Osservatorio Astrofisico di Arcetri

AstroBigné seminars

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The Astrobigné Organizing Committee is currently composed of Crescenzo Tortora (Questo indirizzo email è protetto dagli spambots. È necessario abilitare JavaScript per vederlo. , reference person for the extragalactic group), Laura Inno (Questo indirizzo email è protetto dagli spambots. È necessario abilitare JavaScript per vederlo. , for the planets and star formation group, solar physics area), and Alessio Turchi (Questo indirizzo email è protetto dagli spambots. È necessario abilitare JavaScript per vederlo. , for the technological area), supported by our director Maria Sofia Randich and by the invaluable help of Emanuela Masini with the "real" stuff.

Next Astrobigné

Tuesday 09 July 2019 - 11:45 Aula A

Armando Riccardi and Giovanni Cresci

The ERIS instrument for VLT

ERIS, the Enhanced Resolution Imager and Spectrograph, is a 1-5 μm instrument for the Cassegrain focus of the UT4/VLT. The instrument is the enhanced replacement of SINFONI/SPIFFI and NAOS/CONICA, providing  SPIFFIER, a refurbishment of the J-H-K Integral Field Spectrograph of SINFONI, and a brand new 1-5um imaging camera (NIX) with coronagraphic capability. Both science instruments are served by a single-conjugate high- resolution adaptive optics module, developed by INAF-Arcetri, with two main operational modes: a Natural Guide Star (NGS) mode for high contrast observations and a Laser Guide Star (LGS) mode for large sky-coverage operations. The talk briefly reports the status of the project, currently in AIV phase, the performance of the Adaptive Optics System, the observational modes of the science instruments and the science drivers. INAF provided a  large effort on the ERIS project, receiving 60 nights of GTO. Because the First Light of ERIS is currently foreseen on summer 2020, a prompt effort for the italian science community organising the reserved observational time is  needed.


The Astrobigné concept

Astrobigné is a series of short seminars that are held at the Osservatorio, with the goal of interconnecting the community of people working here, spreading new ideas and results, creating and reinforcing synergies between groups and indiduals. As such, Astrobigne's are meant to be accessible to a broad audience, including astronomers and technology staff, from senior researchers to students. Not by chance, the name "bigné" was chosen to designate something delicious, attractive, quick to grasp and easy to "eat".

In practice, the astrobigne talks:

  • must be short (10 minutes plus 5 for open discussion, strict, 6-8 slides at most)
  • must present only 1-2 key points that people can assimilate quickly
  • should be aimed at triggering later discussions, collaboration, and future activities.
  • at this aim, can also present ongoing work with intermediate results
  • can cover a broad range of topics, including astronomy, technology, historic research, public outreach, organization etc...
  • will NEVER present a general overview of the subject and a complete account of the speaker's work
  • are given in English whenever possible (this is not because we don't love Italian, but we all understand that English is our professional language to be used to foster international collaborations. Not to mention that there usually are non-Italians in the audience).

Astrobigne's take place on Tuesdays, every two weeks in the main auditorium of OAArcetri (Aula A). We usually have two bigne'-talks (10+5minutes each), selected by the organizing committee in order to cover as many different areas of interest as possible. Before the talks, at 11:45, we normally meet in Aula A to socialize and eat real bigne's (pastries!). The talks start at noon, but everybody is strongly advised to come by 11:45 so not to miss the... beginning of the talks!


Past Astrobigné


Season 2018-2019


Tuesday 25 June 2019 - 11:45 Aula A

Virginia Bresci (Alte Energie)

Effects of reacceleration and source grammage on secondary cosmic rays

The ratio between secondary and primary cosmic rays (CRs) is the most important observable source of information. Primary cosmic rays are thought to be accelerated mainly in Supernova Remnant shocks and then released in the interstellar medium where secondary particles can be created by occasional collisions with interstellar matter. As a result, the ratio between the fluxes of secondary and primary particles carries information about the amount of matter CRs have encountered and is expected to monotonically decrease with energy roughly as the inverse of the diffusion coefficient.Recent measurements by AMS-02 revealed some deviations from this behavior: the B/C ratio flattens above some energy and the antiproton over proton fraction is almost constant. These anomalies might be explained by taking into account two effects: firstly, some fraction of secondary particles can be produced within the acceleration region, and hence undergo acceleration immediately after birth, and secondly, there is a non-negligible probability that secondary particles encounter an accelerator (and are reaccelerated) during propagation. Accounting for both effects allows us to well-reproduce both the fluxes of the best measured nuclei and the secondary-to-primary ratios mentioned above.


