In recent times modern cosmology has witnessed a natural progression: Starting from observations of the homogeneous expansion dynamics with supernovae of type Ia and linear perturbations in the CMB the field is now focussing on studying linearly evolving structures in the distribution of galaxies.
A natural next step is cosmology with nonlinearly evolving structures, making up a large fraction of the signal in optical surveys.
In this talk I will present a new approach to studying the non-linear evolution of cosmic structures in observations via large scale Bayesian methods. This new technology infers 3D initial conditions from which observed structures originate, maps out non-linear density and velocity fields, and provides dynamic structure formation histories including a detailed treatment of uncertainties. Data application provides an unprecedented view on the dynamical evolution of structures surrounding us. This will be exemplified by highly detailed dynamical reconstructions of the Coma cluster and Sloan Great Wall but more generally of the entire large scale structure in the Nearby Universe.
The interstellar medium is heated and ionized by radiation, by stellar winds, and finally, by supernova explosions of massive stars. These processes are often correlated in space and time, generating superbubbles filled with hot thin plasma with sizes of typically 100 âˆ’1000 pc. Supernova remnants and superbubbles can be studied best in softX-ray line and continuum emission, since the plasma in their interiors is very hot (10 6 - 10 7 K), while there are also a few cases in which the emission from non-thermal particles dominates that of the thermal gas. I will talk about our studies of the hot interstellar medium in theMilky Way and nearby galaxies. I will discuss the physics of the hot plasma, the evolution and energetics of supernova remnants and superbubbles, and their impact on star formation.
The discovery of the first extra-solar planet around a main-sequence star in 1995 has changed the way we think about the Universe: our solar system is not unique. Twenty years later, we know that planetary systems are ubiquitous, orbit stars spanning a wide range in mass, and form in an astonishing variety of architectures. Yet, one fascinating aspect of planetary systems has received relatively little attention so far: their ultimate fate.
Most planet hosts will eventually evolve into white dwarfs,Earth-sized stellar embers, and the outer parts of their planetary systems (in the solar system, Mars and beyond) can survive largely intact for billions of years. Studying these systems provides detailed measurements of the bulk composition of rocky exo-planetesimals, the efficiency of planet formation around stars with ~1-8 solar masses,and insight into the architecture of the outer planetary systems around the white dwarf progenitors.
On 17th Aug 2017, a strong source of gravitational waves was detected by theLIGO-Virgo collaboration. The signal lasted for 60 secs and the event was followed just 2 seconds later by a short burst of gamma-rays detected by Fermi and Integral.All sources had consistent sky positions within about 30 square degrees. A fast fading optical and near-infrared counterpart was discovered and studied intensively for several weeks.
I will present the results of this unprecedented discovery, the first electromagnetic counterpart of a gravitational wave source, the first identification of a neutron star - neutron star merger and the first direct evidence of the source and origin of the r-process elements.
I will focus on the ePESSTO team's results, showing that this remarkable transient truly opens up the era of multi-messenger astronomy.
We have evidence that heavy elements are synthesized and dispersed in cosmic explosions of various types, though the role and contribution of different physical events in forming heavy elements is still unclear. Rapid localization of cosmic explosions now enables us to conduct detailed studies that illuminate thesequestions.
I will present some examples including in particular near-real time spectroscopic observations, that I expect to lead to revolutionize these fields in the coming decade.
The last two decades since the discovery of the first extrasolar planet have completely revolutionised what we know about planets. In particular, the unprecedented spatial resolution of the millimetre interferometer ALMA has provided us with high resolution images of protoplanetary discs -- the birth environments of planets. These are more detailed images than ever before and are giving us clues about the planet formation processes.
Recent ground-breaking observations are hinting towards planets starting to form when protoplanetary discs are young and massive -- so called self-gravitating discs. In contrast to the standard paradigm for planet formation, these results may now have pushed the likely era of planet formation into the early self-gravitating stage of disc evolution, potentially making this brief phase in a disc’s lifetime more critical for planet formation than previously thought. One such observation is the Elias 2-27 protoplanetary disc which exhibits strong spiral structures out to approximately 250au. Through the results of recent numerical simulations, I will discuss whether Elias 2-27 could be the first observation of a self-gravitating disc. I will also discuss some evolutionary processes that planets and discs go through once planets form in such young discs.
