Gas accretion and star formation in disk galaxies
2016-09-13 11:45 - 12:45 (Europe/Rome) | Aula Gratton
Numerical simulations predict that metal-poor gas accretion from the cosmic web fuels the
formation of disk galaxies. My presentation will summarize observational evidence
for this gas accretion process driving star formation. In particular, I will discuss
a number of properties characterizing large samples of star-forming galaxies that
can be explained by metal-poor gas accretion (e.g., the fundamental metallicity relation,
or the relationship between galaxy morphology and metallicity). Some properties of the
(neutral and ionized) gas around galaxies will be examined too. I will also review the
properties of the extremely metal poor galaxies. They show chemical and dynamical
inhomogeneities that can be naturally explained as due to star-formation feeding from
infall of external metal-poor gas.

Indirect Dark Matter searches with the MAGIC telescopes and prospects with the ASTRI mini-array and the Cherenkov Telescope Array
2016-09-27 11:45 - 12:45 | Aula Gratton

Cosmic rays, gamma-rays, and neutrinos from AGN winds
2016-10-04 11:45 - 12:00 | Aula Gratton
Galaxy scale outflows driven by active galactic nuclei (AGN) are likely to play a key role in the evolution of galaxies. In fact, they can perturb and possibly expel most of the gas out of the galaxy, offering a plausible physical origin for the close connection between the properties of black holes and their host galaxies. AGN-driven outflows can also induce shocks in the interstellar medium, which, in turn, can accelerate relativistic particles.
I will present a study of the non-thermal emissions produced by relativistic particles accelerated by the AGN-driven shocks in NGC 1068. NGC 1068 is a nearby prototypical Seyfert 2 galaxy which shows both starburst and nuclear activities in its central region. NGC 1068 is a strong gamma-ray emitter. It is the brightest of the few non-blazar galaxies detected by the Fermi gamma-ray space telescope.
I will show the gamma-ray and radio spectra predicted by the AGN outflow model, and I will discuss how these results compare with those corresponding to other commonly assumed sources of gamma-ray and radio emissions, like Supernova remnants or AGN jets.
I will compare the neutrino flux expected in the AGN outflow model with constraints from current experiments, and I will provide predictions for the detections by the upcoming KM3NeT neutrino telescope.

Gamma-ray busrts as probes of high redshift galaxies and their environments
2016-10-11 11:45 - 12:45 | Aula Gratton
The launch of the Swift mission has revolutionised the study
of the Gamma-Ray Bursts, enabling the optical follow-up of the early afterglow.
Thanks to the fast broadcast of the GRB coordinates
and to the rapid response mode systems built up in 8-meter class
telescopes, these afterglows have be observed from hours down to a few
minutes after the GRB explosion. The high signal-to noise achievable
allows us to acquire medium-to-high resolution spectra, which carry a lot of
information both on the GRB environment and the Inter-Stellar Medium
of high redshift galaxies. I will give a short review of what we have
learned through the medium-to-high resolution spectroscopy of GRB afterglows,
mainly with UVES and X-shooter at the VLT.

Quasars and their host galaxies in the first Gyr of the Universe
2016-10-12 11:45 - 12:45 | Aula Gratton
Quasars are the brightest (non-transient) objects observed at the highest
redshifts, z>7. Such high redshift quasars are important for several
reasons. Firstly, detailed analysis of quasar spectra provide unique
information about the baryonic and physical condition of the Universe
during the epoch of reionisation. Furthermore, the density of high
redshift quasars puts powerful constraints on the mechanisms that are
required to seed and grow >10^9 Msun supermassive black holes less than a
Gyr after the Big Bang. Lastly, as these massive black holes are thought
to be located in the progenitors of the massive early type galaxies we see
in the local Universe, studying the host galaxies of the most distant
quasars enables us to probe the formation of massive galaxies in the early
Universe.
Because high redshift quasars are rare, multi-band surveys covering large
areas on the sky are required to discover such objects. In this talk I
will describe our successful programme aimed at discovering quasars at the
highest redshifts in various optical and near-infrared surveys, such as
Pan-STARRS1, UKIDSS and VIKING. I will highlight the results of our
search, which includes the discovery of more than 100 new quasars in the
first Gyr of the Universe. I will describe our on-going multi-wavelength
follow-up observations to characterise the distant quasars, their power
source and their environment, in particular our ALMA programmes to study
the galaxies hosting these luminous objects. I will present the results of
these observations, and discuss the implications for massive galaxy and
black hole formation at high redshift and our understanding of the
relation between the black hole mass and the bulge mass of galaxies.

