Colloquium (2013)

An X-ray light echo now propagating through the central molecular zone of our Galaxy has revealed that a major X-ray flare took place there about 100 years ago. The high luminosity and the direction of propagation implicate the central supermassive black hole in our galaxy, which is presently very quiescent. I will discuss this evidence, and the outstanding possibilities for what might have caused this activity. This may not be a particularly rare event; a gaseous object -- possibly centered on a star -- is now plummeting toward the black hole on a highly eccentric orbit and is expected to supply new fuel for enhanced accretion activity during and after its passage through periapse in early 2014. I will present the view of this object from UCLA, based on data obtained at the Keck Observatory.

Most stars -- and hence most solar systems -- form within groups and clusters. The first objective of this talk is to explore how these star forming environments affect solar systems forming within them. The discussion starts with the dynamical evolution of young clusters with N = 100 - 3000 members. We use N-body simulations to study how evolution depends on system size and initial conditions. Multiple realizations of equivalent cases are used to build up a robust statistical description of these systems, e.g., distributions of closest approaches and radial locations. These results provide a framework from which to assess the effects of clusters on solar system formation. Distributions of radial positions are used in conjunction with UV luminosity distributions to estimate the radiation exposure of circumstellar disks. Photoevaporation models determine the efficacy of radiation in removing disk gas and compromising planet formation. The distributions of closest approaches are used in conjunction with scattering cross sections to determine probabilities for solar system disruption. The result of this work is a quantitative determination of the effects of clusters on forming solar systems. The second objective of this talk is to use these results to place constraints on the possible birth environments for our own solar system. These latter results are more uncertain than the first ones, but provide interesting perspectives on our place in the universe.

I will present the current status of the theoretical and observational understanding of spiral-shell patterns in the circumstellar envelopes of dying solar-type stars accompanied by the companions. This talk includes the explanation about the paper honored with the NSC 2012 postdoc publication award. Evolved stars beyond the main sequence, in particular in the Asymptotic Giant Branch (AGB) phase, can be highly obscured in dense circumstellar envelopes due to their intensive mass loss. The difficulty in detecting the obscured AGB stars leads to high uncertainties in the modeling of the late stellar evolutionary phases. In the case that the AGB star has a companion, however, the binary orbital motion leaves an imprint as a spiral-shell pattern on the circumstellar envelope. We develop a new method of determining the characteristics of such binary stars from the properties of the observed circumstellar spiral and incomplete ring patterns, revealing in the images taken with the Hubble Space Telescope and the mm/sub-mm interferometers. We use the shape of such a pattern projected on the plane of the sky as well as molecular line kinematics to further provide the three-dimensional information of the circumstellar pattern. This method is easily applicable to many sources in the AGB and pre-planetary nebula phases, whose detection is highly anticipated with the ALMA.

Supermassive black holes are found at the centres of most galaxies and stellar mass black holes are common throughout galaxies. Observations of these astrophysical black holes will be presented and discussed. Evidence will be presented that supermassive black holes determine the final mass and shape of their host galaxies. The talk concludes with observations of the innermost regions around black holes and approaches to mapping down to the event horizon.

The past and coming few years see the advent of new generations of deep and wide surveys in optical and near-infrared, which enable us to explore the evolution of galaxies on range of redshifts and masses never explored so far. Owing to my involvement to some of the most important of these surveys, I have explored the mass assembly history of galaxies since z=2 and intend to push to z=7 with the coming Hyper-Suprime Cam Survey. As the large-scale behaviour of galaxies is ruled by their dark matter content, an estimate of the mass of their dark matter halos is crucial to gain a good understanding of the history of their mass assembly. Clustering analyses allows us to link galaxy populations to the mass of their host haloes, and I am using this technique to probe the halo masses of galaxies up to z=2. In particular I am interested in the luminous-to-dark mass ratio and its evolution with redshift. These results implied that a halo downsizing is in place since z=2, where galaxy mass assembly happen faster in higher mass haloes at high redshifts while at lower redshifts it migrates to lower mass halos. I also demonstrate that the (stellar) baryonic mass of galaxies are not as well correlated to the mass of their dark matter haloes as expected, and even by involving gaseous mass, the budget of mass is not compatible with the baryonic fraction implied by cosmological studies (CMB). To understand better the origin of these missing baryons, I am exploring directly the mass assembly of galaxies by major mergers. I demonstrate that since z=2 while major merger plays a minor role in mass assembly of the most galaxies, it plays an increasingly important role in the lower mass galaxies, in particular at low redshift, in contradiction with the theoretical predictions. Exploiting the new Hyper-Suprime Cam on the 8.2m Subaru telescope, the HSC survey will open a new era on the exploration of the very high-redshift (z>5), which was limited to the very small fuel;d-of-view of the Hubble-Space Telescope so far. I will introduce the HSC survey and describe how I am intending to extend my exploration of the mass-assembly to z=7. Finally I will conclude on the challenges raised by the exploitation of the current and next generation of large surveys, and how they required development of topics such as Astroinformatics and Virtual Observatory.

