self-shield against radiation pressure while allowing for radiation to escape through optically thin regions. Furthermore, we find that turbulence and RT instabilities enhance the development of optically thick filaments that accrete onto massive stars. Our results suggest that RT features are significant and should be present around accreting massive stars throughout their formation.

TBA

Observations in the local Universe suggest that the mechanism responsible for quenching star formation in galaxies may be intimately linked to their structural transformation from disks to spheroids. In order to test quenching scenarios, however, it is vital to look beyond the local Universe and identify the first generation of quiescent galaxies at high redshift. Using CANDELS, we have examined the rest-frame optical morphologies for a sample of massive, quiescent galaxies at z>1 and find that a significant fraction (~30%) have morphologies dominated by exponential disks. The persistence of massive disks, long after star formation has ceased, implies that in at least some cases quenching precedes morphological transformation. I'll examine what constraints these observations place on the mechanisms responsible for quenching star-formation in the first generation of quiescent galaxies at z~2 and discuss them in context with an emerging picture of massive galaxy formation and evolution.

During the first few Myr of a young star's life, it is encircled by a disk made up of molecular gas, dust, and ice, materials that form the building blocks for future planetary systems. Improvements in observational spatial resolution and sensitivity have allowed us to characterize the protoplanetary disk environment in great detail. Recent observations with the Atacama Large Millimeter/Submillimeter Array (ALMA) have shed light on the particularly key role of the differential evolution of the gas and dust disk disks' chemical composition and the structure of their rocky/solid and gaseous components, which together feed young terrestrial and gas giant planets. I will discuss recent results and new puzzles regarding our understanding of protoplanetary disk chemical and structural evolution, along with future avenues to detect individual young planets forming in situ.

The Submillimeter Array (SMA), located just below the summit of Mauna Kea on the Big Island of Hawaii, is a pioneering radio interferometer designed for arc-second imaging in the submillimeter spectral range. Designed initially for imaging molecular lines and dust continuum in cold interstellar clouds, the SMA has also found application in a wealth of scientific fields, including star formation, disk studies, solar system observations, nearby galaxies, high-z galaxies (including lensing systems), observations of high energy phenomena (black holes, gamma-ray bursts, supernovae, and blazars), and polarized emission from aligned dust grains in a range of environments. In addition to its outstanding record in astronomical research, the SMA is a world leader in the design of wide-bandwidth, high-frequency radio receivers for astronomy. To leverage this expertise, the SMA just commissioned a next generation correlator which vastly increases total bandwidth (to 8 GHz/sideband per polarization) while retaining high spectral resolution (140 kHz) across the entire processed spectral range. I will discuss the SMA's enhanced science capabilities, as well point toward even further upgrade plans.

Of the thousands of known extrasolar planets, why are the dozen or so directly imaged exoplanets among the most important despite their apparently anomalous properties within the general exoplanet population (>10AU, >2MJ)? What are the prospects for (and recent successes in) detecting younger, lower mass and/or closer-in planets via direct imaging? I will discuss the current state of the art in the field of high contrast imaging of extrasolar planets and circumstellar disks, with a particular emphasis on a subset of objects that host both disks and (likely) planets - the so-called “transitional disks”. These young circumstellar disks are almost certainly actively undergoing planet formation, and yet the presence of disk material complicates our ability to isolate light from planets and/or protoplanets embedded within them. I will discuss my recent experiences “killing” one exoplanet candidate lying at/inside a transitional disk gap, and confirming another.

Galaxies form hierarchically, hence the material making up z=0 galaxies may be spread over many Megaparsecs of the IGM and in numerous progenitor galaxies at cosmic epochs z>0. Cosmological simulations allow following the time evolution of the individual 'mass elements' that make up galaxies. I will discuss techniques for performing so-called 'Lagrangian analysis' in mesh-based hydro codes using tracer particles, and several unique applications of such an approach. Among them are studies of the thermal histories of gas accretion, the baryon cycle, the angular momentum acquisition of galaxies, and the origin of stellar IMF variations.

Type Ia supernovae play an important role as standardizable candles for cosmology, providing one of the most important probes into the nature of dark energy. Yet, the nature of the stellar progenitors which give rise to Type Ia supernovae remains elusive. For decades, the leading model explaining Type Ia supernovae properties consisted of a white dwarf accreting to near the Chandrasekhar mass, in the single-degenerate channel. More recently, a variety of lines of evidence point instead towards merging binary white dwarfs, in the double-degenerate channel, as the progenitors of Type Ia supernovae. In this talk, I will focus upon recent advances at the interface between observation and theory which will help crack the Type Ia progenitor problem. In particular, I will present recent multidimensional numerical simulations of both the double-degenerate and single-degenerate channels which I have undertaken with my students and collaborators. I will discuss how these models make clearly-defined predictions for current and planned late-time observations of nearby Type Ia supernovae, which will definitively establish the nature of their stellar progenitors.

