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Space Telescope Science Institute
2011 Hubble Fellows Symposium

New Insights Into the Use of Cosmic Telescopes

S. Mark Ammons (LLNL)

It is not known whether the reionization of the universe at z ~ 6-10 was caused by bright sources alone or with faint sources in concert. I discuss the use of massive clusters as cosmic telescopes to lens faint objects into detectability to constrain the luminosity function at these redshifts. It is debated whether cosmic telescopes are more efficient than blank field surveys in doing so. Multiple-plane lensing simulations indicate that ideal alignment of massive halos can sharply increase etendue of cosmic telescopes, going in some cases as the cube of the integrated line of sight mass. Including realistic assumptions for the intrinsic size and shapes of sources, we also find that detection of z ~ 10 sources is less likely in regions of high magnification (> 20). This suggests that spectroscopic slits should be placed just off the lines of infinite magnification in critical-line surveys for Lyman-alpha emitters at z ~ 10.

Sizing Up the Stars: Fundamental Properties of Stars with Interferometry

Tabetha Boyajian (Georgia State University)

Recent innovations in high-spatial-resolution astronomical techniques, in particular long-baseline optical/infrared interferometry, have enabled us to resolve the disks of nearby, main-sequence stars. The measurement of a star’s angular diameter combined with the distance and bolometric flux provides a direct way to determine the stellar linear radius, effective temperature and luminosity. I will present ongoing observations aimed at measuring the angular diameters of several dozen mid- to late-type main-sequence stars with the CHARA Array. Furthermore, I will discuss the challenges these data bring to current stellar atmospheric and evolutionary models, as well as the development of empirically based relations and calibrations to the stellar effective temperature scale.

Building Massive Galaxies: Hierarchical Assembly and the Structure of Brightest Group Galaxies.

Kevin Bundy (UC Berkeley)

The physical processes that regulate the growth of massive galaxies remain poorly understood. Globally, it is expected that such galaxies assemble at late times, but this basic prediction of hierarchical models is largely untested because cosmic variance in the small volumes sampled by current high-z surveys swamps any potential signal. Thankfully, an array of next-generation panoramic surveys will bring definitive answers. I will discuss early steps to measure galaxy assembly with one such survey, the recently-commissioned Baryon Oscillation Spectroscopic Survey (BOSS). At the same time, detailed observations of focused samples are needed to test the physical mechanisms that drive statistical trends seen in large surveys. I will describe one such effort that compares the assembly history of high-z Brightest Central Galaxies (BCGs) in massive group halos to ellipticals in the field. Despite a larger incidence of morphological disturbances and companions, as well as evidence for extended wings, our sample lies on the field-derived stellar mass fundamental plane and its projections. This suggests a more modest merger history than previously expected for the most massive galaxies and should provide insight on the growth derived from forthcoming surveys.

Stellar and Planetary Characterization with Kepler

Josh Carter (Harvard-Smithsonian Center for Astrophysics)

The Kepler mission has opened a new domain in high-precision time-series photometry allowing for the wholesale detection of planetary systems and the detailed characterization of both stars and planets. The unprecedented quality of the data and the restricted scope has led to the unveiling of rare astrophysical events (such as the triple eclipses of KOI-126) and physical effects heretofore lost in the noise (such as "Doppler Boosting" in close binaries). I present recent results in this vein and discuss future prospects for maximizing the scientific yield of these data.

Working towards Completeness in Extreme Starburst Galaxies at z>1

Caitlin Casey (Univ. of Hawaii - IfA)

Selection effects in the submillimeter/far-infrared inhibit detailed analysis of extreme starbursts at z>1. Submillimeter Galaxy (SMG) detection and characterization biases against warm temperature SEDs (Tdust~50K), against the highest redshift ULIRGs at z>3, and has so far been limited to a small sample of ~100 sources that have reliably identified optical or radio counterparts and spectroscopic redshifts. Recent observations by Herschel PACS and SPIRE in the ~70-500um wavelength range provide a more complete census of high-z ULIRG activity than previous SMG surveys. However, source confusion and lack of spectroscopic identification of reliable counterparts limits the analysis of extreme ULIRGs to the most basic calculations, frought with a priori assumptions (e.g. Tdust/(1+z) degeneracy, far-IR/radio relation, confusion boosting factors, etc). I address the biases on conclusions of SMG work and I present the first observations from a spectroscopic survey of Herschel-bright sources, demonstrating the need to work towards completeness in high-z ULIRGs.

