The interaction of gas rich galaxies via mergers or close encounters can give rise to sudden, violent star formation (SF), often accompanied by the presence of an active galactic nucleus AGN. The merger gives rise to a system whose energy is mostly emitted in the IR with a luminosity above 10E11 L_sun. These dusty environments are the scenery of supernova explosions at a high rate as well as of super-massive black hole (SMBH) growth, thus representing excellent laboratories to study the evolution of galaxies. However, such activity in the innermost nuclear regions (<500pc) remains hidden at most wavelengths, including optical, due to the high concentration of dust and gas, and a direct view is only possible using high resolution observations not strongly affected by extinction, such as near-IR and radio. In this talk I will present exciting observations of a “baby” AGN and a tidal disruption event revealed with very long baseline interferometry.
While there have been frequent discoveries of supernovae, our knowledge of their progenitor stars is still limited. A number of candidate progenitor stars have been directly detected in pre-explosion archival images, but such cases are rare and further confirmations on the disappearance of the candidate stars are needed. Alternatively, studying the local environments of supernovae may provide independent clues on their progenitors. As the progenitor must have been born within a stellar population, the properties of the parent stellar population, such as age and metallicity, can be used to constrain the progenitors of supernovae of different types. Such statistical study of supernova environments have been carried out to derive physical properties of the progenitors and disentangle different paths leading to the distinct supernova types. With the recent advent of integral field spectroscopy, which enables the collection of both spectral and spatial information of the supernova site simultaneously, supernova environment study is advancing in an unprecedented way. In this presentation I will also introduce an ongoing survey of nearby supernova host galaxies using the MUSE integral field spectrograph at the VLT.
The standard model of cosmology, while observationally well supported, remains fundamentally mysterious. In this talk I will discuss some proposed alternative models for dark matter and dark energy, as well as previous and on-going work to investigate the process of structure formation in these models.
Galaxy evolution is driven by a complex combination of internal (nature) and external (nurture) processes. Gas stripping due to ram pressure arises as a galaxy falls into the dense intracluster medium of a galaxy cluster, and is among the most violent environmental experiences a galaxy can have. The most spectacular examples of ram-pressure stripping in action are the so-called "jellyfish galaxies", which display extended tails of optically bright stripped material. I will review several theoretical and observational studies that aim to characterize the effect of gas stripping in galaxy evolution, including the latest results of the large MUSE program GASP, dedicated to studying jellyfish galaxies. Finally, I will, present the recent discovery of a previously unknown connection between ram-pressure stripping and nuclear black hole activity.
Over the last decade, deep studies of nearby galaxies have led to the discovery of vast stellar envelopes that are often rich in substructure. These components are naturally predicted in models of hierarchical galaxy assembly, and their observed properties place important constraints on the amount, nature, and history of satellite accretion. One of the most effective ways of mapping the peripheral regions of galaxies is through resolved star studies. Using wide-field cameras equipped to 8 m class telescopes, it has recently become possible to extend these studies to systems beyond the Local Group. Located at a distance of 3.6 Mpc, M81 is a prime target for wide-field mapping of its resolved stellar content.
In this talk, we present the detailed results from our deep wide-field imaging survey of the M81 group with the Hyper Suprime-Cam (HSC), on the Subaru Telescope. We report on the analysis of the structures, stellar populations, and metallicities of old dwarf galaxies NGC3077, IKN, KDG061, KDG064, BK5N, d0955+70, d1015+69, d1014+68, and d1005+68 as well as young stellar systems around M81, such as Arp’s Loop, Holmberg IX, BK3N, NW-stream, Garland, M82-arc, SE-blob, and S-blob. Several candidates for yet- undiscovered faint dwarf galaxies in the M81 group will also be introduced. The peculiar galaxies NGC3077 has been classified as the irregular galaxy. Okamoto et al. (2015, ApJ 809, L1) discovered an extended halo structure with S-shape elongated tails, obvious feature of tidal interaction. With a help of numerical simulation by Penarrubia et al. (2009, ApJ 698, 222), we will demonstrate that this tidal feature was formed during the latest close encounters between M81, M82, and NGC 3077 which induced star formation in tidally stripped gas far from the main bodies of galaxies. It is not clear whether the latest tidal interaction was the first close encounters of M81, M82 and NGC3077. If NGC3077 is still surrounded by the dark matter halo, it implies that the tidal interaction occurred for the first time in the M81 group. Kinematic studies of inter galactic globular clusters and planetary nebulae would tell us the past history of tidal interaction in this group of galaxies.