Ascende superius - Seek higher things - Moving to higher order statistics in weak lensing
2016-10-18 11:45 - 12:45 | Aula Gratton
Weak lensing has emerged as one of the most promising tool to constrain
cosmological parameters and modified gravity theories by measuring second
order statistical probes such as the cosmic shear two points correlation
function and tomographic power spectra. Thanks to both the wide area and
large redshift range probed, future surveys will deliver such an exquisite
quality dataset that it is worth wondering whether one can move to higher
order statistics. We review here some interesting possibilities showing
that they can be recovered with sufficient precision from future data and
shed further light on the dark energy mystery.

Swinging between accretion and rotation power in binary millisecond pulsars
2016-10-25 11:45 - 12:45 | Aula Gratton
Neutron stars in low mass X-ray binaries are spun-up to millisecond spin periods during a Gyr-long phase of accretion of the matter transferred by a companion star. When the rate of mass transfer decreases at the end of this Gyr-long X-ray bright phase, a radio pulsar powered by the rotation of the neutron star magnetic field turns on. After decades of searches, the evolutionary link between these two classes of sources has been recently proven by the discovery of three sources that were observed to swing between accretion (X-ray bright) and rotation (radio bright) pulsar behaviour. These sources are the prototype of a new class of transitional systems that alternate between accretion and rotation-powered states in response to variations of the rate of mass in-flow, on time scales as short as a couple of weeks. Observations of this and other similar systems indicate that transitions to the accretion phase not only involve bright X-ray outbursts, but also a fainter intermediate X-ray state, possibly caused by centrifugal inhibition and ejection of the matter flow. Transitional ms pulsars are ideal test beds for theories describing the accretion-ejection coupling around a fast magnetized rotator, as well as the evolution of old binary systems. I will review the main observed properties, the prospects of catching more state transitions, and the possibilities to fully exploit the unique observable features of this newly established class.

AGILE highlights in gamma-ray astrophysics and the hunt for GW counterparts
2016-11-08 11:45 - 12:45 | Aula Gratton

Can supermassive black holes influence the evolution of galaxies?
2016-11-10 11:45 - 12:45 | Aula Gratton
Powerful winds driven by active galactic nuclei (AGN) are often invoked to play a fundamental role in the evolution of both supermassive black holes (SMBHs) and their host galaxies, quenching star formation and explaining the tight SMBH-galaxy relations. A strong support of this “quasar mode” feedback came from the recent X-ray observations of a mildly relativistic accretion disk winds in an ultraluminous infrared galaxies and their connection with a large-scale molecular outflows, providing a direct link between the SMBH and the gas out of which stars form. Spectroscopic observations, especially in the X-ray band, show that such accretion disk winds may be common in local AGN and quasars. However, their origin and characteristics are still not fully understood. Detailed theoretical models and simulations focused on radiation, magnetohydrodynamic (MHD) or a combination of these two processes to investigate the possible acceleration mechanisms and dynamics of these winds. Some of these models have been directly compared to X-ray spectra, providing important insights into the wind physics. Fundamental improvements on these studies will come from the unprecedented energy resolution and sensitivity of upcoming X-ray missions, such as Athena, and the synergy with future large facilities at other wavelengths, such as ALMA, E-ELT, SKA.

Extreme-Adaptive-Optics observations of protostellar jets
2016-11-15 11:45 - 12:45 | Aula Gratton
The ejection of matter in form of protostellar jets/outflows plays a fundamental role in the star-formation process as it is tightly connected to the mass accretion mechanism and is expected to directly affect the evolution of the circumstellar disk in which planet formation occurs. Since the typical angular scales of the jet-formation region are of the order of tens of mas for the closest star-forming regions, such region has so far remained unknown from an observational point of view. New instruments equipped with extreme Adaptive Optics systems offer now the opportunity to observe the jets as close as possible to the driving sources so as to gather crucial pieces of information on the ejection process and its connection to the disk.
In this context, I will present the first VLT/SPHERE observations jets from a young object. Using the ZIMPOL instrument we have taken optical images of the young binary Z CMa, which is composed by two eruptive variables: a Herbig star showing recurrent EXor-like outbursts and a FUor source, both driving a jet. The morphology of the two jets, which we trace down to ~70 mas, looks fairly different: the Herbig star appears to emit a poorly collimated compact flow, while the FU Ori drives a highly collimated precessing jet.
For the FUor jet, we discuss the mechanism responsible for the observed jet precession and we provide the first direct measurement of the mass ejection rate and of the ejection efficiency in a FUor source, which we can compare to the same quantities measured in other classes of young stellar objects.
Finally, I will give an overview of what we can expect for protostellar jet observations with other upcoming extreme-AO instruments, such as SHARK at LBT.

