SHARK-VIS: the upcoming high-resolution high-contrast visible imager for LBT
2018-09-18 11:45 - 12:45 (Europe/Rome) | Aula Gratton
SHARK-VIS is the visual channel (400-1000 nm) of SHARK, the upcoming extreme-AO instrument for the LBT optimized for high-contrast observations. The project is led by the OAR AO group and the instrument is currently being built at OAR with the first light foreseen in 2019.
SHARK-VIS will provide LBT with unprecedented high-contrast and high-resolution imaging capabilities in the visible band, thanks to both several technical solutions, aimed at optimizing the PSF stability, and its “fast cadence imaging” approach, based on the use of a high-frame-rate low-noise camera exploited by specific custom algorithms. The instrument will produce diffraction-limit images with an angular resolution down to 15 mas and with frame rates up to 1kHz.
In the first part of the talk, instrument details, expected performances, and the project status will be discussed.
In the second part of the presentation, we will present a summary of the main scientific cases for which SHARK-VIS is expected to provide breakthrough results, also considering the simultaneous use of the SHARK-NIR companion instrument (built at OAPd) and LMIRCAM, which will turn LBT into a unique high-resolution facility with continuous wavelength coverage from 0.4 to 3.5 um. Main science cases include identification of accreting planets in star-forming regions, morphology of jets and disks in young stars, characterization of minor bodies of the Solar system, and investigation of the central regions of bright AGNs.

Four years of science with SPHERE/VLT
2018-10-02 11:45 - 12:45 | Aula Gratton
SPHERE/VLT is an extreme adaptive optics instrument designed to directly image exoplanets. It was designed and build by a European consortium (including laboratories from France, Italy, Germany, Switzerland and the Netherlands) from and saw its first light in 2014. Most of the guaranteed time observations (GTO) are related to exoplanets and young disk. I will briefly present some results from these programs. I will then focus on the “Other Science” part of the GTO, aiming at showing that SPHERE is a versatile instrument able to answer key question in a variety of topics. I will present the results obtained via this program, ranging from 3D mapping of asteroids to star clusters via jets from young stars and evolved stars, including the first direct image of the surface of stars.

The MESSIER surveyor: lifting the veil on the ultra low surface brightness universe
2018-10-09 11:45 - 12:45 | Aula Gratton
The MESSIER satellite has been designed to explore the extremely low surface brightness universe at UV and optical wavelengths. The two driving science cases target the mildly- and highly non-linear regimes of structure formation to test two key predictions of the LCDM scenario: (1) the detection of the putative large number of galaxy satellites, and (2) the identification of the filaments of the cosmic web. The science requirements imply challenging instrumentation issues which have only recently been solved. The satellite will drift scan the entire sky in 6 bands covering the 200-1000 nm wavelength range to reach the unprecedented surface brightness levels of 34 mag/arcsec^2 in the optical and 37 mag/arcsec^2 in the UV. As usual when uncovering new volumes in parameter space, many important secondary science cases will also result as free by-products and will be discussed in some detail: the actual luminosity function of galaxies, the contribution and role of intracluster light, the fluctuations of the cosmological background radiation at UV and optical wavelengths, the warm molecular hydrogen content of galaxies at z=0.25, time-domain studies of supernovae and tidal disruption events, the chemical enrichment of the interstellar medium through mass loss of red giant stars and the accurate measure of the BAO scale at z=0.7 with over 30 million galaxies detected in Lyman-alpha at this redshift. It will provide the first space-based reference UV-optical photometric catalogue of the entire sky, and synergies with GAIA, EUCLID and WFIRST will also be discussed.

Transient spiral arms and galaxy rotation curves
2018-10-16 11:45 - 12:45 | Aula Gratton
The complex spatial structure evident in spiral galaxies is understood either in terms of instabilities of quasi-stationary states, or a result of dissipative non-gravitational interactions. We illustrate here, using numerical simulations, that purely self-gravitating systems evolving from quite simple initial configurations can give rise easily to structures of this kind of which the lifetime can be large compared to the dynamical characteristic time, but short compared to the collisional relaxation time scale. More specifically, for a broad range of non-spherical and non-uniform rotating initial conditions, gravitational relaxation gives rise quite generically to long-lived non-stationary structures of a rich variety, characterized by spiral-like arms, bars and even ring-like structure in special cases. These structures are a feature of the intrinsically out-of-equilibrium nature of the system’s collapse, associated with a part of the system’s mass while the bulk is well virialized. They are characterized by predominantly radial motions in their outermost parts, but also incorporate an extended flattened region which rotates coherently about a well virialized core of triaxial shape with an approximately isotropic velocity dispersion. We briefly discuss the possible relevance of these simple toy models to the observed structure of real galaxies. On the one hand, we discuss the determination of the velocity fields of THINGS galaxies. On the other hand we consider recent observations in our Galaxy (APOGEE and GAIA) that show that the galactic disk seems not to be a time-independent axisymmetric system. We conclude by stressing that these simple models illustrate the possibility that the observed apparent motions of spiral galaxies might be explained by non-trivial non-stationary mass and velocity distributions without invoking a large amount of dark matter halo or a modification of Newtonian gravity.

