By combining radio signals received at telescopes spread across the globe into an interferometer 10,000km in size, it is possible to make images with an angular resolution of ~10 nanoradians: sufficient to discern a human hair at a distance of 10 km. In order to produce these images, it is necessary to perform sophisticated digital signal processing on the sampled representation of the electric field sensed by the radio telescopes in the array. Historically, the high computational demands of this process led to the implementation of custom DSP hardware, but the ever-increasing power of commodity hardware has recently led to the widespread adoption of a more flexible, "software"-based processing system. I will describe the "DiFX" software correlator package that is now used for most high angular resolution radio imaging world-wide, and illustrate several of its applications from recent years, including the first ever image of the wreckage from the collision of two neutron stars, and the first ever image of the shadow of a black hole.

The first direct detection of gravitational waves (GW) opens the new era of gravitational wave astronomy. The strongly lensed GWs seen by 3G detectors accompanied by electromagnetic (EM) signals could be used to test modified theories of gravity, serve as a milestone in precision cosmology, and apply to studying dark matter distributions. I will introduce the event rate observed by 3G detectors as well as those applications of lensed GW-EM system to fundamental physics and cosmology.

FU Orionis-type stars (FUors) are young stellar objects experiencing large optical outbursts due to highly enhanced accretion from the circumstellar disk onto the star. FUors are often surrounded by massive envelopes, which have a significant role in the outburst mechanism. Conversely, the subsequent eruptions might gradually clear up the obscuring envelope material and drive the protostar on its way to become a disk-only T Tauri star; an evolutionary picture proposed more than a decade ago. In this talk I will review recent advances in this field mostly based on observational studies using data from the VLT, SMA, APEX, IRAM, and ALMA. These revealed very compact and bright central sources (indicating significant heating and very optically thick material in the center), a wide variety of envelope structures from tenuous to massive ones (confirming the evolutionary aspects), outflows more powerful than typical in normal protostars, and rich chemistry. These results also highlight the importance of combining data with different spatial resolutions to correctly sample the emission spanning several orders of magnitude in distance scale, from the inner disk at a few au, through the disk-envelope interface at a few hundred au, to the large-scale envelope and outflow cavity at several thousand au.

We apply Bayesian statistics to perform model selection on different reionisation scenarios via the Multinest algorithm. Initially, we recover the results shown by 21CMMC for the parameter estimation of 21cmFAST models. We proceed to test several toy models of the Epoch of Reionisation (EoR) defined in contrasting morphology and scale. We find that LOFAR observations are unlikely to allow model selection even with long integration times. HERA would require 61 dipoles to perform the same analysis in 1080 hours, and becomes comparable to the SKA with 217 dipoles. We find the SKA requires only 324 hours of observation to conclusively distinguish between our models. Once model selection is achievable, an analysis of observational priors is performed finding that neutral fraction checks at specific redshifts add little to no inference. We show the difficulties in model selection at the level of distinguishing fiducial parameters within a model or distinguishing galaxies with a constant versus power law mass-to-light ratio. Finally, we explore the use of the Savage-Dickey density ratio to show the redundancy of the parameter Rmfp within 21cmFAST.

The second observing run (O2) of the Advanced LIGO and Virgo detectors finished with the discovery of GW170817, the first binary neutron star merger detected in gravitational waves. The identification of the electromagnetic counterpart to GW170817 made possible multi-messenger studies that led to a plethora of new science.

The third LIGO/Virgo observing run (O3) started in April 2019 and has already returned several discoveries, including binary neutron star merger candidates and the first neutron star - black hole merger candidate. However, these initial months of operations have already shown that O3 presents new challenges for electromagnetic observers: detected mergers took place at distances larger than 115 Mpc and were coarsely localized over thousands of square degrees. I will discuss recent follow-up of neutron star mergers, focusing in particular on observations performed with the Dark Energy Camera and with the Zwicky Transient Facility, both led by the GROWTH collaboration. I will conclude the talk presenting some lessons that we have learnt so far, waiting for more surprises during the remainder of O3.