Constraining Intermediate-Mass Black Holes in Star Clusters with Hubble

Julio Chaname (Carnegie DTM)

Establishing or ruling out, either through solid mass measurements or upper limits, the presence of intermediate-mass black holes (IMBHs) at the centers of star clusters would profoundly impact our understanding of problems ranging from the formation and long-term dynamical evolution of stellar systems, to the nature of the seeds and the growth mechanisms of supermassive black holes. While there are sound theoretical arguments both for and against their presence in today's clusters, observational studies have so far not yielded truly conclusive IMBH detections. We argue that the most promising approach to solving this issue is provided by the combination of measurements of the proper motions of stars at the centers of Galactic globular clusters and dynamical models able to take full advantage of this type of data set. I will present some results of a program based on HST observations and recently developed tools for dynamical analysis designed to do just that.

The Nature of Transition Disks in Nearby Star-forming Regions

Lucas Cieza (University of Hawaii, IfA)

Circumstellar transition disks are objects with little or no excess emission at < 10 micron but significant excesses at longer wavelengths. Different mechanisms have been proposed to explain their inner opacity holes: planet formation, grain growth, photoevaporation, and tidal truncation in tight binaries. These mechanisms, all relevant to disk evolution in general, can be distinguished when disk masses, accretion rates, and multiplicity information are available. I will discuss our ongoing project aiming to characterize a large sample of Spitzer-selected transition disks located in nearby star-forming regions. We have already completed a study of Ophiuchus objects, presenting the results from Adaptive Optics (AO) imaging, (sub)millimeter photometry, and echelle spectroscopy observations and are currently working on several other regions. Our results show that transition disks are a very heterogeneous group of objects with a wide range of SED morphologies, disk masses ( < 0.5 to 40 Mjup), and accretion rates (<10E-11 to 10E-7 Msolar/yr). Since the properties of our transition disks point toward distinct processes driving the evolution of each object, we have been able to identify very strong candidates for the following disk categories: circumbinary disks, grain-growth dominated disks, photoevaporating disks, debris disks, and (giant) planet-forming disks. I will also discuss the prospects for detailed studies of these fascinating objects with the Atacama Large Millimeter Array (ALMA) and other facilities.

Understanding the Global Course of Galaxy Evolution at z < 1

Michael Cooper (UC Irvine)

Evolution in the global galaxy population over the past 7 Gyr has been dominated by two principal trends: a dramatic decline in the average level of star-formation activity combined with a substantial growth in the stellar mass density within the red galaxy population. While both of these evolutionary trends are well measured at z < 1, the physical mechanisms responsible remain somewhat poorly understood. Using data from the DEEP2 Galaxy Redshift Survey in concert with complementary observations spanning UV to radio wavelengths, I will present recent results that directly constrain the physical processes driving the global transformation in galaxy properties at z < 1. In particular, I will discuss ongoing work to probe the cold gas component of star-forming galaxies at high redshift, which is providing direct constraints on the fuel supply for star formation when the Universe was less than half its current age. Finally, I will conclude by outlining the limitations of the current data sets and how they might be overcome with future ground- and space-based facilities.

Identifying and Characterizing the Lowest-mass Exoplanet Hosts with Near-infrared Spectroscopy

Kevin Covey (Cornell University)

Low-mass M dwarf stars have recently been recognized as high priority targets for exoplanet surveys. M dwarfs possess sufficiently small masses and radii that potentially habitable Earth-like exoplanets can induce reflex velocities and transit depths large enough to be detected with currently available ground-based instrumentation. M dwarfs are quite optically faint, however, and very numerous; the yield of M dwarf exoplanet searches could be significantly enhanced by pre-selecting the most promising exoplanet hosts and obtaining precise radial velocity (RV) measurements at near-infrared wavelengths. I will begin by summarizing a new technique we have developed to diagnose the metallicities of M dwarf stars directly from moderate resolution near-infrared spectra. This method confirms that the exoplanet mass-metallicity correlation identified for solar-type hosts persists into the M dwarf domain, and enables the identification of the lowest mass candidate exoplanet host stars. I will then present results of a commissioning program with the TripleSpec Exoplanet Discovery Instrument (TEDI), which demonstrated an RV precision <40 m/s over several months of monitoring of a nearby M dwarf. I will summarize TEDI's novel design, which achieves precision RV measurements via a Michelson interferometer in series with a moderate resolution spectrograph, and describe our current campaign to search for gas giants in a well defined sample of nearby, metal-rich M dwarfs.

