The Galactic halo is thought to form, at least in part, from the accretion of dark-matter dominated mini-halos. These mini-halos are also responsible for donating the so-called CEMP-no stars to the halo, which are thought to be bona-fide second-generation stars. A recent study has suggested the existence of multiple pathways to form CEMP-no stars, based on the distinct morphological stellar distribution present in the A(C)-[Fe/H] space. In this talk, I will briefly review our current understanding of the chemodynamical nature of the CEMP-no stars and its implication on the nature of the first stars. I also present important evidence regarding Galactic assembly history revealed by the similarity of CEMP-no group morphology present among the metal-poor stars in satellite dwarf galaxies.
I will present key results from the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM), a high resolution survey of molecular gas in galaxy nuclei. First, I will show that CO can be used to easily and accurately measure the mass of the supermassive black holes lurking at galaxy centres. I will discuss substantial ongoing efforts to do this, and present many spectacular new ALMA measurements, the latest of which rival the best black hole measurements to date. This opens the way to literally hundreds of measurements across the Hubble sequence (in both active and non-active galaxies) with a unique method. Second, I will briefly show how the same data allow to study the spatially-resolved properties of the giant molecular clouds in all the galaxies studied. This will yield cloud censuses in non-local galaxies (including early-type galaxies) for the first time, providing a new tool to understand and contrast the star formation efficiency across galaxies. Already, it appears that basic cloud properties are not universal and vary systematically along the Hubble sequence, contrary to long-held assumptions.
The appearance of the first stars and galaxies at the cosmic dawn represents a transformational yet unexplored episode of the Universe's history. I will present the measurement of an absorption feature in the sky-averaged radio spectrum centered at 78 MHz by the EDGES Low-Band experiment. This feature is broadly consistent with the absorption of photons from the microwave background by neutral hydrogen gas in the intergalactic medium at z~17 due to significant star formation about 180 million years after the Big Bang. If independently verified, this measurement could correspond to the signature of the cosmic dawn. However, the large amplitude and sharp profile of the measured feature are in tension with standard physical models. In my talk I will describe the EDGES Low-Band measurement of the radio spectrum over the range 50-100 MHz, which was conducted from the desert of Western Australia, as well as some of the proposed physical implications if the signal is confirmed to be of cosmological origin.
Ultrahigh intensity lasers have been developed for the exploration of strong field physics in a number of institutes around the world. At Center for Relativistic Laser Science of Institute for Basic Science two PW laser beamlines have been utilized for investigating relativistic laser- matter interactions, and one of them has been upgraded recently to a 20 fs, 4 PW laser . With the PW lasers we succeeded in generating multi-GeV electron beams and collisionless electrostatic shock. We plan to carry out the Compton backscattering to generate MeV gamma- rays from the interaction of a GeV electron beam and another laser beam, offering an opportunity to measure strong field QED effects. In addition, we plan to carry out the investigation of laboratory astrophysics, such as plasma instabilities, shock acceleration, and magnetic reconnection.
 J. H. Sung et al., “4.2 PW, 20 fs Ti:Sapphire Laser at 0.1 Hz,” Opt. Lett. 42, 2058 (2017).
Adaptive optics is a powerful method to study big (D > 100 km) asteroids. In particular, the VLT/SPHERE instrument with ZIMPOL imaging polarimeter offers a diffraction-limited image, with an angular resolution of 20 mas, albeit with a complex and variable point-spread function (PSF), reaching the Strehl ratio 0.095 (in V). Moreover, a myopic deconvolution with a stellar PSF and additional priors is used to improve the resolution further. The pixel scale 3.6 mas corresponds to 3 km to at the distance of 1 au. Consequently, we obtain not only the overall shape, absolute size, and volume, but also surface topography and craters counts (D_c > 30 km).
With the goal to resolve several tens of big asteroids, this represents an important observational constraint for the main asteroid belt, its overall collisional evolution, and also for individual asteroid families, because families--craters identifications are now possible. We demonstrate this for the asteroid (89) Julia and its family (Vernazza etal. 2018). A 70-km crater (called Nonza) was identified on the AO images, with the help of lightcurve inversion, occultations, and shape reconstruction. A series of hydrodynamical/collisional/orbital models was then used to compare the excavated volume, the ejected volume, the largest fragment and the SFD of family members. The dynamical age of the Julia family is from 10 to 120 Myr. Additional asteroids with (or without) families are under investigation.
One of the most important problems of astrochemistry is to understand how, when and where complex organic and potentially prebiotic molecules are formed - and what is the link between the rich chemistry observed toward some star-forming regions and the emerging Solar System. From an observational point of view, ALMA is revolutionizing the field with its high sensitivity for faint lines, high spectral resolution limiting line confusion, and high angular resolution making it possible to study the structure of young protostars down to scales of their emerging protoplanetary disks.
In this talk, I will present some of the results from a large ALMA survey of the low-mass protostellar binary and astrochemical template source, IRAS 16293-2422. The program, "Protostellar Interferometric Line Survey (PILS)", is more than an order of magnitude more sensitive than previous surveys of chemical complexity and provide images of the inner 25 AU of the gas around each of the young stars. The high sensitivity and spectral resolution of ALMA has allowed us to detect a wealth of species for the first time toward solar-type protostars as well as the ISM in general - for example, molecules of importance for prebiotic chemistry such as peptide-bond containing species and simple sugars. Also, the data show the presence of numerous rare isotopologues of complex organic molecules and other species: the exact measurements of the abundances of these isotopologues shed new light onto the formation of such complex species and provide a chemical link between the embedded protostellar stages and our own Solar System including the composition of comets. Finally, I will discuss some of the issues encountered dealing with these complex datasets with spectra reaching the confusion limit and providing new challenges for laboratory spectroscopy.