Germano Sacco (Star Formation)

CSI: a new INAF unit to support optical and infrared spectroscopy

Recent scientific and technological progresses drove a rapid increase of the complexity of observational programs in the field of both Galactic and Extragalactic spectroscopy. Current and ongoing spectroscopic surveys will  observe samples composed of more 10^6 objects, integral field spectrographs produce large data cubes and instrument for for studying exoplanets combine spectroscopy with techniquesfor high contrast imaging. These changes provides several opportunities but also challenges. In particular, the analysis and the interpretation of spectroscopic data is not carried out by small groups of astronomers based in the same institutes, but by large teams distributed over may institutes and composed not only of astronomers but also of statisticians and computer scientists.For this reason the INAF division for Optical and Infrared astronomy (UTG-I) has started the constitution of a new INAF unit to support observational projects in the field of optical and infrared astronomy. A workshop to discuss the goals and the organisation of this unit was held in Rome two weeks ago. In this short talk I will summarise the outcome of this workshop and future steps towards the constitution of this unit.


Tuesday 28 May 2019 

Antonella Gasperini

The role of Italian astronomers in the IAU from the foundation to the Second World War  

Even though Italy officially joined the IAU in 1921, Italian astronomers were involved in its birth as early as 1919, when Annibale Riccò Director of the Astrophysical Observatory of Catania, proposed to the IAU Committee to hold its first General Assembly in Rome. This contribution will analyze the role played by Italian astronomers in the development of the IAU from its foundation to the Second World War. The recent project of reordering of the astronomical historical archives in Italy permits for the first time a more in-depth study of the relations between Italian astronomers and the international scientific community. I will show some precious documents preserved in the historical archive of the Arcetri Observatory.


Tuesday 30 April 2019 - 11:45 Aula A

Milena Valentini (Visiting, Extragalactic, from Sissa)

The distribution of metals in simulated disc galaxies

I will discuss the scenario of chemical evolution that emerges from the distribution of metals in simulated disc galaxies, by analyzing predictions from a suite of cosmological simulations with initial conditions of a Milky Way-sized halo. I investigate the metal content of gas and stars, and explore how the variation of the essential elements contributing to define the model of chemical evolution (e.g. the initial mass function) determines final metal abundance trends.
I will also introduce a new methodology to generate synthetic stars from star particles. This technique takes properties of star particles from simulations as input and allows to obtain a catalogue of mock stars, provided with photometric properties. The goal of this method is to translate the populations of star particles of a simulation into stellar populations, thereby enabling a direct and accurate comparison with observations. This technique will be of paramount importance with ongoing survey data releases (e.g. GAIA and surveys of resolved stellar populations).


Marco Padovani (Post-Doc, Star formation group)

Synchrotron emission in molecular cloud cores: the SKA view

Understanding the role of magnetic fields in star-forming regions is of fundamental importance. In the near future, the exceptional sensitivity of the Square Kilometre Array (SKA) will offer a unique opportunity to evaluate the magnetic field strength in molecular clouds and cloud cores through synchrotron emission observations. The most recent Voyager 1 data, together with Galactic syn- chrotron emission and Alpha Magnetic Spectrometer data, constrain the flux of interstellar cosmic-ray electrons between about 3 MeV and 832 GeV, in particular in the energy range relevant for synchrotron emission in molecular cloud cores at SKA frequencies. Synchrotron radiation is entirely due to primary cosmic-ray electrons, the relativistic flux of secondary leptons being completely negligible. We explore the capability of SKA in detecting synchrotron emission in two starless molecular cloud cores in the southern hemisphere, B68 and FeSt 1-457, and we find that it will be possible to reach signal-to-noise ratios of the order of 2-23 at the lowest frequencies observable by SKA (60-218 MHz) with one hour of integration.