The frequencies of oscillations observed on a stellar surface carry information about the properties of the stellar interior. Asteroseismology, i.e., the unravelling of this information, has made a huge leap thanks to the photometric observations obtained with NASA' Kepler mission, launched in 2009 to search for planets around other stars. In my talk I focus on the study of red-giant stars, showing a broad range of oscillations, probing both the outer parts and the deep core of the stars. Amongst other remarkable results, this has allowed distinguishing stars according to their nuclear energy source and provided detailed information about the properties of internal rotation in these late stages of stellar evolution.
The Dark Energy Survey has combined analyses of galaxy clustering andweak gravitational lensing two-point correlation functions in itsfirst year (Y1) of observations. This combination of measurementsprovides information on the amplitude of density fluctuations(S8=0.794+0.029-0.027) and the dark energy equation of state(w=-0.80+0.20-0.22) that is competitive and consistent with Planck CMBdata. When joint with probes of cosmic geometry, it yields the bestmeasurement of these parameters to date. I will review these resultsand the technical advances that facilitated them. In addition, I willalso present a novel probe that provides a DES lensing view of thefull PDF of the matter density field.
The Panchromatic Hubble Andromeda Treasury is an HST multicycle program to image the north east quadrant of M31 to deep limits in the UV, optical, and near-IR. The HST imaging has resolved the galaxy into over 150 million stars (comparable to ~1/2 the number of stars in SDSS), all with common distances and foreground extinctions. As its legacy, this survey adds M31 to the Milky Way and Magellanic Clouds as a fundamental calibrator of stellar evolution and star-formation processes for understanding the stellar populations of distant galaxies. I will briefly describe the survey strategy, data reduction, and key data products. I will then highlight new work using the NIR stellar populations to constrain the large scale properties of the cold ISM, with 25 pc resolution. These new maps offer the highest resolution available inM31, and point to surprising challenges facing models of dust emission.
Time domain studies have revolutionized stellar astrophysics. In particular, planet transit studies have proven to be extremely effective at detecting oscillations in luminous red giant stars. When combined with spectroscopy, this permits extremely precise distances, masses and ages for populations that sample a significant fraction of the Milky Way galaxy. I will review the current state of the art in asteroseismology, focusing on the joint APOGEE-Kepler (APOKASC) sample of almost 7,000 evolved stars with high resolution spectra, masses and ages. I will also discuss using asteroseismic samples as age calibrators for high resolution surveys in general and will argue that the combination of asteroseismology and the Gaia mission will be extremely fruitful. I'll close with some results on surprising populations in the Galaxy uncovered by seismic data and tests of stellar models and isochrones.
Gravitational lensing has become a versatile tool to probe the mass distribution in the Universe. In this talk, I will start by following the chronological order to discuss the emergence of gravitational lensing as powerful modern cosmological tool that has nowadays branched in many sub-areas. Gravitational lensing in 2017 is a central piece of all ongoing and future wide field surveys (KiDS, DES, LSST, Euclid). Within this exciting new era, I will discuss the expected outcome of the current and future lensing studies, what can be learned from it and in combination with other wavelength surveys.
Massive elliptical galaxies exhibit the most massive black holes,
most extreme stellar initial mass functions, and most dramatic
size evolution over cosmic time. Yet, their complex formation
histories remain obscure. I will describe the ongoing MASSIVE
Survey, a volume-limited, multi-wavelength, spectroscopic and
photometric survey of the structure and dynamics of the 100 most
massive early-type galaxies within 100 Mpc. A combination of
integral-field spectroscopy on sub-arcsecond and large scales
enables us to perform simultaneous dynamical modeling of the
supermassive black holes, stars, and dark matter. I will also
highlight properties of other mass components -- cold, warm, and
hot gas -- from our multi-wavelength datasets. I will discuss
the implications of these galaxies for ongoing black hole studies
such as the Event Horizon Telescope and the pulsar timing array
experiments searching for gravitational radiation.
We have completed large and complete ALMA surveys of the disks around young stellar objects in two star-forming regions, Lupus and sigma Orionis. The data reveal dust structure and gas masses and the samples are large enough to reveal correlations with stellar mass. By comparing the two regions, we follow the evolution of the dust and gas content from ~1 to ~4 Myr, the period when giant planets are expected to form.