The age-old question "Where do we come from?" has been central to many scientific endeavours. The field of Astrobiology has reformulated this question to "How did life originate?". Carbon is the element on which all life on Earth is based. If we want to understand the origin of life, we must look for the origin of its building blocks. A great source of organic material is provided by a class of meteorites called the carbonaceous chondrites. Several of life's building blocks are directly present in carbonaceous chondrites as small soluble molecules (e.g. amino acids, nucleobases, carboxylic acids), but the majority of the organic carbon is locked up in an insoluble macromolecular network. In this talk, I will discuss several phases of carbon in space, from interstellar molecules and laboratory experiments, to the macromolecular networks of organic carbon that are found in meteorites, and end with the latest discoveries of large (up to 10 micrometers) organic carbon inclusions in meteorites. This pathway incidentally also follows my carrier in Astrochemistry and Astrobiology, and I hope to provide more insight into the origin of the building blocks of life on Earth.

Submillimeter-wave 10 kilo-pixel camera with wide field-of-view may bring a revolution in research of cosmic microwave background and high-z submillimeter galaxies. We have been developing superconducting "CCD"-like cameras for future radio astronomy after ALMA receiver developments. ALMA is a powerful instruments with capability of high spatial and spectral resolution, however, the field of view is quite limited to 21 arc second at 300 GHz. Wide field observation with a large format imaging array isn't only a complementary for ALMA but also suitable for study of large scale structure of the universe. Microwave kinetic inductance detector (MKID) or superconducting micro-resonator is a promising technology for this purpose because large arrays can be read out using frequency-domain multiplexing with a microwave low-noise amplifier. MKID can detect higher frequencies than the gap frequency of a superconducting material, for example, Aluminum gap frequency of 90 GHz. We have demonstrated a submillimeter 100 pixel camera which consists of Aluminum antenna coupled MKIDs and Si-lens array. The dark noise equivalent power (NEP) was achieved to be 6 x 10^{-18} W/rHz. Beam pattern of the MKID camera has been measured. We are developing MKID cameras for two future projects. LiteBIRD is a future satellite to detect B-mode polarization of cosmic microwave background (CMB) led by KEK, which can explore the cosmological inflation. It consists of a small (60 cm) crossed Dragone telescope and a low-noise imaging array to observe CMB with a sensitivity of r (tensol-to-scalar ratio) ~ 0.001 at large angular scales. To reduce foreground contamination from diffuse galactic plane, it observes 50 - 270 GHz with dual-polarization imaging array. A 10m-class telescope for terahertz observations is planned by Tsukuba University at Dome Fuji (Alt. 3800 m) on Antarctica. A wide field-of-view (~1 degree) survey of submillimeter galaxies is planned with a 10 kilo-pixel array detector covering 400 GHz - 1.5 THz.

The number counts and large-scale distribution of galaxy clusters are powerful probes of the structure and composition of the universe. In the era of precision cosmology from deep wide surveys, dark matter N-body simulations play an essential role in modeling the non-linear gravitational effects and interpreting the survey results. In this talk, I will first discuss what we have learned from these simulations, how much we still need to improve them for upcoming surveys, and what the potential dangerous systematics are. I will then present the results from my cluster simulation project “Rhapsody” ― a statistical sample of high-resolution re-simulated clusters ― which allows us to statistically characterize the distribution of and correlation between cluster properties at fixed mass. I will focus on how we can use the understanding of the clusters’ formation history to optimize the use of cluster mass tracers, to model the covariances between different mass proxies, and to reduce systematic errors in cluster cosmology.

