Arcetri Astrophysical Observatory

AstroBigné seminars

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The Astrobigné Organizing Committee is currently composed of Crescenzo Tortora (This email address is being protected from spambots. You need JavaScript enabled to view it. , reference person for the extragalactic group), Nicoletta Sanna (This email address is being protected from spambots. You need JavaScript enabled to view it. , galactic group), and Alessio Turchi (This email address is being protected from spambots. You need JavaScript enabled to view it. , 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 01 October 2019 - 11:45 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.

 


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

 

 


 

Previous seasons