Radio pulsars are precise clocks that can be timed using a detailed model of the pulsar, its binary orbit, and the ionised interstellar medium along our line of sight. This timing model can be used to test theories of dense matter, gravity in the strong field, and a set of the most stable pulsars can even be used as a Galactic-scale gravitational wave detector. In this talk I will describe my work to improve the timing models of pulsars through precision pulsar timing and by modelling their scintillation. I will highlight recent results for the nearest and brightest millisecond pulsar PSR J0437-4715, which include precise new distance and mass measurements, and a relativistic binary PSR J1141-6545. Finally, I will describe how these techniques will be useful for next-generation instruments including the Parkes ultra-wideband receiver, and the impressive MeerKAT radio telescope in South Africa.

The measurement of the cosmic 21-cm signal with the SKA will transform our understanding of the epochs of reionization and cosmic dawn. The properties of the first stars and galaxies are encoded in the patterns of the signal. Interpreting these patterns requires accurate and efficient models. I will present an update of the 21cm FAST semi-numerical simulation, which separately accounts for star-formation inside the very first galaxies. This unseen and transient population of galaxies obtain their gas through molecular cooling from the intergalactic medium, and could have markedly different properties from the more massive galaxies observed with Hubble and eventually JWST. I demonstrate that if the recently-reported EDGES signal at z~17 is genuinely cosmological, these molecularly-cooled "mini-halo" galaxies must have played a dominant role during Cosmic Dawn.

The first half of my talk will be a brief introduction to the facilities that fall under the Caltech Optical Observatories umbrella, namely Palomar and Keck, including some of the new capabilities and instrumentation that are enabling for time-domain and exoplanet science. In the second half of my talk, I will describe the history and development of microwave kinetic inductance detectors, a type of superconducting detector that offers unique capabilities for astronomy and is now being deployed on telescopes.

Renee Spiewak's 33-36 month review.

I will describe the status, results and future of the SALT transient follow-up program, which began in 2016 and will continue until at least 2021. This multi-partner high priority programme is awarded ~300 ksec per semester, with a significant fraction (>50%) given for the highest priority target of opportunity time. The programme studies transients across a wide range of classes, currently including (from closest to most distant): cataclysmic variables; novae and other associated eruptive variables; low and high mass X-ray binaries; OGLE and Gaia transients, including tidal disruption and black hole microlensing events; super-luminous and unusual core-collapse supernovae; multi-messenger transients (gravitational wave and neutrino events); flaring blazars, AGN and GRBs. South Africa's support of LSST, through funding of PI Affiliate programmes, is described in context with the recent strategic decision to focus on key astronomy research areas, which includes transient astronomy. These plans include harnessing the many optical facilities at the SAAO into an "intelligent observatory", for automated source followup studies, which will also involve the ThunderKAT transient programme on the MeerKAT radio telescope. These coordinated facilities are also planned to form a cornerstone of the proposed BRICS flagship programme on transient astronomy, to be developed over the coming decade, harnessing both existing and future multi-wavelength facilities within the BRICS countries.

Student Review: Debatri Chattopadhyay - Mid-Candidature Review - Debatri Chattopadhyay
Host: Jarrod Hurley

Powerful relativistic jets are one of the main ways in which accreting black holes provide kinetic feedback to their surroundings. Jets launched from or redirected by the accretion flow that powers them are expected to be affected by the dynamics of the flow. Recent X-ray timing observations of accreting stellar-mass black holes have shown evidence for Lense-Thirring precession when the black hole spin axis is misaligned with the orbital plane of its companion star. While the interplay between the dynamics of the accretion flow and the launching of the jets is still unclear, theoretical simulations have suggested that the jets and a precessing accretion flow can be coupled by pressure or magnetic torques.

In this talk, I will present high-resolution, time-resolved radio imaging of the 2015 outburst of the black hole X-ray binary system V404 Cygni, showing that at the peak of the outburst the jet orientation was changing on timescales of minutes to hours. I will show that this can be modelled as the Lense-Thirring precession of a vertically extended slim disk that arises from the super-Eddington accretion rate. This scenario would suggest that the dynamics of the precessing inner accretion disk could play a role in either directly launching or redirecting the jets within the inner few hundred gravitational radii. I will discuss the implications of these results, and conclude by briefly considering the likely prevalence of such phenomena, and how this could be further explored via new imaging algorithms.