The discovery of the first extra-solar planet around a main-sequence
star in 1995 has changed the way we think about the Universe: our
solar system is not unique. Twenty years later, we know that planetary
systems are ubiquitous, orbit stars spanning a wide range in mass, and
form in an astonishing variety of architectures. Yet, one fascinating
aspect of planetary systems has received relatively little attention
so far: their ultimate fate.
Most planet hosts will eventually evolve into white dwarfs,
Earth-sized stellar embers, and the outer parts of their planetary
systems (in the solar system, Mars and beyond) can survive largely
intact for billions of years. Scattered and tidally disrupted
planetesimals are directly observed via transits in a single system,
discs of dusty debris are detected around a few dozen white
dwarfs. However, the most powerful probe for detecting evolved
planetary systems is metal pollution of the otherwise pristine H/He
High-resolution optical and ultraviolet spectroscopy of these stars
provides a unique window into the bulk abundances of
exo-planetesimals, analogous to the way we use of meteorites to
determine the composition of the solar-system. The derived abundances
unambiguously demonstrate that the disrupted planetary bodies were
rocky in nature, with strong evidence for a significant water content
in some cases. These results provide critically important input into
the models of planet formation.
Over the last 20 years we have understood the role that stellar mass has in
regulating the star formation history of galaxies, at least over the redshift
range 0 < z < 2. Here I present an analysis of the star formation histories of
some 75,000 galaxies in the redshift range 0.5 < z < 1.3 from the VIMOS Public
Extragalactic Redshift Survey (VIPERS), and primarily of the very high mass
objects observed in that survey,
that shows how other parameters play an equally important role in shaping the
overall evolution of galaxies, and their transition from the blue cloud to the
Deep extragalactic surveys at optical and infrared wavelengths have allowed us to estimate the stellar content and star-formation activity for millions of galaxies across cosmic time. By comparison, the gaseous phase which fuels galaxy growth has been studied for a far smaller number of galaxies. The last decade has, however, seen steady progress in this field as a consequence of new observational techniques and upgraded/new observatories like IRAM/NOEMA, ALMA and Herschel. I will review how, from rapidly growing samples of galaxies with measurements of the gas content, a consensus is beginning to emerge on the link between the amount of gas and other galaxy properties like star formation rate, stellar mass, and ultimately the position of galaxies in the cosmic dark-matter web. This improved understanding of galaxy scaling relations (in particular those observed by galaxies on the main sequence of star-forming galaxies) has allowed us to produce estimates of the overall baryon budget of the universe out to at least redshift z~3. I will also describe current efforts to establish the gas content of two less well understood populations of galaxies - starburst galaxies and passive/quenched galaxies - and discuss how a robust characterization of the gas in these systems is key to identifying how they have formed and evolved.
Thanks to the revolutionary capabilities of the Hubble Space Telescope we have
made enormous progress in our exploration of galaxies across cosmic history
over the last two decades. Hubble allowed us to push the observational
frontier back to z~10-11, only ~400 Myr after the Big Bang. To date, we have
identified ~1000 likely galaxies at z>6, with up to 20 credible candidates at
z~9-11, one of which is even spectroscopically confirmed at z~11. These
unprecedented samples allow us to directly track the build-up of galaxies in
the heart of the cosmic reionization epoch, providing an increasingly more
complete picture. For instance, in combination with deep data from the Spitzer
Space Telescope we can now even probe the evolution of the stellar mass
density over 97% of cosmic history. In this talk I will provide an overview of
recent observational progress coming from very deep HST and Spitzer/IRAC
observations as well as from ground-based imaging and spectroscopy to study
the first generations of galaxies, and I will highlight the exciting
possibilities that are just ahead of us based on several major upcoming and
The formation of the central regions of disk galaxies that we call galactic bulges remains a debated topic in modern galaxy evolution.
In this respect, the bulge of the Milky Way offers a unique opportunity to investigate in detail the role that different processes (secular evolution, dynamical instabilities, hierarchical merging, dissipational collapse etc..) may have played in the Galaxy formation and evolution. Indeed, it is only in the bulge of the Milky Way that all stars can be individually resolved, allowing to correlate the global structural properties of the bulge with the characteristics of its stellar population, such as age, chemical content, and kinematics. However, this advantage comes with the need of covering a large area on sky (~500 sqdeg). In this respect, large observation programmes and surveys are now providing a global view of the bulge stellar population properties that can be used to constraint formation and evolution models.