What is the role of the environment in shaping early-type galaxy sizes? Has it changed in the last 10 Gyr?
2018-10-18 15:00 | Aula Gratton
Understanding galaxy evolution requires understanding the impact of cosmic time, environment, mass, and halo growth at least, because likely a combination of them leads to the quenching of star formation and the emergence of the galaxy populations we see in the nearby Universe. In the talk, I will present the picture coming out from two mass-selected samples of red-sequence early-type galaxies in the general field.

Highlights from the ESA Rosetta mission
2018-10-23 11:45 - 12:45
The Rosetta/Philae mission of the European Space Agency marked a turning point in cometary space exploration. Launched on March 2004, Rosetta needed 10 years of interplanetary journey to arrive around its main target, the comet 67P/Churyumov-Gerasimenko. Rosetta orbited around the comet for about two years, providing the unique opportunity to continuously investigate the 67P nucleus composition, activity, and its evolution during the orbit. For the first time in the history of the space exploration, Rosetta delivered a lander, Philae, on a cometary surface.
A large complement of scientiﬁc experiments designed to complete the most detailed study of a comet ever attempted are on board Rosetta, including cameras, spectrometers, radio science, dust and plasma analyser and so on. More than 80,000 images of the comet have been acquired with the OSIRIS imaging system with a spatial resolution ranging from several meters to a few centimeters per pixel. I will present the main scientific results of this extraordinary space mission on the structure, geomorphology, and surface composition of the comet, and their implications on the formation of our solar system.

Cepheid variables in the Gaia Data Release 2 and the extragalactic distance scale
2018-10-30 11:45 - 12:45
Classical Cepheids are the most important primary indicators for the extragalactic distance scale.
Establishing the precise zero points of their Period-Luminosity and Period-Wesenheit (PL/PW) relations
has profound consequences on the estimate of H0. Type II Cepheids are also important distance indicators and tracers of old stellar populations. The recent Data Release 2 (DR2) of the Gaia Spacecraft includes photometry and parallaxes for
thousands of classical and type II cepheids. Adopting a subsample of well studied objects, we use the Gaia parallaxes to derive new optical/Near Infra-Red PL/PW relations for the Galactic Cepheids. We use these information, coupled with proprietary data from the Vista Magellanic Cloud (VMC) survey, to discuss the zero point of the Gaia parallaxes and its impact on the extragalactic distance scale and the measurement of H0.

colloquium - Beate Stelzer
2018-11-06 11:45 - 12:45 | Aula Gratton

eROSITA: Stellar science with a new X-ray All-Sky Survey
2018-11-06 11:45 - 12:45 | Aula Gratton
Nearly 30 years after ROSAT, the german-russian mission eROSITA, planned for
launch in spring 2019, is going to perform a new X-ray All-Sky Survey.
The majority of sources that will be detected with eROSITA are
late-type stars. I present eROSITA science cases for pre-main sequence and
for hydrogen-burning stars based on current studies with other
X-ray instruments. New momentum is expected from eROSITA especially
for stellar population and variability studies. These comprise a wide range
of topics including studies of the dynamics of stellar coronae (through
flares and activity cycles), search for X-rays from accretion outbursts
in young stars, and the use of X-rays as diagnostics for
stellar angular momentum evolution and the structure of the galactic
stellar disk.

colloquium - Fabrizio Nicastro
2018-11-08 11:45 - 12:45 | Aula Gratton

Missing Baryons and the Warm-Hot Intergalactic Medium
2018-11-08 11:45 - 12:45 | Aula Gratton
It has been known for decades that the observed number of baryons in the local Universe falls about 30-40% short of the total number of baryons predicted by Big-Bang Nucleosynthesis, inferred by density fluctuations of the Cosmic Microwave Background and seen during the first 2-3 billion years of the universe (redshift z>2-3) in the so called “Lyman-α Forest”. While theory provides a reasonable solution to this paradox, by locating the missing baryons in hot and tenuous filamentary gas connecting galaxies, it also sanctions the difficulty of detecting them because their by far largest constituent, hydrogen, is mostly ionized and therefore virtually invisible in ordinary signal-to-noise Far-Ultraviolet spectra. Indeed, despite the large observational efforts, only a few marginal claims of detection have been made so far.Here I will first review the observational efforts pursued over the past 15 years by several groups and will then present our recent results that show that the missing baryons are indeed found in a tenuous warm-hot and moderately enriched medium that traces large concentrations of galaxies and permeates the space between and around them. The detection of these baryons is hampered by foreground ISM contamination, which is hard to correct for, due to our poor knowledge of inner-shell resonant transitions from metals in the X-ray band. Despite these intrinsic difficulties, I will show that the number of OVII systems detected down to the sensitivity threshold of our data, agrees well with numerical simulation predictions for the long-sought hot intergalactic medium, and its detection adds a fundamental tile to the long-standing missing baryon puzzle. Finally, I will comment on the implications of these new results for future high resolution X-ray missions.