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.
Cosmology enjoyed a remarkable development over the last century. Astronomical observations revealed that galaxies like our own are not distributed at random throughout space, but rather delineate a quite remarkable structure, reminiscent of the skeletal framework of a sponge. How could that be? We now have developed a compelling picture of how these galaxies and their distribution developed over time, under the influence of gravity. We trace their origin to the earliest moment of the Universe. Most effective in achieving the current understanding has been the study of the sky background light called the Cosmic Microwave Background. This light, which is invisible to the naked eye but easily measurable with modern sensors, travelled uninterrupted for 13.8 billion years throughout the Universe. It last interacted with the material content of the Universe when the universe was very much hotter, denser, and homogeneous than it is now. It thus bears witness to the prevailing physical conditions back then and shades light on the process which generated the primordial seeds out of which structures grew. As a result, recent observations bring amazing confirmation of ideas put forward in the 80's and open a window on physics in a range of scales, time and energies which was hitherto inaccessible. I will describe how we came to the arresting conclusion that we are the children of quantum fluctuations of the vacuum!
Studying the star forming activity around type 1 Active Galactic Nuclei (AGN) has proven difficult due to the bright nucleus of AGNs outshines the classical starburst indicators, especially at optical and near-infrared spectral range. The mid-infrared IRS/Spitzer spectrum of several Palomar Green Quasi Stellar Objects (QSOs) have revealed the presence of Polycyclic Aromatic Hydrocarbons (PAHs) features in the nuclear spectrum, suggesting that starburst are present in most QSOs at kpc scales (~3 -21 kpc) from the nucleus. We use the high angular resolution spectrum at N-band (~7.5-12 um) obtained with 10.4m Gran Telescopio CANARIAS to study the inner (< 1 kpc) star formation activity in a sample of local (z < 0.1) and MIR-bright (f_N > 0.02 Jy) QSOs. We measure the PAH at 11.3 um and calculate the inner star formation rate (SFR) at scales of few hundred pc (~300-1000 pc). The PAH is clearly detected in the 38 per cent of the sample, while an upper limit is reported for the rest. Using the same PAH and technique we measure the SFR at scales of few kpc using the IRS/Spitzer spectrum of objects in our sample. Comparing the inner and larger (Spitzer) aperture SFRs we conclude that star formation activity in QSOs is mostly concentrated within ~1 kpc. Finally, we find that our estimation of the SFR at scale of ~1kpc correlate with the black hole accretion rate as predicted by merger galaxy simulations at similar scales.
Understanding the temporal and spectral variations in X-ray binaries is extremely important in order to explore the various processes in accretion disk i.e. production of soft X-ray and hard X-rays, Comptonizing region, reflection component, origin of jet, ejection mechanisms etc.. These sources show astounding variability on a time scale of microsecond to days in a broad spectral domain of 0.1 - 200 keV and any profound knowledge of these phenomenon can potentially be invoked to understand the spectro-temporal activity in AGNs. I will discuss various statistical methods and procedures often used to study X-ray binaries in order to probe the X-ray emitting region/regions in accretion disk, considered to be occurring close to the compact object. I will discuss, how the magnitude of cross correlation function, autocorrelation function, power density spectrum and Fourier time lags between soft and hard X-ray shall constrain the Comptonization region in X-ray binaries, whose geometry is still a matter of debate. I will briefly elaborate on few primary results unveiled by Astrosat and RXTE connected to the X-ray binaries. I will show a ongoing study using RXTE and Nustar data of a neutron star source GX 17+2 emitting close to the Eddington luminosity and constrain the X-ray production mechanism.
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 cosmic web is the large-scale metric in which galaxies form and evolve. Evidences of the role of the cosmic web in driving some galaxy properties have been measured from simulations and at low redshift from spectroscopic surveys. They support a picture in which the geometry of the large-scale environment drives anisotropic tides which impact the dynamics and, at a second order, the assembly history of galaxies. But extracting the cosmic web from observed datasets is still a challenge, in particular at high redshift where large and complete spectroscopic surveys are extremely costly. At these redshifts, though, we expect a stronger dependency of galaxy properties on the geometry of the accretion, which makes this extraction pivotal to understand galaxy evolution.
I will give an overview of the current status of cosmic web analysis from high redshift observations, either photometric data or lyman-alpha forest surveys. While relying on a pilot study in COSMOS and forecasts from the simulated horizon-AGN lightcone, I will present results about the evolution of galaxies within both cosmic web filaments and nodes, and I will show how this study can be extended with future probes including LSST, Euclid, PFS and MOSAIC on the ELT.
Ultra Metal-Poor (UMP) stars, with heavy metal abundances less than 1/10,000th that of the Sun, are formed from gas clouds polluted by the very first (Population III) stars to be born after the Big-Bang. These Pop. III stars are thought to be massive and short-lived, ending their lives in explosive events such as supernova type II. By studying the detailed chemical abundance patterns of UMP stars, it is possible to infer the main characteristics of their Pop. III progenitors, such as frequency, mass distribution, and explosion energies. In this talk, I will present a Monte Carlo approach to finding suitable stellar progenitors for UMP stars, based on the discovery of a new UMP star in the Galactic Halo. Results suggest that at least two types of progenitors are needed at the lowest metallicities, to account for the observed chemical abundances of UMP stars in the Milky Way. These results place important constraints on the initial mass function at early times, as well as models of the chemical evolution of the Galaxy and the Universe. I will also discuss the importance of a new observing effort, called J-PLUS (Javalambre Photometric Local Universe Survey), in selecting low-metallicity and carbon-enhanced stars, using narrow-band photometry and machine learning techniques.
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.