A hard X-ray view of non-local AGNs
2016-11-22 11:45 - 12:45 | Aula Gratton
The Cosmic X-ray Background (CXB) provides a record of cosmic accretion history
onto actively accreting supermassive black holes. The direct resolution of the
CXB into discrete sources can therefore provide a census of AGN populations
across cosmic time.
Population synthesis models are able to explain the CXB as mixture of AGN
populations with different luminosities and obscuration degree provided a
consistent population of heavily obscured AGN, called Compton Thick (CT),
expected to contribute significantly (20-30%) to the CXB peak at 20-30 keV, is
postulated. Unfortunately, several parameter degeneracies in the modelings at
energies > 10 keV result in an order of magnitude uncertainty in the estimation
of the fraction of CT AGN. Furthermore, the direct detection of these sources at
10 keV,
is capable of resolving a sizable part (>~ 30%) of the CXB at energies around
its peak of emissivity and of obtaining a direct and almost unobscured view of
obscured AGN up to z~3 therefore starting to address the main concerns in the
modelings of the CXB. In this regard I will report on the first spectral
characterization of these AGN populations, through broad-band (0.5-24 keV)
spectral analysis of a hard-band selected sample of AGN from the NuSTAR survey
program.

Storia della nascita e la sorte dei “telescopi Mussolini"
2016-11-24 11:45 - 12:45 | Aula Gratton
In May 1938, during the state visit to Italy Hitler asked Mussolini “to accept as a token of our reverence and friendship a Zeiss telescope and the complete equipment of an observatory”. This equipment included three big telescopes (a 26-inch refractor, a 1-m Schmidt refractor and a double astrograph) with three domes and auxiliary apparatus (a new-type transit instrument, a registering microphotometer, a comparator etc). All telescopes together with domes were going to be produced by Zeiss. It was decided to build the National Astronomical Observatory in Monte Porzio Catone for hosting the astronomical equipment. However, due to the WWII tragic events these plans were not fulfilled. Three domes for big telescopes (with necessary motors for rising floor and moving roof) were completed, moved to Italy and mounted. However, after 8 September, 1943 they were unmounted and moved back to Germany to the Zeiss factory. The domes and auxiliary instruments were distributed between German observatories. Three big telescopes were not paid by the German government and stayed in the Zeiss factory. They never came to Italy. In 1945 these telescopes were taken to the Soviet Union as war reparation. They were sent to Soviet observatories those most affected by the war.

Da Halley a Rosetta: esplorazione delle comete
2016-11-29 11:45 - 12:45 | Aula Gratton
Le analisi compositive dei nuclei cometari esplorati da vicino ( Halley/Giotto, Borrelly/DS1, Stardust/Wild-2, Tempel1/Deep Impact, soprattutto 67P-CG/Rosetta) hanno fornito informazioni decisive sull’origine delle comete, sul meccanismo della loro attività emissiva, sulla loro possibile fonte di molecole prebiologiche verso ambienti planetari abitabili.
Tutto questo è riassunto per la prima volta in un libro recentemente pubblicato da Hoepli (L’ ESPLORAZIONE DELLE COMETE, da Halley a Rosetta).

New channels of single and binary evolution and nucleosynthesis
2016-12-06 11:45 - 12:45 | Aula Gratton
In this talk I will present our new findings on an exotic group of evolved objects: post-asymptotic giant branch (post-AGB) and post-red giant branch (post-RGB) stars. These objects bear the signatures of the entire morphological and nucleosynthetic changes that occur during and prior to the red giant evolutionary phases. Therefore, they provide excellent constraints for single and binary star evolution and nucleosynthesis. These objects have also revealed new evolutionary channels and AGB nucleosynthesis which is vital for understanding the complex chemical evolution of our Galaxy as well as external galaxies.

Electromagnetic follow-up of gravitational wave candidates: perspectives and first results of the Italian project GRAWITA
2016-12-13 11:45 - 12:45 | RM
Detecting an electromagnetic (EM) emission associated with a gravitational wave (GW) signal is one of the main goal of the newly born gw astronomy. Merger of neutron stars and/or black holes and core-collapse of massive stars are expected to cause rapid transient EM signals like gamma-ray bursts (GRBs), core-collapse supernovae, soft-gamma ray repeaters and pulsar glitches.
The Advanced LIGO detectors on September 14th, for the first time, detected a binary black hole merger (GW150914) for which a detectable electromagnetic counterpart is little expected. This detection showed that EM follow-up facilities are able to react quickly to GW signals covering radio, optical, near-infrared, X-ray, and gamma-ray wavelengths with ground- and space-based over the entire gravitational sky localization even if they have to deal with large position uncertainties up to hundreds square degrees.
Therefore wide-field cameras and rapid follow-up observations are crucial to characterize the EM candidates and the first EM counterpart identification.
In this talk I want to present the activities we are currently currying on to optimize the response of the GRAWITA network of facilities to expected GW triggers and our first results. The GRAWITA project is representing an efficient operational framework capable of fast reaction on large error box triggers and direct identification and characterization of the candidates.
All the activities we will describe are expect to provide means and opportunities to the Italian and European astronomical communities to have a leading role in the GW astronomy and Time Domain Astronomy fields.