The Mysterious Multiple Populations in Globular Clusters: The Role of Stellar Rotation and Massive Binaries

Selma de Mink (STScI)

Star clusters are not as simple as we thought they were. Star-to-star abundance variations, multiple main sequences and giant branches reveal the presence of more than one stellar generations within globular clusters. It is thought that certain stars of the first stellar generation polluted the cluster with their ejecta, out of which subsequent stellar generations were formed. The nature of the ''polluters'' remains topic of a vivid debate. Two potential sources have been proposed so far: AGB stars and fast rotating massive stars. Although promising, it remains a challenge to explain the large mass budget needed to form subsequent generations that are more numerous than the first. I will discuss the claimed evidence for large age-spreads in the light of stellar rotation and why interacting binaries provide a promising alternative source of enrichment.

Fundamental Tests of Theory with Ultracool Binaries

Trent Dupuy (CfA/SAO)

Mass is the fundamental parameter that governs the evolution of stars, brown dwarfs, and gas-giant planets. Thus, direct mass measurements are essential to test the evolutionary and atmospheric models that underpin studies of low-mass objects. I will present results from my program to test models using precise dynamical masses (as good as 2%) for ultracool binaries, based on infrared parallaxes, near-infrared spectroscopy, and Keck laser guide star adaptive optics astrometry. In just the last 3 years, we have more than tripled the number of late-M, L, and T dwarf binaries with dynamical masses. 1. For most field binaries, based on direct measurements of their luminosities and masses, we find that the temperatures predicted by evolutionary models are discrepant with those derived from fitting the observed spectra with model atmospheres, indicating systematic errors of ~200 K in temperature (or 30% to 40% in radius). 2. For the only substellar binary with both a well-determined mass and age, we find that evolutionary models systematically underpredict luminosities by a factor of ~2, meaning that model-based substellar mass determinations (e.g., for directly imaged extrasolar planets and the low-mass IMF) may be systematically overestimating the masses. 3. We have employed this large sample of binary orbits to carry out a novel test of the earliest evolutionary stages, by using the distribution of orbital eccentricities to distinguish between competing models of brown dwarf formation.

A Candidate Detection of the First Hydrostatic Core

Melissa Enoch

The first hydrostatic core (FHSC) represents a very early phase in the low-mass star formation process, after collapse of the parent core has begun but before a true protostar has formed. This large (few AU), cool (100 K), pressure-supported core of molecular hydrogen is expected from theory, but has yet to be observationally verified. Cold Spitzer was uniquely capable of detecting the thermal emission from this early phase. I will present observations of an excellent candidate for the FHSC phase: Per-Bolo 58, a dense core in Perseus that was previously believed to be starless. The 70 micron flux from deep MIPS observations is consistent with radiative transfer models of the FHSC. While we are currently unable to rule out the presence of a more evolved protostar, if present it would be one of the lowest luminosity protostellar objects yet observed, with an internal luminosity of ~0.01 Lsun. I will discuss these possibilities, as well as ongoing follow-up observations to clarify the evolutionary state of this intriguing source.

Planetary Systems from Kepler

Daniel Fabrycky (UC Santa Cruz)

On Feb. 2, the Kepler space mission released its first 4 months of data on all targets. Out of 997 targets with a candidate transiting exoplanet, 170 of them host multiple candidates. Deviations in transit timing allows us to confirm that some of these systems are indeed planetary (Kepler-9, Kepler-11), and continued monitoring of these and other systems (the ultra-compact KOI-500, the coorbital KOI-730) will challenge and refine theories of the formation of planetary systems.

Understanding Galaxy Growth Using Fundamental Relations

Kristian Finlator (University of California Santa Barbara)

I will consider what can be learned about the processes that dominate galaxy growth from two observable metrics of star formation. First, I will discuss the scatter in the relation between star formation rate and stellar mass. This encodes information regarding the star formation duty cycle and the role of galaxy environment in regulating star formation. I will discuss the imprint of environmental effects on this scatter as well as prospects for using observations to measure it. Next, I will discuss the implications of the evolving mass-metallicity relation of star-forming galaxies. Hydrodynamic simulations suggest that gas-phase metallicities reflect a slowly-evolving equilibrium between the rate at which stars enrich and inflows dilute the metallicities of gas reservoirs. The resulting "equilibrium metallicity" encodes information regarding both inflows and outflows. I will show how comparisons between recent observations and simulations may be used to test this idea. Finally, I will discuss why departures from these mean trends are expected to correlate and show how this idea may be used as a complementary test of galaxy evolution models.