 Tuesday 19 March 2019 - 11:45 Aula A

Amali Vaz (Visiting, LBT)

Observing with the LBT Interferometer

LBTI is the instrument that uses LBT to its full potential, combining light from both primary mirrors and exploiting the correction of both adaptive secondaries in parallel. While historically a PI instrument, it is now starting to be offered to the astronomy community. In my talk I will briefly describe LBTI, its operating modes and give examples of past results made possible by the high resolution of the virtual 24-meters aperture and double AO correction. I will also give a few pointers on how to apply for it in order to better exploit its unique capabilities.


Antonio Garufi (Post-Doc, Star formation group)

From planet-forming disks to protoplanetary disks (back in time)

Increasing evidence suggest that most of the giant planet formation occurs early in the circumstellar disk evolution. I summarize our understanding of the role of forming planets in sculpting the recurrently observed disk sub-structures and show our current work on the imaging of earlier sources from both VLT/SPHERE and ALMA. Our ultimate goal is a better depiction of the morphology of protoplanetary disks from less than 1 Myr after the stellar formation to the late stages of disk dissipation 5-10 Myr later.

Tuesday 05 March 2019 - 11:45 Aula A

Anna Brucalassi (postdoc, Stellar populations & Infrared Astronomy )

Search for giant planets in M67: excess of Hot-Jupiters.

We have carried out a search for massive planets around main-sequence and evolved stars in the open cluster M67 using precise radial velocity measurements. In my talk I will present our stars sample, the science motivations of our research and the different detections in our survey. Our results show how in contrast with early reports and in agreement with recent findings massive planets around stars of open clusters are as frequent as those around field stars. Interesting, we found that the rate of Hot Jupiters (HJs) in the cluster (~5.7% for single stars and ~4.5% for the full sample) is substantially higher than in the field. High metallicity is not a cause for the excess of HJs in M67, nor can the excess be attributed to high stellar masses. When combining this rate with the non-zero eccentricity of the orbits, our findings are qualitatively consistent with a HJ formation scenario dominated by strong encounters with other stars or binary companions and subsequent planet-planet scattering, as predicted by N-body simulations.


Linda Podio (Researcher, Star Formation)

Organic molecules in planet-forming disks

A key open question in astrochemistry is how chemical complexity builds up along the formation process of Sun-like stars from prestellar cores to protoplanetary disks and ultimately to planets. A big step ahead is now possible thanks to the ALMA interferometer which allows us to unveil the disks chemical content at unprecedented resolution and sensitivity. I will show the first detections and resolved images of organic molecules in planet-forming disks and I will discuss how these are revolutionising our comprehension of the inheritance and formation of volatile organics in disks.

Tuesday 19 February 2019 - 11:45 Aula A

Lauren Shatz (Visiting, AO)

Optimization of a Pyramid Wavefront Sensor for Extreme Adaptive Optics

Within the next decade, the world will see a new generation of telescopes with diameters up to 40m, called the Extremely Large Telescopes [ELTs]. One of the most exciting promises of ELTs is the detection and characterization of exoplanets. Astronomers have developed adaptive optics (AO) systems which uses a wavefront sensor united with a deformable mirror to compensate in real time the effects of atmospheric turbulence on image quality. Extreme adaptive optics (exAO) systems in combination with state-of-the-art coronagraphs take these corrections to a new level to provide the contrast and resolution needed to see these faint, small objects. To optimize a high contrast pyramid wavefront sensor for a ELT exAO system, we are developing the theoretical framework of a three-sided pyramid wavefront sensor (3PWFS). I present current results comparing the characterization of a 3PWFS through end-to-end simulations and through the use of a Spatial Light Modulator (SLM) as a pyramidal optic on the LOOPS adaptive optics testbench at the Laboratoire d’Astrophysique de Marseille.


Ang Liu (PhD, extragalactic group)

Testing the rotation versus merger scenario in the galaxy cluster Abell 2107

We search for global rotation of the intracluster medium in galaxy cluster Abell 2107, where previous studies have detected rotational motion in the dynamics of member galaxies. With Chandra data of this cluster, we identify the possible rotation axis with the line that maximizes the difference between the redshift measured in the two halves divided by the line itself. Then, we measure the redshift in linear regions parallel to the preferred rotation axis, and find a significant gradient as a function of the projected distance from the rotation axis, compatible with a rotation pattern, but can also be interpreted by an unnoticed off-center, head-on collision between two comparable halos. In summary, our analysis confirms the peculiar dynamical nature of Abell 2107, but is not able to resolve the rotation vs merger scenario, which is a clear science case for the next-generation X-ray facilities carrying X-ray bolometers onboard.