Classical Cepheids are an important component in extra-galactic distance scale work, as its famous period-luminosity (PL) relation can be used to derive the Hubble constant via the calibration of various secondary distance indicators. Boosted by the HST H0 Key Project, past works on Classical Cepheids have been focused on the investigation of long period Cepheids (with pulsation periods from 10 to 60 days) in the V and I bands. One such example is the extensive calibration of VI band PL relations in literature. In this talk, I will present new directions of Cepheid research emerged in recent years. The first one is the moving of the calibration of PL relation from optical to mid-infrared (MIR). The biggest advantage of using the MIR PL relations is the extinction is negligible in these wavelengths, at which extinction is one of main systematic errors in Cepheid distance (hence propagated to the errors for Hubble constant). The MIR PL relations also hold the promise to derive Hubble constant with 2-3% accuracy in near future. The second direction is the investigation of Cepheids with periods longer than 80 days, the so-called ultra-long period Cepheids (ULPCs). These ULPCs are ignored in the past, however Bird et al (2009) proposed they can reach to a distance of 100Mpc, well beyond the ~40Mpc distance based on shorter period Cepheids using HST. An on-going search of ULPCs in M31 using PTF data is highlighted in this talk. Finally, I will ended my talk with the recent investigation of projection factor (p-factor) -- an important parameter when calibrating the PL relation using Baade-Wesselink (BW) type technique. The value of p-factor was found to be larger than the previous adopted, which could have impact on the derived Hubble constant via the Cepheid PL relations calibrated with BW methods.

I will present high angular resolution and wide-field interferometric continuum observations of the Orion Molecular Cloud (OMC) utilizing the Submilllimeter Array (SMA) and Jansky Very Large Array (JVLA), covering 25'/3.1 pc length of the the northern part of the OMC filaments. We detect at least 69 spatially resolved continuum sources associated with OMC filamentary structures through thermal dust emission. Their estimated masses and a projected source sizes range from 0.09 to 5.8 solar masses and 1010 to 19000 AU, respectively. An analysis based on the Jeans theorem suggests that these sources are most likely gravitationally unstable. Comparison of multi-wavelength datasets indicates that approximately half of the detected continuum sources are associated with outflows, infrared sources, and ionized jets. These sources show the evolutionary stage from prestellar core to Class 0/ I phases. We found the source separation within the OMC filaments peaked at 0.02 pc and 0.05 pc. This spatial distribution is part of a larger hierarchical structure, that also includes fragmentation scales of GMCs ( 5 degree/ 37 pc), large-scale clumps (1.3 pc), small-scale clumps (0.3 pc). This suggests that hierarchical fragmentation operates within the Orion A molecular cloud. Fragmentation spacings are roughly consistent with the local thermal fragmentation length in large-scale clumps ( 0.3 pc), while fragmentation spacings in dense cores measured from the SMA observations is smaller than the local fragmentation length. These smaller observed spacings can be explained by either that helical magnetic field or global filament collapse. This will be my last talk in IAA before I leave Taiwan. I also would like to make summary of my research projects and project experiences at IAA in the past years.

Observations on distance <300 pc molecular clouds have shown that the nearby young YSO clusters form at the convergences of the molecular filaments. The preliminary analytical hub-filament model was proposed for describing this phenomenon. Our survey on a few most luminous Galactic OB cluster forming regions shows that their parent giant molecular clouds also have the hub-filament geometrical configuration. At the convergences of the filaments, the high density and the high external pressure may promote the accretion and the star-forming efficiency. I will elaborate the overall geometry and kinematics of the luminous OB cluster forming molecular clouds with two case studies, based on the synthesized SMA+IRAM-30m observations. One case is the molecular cloud G10.6-0.4 located in the near 3 kpc spiral arm. The other is the unique Galactic mini-starburst region W49A. We hope to shed some light on the paradigm of the formation of gravitationally bound massive cluster.