The Last Remnants of Primordial Disk Material

Elise Furlan (JPL, Caltech)

We present a study of weak-lined T Tauri stars (WTTS) with infrared excesses of varying strength. These young pre-main-sequence stars are peculiar, since they lack signatures of accretion, but seem to be still surrounded by dusty disks. Most WTTS are diskless, implying that gas and dust in primordial circumstellar disks dissipate on similar timescales. Thus, WTTS with infrared excesses offer us a rare glimpse into the conditions of remnant protoplanetary disks. We analyze mid-infrared spectra obtained with the Infrared Spectrograph on the Spitzer Space Telescope; these spectra reveal the degree of dust depletion in these systems, the composition of the dust, and its distribution in the disk. Our study sheds light on the late stages of disk dissipation, which are crucial for understanding and constraining planet formation.

The Variable Ultraviolet Universe

Suvi Gezari (Johns Hopkins University)

The GALEX Time Domain Survey (TDS) has opened a new window into the variable ultraviolet Universe. I will present results from 3 years of GALEX TDS NUV observations in spatial and temporal coordination with the optical Pan-STARRS Medium Deep Survey. The regular cadence (2 days) and wide field (37 deg^2) of GALEX TDS has yielded the discovery and characterization of over 2000 UV variable sources, including 100 RR Lyrae and Mdwarf flare stars, 600 quasars and active galactic nuclei, and several core-collapse SNe caught rising in the UV following shock breakout. We use cross-matches with optical imaging, X-ray, and spectroscopy catalogs, in combination with UV variability statistics to classify sources. In addition, we cross-match the UV variable sources with optical transients detected in the Pan-STARRS Medium Deep Survey to study simultaneous UV and optical variability. This data set demonstrates the power of a space-based UV survey when coordinated with a ground-based optical synoptic survey to provide a rich sample of variable and transient sources, whose rates and detailed UV and optical properties facilitate the systematic study of known, rare, and exotic astrophysical phenomena in a new wavelength regime.

Main-Belt Comets: Ice in the Inner Solar System

Henry Hsieh (Univ. of Hawaii - IfA)

Identified as a new class of solar system bodies just 5 years ago, main-belt comets (MBCs) exhibit cometary activity apparently driven by the sublimation of volatile ices, yet are dynamically indistinguishable from main-belt asteroids. Dynamical analyses show that MBCs are unlikely to be captured from the outer solar system, and are probably native to the main belt. Besides further blurring classical distinctions between asteroids and comets, MBCs present new opportunities to map the distribution of present-day volatile material in the inner solar system, constrain the thermal properties of asteroid regolith, and probe the temperature and compositional structure of the protosolar disk. Their existence also lends new support to the idea that main-belt objects could have been a major primordial source of terrestrial water and offers the opportunity to directly investigate that idea. I will discuss the observations that led to the identification of this new class, the properties of the currently known MBCs, and the latest developments in this young and fast-developing area of solar system research.

Milky Way Asymmetries and Substructure in SDSS III

Mario Juric (Harvard University)

The 8th release of the Sloan Digital Sky Survey featured a new 2000 deg^2 of imaging, largely in the southern Galactic hemisphere. This allows us to perform model-free examination of North-South and East-West symmetry of the Milky Way, and detect and characterize structures in the Galactic disk and halo. Using these data, we show that the Virgo overdensity is significantly more extended (~3000deg^2) than previously estimated. However, we demonstrate it is unlikely to be a global feature of the halo (e.g., triaxiallity). Instead, combined with previously published measurement of kinematics, the Virgo overdensity is shown to be consistent with a strongly disrupted tidal stream observed near perigalacticon. Secondly, we map and conclusively demonstrate the extent and existence of the "thick disk asymmetry", a major ring-like feature in the thick disk at 3-5 kpc (heliocentric) towards the Galactic anticenter. While clearly detected in the nearly-synoptic SDSS III maps, its nature remains unclear; a merger remnant, a warp in the disk, or an effect of spiral structure may all serve as explanations of its origin. Follow-up observations are ongoing to better understand its nature.

Testing Early Universe Physics with the CMB

Ryan Keisler (University of Chicago)

Increasingly precise measurements of the cosmic microwave background (CMB) will strongly test our assumptions about the physics of the early universe. Does the primordial helium abundance inferred from the CMB agree with that predicted by BBN? Were neutrinos the only relativistic particle species present during recombination? Were the CMB photons gravitationally deflected by intervening structure as we expect them to have been? I will present new results from the South Pole Telescope which address these questions.

