Osservatorio Astrofisico di Arcetri

AstroBigné seminars

Lists of bigné's Current season - Previous seasons -- Sign up for a presentation (doodle link)!!!

 For any kind of info plese contact Questo indirizzo email è protetto dagli spambots. È necessario abilitare JavaScript per vederlo..

 If you wish to give a presentation, please  contact Questo indirizzo email è protetto dagli spambots. È necessario abilitare JavaScript per vederlo. and then fill in the doodle

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), Nicoletta Sanna (Questo indirizzo email è protetto dagli spambots. È necessario abilitare JavaScript per vederlo. , galactic group), 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 28 January 2020 - 11:45 Aula A


Asa Skuladottir [Extragalactic]

Evidence for ≳ 4 Gyr timescales of neutron star mergers from Galactic archaeology

The nucleosynthetic site of the rapid (r) neutron-capture process is currently being debated. The direct detection of the neutron star merger GW170817 has confirmed such events as important site of the r-process. However, the long estimated timescales for this event are at odds with chemical evolution models of the Milky Way, which are only able to reproduce the observed abundances if short time-delays of the r-process are assumed. Different scenarios have been invoked to solve this discrepancy, but none of these can self-consistently explain the observed r-process abundances in several galaxies at once. The key to solving this puzzle is therefore to combine all the available evidence in the Milky Way and its dwarf satellite galaxy. This data can only be explained if there are (at least) two distinct r-process sites: a quick source with timescales comparable to core-collapse supernovae, ≲ 10^8 yr, and a delayed source with characteristic timescales ≳ 4 Gyr. The delayed r-process source is most probably neutron star mergers, as the timescale fits well with that estimated for GW170817. Given the short timescales of the quick source, it is likely associated with massive stars, though a specific fast-track channel for compact object mergers cannot be excluded at this point.

Simone Bianchi [Extragalactic]

The time signal in Florence

I review a century of time signal in Florence, starting from the 1850s when true solar time from the clock on the tower of Palazzo Vecchio was transmitted telegraphically to the railway stations of the Grand Duchy of Tuscany. At the onset of Italian Unification, midday was signaled to the city by means of a flag lowered on the Torrino, the tower of the old Astronomical Observatory of Florence. In the short period when Florence was the Italian Capital (1865-1871), the time signal from the Torrino served to regulate communication and transport services in the nation; after that, it continued as a city service only. At the end of the 19th century, the flag was substituted by the firing of the votapentole cannon from the Belvedere Fortress. From the Great War, the service began to be regulated by the astronomers of the newer Arcetri Observatory. Except for a brief interruption during the Second World War, the time signal continued until the early 1950s.


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 2019-2020

Tuesday 14 January 2020 - 11:45 Aula A

Giovanni Morlino [High energy]

Contribution of starburst nuclei to the diffuse gamma-ray and neutrino flux

In nuclei of starburst galaxies, the combination of an enhanced rate of supernova explosions and a high gas density suggests that cosmic rays can be efficiently produced, and that most of them lose their energy before escaping these regions, resulting in a large flux of secondary products, including neutrinos. Although the flux inferred from an individual starburst region is expected to be well below the sensitivity of current neutrino telescopes, such sources may provide a substantial contribution to the diffuse neutrino flux measured by IceCube. Using a physically motivated model, I'll show that starburst nuclei alone can account for the observed diffuse neutrino flux above 200 TeV, while below such energy additional contributions are needed which can be possibly provided by Galactic sources or atmospheric neutrinos.

Valdemaro Biliotti [tecnology], talk in Italian

The control electronics for the Amici Telescope

Nel talk sarà descritto il sistema di controllo assi per il telescopio, non dimenticando i criteri che hanno guidato le scelte del progetto, e come queste sono state implementate al telescopio.

Tuesday 26 November 2019 - 11:45 Aula A

Giada Casali [stellar group]

Stellar dating using [C/N] as chemical clock

In the era of large high-resolution spectroscopic surveys such as Gaia-ESO and APOGEE, high-quality spectra can contribute to our understanding of the Galactic chemical evolution by providing abundances of elements that belong to the different nucleosynthesis channels, and also by providing constraints to one of the most elusive astrophysical quantities: stellar age. Some abundance ratios, such as [C/N], have been proven to be excellent indicators of stellar ages. We aim at providing an mpirical relationship between stellar ages and [C/N] using open star clusters, observed by the Gaia-ESO and APOGEE surveys, as calibrators. Finally we apply our relationship to selected giant field stars in the Gaia-ESO and APOGEE surveys. With this empirical relationship, we are able to provide an age estimate for giant stars in which C and N abundances are measured. Our method can therefore be considered as an additional tool to give an independent estimate of the age of giant stars.

Paolo Tozzi [outreach], talk in Italian

Tutto quello che avreste voluto sapere sulle Notti d'estate

Comunicare la scienza in forma spettacolare è sempre più spesso una modalità apprezzata dal grande pubblico.  Nelle Notti d'Estate ad Arcetri, cerchiamo da anni di coniugare un contenuto scientifico di alta qualità con un format vicino a quello di un festival.  Daremo uno sguardo alle Notti d'estate 2019, e alle  prospettive per il 2020.