Understanding the formation and evolution processes of galaxies remains among the most important unsolved problems in present-day astrophysics and cosmology. A reliable and detailed description of the mass-density profile and structural properties of galaxies through cosmic time is a much-needed step forward but – whereas nearby systems have been thoroughly analyzed – painfully little is known about more distant objects, since observational limitations make it difficult to employ the traditional diagnostic tools. During this talk I will describe a method to overcome these difficulties based on combining in a self-consistent way the information obtained from two independent and complementary techniques: strong gravitational lensing and stellar dynamics. This provides a robust way to conduct detailed studies of both elliptical and disk galaxies beyond the local Universe. I will then detail the results of the application of this method to the analysis of a sample of 16 lens elliptical galaxies in the redshift range z = 0.08 - 0.33, for which both HST imaging observations and two-dimensional kinematic maps (obtained from VLT VIMOS spectroscopical observations) are available. I will also illustrate how this approach can be extended to study in detail the dark and luminous mass structure of lens disk galaxies, and to put firm constraints on the initial mass function of massive galaxies.

Better measurements of H0 - the current expansion rate of the Universe, provide critical independent constraints on dark energy, spatial curvature of the Universe, neutrino physics, and validity of general relativity. The Mega-maser Cosmology Project (MCP) aims to determine the Hubble Constant at high accuracy by measuring the angular-diameter distance to galaxies in the Hubble Flow. The MCP has discovered 9 new mega-maser disks in Sy2 nuclei suitable for distance determination. A geometric distance measurement to a galaxy at 140 Mpc, via micro- arc-second astrometry of its circum-nuclear mega-maser disk, has been demonstrated. The current status of the MCP measurements of Ho, and future prospects, will be described. The MCP also enables accurate determination of the central black-hole mass in mega-maser galaxies. The large intrinsic scatter of BH masses in a narrow range of the velocity dispersion in the mega-maser galaxy bulges raise questions about the validity of the well-known M-σ relation of BH mass and the spherical component of galaxies. The relationship of the thin Keplerian accretion disks delineated by the mega-masers with the obscuring material of the AGN will also be briefly discussed. Timing permitting, other key projects at the NRAO will be also described.

The first stars of the universe have attracted the strong interest of astronomers, as the first stars could re-ionized the universe and must be key objects to delineate the dark age of the universe. It has been thought that the first stars are very massive and luminous, however, it is difficult to detect individual stars even with JWST. To overcome the faintness of individual stars, we have tried to observe the near-infrared background to detect the integrated redshifted light of the first stars. This is a challenging observation, since there exist bright foreground backgrounds, however the space probes, COBE, IRTS, AKARI and Spitzer succeeded in detecting excess sky brightness and fluctuation that can not be explained with known foreground emission sources. In addition to these results, I will present the recent result of the sounding rocket experiment, CIBER, and its implications for the study of the first stars.

Our understanding of the high-mass star formation process, in contrast to that of their low-mass counterpart, remains relatively poor till today. In particular, what constitutes the initial condition for massive star formation is not yet well characterized. In this talk, I will introduce recent studies of the chemical signatures of massive star forming regions through molecular line observations, with an emphasis over those of cold and dense molecular clumps that are probably associated with the earliest phase of massive star and cluster formation.

Small bodies in the warm inner solar system have long been assumed to lack volatile material (i.e. ice) due to their close proximity to the Sun. However, recent work has pointed to the existence of preserved, and occasionally actively sublimating, water ice on objects in the main asteroid belt. These surprising discoveries carry exciting implications for our ability to understand the formation of our solar system and other extrasolar planetary systems, and possibly also the primordial delivery of terrestrial water and the origin of life on Earth itself. I will describe my own work on some of these icy inner solar system objects, known as main-belt comets, and discuss ongoing research efforts aimed at better understanding the extent and nature of preserved volatile material in the inner solar system.

The abundance of dark matter substructure in the halos of ordinary galaxies is sensitive to both the physics of dark matter and the physics of inflation in the early universe. Strong gravitational lensing provides one of the only probes of the abundance of DM halo substructure, but existing constraints on substructure from lensing have been weak because of the small sample sizes available. I will describe how the advent of the Atacama Large Millimeter/submillimeter Array (ALMA) has opened a new window onto DM substructure. Large numbers of lensed, dusty star-forming galaxies at high redshift have been discovered by Herschel and the South Pole Telescope, and ALMA observations of these lensed systems will allow reconstruction of the mass distributions of the lensing galaxies with unprecedented resolution. I will describe early results from this program, and I will discuss forecasts for ALMA as a probe of the properties of dark matter.