Tuesday 29 January 2019 - 11:45 Aula A

Paola di Ninni (Post-Doc, Radio)

Electromagnetic characterization of LOFAR LBA-outer array

The Electro-Magnetic (EM) characterization of a radio telescope is an essential step of the calibration procedure.
This step represents a challenging task for a Low Frequency Aperture Array (LFAA), a system composed by a multitude of small antennas operating in a complex environment.
Experimental and numerical EM characterization is presented for a Low Band Antenna-outer (LBA-outer) array of LOw Frequency Array (LOFAR). LOFAR is a LFAA radio telescope available to the astronomical community nowadays and it is considered a technological pathfinder for the Square Kilometre Array (SKA).
Measurements acquired by means of an UAV-based system and data simulated with a computational EM software have been employed for the LBA-outer array EM characterization.

Carolina Belli (Post-Doc, Radio)

Sysml: a language for system modelling. Applications to SKA

During the preparation of the documentation for the SKA Low Frequency Aperture Array, a system modelling tool has been used to aid the system design. The tool adopts the SysML graphics language to describe the system product breakdown structure, to identify the internal and external connection between its elements, the interfaces that characterise the system, and to describe the functions and the data flow associated with each element. The derived diagrams were used in the documents prepared for the instrument critical design review.
The main advantage in applying such an approach is the ease of modification and maintenance of the documentation. As the elements composing the system and their relations are defined inside the abstract model, any change is automatically reflected in a consistent ways in all diagrams describing the instrument.

Simone Chiarucci (Post-Doc, Radio)

RFI analysis for LFAA with a digital signal processing model

A complex system like the LFAA requires extensive simulations to test its compliance with the system specifications. For this reason, a detailed modelling of the signal processing chain is essential. The LFAA digital section, starting from the samples produced by the ADC and ending with the beamformed samples transmitted to the CSP, have been simulated using an end-to-end MATLAB model in the time domain.
In order to test the robustness of the design against the expected RFI levels on the SKA site in Western Australia, the digital model has been used to evaluated the impact of the intermodulation product and harmonics to the final beamformed signal.
In such fashion, it has been possible to demonstrate the model compliance to LFAA requirements highlighting possible design problems.

Tuesday 15 January 2019 - 11:45 Aula A

Niccolò Tomei [UniFI]  (PHD)

Mean-field dynamo in relativistic disks accreting onto rotating black holes

Mean field dynamo is one of the best candidates in amplifying magnetic fields in AGNs. I will present some general aspects about GRMHD dynamo and a simple model which tries to explain some observations related to SGR A* emission

Guido Agapito [OAA]  (Technology)

SOUL: upgrading the SCAO system at the Large Binocular Telescope
We present the commissioning status of SOUL: the Single conjugated adaptive Optics Upgrade for LBT. SOUL upgrades the wavefront sensors replacing the existing CCD detector with an EMCCD camera and the rest of the system in order to improve sky coverage, contrast and SR. The left focal stations, LBTI SX and LUCI1, have been already upgraded, the first on-sky PSFs have been taken in October and LBTI SX has been released for science. We have verified that AO performance is in good agreement with the expected values and science verification will be done in the next months. Integration of LBTI DX is started few days ago and LUCI2 will be upgraded during the summer shutdown.

 Tuesday 18 December 2018 - 11:45 Aula A

Monica Rainer [OAA]  (Software)

GOFIO or how to personalize a data reduction pipeline
GOFIO is the reduction software for the infrared GIANO-B spectrograph and it is the result of a close cooperation with the various scientific groups interested in the instrument. As such it is highly customizable, and in continuous evolution. I will focus on the importance of interacting with the astronomical community when providing data reduction softwares.

Jacopo Soldateschi [UniFI]  (PHD)

The Hitchhiker’s Guide to Gravity: Scalar-Tensor Theories in Neutron Stars as an Extension of Einstein’s Legacy
The General Theory of Relativity might not be the definitive theory of gravity. Scalar-tensor theories of gravity can extend Einstein’s theory to account for some of the most outstanding problems in physics. We study, by means of numerical simulations, the effects brought by these theories in the case of the most extreme material objects in the universe: neutron stars.