Tuesday 12 November 2019 - 11:45 Aula A

Antonino Marasco [extragalactic]

Extra-planar HII and galactic fountain cycle in nearby late-type galaxies

In the last two decades, deep HI observations of nearby late-type galaxies have revealed the presence of extra-planar HI layers extending up to a few kpc above the galaxy midplane and accounting for ~10% of the total HI content. In the few cases studied in detail, these HI layers were found to be characterised by a slow-rotating, globally inflowing kinematics, which is expected by gas in a galactic fountain cycle triggered by stellar feedback. We now present a homogenous and detailed analysis for a sample of 13 late-type galaxies with deep HI observations from the HALOGAS project. For each system we have masked out the HI emission coming from the rotating thin disk and produced synthetic data-cubes to model the leftover extra-planar emission. Our model features 3 structural and 4 kinematical global parameters, which are fit to the data via a Bayesian MCMC method. We found that extra-planar HI layers are ubiquitous in disc galaxies, with HI masses that are in excellent agreement with predictions from simple models of galactic fountain powered by stellar feedback. In most cases, the kinematics show a global inflow with speed of 20-30 km/s in the vertical and radial directions, along with a vertical rotational lag of 5-20 km/s/kpc, suggesting an interaction between the material outflowing from the disc and the circumgalactic medium.


Giacomo Venturi [extragalactic]

The role of AGN outflows and jets from isolated to merging galaxies

Active galactic nuclei (AGN), through the effect of outflows and jets, are believed to play a major role in the formation and evolution of their host galaxies, by sweeping away the gas and quenching star formation.
In the so-called “radio-loud” AGN, relativistic jets are considered important actors in shaping the host galaxy properties by interacting with its interstellar medium (ISM) and accelerating massive outflows. However, by inspecting nearby “radio-quiet” Seyfert galaxies in detail with MUSE at VLT, we found that also low-power AGN jets can have a significant impact on the galaxy ISM, with some unexpected peculiar effects and potentially important implications!
Finally, I will present a highlight on a recently started project which, by targeting galaxies across different merging stages, aims to investigate the role of mergers in launching outflows, triggering AGN activity and exerting feedback on the intense star formation in the host galaxies, from galactic down to nuclear scales (through a combination of wide-field and AO-assisted VLT/MUSE observations).


Tuesday 29 October 2019 - 11:45 Aula A

Stefano Menchiari [high-energy group]

Development of a robust algorithm for source detection in very high energy gamma-ray surveys of the Galaxy

In the next decades, with the new generation of gamma-ray telescopes such as the upcoming Cherenkov Telescope Array (CTA), we will be able to investigate the high energy sky as never before. One of the main scientific goals of CTA is to create the deepest and most complete Galactic plane survey, composed of more than 1500hrs of observation. Thanks to the excellent sensitivity of CTA, the survey will be able to probe deeply the Milky Way plane, allowing us to explore the whole Galactic disk and to detect the faintest sources. As the detection sensitivity will improve, the problem of confusion between overlapping sources along the line-of-sight will grow. The correct identification of as many sources as possible is of primary importance, not only to better constrain their individual properties but also to avoid biasing source population studies. We present the development of a robust multi-template fitting algorithm for the study of candidate gamma-ray sources in surveys of the Galactic plane. The developed code, in combination with a seeking algorithm used to detect gamma-ray excesses, creates a catalog pipeline for the analysis of surveys. The presented algorithm is capable of making morphological classification and calculating the statistical significance of source candidates using a sequential multi-template fitting strategy, which consists in testing all the objects detected by the seeking algorithm with different morphological templates, such as Gaussian, shell-like shapes and also a combination of two 2D Sersic profiles. As the latter is able to reproduce several kinds of morphologies, the resulting fitted parameters are used for the classification purpose. We will illustrate the detection and fitting performance of the algorithm using the simulated CTA Galactic Plane Survey (DC-1). As a result, we found both high-grade fit quality and detection efficiency for TeV emitting objects such as PWNe, SNRs, and composite sources. We also obtained satisfactory results in the case of statistically non-significant extremely faint sources.


Francesca Brunetti [Biblioteca], talk in italian

Orientarsi in biblioteca: la strada più veloce per accedere alle risorse informative

La biblioteca di Arcetri è un polo di un'unica grande biblioteca geograficamente distrbuita, accessibile da Polvere di Stelle: il portale dei beni culturali dell'astronomia italiana. Un patrimonio informativo a disposizione di ricercatori, di studiosi, di studenti e di appassionati della materia. Come orientarsi, quali strumenti usare per avere a disposizione nel minor tempo possibile le risorse informative che cerchiamo?