The formation of stars and planets are connected through disks. Disk formation, once thought to be a trivial consequence of angular momentum conservation, is greatly complicated by the magnetic field that is observed to be present in the dense, star-forming cores of molecular clouds. Indeed, in the simplest case of perfect coupling between the magnetic field and bulk neutral core material (the ideal MHD limit), both analytic work and numerical simulations have shown that the formation of rotationally supported disks is suppressed by excessive magnetic braking in dense cores magnetized to the observed level, leading to the so-called ``magnetic braking catastrophe'' in disk formation. I will discuss possible resolutions to this fundamental problem, including non-ideal MHD effects, misalignment between the magnetic field and rotation axis, turbulence-enhanced magnetic reconnection, and outflow stripping of the slowly rotating protostellar envelope. How protostellar disks form and grow remains an open question.

The James Webb Space Telescope (JWST) is the next great observatory currently in development by the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA) and the Canadian Space Agency (CSA). The JWST will peer into deep space using it's 6.5 meter segmented primary mirror and it is infrared optimized to operate at 1 - 25 micron wavelengths. The four main science themes for JWST are: First Light and Reionization, the Assembly of Galaxies, the Birth of Stars and Planetary Systems, and Planetary Systems and the Origins of Life. In this talk, I will introduce you to the JWST and discuss some of its key instrument modes that will have a very strong impact on my own field of research - the birth and early evolution of stars and their planetary systems. I will also highlight some star and planet formation research projects that I have done using 8 meter-class telescopes in that will help to pave the way for future observations with JWST.

My talk will include two parts. First I will take about interferometric observations and modeling of embedded young stellar objects. Protostars are surrounded by their natal envelopes in the early stage, while the earliest disks form inside the envelopes. To understand the envelope properties and to reveal the embedded circumstellar disk, we compare CARMA observations with theoretical collapse models using radiative transfer calculation and Bayesian inference. Implications of the modeling work will be discussed. Then I will introduce the Variable Young Stellar Objects Survey (VYSOS) project, which consists of two new robotic telescopes dedicated to monitor nearby star forming regions. Observations of VYSOS have started in search of new eruptive events around young stars such as FUor and EXor outbursts.

Presentation Summary: After a brief summary of the nature of CFHT Corp. and recent metrics illustrating the scientific success of CFHT, the future of the Observatory is described through various initiatives designed to broaden the CFHT partnership, develop new capabilities, and take steps toward the replacement of CFHT with a powerful new facility dedicated to highly multiplexed wide-field spectroscopy. CFHT, in the context of the evolving landscape on Mauna Kea will also be discussed, as CFHT positions itself among a backdrop of some older facilities being decommissioned while new Mauna Kea facilities are on the planning horizon.

We estimated the cross-power spectra of a galaxy sample from the Wide-field Infrared Survey Explorer (WISE) survey with the 7-year Wilkinson Microwave Anisotropy Probe (WMAP) temperature anisotropy maps. A conservatively-selected galaxy sample covers ~13000sq.deg, with a median redshift of z=0.15. Cross-power spectra show correlations between the two data sets with no discernible dependence on the WMAP Q, V and W frequency bands. We interpret these results in terms of the the Integrated Sachs-Wolfe (ISW) effect: for the |b|>20 deg sample at l=6-87, we measure the amplitude (normalized to be 1 for vanilla LambdaCDM expectation) of the signal to be 3.4+-1.1, i.e., 3.1 sigma detection. We discuss other possibilities, but at face value, the detection of the linear ISW effect in a flat universe is caused by large scale decaying potentials, a sign of accelerated expansion driven by Dark Energy.