Tuesday 4 December 2018 - 11:45 Aula A

Maria Angela Corazzi [UniFI]  (PHD)

Photoprocessing of formamide ice: route towards prebiotic chemistry in space
Formamide was first detected in gas phase in Orion-KL and SgrB2. It is the simplest molecule containing the peptide linkage and the chemical reactions of molecules like formamide are considered a plausible pathway for synthesis of biomolecules under prebiotic conditions. In laboratory, we studied formamide under simulated space conditions.

Andrea Sacchi [UniFI]  (PHD)

Tidal Disruption "Failure": the effects of a stellar counter-rotation on a tidal disruption event
A tidal disruption event is the violent rupture of a star passing too close to a supermassive black hole. We found out that an initial retrograde rotation (with respect to the orbital angular momentum) could prevent the disruption of the star. Through hydrodynamical simulations we investigate the observational prospects of such an event.

Mathieu van der Swaelmen [OAA]  (Stellar populations)

Alpha-elements over the first kpc of the Large Magellanic Cloud
The Large Magallenic Cloud (LMC) is one of the closest galaxies interacting with the Milky Way. The LMC exhibits a bar like structure at its center, which is embedded in an old stellar disc. In order to investigate the relation between the bar and the disc and the chemical evolution of the LMC, we performed a detailed chemical tagging of 250 LMC field giant stars observed in three fields over the first kiloparsecs.


Tuesday 20 November 2018 - 11:45 Aula A

Juraj Kojs [Univ. of Miami]  (Music)

Sonoric traces
The musician, composer, and performer Juraj Kojs, director of the Foundation for Emerging Technologies and teacher at the University “Frost School of Music" in Miami (Florida, USA), will tell us about his innovative way to produce music (“sonoric traces”), inspired by an environment. He would also like to know from us what our activity is about, as a source of inspiration.


Tuesday 23 October 2018 - 11:45 Aula A

Carlo Baffa [OAA]  (Outreach)

Alternanza scuola lavoro - un investimento per il futuro
Riportiamo la soddisfacente esperienza dell'alternanza scuola lavoro, che ha dato un ottimo esito e chiamiamo a raccolta nuovi volontari per questa iniziativa che sembra essere un buon investimento per il futuro.

Stefano Zibetti [OAA]  (Extragalactic)

"Birth, life and fate of massive galaxies and their central beating heart"
We will report on the Conference on "Birth, life and fate of massive galaxies and their central beating heart" hel on 3-7 September 2018 in Favignana.


Tuesday 25 September 2018 - 11:45 Aula A

Alessandra Zanazzi [OAA]  (Outreach)

The Astrotourism Project in Florence
I will present a pilot project by INAF and the Arcetri Observatory, aiming at promoting an astro-tourism programme in Florence and its surroundings. This initiative aims at searching a new cultural format exploiting synergies between art and science and working in cooperation with local Institutions. We will promote itineraries including astronomical monuments, relevant places and museums in the Florence area through guidebooks, maps, guided tours. The visitors will discover the sky in the renowned monuments, but also along unconventional paths and outside the mainstream of mass tourism.

Francesca Bacciotti [OAA]  (Star formation)

Polarimetry of protoplanetary disks with ALMA: new clues on the dust properties
Polarimetric data of Class II rotating disk/jet systems were obtained with ALMA with the aim of determining the magnetic field configuration. The observed properties, however, support dust self-scattering as the origin of the polarization. In this case polarimetry gives access to information on the dust properties which complement the results obtainable from unpolarized emission. This can to be of great interest in studies of the evolution of protoplanetary disks.

Massimo Mazzoni & Fabrizio Mazzucconi [OAA]  (Outreach)

A real All-stars game: the Olympic Games of Astronomy
Whilst the role of Astronomy, in the ministerial programs for high-school, has become in the years similar to that of Cinderella, the Italian scientific community is making continuous efforts to promote the students' interest in the starry sky. In this task, SAIt and INAF are at the forefront. Special lectures, winter training courses and then summer stages, regional and national selections are aimed to develop in those young minds a real appreciation for science in general, also through a healthy and friendly competition. At the end, a selected small group is supported to reach Countries beyond the edge of the usual maps (Kyrgyzstan; Wei-Hai, China; Colombus, Sry Lanka) and to do its best there. And, often, their score is not that bad (including recently one gold medal e two brass medals).



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