Study of reionization has now experiencing a surge of new insights, but the long-standing problem "what reionized the universe" still remains unsolved. Hubble observations have placed a now-commonly-held view that the intrinsically faint galaxies are responsible for driving the reionization process, but with a fundamental assumption of large escape fractions >10%. A further puzzle comes from the recent deep spectroscopy of luminous galaxies and the spatial opacity fluctuation of the intergalactic medium (IGM) at z>5.7, which suggests a possibly important role of luminous systems and active galactic nuclei/quasars (QSOs). In the theoretical front, simulating early galaxies and the reionization process and is extremely challenging, requring the understanding of the physics over a huge dynamic range from the scale of molecular clouds to the intergalactic medium. To shed light on theses issues, we introduce a new spectroscopic programme surveying 56 QSO fields and a power of direct 3D mapping of galaxies and the their environment, which will be enabled by JWST, ELT, and SKA

The University of Tokyo Atacama Observatory (TAO) Project is to
construct and operate a 6.5m infrared telescope at the summit of Co.
Chajnantor (altitude 5640m) in northern Chile by UTokyo. Thanks to the
dry climate and the high altitude, excellent observation condition in
the NIR to MIR wavelengths is verified with a pathfinder 1-m telescope
miniTAO. The 6.5m telescope has two Nasmyth foci where two facility
instruments, SWIMS for the near-infrared and MIMIZUKU for the mid-
infrared, will be installed and two folded- Cassegrain foci for carry-in
instruments. I will give project overview and the curren status of TAO
project, as well as key science topics.

As we progress into an era of increasingly large astronomy datasets, Science Platforms with both data storage and analysis tools are needed to take full advantage of data-intensive surveys. The NOAO Data Lab (datalab.noao.edu) is developing a suite of analysis tools for users to work close to the data, and thus optimize the scientific productivity of the astronomy community. We currently host datasets from NOAO facilities such as the Dark Energy Survey (DES), the DESI imaging Legacy Surveys (LS), the Dark Energy Camera Plane Survey (DECaPS), and the nearly all-sky NOAO Source Catalog (NSC). We also host complementary datasets including Gaia DR2 and All-WISE, and we are further preparing for large spectroscopic datasets like DESI. The Dark Energy Spectroscopic Instrument (DESI) had its first light recently, and will obtain spectra for 40 million galaxies and quasars over the course of the next 5 years. After an overview of the Data Lab and datasets, I will showcase scientific applications on topics covering extragalactic large-scale structures, star/galaxy separation, finding dwarf galaxies, and probing stellar populations in the Galactic Plane. Lastly, I will describe our vision for future developments as we tackle the next technical and scientific challenges, several of which are shared with other data centers and science platforms, and may be relevant to the ASTRO 3D programs.

TBA

The redshift 2 universe is one of the most interesting epochs of galaxy evolution. It is the era with the peak
of the cosmic star formation rate. Between redshift 3 and 1 the total stellar mass density in galaxies increased from
15% to 70%. It is also the time of rapid galaxy assembly and the epoch where galaxy morphology was determined.

Observations of z=2 star-forming galaxies reveal physical properties that are unparalleled in the z=0 Universe.
Gas-rich, extended, fast rotating and highly turbulent disks have been found with star formation rates that are a factor of 10 to 100
larger than in present-day Milky-Way type galaxies. Kpc-sized, massive gas clumps dominate the appearance of these galaxies. Even more interesting
are recent observations of declining rotation curves in the outer parts of these disks and dynamical masses, inferred from their rotation velocities
that are equal to the observed baryonic mass leaving no room for dark matter.

I will summarize the newest observations and the puzzles and challenges that they generate for our theoretical understanding of cosmic galaxy formation and galactic dynamics.

Most galaxies consist of a dispersion-dominated bulge region and a regularly rotating disk. These components have built up their mass separately through different processes, yet are evolving together. It has become commonplace to separate the light from bulge and disk regions to better understand their formation and contribution to their host galaxy. The same techniques can also be applied to IFS data of other galaxy components, such as bars and spiral arms. I will detail some of the latest results from the MaNGA galaxy survey, including efforts to study stellar populations in lenticular galaxies within bulge and disk regions, and an investigation into the influence of bars on the secular evolution of disk galaxies.