colloquium - Svetlana Zhukovska
2018-11-12 11:45 - 12:45 | Aula Gratton

AGB stars and the cosmic dust cycle
2018-11-12 11:45 - 12:45 | Aula Gratton
Theoretical and observational studies of dust condensed in outflows from AGB stars have substantially advanced the understanding of the dust mixture from individual stars. This detailed information incorporated into models of the lifecycle of interstellar grains allows us to evaluate the contribution of AGB stellar populations to the galactic dust budget, their role in the dust production in galaxies of various morphological types. I will highlight some questions of galactic evolution that can be answered by these models in combination with modern infrared observations. I will also present models of dust evolution in an inhomogeneous, multi-phase ISM that shed light on the dust mass growth in clouds, an important dust formation mechanism in evolved galaxies.

colloquium - Fabrizio Arrigoni Battaia
2018-11-20 11:45 - 12:45 | Aula Gratton

Characterizing the circum/inter-galactic gas in emission around z~2-3 quasars
2018-11-20 11:45 - 12:45 | Aula Gratton
Recently, enormous (> 200 kpc) Lyman-alpha nebulae (ELAN) have been discovered around radio-quiet z~2-3 quasars. Being currently explained as powered by the ionizing radiation of quasars, these bright large-scale nebulosities suggest the possibility of studying the circum/inter-galactic gas in emission around individual systems on very large scales. Motivated by these discoveries, we have been conducting a statistical census of z~2-3 quasars using the narrow-band and IFU technique with the aim to determine the frequency of this phenomenon, as well as to study their size, luminosity, covering factor, and the gas physical properties.
In the first part of my talk I will present the results of the QSO MUSEUM survey
(Quasar Snapshot Observations with MUse: Searching for Extended Ultraviolet eMission), which comprises 61 z~3 quasars observed with the MUSE/VLT instrument.
In the second part of the talk I will then focus on one of these objects which suggests that
Lyman-alpha could be used to trace the inspiraling motions of the cool circum-galactic medium,
predicted to take place on hundreds of kpc within massive halos.
I will conclude by summarizing my on-going observational effort in characterizing the ELAN phenomenon, and large-scale gas structures around quasars.

Exploring the solar chromosphere with ground-based telescopes
2018-11-27 11:45 - 12:45 | Aula Gratton
The Sun’s atmosphere consists of the photosphere, chromosphere and corona. The solar chromosphere bridges the photosphere and the corona. This dynamic layer is filled with events that evolve in a fraction of time and are very small in spatial scales. We use the biggest solar telescopes to zoom into this layer in order to understand such dynamic events.

In the talk, we discuss detailed observations of two different events guided by high-resolution and high-cadence observations. The first topic covers a statistical study of long thin jets called “spicules.” Spicules wiggle and sway around to give an impression of waves propagating along them. These waves can travel with speeds of hundreds of kilometres per second, energising the solar chromosphere. The second topic is about swirling-whirling events that look like tornadoes. These churn matter from the lower photosphere to the chromosphere. Studying the behaviour of these events is vital in understanding a decade-long question in solar physics, that addresses the heating of the Sun’s atmosphere.
A future goal is to support such observation by performing Magnetohydrodynamic (MHD) simulations using LareXd, developed here at Centre for Fusion Space and Astrophysics (CFSA), University of Warwick. In the end, we would have a glimpse of what the future of ground-based observations holds. We will see the latest progress on next-generation solar telescope Daniel K. Inouye Solar Telescope (DKIST) and what we at CFSA, Warwick are expecting from it.