Tuesday 15 October 2019 - 11:45 Aula A

Rossella Spiga [Arcetri, Comunicazione]

La comunicazione scientifica all'Osservatorio di Arcetri - le basi di un piano d'azione congiunto

Input sulla strategia locale e nazionale per la comunicazione delle attività scientifiche e di outreach dell'Osservatorio Astrofisico di Arcetri. Presentazione delle attività dell'ufficio comunicazione da implementare in sinergia con i gruppi di ricerca locali e con la struttura nazionale INAF per la comunicazione.


Salvatore Ferrone [Ithaca College]

Spectral and Physical Properties of High Reflectance Boulders on the Surface of NASA'S OSIRIS-REx Target Asteroid 101955 Bennu

The OSIRIS-REx asteroid sample return mission is currently in the reconnaissance phase in which target sample sites on Rubble Pile Asteroid 101955 Bennu are being studied in close proximity and at high resolution. The spacecraft is equipped with high resolution imagers as well a visible and near infrared spectrometer. In this study, we present global spectroscopic analysis of Bennu to probe if there is a relationship between spectral and geologic features. Results to date indicate (1) distributions of spectral properties are single peaked and skew; and (2) that correlations of these spectral properties with surface textures are weak. This could imply there is only one boulder population on Bennu, which would support a formation process of a disruption event of a parent body over a collision between two smaller parent bodies. The skewness of the distribution of the spectral features on Bennu could imply space weathering, which is an optical alteration of the surface due to exposure to solar particles, galactic particles, and micro-meteorites impacts. If we are able to provide enough evidence in support of space weathering driving the spectral variations, we may be able to form age relationships on Bennu. 


Tuesday 01 October 2019 - 11:00 Aula A

Premiazione del Premio Magini

Marco Cilibrasi [UniPi]

Satellites Form Fast & Late: a Population Synthesis for the Galilean Moons

The satellites of Jupiter are thought to form in a circumplanetary disc (CPD), i.e. a small disc forming around a giant planet when a gap is opened in the protoplanetary disc. We study the forma-tion and orbital evolution of moons with a population synthesis approach, by varying the dust-to-gas ratio, the disc dispersal timescale and the dust refilling timescale in such a disc. The CPD initial conditions (density and temperature) are directly drawn from the results of 3D radiative hydrody-namical simulations. The disc evolution is taken into account within the population synthesis, and the satellitesimals were assumed to initially grow via streaming instability, then via dust accretion, while they migrate through the disc.
We find that the moons form fast, often within 104 years, due to the short orbital timescales in the disc. They form in sequence, and many are lost into the planet due to fast type I migration, polluting Jupiter’s envelope with typically 15 Earth-masses of metals. The last generation of surviving moons can form very late in the evolution of the giant planet when the disc has already lost more than 99% of its mass. The late circumplanetary disc is cold enough to sustain water ice, hence not surprisingly 85% of the moon population has icy composition. The distribution of the satellite-masses is peaking slightly above Galilean masses, up until a few Earth-masses, in a regime which is observable with the current instrumentation around Jupiter-analog exoplanets orbiting sufficiently close to their host stars.

 Antonio Pensabene [UniFi]

The ALMA view of the high redshift relation between supermassive black holes and their host galaxies

The existence of tight correlations between supermassive black holes (BHs) and their host galaxies properties in the local Universe suggests a closely linked evolution. Investigating these relations up to the high redshifts (z > 6) is thus crucial to understand the interplay between star-formation and BH growth across the cosmic time and to set constraints on galaxy formation and evolution models. In this work, I present the relation between black hole mass (MBH) and the host galaxy dynamical mass (Mgal) for a sample of 10 high-z (z ~ 2 – 7) quasars for which we have obtained measurements of the host galaxy kinematics from archival data of the Atacama Large (Sub-)Millimeter Array (ALMA). Thanks to the unparalleled capabilities of ALMA, we are now able to spatially resolve the kinematics of cold gas traced by bright atomic/molecular lines such [CII] or CO and measure the galaxy masses through a full kinematical modelling of galaxy disks even at the highest redshifts, thus avoiding all possible biases and effects introduced by the rough estimates usually adopted so far (photometric measurements of stellar masses, virial estimates, etc.). Up to redshift z ∼ 5, the MBH/Mgal ratio is consistent with the extrapolation of the relation inferred at z < 3. At z > 5 we find a steady decrease of the MBH/Mgal ratio with increasing redshift, possibly witnessing the phase of fast growth of the BHs compared to the host galaxies. I will discuss how these results fit within the coevolution scenario and highlight the constraints that they pose on models of galaxy evolution.

 Elisabeta Lusso [UniFi]

Visit to the telescope complex of La Palma

For the third year, the astrophysiscs students of the course of Complementi di Astronomia visited El Roque de Los Muchachos telescopes in La Palma to experience how the ground-based telescopes work in one of the most important observing sites in the world. They also had the opportunity of spending an observing night at the TNG acquiring data on extragalactic targets, selected by them and later analyzed during the laboratory classes.





Previous seasons