The Universe’s largest galaxy clusters likely built the majority of their massive >10^11 M⊙ galaxies in simultaneous, short-lived bursts of activity well before virialization. The most challenging observational hurdle in identifying such pre-virialized “protoclusters” is their very large volumes, ~10^4 comoving Mpc^3 at z > 2, subtending areas ~half a degree on the sky. Thus the contrast afforded by an overabundance of very rare galaxies in comparison to the background can more easily distinguish overdense structures from the surrounding, normal density field. I will present five 2 < z < 3 proto-clusters from the literature which are found to contain up to 12 dusty starbursts or luminous AGN galaxies each, a phenomenon that is unlikely to occur by chance even in overdense environments. These are contrasted with three higher-redshift (4 < z < 5.5) dusty star-forming galaxy (DSFG) groups, whose evolutionary fate is less clear. Measurements of DSFGs’ gas depletion times suggest that they are indeed short-lived on ~100 Myr timescales, and accordingly the probability of finding a structure containing more than 8 such systems is 0.2%, unless their ‘triggering’ is correlated on very large spatial scales, ~10 Mpc across. The volume density of DSFG-rich protoclusters is found to be comparable to all >10^15 M⊙ galaxy clusters in the nearby Universe, a factor of five larger than expected in some simulations. Some tension yet exists between measurements and simulations. However, improved observations of protoclusters over large regions of sky will certainly shed more light on the assembly of galaxy clusters, thus fundamental parameters governing cosmology, and also the role of environment in shaping the formation and evolution of galaxies.

Supermassive black holes, and the active galactic nuclei (AGN) that they power, are thought to play an integral role in the evolution of galaxies by acting to regulate, and eventually suppress, the star formation activity of their host galaxies. I will discuss recent efforts to test this proposed connection by studying the demographics of galaxies undergoing active black hole growth. In particular, I will highlight recent results from the CANDELS survey, whose panchromatic Hubble ACS and WFC3 imaging is now allowing us to characterize the morphologies and stellar populations of thousands of AGN hosts out to z=2, the era when star formation activity and black hole growth in the Universe are at their peak. I will discuss what CANDELS is currently revealing about the mechanisms that fuel AGN activity at this epoch and the connection between black hole growth and the emergence of the first generation of passive galaxies in the Universe.

Carbon monoxide (CO) has been the primary tracer of cold molecular gas mass and dynamics in galaxies because H_2, the dominant species, lacks a permanent dipole moment. Prior to the Herschel Space Observatory, CO observations were limited predominantly to the lowest-lying rotational transitions in the millimeter-wave part of the spectrum: J = 1 — 0 and J = 2 — 1. Spectrometers aboard Herschel opened up observations to high-level submillimeter and far-infrared CO rotational transitions, leading to the discovery of copious warm molecular gas in galaxies. Indeed, at temperatures of hundreds of Kelvin and comprising 10% of the molecular gas in star-forming galaxies, this warm gas has 100 times the luminosity-to-mass ratio of the gas probed with the lowest-lying transitions. It appears that this warm component of molecular gas is mechanically heated (likely in shocks), and it has implications for stellar feedback into the interstellar medium in galaxies. I will discuss the results of our census of this molecular gas in 87 galaxies in the Herschel Science Archive, I will mention implications for ALMA and other ground-based observations of high-redshift galaxies, and I will describe new superconducting spectrometer technology we are developing to enable millimeter-wave multi-object spectroscopy of galaxies with CO and high-redshift [CII].

In recent years, the number of known galaxy clusters has grown dramatically, thanks in large part to the success of surveys utilizing the Sunyaev Zel'dovich effect. In particular, surveys like the South Pole Telescope 2500 deg^2 survey have discovered hundreds of distant clusters, allowing us to trace for the first time the evolution of clusters from shortly after their collapse (z~2) to present day (z~0). In this talk, I will highlight recent efforts to understand the observed evolution in the most massive clusters, in terms of the large-scale hot intracluster gas, the cooling gas in the very center of the cluster, the most massive central galaxy, and the supermassive black hole at the very center. In addition, I will attempt summarize the current state of galaxy cluster surveys and briefly discuss the potential of next-generation surveys.