Probing Accretion Physics with X-ray Variability of AGN and New Methods of Estimating Black Hole Mass

Brandon Kelly (Harvard-Smithsonian Center for Astrophysics)

Many aspects of accretion and jet physics scale simply with mass, suggesting that AGN should be scaled up versions of galactic black holes (GBHs). This is fortuitous because GBHs are easier to study as they are brighter and have many important physical time scales much shorter than a human lifetime. GBHs thus offer a laboratory in which to study accretion physics on time scales not accessible for SMBHs, and insight gained from GBH studies may be extrapolated to SMBHs. This is particularly important for obtaining observational insight into AGN feedback, as the relative importance and efficiency of AGN feedback likely depends on the AGN accretion mode. Recent studies have indicated that many aspects of the spectral and timing properties of both GBHs and AGN scale simply with mass and accretion rate. I will discuss a model that I have developed to characterize the aperiodic X-ray variability of AGN, and recent results on how properties of the X-ray variability scales with black hole mass. I will also discuss my ongoing work on developing the X-ray variability as a tool for estimating black hole mass.

Detectability of Gas Infall into Galaxies

Dusan Keres (UC Berkeley)

Theoretical models of galaxy formation predict that accretion of cold gas from the intergalactic medium is a major gas supply channel of galaxies. Observations of global star formation history and evolution of dense gas content of galaxies over cosmic time also indicate the need for accretion of gas into cold galactic component throughout the Hubble time. However, direct observational evidence for such infalling gas is scarce, even at high redshift where cold gas is expected to infall at high rates. Until recently theoretical prediction were not mature enough to enable proper comparison of models with observations. I will review recent progress on making more quantitative predictions for the detection prospects of the cold infalling gas in regions around galaxies. New theoretical results indicate that signatures of gas infall in high redshift galaxies are more subtle than what was previously thought.

Stars that Go Boom

Mukremin Kilic (Smithsonian Astrophysical Observatory)

Short period binary white dwarfs may merge within a Hubble time due to gravitational wave radiation. We have begun a targeted survey to find merging white dwarf systems, and our first results have tripled the number of known merging white dwarf systems. Our sample includes systems with orbital periods as short as 40 minutes and with merger times less than 40 Myr. I will discuss the characteristics of this merger sample and potential links to Type Ia and underluminous supernovae.

Chemical Evolution of Milky Way Satellites and High-Resolution Follow-Up

Evan Kirby (Caltech)

Last year, I presented the elemental abundance distributions of Milky Way dwarf satellite galaxies. These observation were based on Keck/DEIMOS medium-resolution spectroscopy. This year, I will present a simple chemical evolution model that can explain the abundance distributions of the fainter, older satellites but not the brighter, more complex satellites. I will also present high-resolution spectral follow-up of some metal-poor stars discovered with DEIMOS. These new spectra access elements that the DEIMOS data did not, such as the neutron-capture element barium.

A Young Exoplanet Caught at Formation

Adam Kraus (Univ. of Hawaii - IfA)

Young and directly-imaged exoplanets offer critical tests of planet-formation models that can't be matched by RV surveys of mature stars. These targets have been extremely elusive to date, with no exoplanets younger than 10-20 Myr and only a handful of direct-imaged exoplanets at all ages. We will report the first direct detection of a young exoplanet during its epoch of formation (T~2 Myr); this discovery was achieved using adaptive optics imaging combined with nonredundant mask interferometry, a technique that achieves extremely deep sensitivity at the diffraction limit of the telescope. The new planet is embedded in a protoplanetary disk with a large cleared gap (a ``transitional disk'') and orbits within that gap. I will discuss this discovery in the context of an ongoing survey to identify planets in transition disk gaps, including its implications for the process, epoch, and duration of planet formation.

Rest-Frame Optical Imaging of z ~ 2-3 Star-Forming Galaxies with HST/WFC3

David Law (UCLA)

I will describe some results from our recent HST/WFC3 rest-frame optical imaging survey of star-forming galaxies in the redshift range 1.5 < z < 3.5. With 42 orbits of F160W imaging distributed amongst 10 fields, our survey covers ~ 65 square arcmin to a depth of 27.9 AB and contains > 300 spectroscopically confirmed galaxies with stellar masses in the range M* = 1e9 - 1e11 solar masses. I will discuss the typical morphological properties of these galaxies and the evidence for a growth in galaxy structures at fixed stellar mass of the form r ~ (1+z)^-1, whereby star forming galaxies appear to evolve onto the local late-type mass-radius relation by z ~ 1. In addition, I will discuss the apparent relation between galaxy morphology and the characteristics of galactic-scale gasesous outflows.