I will review our current understanding of the three-dimensional structure, chemical composition, age and kinematics of the bulge as obtained from recent photometric (e.g. VVV/X, OGLE) and spectroscopic (e.g. ARGOS, GIBS, Gaia-ESO, APOGEE-N) surveys.
In this talk I will describe some early results from the Toronto/Yale/Harvard Dragonfly Telephoto Array (a.k.a. Dragonfly), a robotic imaging system optimized for the detection of extended ultra low surface brightness structures. Dragonfly's wide-field low surface brightness imaging performance makes it capable of directly imaging low surface brightness structures (such as galactic streams, galaxy stellar halos and faint dwarf galaxies) about 10x fainter than is possible with conventional telescopes. With its latest upgrade to 48 lenses, Dragonfly has become the world's largest all-refracting telescope. In this talk I'll describe how Dragonfly works and show some early results, mainly focusing on the properties of ultra-faint stellar halos, enormous stellar disks, and a new class of ghostlike ultra-diffuse galaxies, some of which are as big as the Milky Way but have about 1/100 of its stellar mass. I will also report on our plans to upgrade the array order to map out directly gaseous structures in the intergalactic medium, thereby tracing out the Cosmic Web, the large-scale network of dark matter filaments that is believed to connect galaxies to each other, and which is thought to be the largest coherent structure in the Universe.
Weak gravitational lensing is a unique technique to map the distribution of dark matter in the universe. It is also a sensitive probe of large scale structures in the universe and cosmological parameters. I will first briefly describe the principles of weak lensing. I will then review the current observational status of this field, highlighting several new measurements especially from the ongoing Dark Energy Survey (DES). I will then discuss the status of tensions between cosmological probes and results for a new integrated approach to combine them.
Observations of celestial objects are inherently a 2D mapping on the
sphere but astrophysical studies usually require the knowledge of 3D
positions. For most extragalactic sources, this estimation relies on
photometric redshifts which require strong assumptions and can lead to
catastrophic failures. In this talk I will show how it is possible to
use clustering measurements to infer redshifts for any type of
extragalactic sources. I will show how to turn this idea into a new
tool for redshift estimation and show how accurate it is. I will then
present applications of this "clustering-redshift" technique using
various datasets at UV, optical, IR and radio wavelengths, and will
show a number of surprises.
In this talk I will review the state-of-the-art work on exoplanet characterization, mainly focusing on ground-based techniques. I will discuss what we do now, can do in the near future with instruments like CRIRES+, and later with the European Extremely Large Telescope. Detailed knowledge of the chemical composition and climate of Earth-like planets such as Proxima b and the seven TRAPPIST sisters are within reach.
The MUSE Hubble Deep Field Survey is deepest spectroscopic survey ever performed over the entire Ultra Deep Field (UDF) area. It provides ~1700 spectroscopic redshifts, an order of magnitude more compared to the data that has been accumulated on the UDF over the past decade, up to AB 30 in magnitude and 6.7 in redshift. The depth and high quality of the data enables new and detailed studies of the physical properties of the galaxy population and their environments over a large redshift range. In this talk I will show in advance of publication a number of important results achieved by the survey on a diversity of topics: investigation of bias in photometric redshift, spatially resolved stellar kinematics at z~1, properties of CIII emitters, FeII emission in stellar forming galaxies, Lya luminosity function and its impact for reiniozation, Lya extreme EW objects undetected in UDF, Lya extended halos, evolution of the galaxy major merger rate with redshift, etc.
ALMA has been producing stunning images and results for stars across
the mass and evolutionary ranges. In this talk, I will focus on some results
for Asymptotic Giant Branch Stars (AGB), Planetary Nebulae, Red
Supergiants (RSG) and Supernovae. An area of particular interest is the
shaping process by which AGB stars evolve to form often highly axisymmetric
Planetary Nebulae - what are the roles of binarity and magnetic fields? As
well as the mechanisms by which some of the stars are losing large amounts
of mass (10-7 to 10-4 Msun/yr) to the interstellar medium. Finally I will
discuss how ALMA long baseline and high frequency data are starting to
help answer some of the long-standing questions in stellar evolution.