Magnetic fields are present everywhere in the Universe, from substellar systems to large-scale structures, such as cosmic filaments, walls and voids. They are important in various astrophysical aspects. Without them, stars cannot be formed, and quasars cannot shine. While we have some understanding of the properties of stellar-scale magnetic fields, our knowledge of magnetic fields beyond galactic scales is very primitive. The situation will however change with the coming of new instruments, e.g. the SKA. In this talk I will first present an overview on cosmic magnetism. Then I will show results of two recent studies on cosmic magnetic fields by my collaboration. The first is a MHD simulation study of the evolution of magnetic fields of cluster and larger scales. The second is an investigation of how polarized radiation is transported through magnetized inhomogeneous multi-phase cosmological media. I will discuss how these studies will help to improve our understanding of properties, evolution and origin of the cosmic magnetic fields. I will also discuss certain technical difficulties and obstacles that we need to overcome in order to properly diagnose magnetic fields in large cosmic structures.

Stars on the asymptotic giant branch (AGB) are thought to be responsible for the majority of the dust injected into the interstellar medium. Infrared surveys on local group galaxies provide an ideal opportunity to investigate how the composition and quantity of dust produced by asymptotic giant branch (AGB) stars depends on metallicity on a galactic scale. Here, I discuss recent work on dust production in nearby dwarf galaxies, with particular focus on oxygen-rich dust in the Magellanic Clouds.

Astronomers have successfully discovered a number of extrasolar planets over the last twenty years. Our interests are now focused on direct detection of exoplanets similar to Jupiter, Saturn and Earth, understanding the similarities or diversities of such planetary systems, and how they form and evolve. Recent advances in technology, infrared imaging and the construction of large telescopes have provided dramatic progress in such studies. SEEDS (Strategic Explorations of Exoplanets and Disks) is an ongoing large survey for exoplanets and protoplanetary disks at Subaru, one of the largest optical and infrared telescopes in the world. We describe the outline of this survey and present results from its first three years, including the detection of several new planets/companions. We also show our discoveries of the detailed structures of protoplanetary disks, i.e., potential signposts of young planets.

The high stellar densities in galactic centres, combined with an accretion disk around the massive black hole, mean that stars will inevitably interact with the disk. This interaction can cause stars to be captured into the disk and migrate inward in a process similar to planetary migration. In addition to growing the black hole, the final plunge of the star through the accretion disk and into the black hole will result in an observational signature of high energy x-rays and gamma-rays. I will present early results from the StarDisk model, developed as part of the Silk Road Project (NAOC), which will soon self-consistently model the stellar dynamics, hydrodynamics and the feedback between stars and gas in galactic centres.

There are mounting evidences for AGN feedback in groups and clusters of galaxies. Understanding feedback in clusters is crucial for cluster cosmology apart from understanding the cluster thermal history. I will report the results of our study of fractional entropy enhancement in the intra-cluster medium (ICM) of the clusters from the representative XMM-Newton cluster structure survey (REXCESS). We use the `thermodynamic' entropy enhancement to make the first estimate of the total, as well as radial, non-gravitational energy deposition up to r500 for a large, nearly flux-limited, sample of clusters. We find that the total energy deposition is proportional to the cluster temperature (and hence mass), and that the centrally peaked energy deposition per particle as a function of gas mass shows a similar profile in all clusters. In the cluster core the energy deposition is also correlated with the radio luminosity. We also show that the recently proposed 'Universal' nature of cluster pressure profiles points towards 'Universal' prescription of entropy injection which is indicative of AGN heating. Taken together, the results strongly support models of entropy enhancement through AGN feedback.

High Energy experimental particle astrophysics is now a field of growing interests and has been well established. It marks the intersection of astrophysics, particle physics and cosmology. In general, particle astrophysics has two main elements. One is multi-messenger astronomy and the other is fundamental physics with cosmic messengers. It opens new windows to the universe and provides us new approaches to understanding the fundamental properties of matter and the universe. The main focus of this talk is on the development of experimental techniques for Earth-bound Cherenkov gamma-ray and neutrino detectors. Consequently, more emphasis is given to the physics results from these experiments, particularly on the physics of Active Galactic Nucleus (AGN) and related subjects. At last, the Cherenkov Telescope Array (CTA) project which is a worldwide effort experiment on Tera-electronvolt gamma-ray astronomy in the next decade will be introduced. In addition, I will also discuss the prospective CTA physics impacts on AGN research.