Studying the First Galaxies with the Cosmological 21cm Line

Andrei Mesinger (Princeton University)

The first stars and galaxies are likely very different from their modern-day progeny and are at the forefront of astrophysical research. Unfortunately, it is very unlikely they can be directly observed in the near future. However, indirectly observing them through their impact on the intergalactic medium is a realistic short-term goal. I will discuss how this can be achieved using the redshifted cosmological 21cm line, which can offer us a glimpse into the cosmic dawn. However, to interpret such a bounty of information, we need efficient modeling tools capable of exploring the dauntingly large parameter space, such as our newly developed 21cmFAST.

Stellar Forensics with Explosions: Supernovae, Gamma-Ray Bursts, and their Environments

Maryam Modjaz (Columbia University)

Long-duration gamma-ray bursts (GRBs) and Type Ib/c Supernovae (SN Ib/c) are nature's most magnificent explosions from massive stars. While GRBs launch relativistic jets, SN Ib/c are core-collapse explosions whose progenitors have been stripped of their hydrogen and helium envelopes. Yet for over a decade, one of the key outstanding questions is what conditions lead to each kind of explosion in massive stripped stars. Determining the fates of massive stars is not only a vibrant topic in itself, but also impacts using GRBs as star formation indicators over distances up to 13 billion light-years, understanding the SNe from the first generation of stars and mapping the chemical enrichment history of the universe. I will present a number of comprehensive observational studies that probe the progenitor environments and metallicities of SNe with and without GRBs, as well as of different types of SN Ib/c, notably Pair-Instability SNe. I will conclude with an outlook on how the most promising venues of research - using the innovative and large-scale Palomar Transient Factory - are shedding new light on the diverse deaths of massive stars.

Resolving the Chemistry in Protoplanetary Disks

Karin Oberg (Harvard-Smithsonian CfA)

The disks around pre-main-sequence stars provide the reservoirs of raw material and initial conditions for the formation of planetary systems. Disk chemistry thus sets the stage for the composition of planetesimals and eventually planets; comet compositions in our own solar system reveals that efficient astrophysical pathways to chemical complexity exists. Understanding chemistry is also important to develop molecular tracers of otherwise inaccessible disk physics. DISCS is a Submillimeter Array (SMA) program aimed at assessing the impact of protoplanetary disk physics on disk chemistry by spatially and spectrally resolving millimeter emission from 8 key molecules and ions (CO, HCO+, DCO+, N2H+, HCN, DCN, CN, H2CO) in 12 nearby protoplanetary disks. The sample spans a range of physical environments, including stellar types from M1 to A0, orders of magnitude in accretion luminosity and X-ray flux, as well as a range of dust structures. The results of this survey will be reviewed together with ongoing model efforts to interpret the disk emission and especially the different radial profiles of different molecular lines. ALMA's commission this year has the potential to transform our understanding of the chemistry active during planet formation, and ALMA's role as a driver for current experimental developments will be briefly discussed.

Hunting for the First Generations of Galaxies with HST

Pascal Oesch (UC Santa Cruz)

Over the past year and a half, the refurbished HST has revolutionized z>6 galaxy science as it gained ~40x higher efficiency to observe in the near-IR with the WFC3/IR camera. This has allowed us to definitely push the observational frontier of galaxies into the reionization epoch. Based on our HUDF09 survey and additional WFC3/IR imaging over the GOODS-South field, it became possible to identify >100 z~7-8 galaxies; and even one single, robust z~10 candidate. With these samples we can directly track the evolution of galaxies across the reionization epoch and start to constrain their role in this important process of cosmic history. One of the most intriguing results from this study is that the well-established evolutionary trends of the UV luminosity function that are observed from z~2 to z~6 can likely not be extended into the reionization epoch. The galaxy population appears to undergo faster growth in the first few hundred Myr of cosmic time than expected from lower redshift extrapolations. In this talk, I will highlight our recent progress in understanding the first generations of galaxies from the HUDF09 survey and what this implies for cosmic reionization by low luminosity galaxies.