The 10-meter South Pole Telescope (SPT) is a millimeter wavelength telescope designed to conduct sensitive measurements of the cosmic microwave background (CMB) at arc-minute resolution. The SPT has successfully conducted a 2500 square degree survey to find clusters of galaxies from their distortion of the CMB, known as the Sunyaev-Zel'dovich (SZ) effect. The surface brightness of the SZ effect is redshift independent which allows an SZ survey to provide a nearly mass limited cluster sample out to the earliest epochs of cluster formation. The SPT has identified ~700 of cluster candidates. Of these, ~500 have been optically confirmed, with the majority being newly discovered clusters at z > 0.5. I will summarize the main results from the SPT cluster survey, including cosmological constraints from their measurement of the growth of structure.
Supernova 1987A will turn 30 years old on the 23rd of February. It remains the first naked eye supernova in the last 4 centuries and has provided us with a wealth of data and insights into the evolution and death of massive stars. The talk will present an episodic trip through the early observations tying them into the understanding that in many cases was developed many years later. The current state of the supernova which is well on the way to becoming a supernova remnant will be discussed alongside the latest observations from Herschel, HST, VLT, ALMA and ATCA.
Next generation probes of the galaxy distribution and the microwave background sky will be treasure troves of cosmological information. How do we exploit them to address the enduring puzzles of the physics of the beginning, gravitational clustering, and the accelerating expansion? Progress depends crucially on the ability to connect theory and data through statistical modelling. I will present recent methodological breakthroughs to overcome the challenges inherent in physics-based principled analysis of large cosmological data sets: 1) efficient full forward statistical models of large scale structure data; 2) new ways of parsimonious modelling of systematics while respecting the physical structure underlying the signal; 3) new iterative techniques for fast solution of inverse problems; and 4) the ability to develop robust and informative cosmological observables based on underdense environments, ie cosmic voids.
After more than 12 years the Rosetta spacecraft crash-landed on comet Churyumov-Gerasimenko on September 30, 2016. It has traveled billions of kilometers, just to study a black, small (4 km diameter) boulder named 67P/Churyumov-Gerasimenko. The results of this mission now seem to fully justify the time and money spent in the last decades on this endeavor. In the talk I will look back on the craziest mission ever flown by the European Space Agency and point out its scientific highlights and its technical challenges. I will show how the results of this mission change our understanding about the formation of the solar system, the Earth and finally life itself.
One of the biggest challenges to understanding how galaxies work is decoding the role of the central supermassive black hole. Without feedback from the black hole (?AGN feedback?), galaxy evolution models fail to produce realistic massive galaxies and galaxy clusters. Somehow, accretion of matter onto the central black hole of a massive galaxy is tuned so that it regulates radiative cooling and the condensation of gas in a volume of space many orders of magnitude larger than the zone of gravitational influence around a black hole. The effects of these black holes is most easily seen in the observations of the most massive galaxies in the universe, the central galaxies of galaxy clusters. Strong observational evidence now indicates the activity of the AGN is closely coupled to the thermodynamic state of the circumgalactic medium, where most of a galaxy?s baryons reside. I will discuss how this relationship could arise and how a feedback mechanism that maintains the circumgalactic medium in a marginally unstable state can regulate star formation within galaxies.
Gaia mission is underway conducting its nominal 5-year survey of the sky. The first Gaia data release (Gaia DR1) took place 14 September 2016. Exploitation is at full speed with preprints appearing on a regular basis. At the moment two and half years of routine phase has been completed and preparations for the second data release (Gaia DR2) are in full swing. In the presentation the status of the mission is outlined with a short explanation of some operational aspects and their impact on the mission. A selection of early results from Gaia DR1 is presented. With a few examples extracted from the early mission data the further potential of Gaia is demonstrated. An outline of the contents for Gaia DR2 is provided.
In the last century our observations of the Universe have revealed deep mysteries that remain challenging enigma for our understanding of fundamental physics. What is Dark Matter that embraces the visible structures in the Cosmos? What is the putative Dark Energy that accelerates the expansion of the Universe?
In my presentation, I will in the first part, present new high precision measurements on the Dark Matter mapping of massive galaxy clusters using the Hubble Frontier Fields observations. These and future similar observations may ultimately help us uncover physical properties of the Dark Matter.
In the second part, I will present extended-BOSS the current Sloan spectroscopic surveys as well as other projects that will help us constrain in particular the nature of Dark Energy and the mass of neutrinos.
Finally, I will present recent technology developments of high-density fiber positioner systems for the coming and future generation of wide field spectroscopic surveys that are planned to significantly improve in precision cosmological measurements.