I will present the analysis of the resolved properties of a sample of highly magnified gravitational arcs. These are typical z~1 disc galaxies that are gravitationally lensed by massive galaxy clusters, which allows us to probe their properties at spatial scales of a few hundreds of parsecs. I will particularly focus on properties derived using MUSE IFU data: the kinematics and ionised gas turbulence of these galaxies, as well as their metallicity. We model both lensing and observational effects to study the intrinsic velocity dispersion and metallicity gradient of these objects. Surprisingly, despite their high turbulence and large star-forming regions, typical of z~1 galaxies, the kinematics and metallicity gradient of these objects is quite similar to what is found in local (mature) discs.

Aditya 33 month review.

Investigating the evolutionary paths of galaxies can reveal valuable information on the conditions of the early Universe, the build-up of the Cosmic Web, the formation of stars and much more. Smooth elliptical early-type galaxies (ETGs) are a "red and dead" population that make up the most massive and old galaxies in the Universe. Their detailed kinematics, revealed through 3D integral-field spectroscopy, has shifted our view of this seemingly homogenous population to a diverse and complex class of galaxy. An increasingly popular theory of ETG evolution shows they could have evolved through two distinct phases: a starburst and steady accretion of gas-poor galaxies. However, a wealth of observational evidence directly conflicts this theory for some ETGs, highlighting the importance of investigating a wider variety of systems through new methods. I will present research that leverages the current leading-edge integral-field instruments to investigate the evolution of ETGs. I look to distant quiescent galaxies in one of the densest regions of the early Universe and at the fossil record of a local galaxy to shed light on some of the unsolved mysteries of how ETGs evolved.

Nature Astronomy, launched in January 2017, is a new research journal published by Springer Nature. Sitting alongside our sister journal Nature, we aim to publish high impact research in the fields of astronomy, astrophysics and planetary science. In this talk I will cover the motivation and scope of the journal, the types of manuscripts we publish, the editorial process and what we look for in papers. I will also cover common pitfalls of writing and submitting papers and I will share hints and tips on how to maximize the impact of your paper, from writing an engaging but informative title and a properly contextualized but concise abstract, to structuring your paper in a way that your results are communicated succinctly.

Pulsars, rapidly-rotating and highly-magnetised neutron stars, can be utilised as tools in the study of many aspects of fundamental physical, most notably in the application of binary pulsars to the study of gravitational theories such as General Relativity. The discovery of ever-more relativistic binary systems than those presently known will allow for such tests to probe even deeper into the nature of gravity. Here, I will present results from the processing of 44% of the the HTRU-South Low Latitude pulsar survey (HTRU-S LowLat), the most sensitive blind survey of the southern Galactic plane taken to date. This includes the discovery and long-term timing of 40 new radio pulsars identified through the continued application of a novel “partially-coherent segmented acceleration search” technique, which was specifically designed to discover highly-relativistic binary systems. These pulsars display a range of scientifically-interesting behaviours including glitching, pulse-nulling and binary motion, and appear to comprise a population of generally older, lower-luminosity pulsars as compared to the previously-known population. In addition, I will also present an in-depth report on PSR J1757-1854, the only relativistic binary pulsar to have been discovered in HTRU-S LowLat to date. This extreme double neutron star system (which remains the most accelerated pulsar binary ever discovered) promises to provide new insights into gravitational theories within the coming years.

Gas accretion and galactic winds are the two most important and yet the most poorly understood ingredients of galaxy evolution models. The physical/chemical conditions of the circumgalactic medium (CGM-- a dynamic, complex, multiphase gas reservoir surrounding galaxies) retain imprints of gas accretion and galactic winds. Moreover, it is now well-established that the metal-enriched, ionized CGM harbors gas and metal masses comparable to those in galaxies themselves and can account for the "missing baryons" in galaxies. Consequently, the CGM has received significant attention from both the theoretical and observational astronomical communities. To this end, we are conducting two major, and by far the largest, surveys on the CGM using ~120 hours of MUSE GTO observations. Our high-z (z > 3) sample comprises ~100 Lyman alpha emitters and the low-z (z < 1) sample comprises ~300 low-mass, star-forming galaxies. We use high S/N spectra of background quasars, obtained with the VLT/UVES (for high-z) and HST/COS (for low-z), to study their CGM using absorption line spectroscopy. An overview of the initial main results of these surveys will be presented in the talk. In particular, the dependence of the CGM properties on the SFR, stellar mass, impact parameter, and on redshift will be discussed.