The Isolated, the Energetic, and the Unseen: A Tale of Bright Supernovae

Jose Prieto (Carnegie Observatories)

The All-Sky Automated Survey for the Brightest Supernovae (ASAS-SN) is using small telescopes with wide field cameras to search for the brightest supernovae explosions. I will present the study of three bright supernovae in nearby galaxies and their environments, connecting them to different progenitor systems. Through these examples I will highlight the importance of metallicity as a key factor in stellar evolution and supernovae progenitors.

The Evolution of the Star Formation-Density Relation

Ryan Quadri (Carnegie Observatories)

It has long been known that galaxies with little or no ongoing star formation (SF) primarily occupy dense environments at z~0. Recently significant work has gone into understanding how the relationship between galaxy properties and environment evolves with time. But such studies become quite challenging at z>1, and involve several trade-offs. Here I present new results on the evolving relationships between environment, stellar mass, and star formation, and show that in certain respects the universe at z~1.5 is not so different than the local universe.

Systematics in the UV Dust Attenuation Curve at High Redshift

Naveen Reddy (National Optical Astronomy Observatory)

I review recent evidence that suggests that the dust corrections applied to high-redshift galaxies are strongly dependent on the age of the stellar population, such that relatively young galaxies at high redshift appear to follow a steeper UV dust attenuation curve. I will discuss the implications of these results for estimating bolometric star formation rates of young galaxies at high redshift, and present a simple picture where the distribution of the stars and dust within galaxies changes as a function of time.

Modeling Redshift Space Distortions in the Quasi-Linear Regime

Beth Reid (Lawrence Berkeley National Lab)

Ongoing spectroscopic surveys like the Baryon Oscillation Spectroscopic Survey have the statistical power to constrain the growth of cosmic structure through redshift space distortions at the percent level. I will discuss progress in improving our theoretical models in the quasi-linear regime to the accuracy demanded by the data.

Did Star-Forming Galaxies Reionize the Universe?

Brant Robertson (California Institute of Technology)

Star-forming galaxies represent a valuable tracer of cosmic history. Recent observational progress with the Hubble Space Telescope has led to the discovery and study of the earliest-known galaxies at a time when the universe was only ~800 million years old. Intense ultraviolet radiation from these early galaxies probably induced a major event in cosmic history: the reionization of intergalactic hydrogen. In this talk I will briefly review the status of HST observations of distant star-forming galaxies, and focus on current theoretical challenges in interpreting the data and understanding the connection between these distant galaxies and the process of cosmic reionization.

Modeling star formation throughout the Milky-Way

Thomas Robitaille (Harvard-Smithsonian Center for Astrophysics)

In this talk I will present results from work I have carried out using the Spitzer/GLIMPSE and MIPSGAL surveys to study intermediate and high-mass star formation on the scale of the Milky-Way. I will discuss a census of thousands of young stellar objects in the Galactic plane, and in particular recent work I have done on a population synthesis model to determine the present rate of star formation in the Galaxy. I will briefly discuss how future estimates of the Galactic star formation rate will benefit from the wealth of existing and future Galactic plane surveys (UKIDSS, BGPS, HiGal, etc.).

Runway Growth During Planet Formation

Hilke Schlichting (UCLA)

Runway growth is an important stage in planet formation during which large protoplanets form, while most of the initial mass remains in small planetesimals. The amount of mass converted into large protoplanets and their resulting size distribution are not well understood. I will present recent results from our analytic and numerical work on runway growth. I will show that this growth leads to protoplanet size distribution given by N(> R) propto R^{-3} where N(> R) is the number of objects with radii greater than R (i.e., a differential size distribution power-law index of 4). I will compare our results to the Kuiper belt in our Solar system, which is thought to be a relic of runaway growth, and show that they agree with the observed Kuiper belt size distribution and that they explain the total mass that is present in large Kuiper belt objects (KBOs) today. Our findings suggest that the current mass in large KBOs is primordial and that it has not been significantly depleted since formation. Our work also predicts a maximum mass-ratio of Kuiper belt binaries that formed by dynamical processes of 10, which is consistent with the observed clustering in binary companion sizes that is seen in the cold classical Kuiper belt. Finally, our findings also apply to growth in debris disks, as long as frequent planetesimal-planetesimal collisions are not important during the growth.