Galaxy clusters have become promising probes of cosmology thanks to recent advances in instrumentation. Both galaxy cluster surveys and pointed galaxy cluster observations provide insight into the nature of dark energy and dark matter. A variety of physical phenomena generate cluster observables which span from radio to X-ray. To use galaxy clusters for cosmology, however, we must combine these different wavelength observations, which scale independently with a cluster's physical properties. One of these observables, the Sunyaev-Zel'dovich (SZ) effect provides a lever arm to understand the baryonic content at the outskirts of galaxy clusters. Caltech has contributed significantly to the development of detectors and instrumentation to measure the Sunyaev Zel’dovich effect. The SZ observing program of one of the instruments, Bolocam, has fully matured over the last year. Thanks in large part to the ASIAA-branch of the CLASH program, our data has contributed to a variety of cluster analyses. I will give an overview of my work calibrating integrated SZ values with X-ray determined masses. This work includes a detailed study of sources of systematic error, including, selection function effects, large-scale signal filtering, and alternative mass models. The full Bolocam X-ray SZ catalog (BOXSZ) results are expected to be released early 2013.

Recent findings on the kinematic properties of the circumgalactic medium from absorption-line studies will be summarized in this talk.

Understanding the formation and evolution of the first stars and galaxies is one of the most exciting frontiers in astronomy. Since the universe was filled with neutral hydrogen at early times, the most promising method for observing the epoch of the first stars is using the prominent 21-cm spectral line of hydrogen. Current observational efforts are focused on a cosmic age of 500 million years, with earlier times considered much more challenging. We show that stars from a much earlier era may be observable as a result of a recently noticed effect of different motions of the dark matter and the ordinary matter in the early universe. We produce simulated maps of the first stars and show that these relative motions significantly enhance large-scale fluctuations and produce prominent structure on the scale of a degree in the 21-cm intensity distribution. The particular form expected for this structure should make it easier to confirm the existence of million solar-mass halos at early times.

The potential of Very Long Baseline Interferometry (VLBI) observations has increased steadily in recent years, to the point where it is now possible to accurately localise compact mJy objects - in 3D - at distances of 10 kpc. With current instrumentation, most of the known Galactic radio pulsar population is already accessible to precision mapping. I will present results from recent and ongoing VLBI programs showing how astrometric observations of both individual pulsars and pulsar ensembles can be used to provide information about stellar evolution, fundamental physics and the ISM. I will also examine how techniques which have until now been used in primarily in pulsar astrometry might give considerable benefits for other Galactic (and even extra-Galactic) targets.

We investigate whether lines of sight containing multiple cluster-scale halos are the best cosmic telescopes for lensing high-redshift (z~10) sources into detectability. For lines of sight of fixed angular size and total mass, we test how the lensing cross section and the number of faint galaxies detected at high redshift change as that mass is distributed among multiple halos, as well as which physical properties of the halos are most important. We find that multiple projected halos are can result in improvement in the detection of faint, high-z sources compared to single halos of equivalent total mass due to the interactions among the lensing potentials when the projected halos overlap. Using integrated LRG luminosity density as a tracer of mass, we have identified lines of sight in the SDSS that are likely to contain the largest total integrated masses. These fields contain a diversity of single massive clusters and chance alignments of multiple halos in projection, and are likely to be among the best gravitational lenses known. Our ongoing galaxy spectroscopy in the first of these fields reveals the presence of large total masses (> 3 x 10^15 M_sun) along the line of sight and multiple cluster-scale structures.

One of the most fundamental problems in theories of planet formation in protoplanetary disks is planetary migration that arises from resonant, tidal interactions between protoplanets and the natal disks. As shown by many previous studies, the interactions generally drain the angular momentum of planets so efficiently and jeopardize the existence of any planetary system around the central stars. In this talk, I will present all the key results of my PhD thesis work, wherein planet traps - specific sites in protoplanetary disks at which planets undergoing rapid type I migration are captured - are intensively investigated. We will discuss how disk inhomogeneities, one of the most general properties of planetary disks, give rise to planet traps and how planet traps affect the formation and evolution of planetary systems. Comparisons with a large number of observed exoplanets enable us to verify our picture of planet formation based on planet traps.