Recent years have seen enormous progress in studies of galaxies
in the first billion years of the universe, during the epoch of
reionization. I will discuss state-of-the-art observations with
HST, Spitzer, ALMA, and ground-based facilities, focusing on
how they are used to identify, spectroscopically confirm, and
characterize the earliest star-forming and quiescent galaxies.
I will discuss evidence for ubiquitous strong nebular emission lines,
and implications for stellar mass build up and reionization of the
intergalactic medium. Finally, I will describe preparations
expectations for next-generation facilities such as the James Webb
Space Telescope.

Our standard cosmological model predicts that most of the matter in the universe is distributed into a network of filaments - the Cosmic Web - in which galaxies form and evolve. Because most of this material is too diffuse to form stars, its direct imaging has remained elusive for several decades leaving fundamental questions about the structure of the universe still open, including: How are galaxies linked to each other? What are the morphological and physical properties of the Cosmic Web on both large and small scales? How do galaxies accrete gas from the Cosmic Web? In this talk, I will tackle these questions using the results of a new program to directly detect and study high-redshift cosmic gas in emission using bright quasars and galaxies as external "sources of illumination". In particular, I will show results from ultra-deep narrow-band imaging and integral-field-spectroscopy with both MUSE/VLT and the Keck Cosmic Web Imager (KCWI) that revealed numerous giant Lyman-alpha emitting filaments extending up to several hundred kpc around quasars and bright galaxies. I will discuss how the unexpectedly high luminosities of these systems, together with the constraints from Helium and metal extended emission, represent a challenge for our current understanding of cosmological structure formation. In particular, I will show that current observations suggest that intergalactic gas around high-redshift galaxies and quasars has a much broader density distribution of cold material than expected from cosmological simulations and I will present our first attempts to understand the origin and nature of these structures using high-resolution hydrodynamical models. At the same time, current galaxy formation models lack an efficient mechanism to prevent too much intergalactic gas cooling onto galaxies at later epochs and rely on very strong "ejective" feedback. In the final part of the talk (if time allows), I will show how the interaction between high-energy radiation from star-forming galaxies and the gas surrounding them provides a natural way to prevent "excessive" intergalactic gas cooling onto galaxies and I will discuss HST/COS observations that provide support for the importance of this effect.

One of the outstanding problems in galaxy evolution studies is to link
the evolution of the star formation rate of galaxies to their molecular
gas content. Observationally, the last decade of studies have led to a
clear picture of the cosmic star formation history, which peaked at z~2
and has declined since then. However, it is unclear whether the
declining star formation rates are simply the result of lower molecular
gas masses, or whether the star formation efficiency has also evolved.
In this talk, I will discuss how the molecular gas contents of galaxies
are measured and highlight the difficulties of doing so at high
redshift. I will describe one of the most popular approaches, which
relies upon the dust continuum emission, and will present our recent
work where we test the validity of the dust continuum calibration
via a unique sample of z~2 galaxies with observations of both dust
continuum and CO(1-0) line emission.

In recent years cosmological hydro-dynamical simulations of representative volumes have reached a level of maturity where they
can be compared effectively against observational data. They can also be used to shed some lights onto galaxy formation processes
and how they affect the distribution of baryonic and dark matter. Understanding these effects is a key element required to fully
unlock the science of the next generation cosmological probes such as the Euclid mission.
In this talk, I will review some results from the EAGLE set of cosmological simulations focusing on the aspects highlighted above. I
will then discuss the challenges that lay ahead in terms of simulation complexity and how we are tackling some of them using our
new modern and open-source simulation code SWIFT.

I will review our series of successful programs to dissect the interstellar medium of distant, star-forming galaxies with the Atacama Large Millimeter Array (ALMA). In particular, I will discuss surveys of the set of HI-selected galaxies known as the damped Lya systems (DLAs). We resolve, in part, a decades-old struggle to identify the galactic counterparts of these DLAs and thereby place them firmly in the modern picture of galaxy formation. I will also highlight high spectral and spatial resolution observations of the Wolfe Disk, a z~4 galaxy with a Milky Way-like rotation curve.