colloquium - Juie Shetye
2018-11-27 11:45 - 12:45 | Aula Gratton

Colloqium - Donatella Romano
2018-12-04 11:44 - 12:45 | Aula Gratton

The evolution of CNO isotope ratios: a litmus test for stellar IMF variations in galaxies across cosmic time
2018-12-04 11:45 - 12:45 | Aula Gratton
Determining the shape of the stellar initial mass function (IMF) and whether it is constant or varies in space and time is the Holy Grail of modern astrophysics, with profound implications for all theories of star and galaxy formation. On a theoretical ground, the extreme conditions for star formation (SF) encountered in the most powerful starbursts in the Universe are expected to favour the formation of massive stars. Direct methods of IMF determination, however, cannot probe such systems, because of the severe dust obscuration affecting their starlight. The next best option is to observe CNO bearing molecules in the interstellar medium at millimetre/submillimetre wavelengths, which, in principle, provides the best indirect evidence for IMF variations. In this talk, I discuss some recent findings on this issue. First, I reassess the roles of different types of stars in the production of CNO isotopes, by using a proprietary chemical evolution code and up-to-date Milky Way data from the literature. The model is then extended to discuss extragalactic data. I show that, though significant uncertainties still hamper our knowledge of the evolution of CNO isotopes in galaxies, compelling evidence for an IMF skewed towards high-mass stars can be found for galaxy-wide starbursts. In particular, I show the results for a sample of submillimetre galaxies observed by our team with the Atacama Large Millimetre Array at the peak of the SF activity of the Universe, for which we measure a ratio 13C/18O of about 1. This isotope ratio is especially sensitive to IMF variations, and little affected by observational uncertainties. At the end, ongoing and future developments of our work are briefly outlined.

Paolo Dal Pozzo Toscanelli, Cosimo de’ Medici and the Sky of the Magi: a new reading of the Florentine Celestial Hemispheres in the Sagrestia Vecchia at San Lorenzo and in the Pazzi Chapel at Santa Croce.
2018-12-06 11:45 - 12:45 | Aula Gratton
After 30 years since the historical pubblication of the analysis
conducted by Forti, Lapi Ballerini, Monsignori Fossi and Ranfagni (1987), I
offer a careful re-examination of the two famous florentine starry vaults of
the early Renaissance, taking into account the recent restoration of the
hemisphere of the Pazzi Chapel and the almost coeval maps drawn by Paolo
Dal Pozzo Toscanelli for his studies of comets in 1456 (Halley) and 1457.
The authorship by the Tuscan cosmographer is confirmed in the Sagrestia
Vecchia on the basis of a comparison between a sample of stars from the
dome, Toscanelli’s maps and Ptolemy’s Catalogue. The Pazzi Chapel instead,
reveals on close inspection to be a clumsy, derivative later work.
While the double date proposed in 1987, the enigmatic 4/5 july 1442, still
remains astronomically the most probable, I will show that the exactness of
the planetary positions have been overestimated, unfairly provoking a lack of
attention for other candidate dates, more astrologically meaningful if not
depicted with satisfying correctness. Relying indeed on the astrological
techniques and interests of the time, I propose to assess the 1442 and the
1439 most probable candidate horoscopes following the very appropriate line
of reasoning introduced by Dieter Blume (2000), i.e. considering the
congruence of the sky charts with principles and rules of astral divination as
well as with the political situation in Florence and with the cultural needs of
the clients.
Finally, I single out as most probable the second date (even exhibiting a
marginal evidence for it on the basis of Lorenzo de’ Medici’s calendarial
concerns), and I offer a new hypothetical explanation for this preference,
linking medicean interest in the magian narrative and the Star of Bethlehem,
astrological speculation and political propaganda.

colloquium - Marco Padovani
2018-12-11 11:45 - 12:45 | Aula Gratton

The role of cosmic rays on physical and chemical processes of the interstellar medium
2018-12-11 11:45 - 12:45 | Aula Gratton
The study of the interaction of cosmic rays with the interstellar matter is a multi-disciplinary investigation that involves the analysis of several physical and chemical processes: ionisation of atomic and molecular hydrogen, energy loss by elastic and inelastic collisions, energy deposition by primary and secondary electrons, gamma-ray production by pion decay, the production of light elements by spallation reactions, and much more. Cosmic-ray ionisation activates the rich chemistry of dense molecular clouds and determines the degree of coupling of the gas with the local magnetic field, which in turn controls the collapse timescale and the star-formation efficiency of a molecular cloud. In recent years a wealth of observations from the ground and from space has provided information and constraints that still need to be incorporated in a consistent global theoretical framework. My goal is to use the results of chemical models and state-of-the-art numerical simulations supplemented by dedicated observations to provide a unifying interpretation of the data with a model of cosmic-ray propagation specifically developed to make predictions that can be tested against the observations. Finally, I will talk about my most recent study: a mechanism able to accelerate local thermal particles in protostars that can be used to explain the high ionisation rate as well as the synchrotron emission observed towards protostellar sources.

colloquium - Gioia Rau
2018-12-18 11:45 - 12:45 | Aula Gratton