The properties of unseen first galaxies in our Universe are encoded in the 3D structure of the cosmic 21-cm signal. Here I introduce a flexible parametrization for high-z galaxies’ properties, including their star formation rates, ionizing escape fraction and their evolution with the mass of the host dark matter halos. With this parametrization, I self-consistently calculate the corresponding 21-cm signal during reionization and the cosmic dawn. Using a Monte Carlo Markov Chain sampler of 3D simulations, 21CMMC, I demonstrate how combining high-z luminosity functions with a mock 21-cm signal improve the parameter recovery. In our model, the turn-over magnitude on high-z luminosity functions can be constrained using the 21-cm signal.
Mount Kent Observatory at the University of Southern Queensland is host to Australia's newest astronomical research facilities. MINERVA-Australis is the only Southern hemisphere precise radial velocity facility wholly dedicated to follow-up of thousands of planets to be identified by NASA's Transiting Exoplanet Survey satellite (TESS). Mass measurements of these planets are critically necessary to maximise the scientific impact of the TESS mission, to understand the composition of exoplanets and the transition between rocky and gaseous worlds. MINERVA-Australis is now operational. I present first-light results and give an update on the status of the project, which will ultimately host six 0.7m telescopes feeding a stabilised spectrograph.
The Stellar Observations Network Group (SONG) is establishing a node at Mount Kent. SONG-Australia will complete the global longitude coverage, delivering breakthroughs in fundamental understanding of the interiors of stars for decades to come. SONG-Australia is designed on a "MINERVA" model, whereby fibres from multiple small telescopes feed a single high-resolution spectrograph. This approach provides expandability and reduces cost by using factory-built components that have been well-tested by the MINERVA teams. As a result of these innovations, SONG-Australia is expected to be fully operational by late 2019.
During the first part of my talk, I will briefly present the first Data Release (DR1) of the SkyMapper Southern Survey. The DR1 covers approximately 20,000 square degrees from the Shallow Survey component, complete to roughly 18 mag in all six SkyMapper filters (uvgriz). This database contains over 2.1 billion photometric measurements for about 285 million unique astrophysical objects, which will serve as the calibration source for upcoming Main Survey component (Data Release 2). The second part of my talk will focus on the SkyMapper follow-up program to search for optical counterparts of gravitational wave (GW) events and fast radio bursts (FRB) found by advanced LIGO/Virgo and Australian-based radio facilities, respectively. The identification of electromagnetic counterpart is essential for improving our current observational interpretation of their astrophysical nature. I will discuss lessons from recent case studies but also introduce our strategy for preparing efficient multi-messenger observations in our next observing run.
One of the biggest challenges in modern cosmology is to understand the first generation of stars and galaxies that formed during the cosmic Dark Ages. Since they reside in the observationally unexplored territory, we need to predict the properties of the first galaxies by pushing numerical simulations to new levels of physical realism and detail. In this talk, I will present the results of our highly-resolved cosmological ab-initio simulations to understand the assembly process of first galaxies under the feedback from the first generation of stars, the so-called Population III. Also, I will illustrate how first galaxies can be connected with their local descendants in terms of chemical abundances in the local ultra-faint dwarf galaxies.
The recent discoveries of gravitational waves from the advanced LIGO have already been critical cosmological resources. Here, I will present cosmological implications of gravitational wave detection, and show how current and future gravitational observatories can advance our knowledge on the nature of dark matter and dark energy.