Gravitational Recoils of Super-massive Black Holes in Massive Gas-rich Galaxies

Debora Sijacki (Harvard College Observatory )

I will present results from high-resolution hydrodynamical simulation which track the evolution of gravitationally recoiled super-massive black holes (BHs) in massive gas-rich galaxies. The presence of a massive gaseous disc allows recoiled BHs to return to the center on a much shorter timescale than for purely stellar discs. Also, BH accretion and feedback can strongly modify the orbit of recoiled BHs and hence their return timescale, besides affecting the distribution of gas and stars in the galactic center. However, the dynamical interaction of kicked BHs with the surrounding medium is in general complex and can facilitate both a fast return to the center as well as a significant delay. In major merger simulations of gas-rich galaxies, I find that gravitational recoils increase the scatter in the BH mass -- host galaxy relationships compared to simulations without kicks, with the BH mass being more sensitive to recoil kicks than the bulge mass. A generic result of my numerical models is that the clumpy massive discs suggested by recent high-redshift observations, as well as the remnants of gas-rich mergers, exhibit a gravitational potential that falls steeply in the central regions, due to the dissipative concentration of baryons. As a result, super-massive BHs should only rarely be able to escape from massive galaxies at high redshifts, which is the epoch where the bulk of BH recoils is expected to occur.

The Dark Matter at the End of the Milky Way

Louis Strigari (Stanford University)

Direct experimental searches for particle dark matter in our Galaxy are extremely sensitive to the highest velocity dark matter particles that are bound to the Galaxy. Combining theoretical predictions (N-body simulations) for the predicted spatial and velocity distribution of dark matter in the Galaxy with observations of stellar and gas kinematics, we can understand how different direct dark matter detection experiments are sensitive to the distribution of dark matter in the Galactic halo. Theoretical modeling combined with observations also allows us to estimate our ability reconstruct the mass and cross section of dark matter particles from future data sets. In this talk I will discuss new results on our understanding of the Galactic dark matter distribution, and interpret these results in the context of the recent experimental limits on particle dark matter in the Milky Way.

Wide Binary Stars in Dwarf Galaxies: Prospects for a New Test of Lambda-CDM Cosmology

Matthew Walker (Harvard College Observatory)

The scale-free hierarchy of cold dark matter (CDM) halos produced in cosmological N-body simulations implies the existence of scores of completely dark 'subhalos' (and 'sub-subhalos', etc.). One of very few observable signatures of such halos would be a truncation (due to disruptive encounters) of the separation function of wide binary stars in the ancient stellar populations of nearby dwarf galaxies. I will discuss prospects for detecting such a signal and identify the most suitable target galaxies.

Searching for Clues to the Black Hole-Galaxy Relationship Through Nearby AGN Surveys

Lisa Winter (University of Colorado)

While feedback from the central supermassive black hole likely affects the host galaxy evolution in the distant universe, we can not directly observe these processes at work. We can, however, easily observe the host galaxy and AGN properties of nearby sources. Previous surveys of outflows in local AGN relied on biased samples of the UV/soft X-ray brightest sources, making their results also biased. To understand the true outflow properties in a local sample of AGN, we present our results from optical and X-ray spectroscopic follow-ups of a sample of Seyfert 1s detected in the very hard X-rays (14-195 keV) with the Swift Burst Alert Telescope. Due to the high energy selection, this survey is largely unbiased to the gas and dust which obscures softer bands. We find that outflows are detected in a majority of the sample and may be present in all local Seyfert 1s. This implies a covering fraction of the outflows much larger than previous results.

From the First Stars to Galaxy Formation

John Wise (Princeton University)

The first stars and galaxies had a profound impact on the universe, leading to reionization and the chemical enrichment of the intergalactic medium. Here I present results from adaptive mesh refinement radiation hydrodynamics simulations that focus on the formation of the first galaxies with a self-consistent transition from massive metal-free stars to metal-enriched stars that populate the first galaxies. These results provide invaluable insight for interpreting the latest and future galaxy observations prior to reionization.

NOMADS: Physical Origins of Line-Emitting Gas in High-Redshift (1 < z < 3) Galaxies

Shelley Wright (UC Berkeley)

Integral field spectroscopy coupled with adaptive optics (AO) on 8-10m telescopes has recently become a powerful observational tool for studying galaxies in the early universe (z > 1) at sub-kiloparsec scales. I will present the latest results of an ongoing survey (NOMADS) using Keck AO and OSIRIS to observe spatially resolved optical emission lines (e.g., Hα, and [N II]) from high-redshift (1 < z < 3) star forming galaxies. The primary goals of this survey are to study the dynamics, chemical abundances, and active galactic nuclei (AGN) in early galaxies. The high spatial resolution afforded by AO and the 2D capability of an integral field spectrograph has allowed the discovery of some of the lowest luminosity AGN known at this epoch, and I will discuss the potential impact on high-redshift metallicity studies and galaxy formation.