Osservatorio Astronomico di Roma

Lyα-Lyman Continuum connection in 3.5 ≤ z ≤ 4.3 star-forming galaxies from the VUDS survey
2018-02-20 11:45 - 12:45 (Europe/Rome) | Aula Gratton
Understanding the processes that led to the reionization of the Universe is among the most challenging tasks of modern extra-galactic astronomy. The main responsible for this phenomenon are thought to be high redshift star-forming galaxies. However, it is very difficult to constrain their contribution and only few detections of Lyman Continuum (LyC) emitters have been reported so far. Following theoretical models, several so-called indirect indicators of LyC radiation have been proposed, such as a strong Lyα emission, a large OIII/OII ratio, the compactness of the UV continuum and others. Using these pre-selection criteria has indeed proved to be a powerful method to identify LyC leakers at low redshift but there is a lack of consistent studies that relates these indicators to the LyC emission at high redshifts.
We have used ultra-deep spectra from the Vimos Ultra Deep Survey (VUDS) to investigate the LyC properties of z~4 star-forming galaxies. We initially investigated the LyC emission from a stack of ~33 sources free from foreground contamination, selected after a very careful cleaning procedure based on the inspection of multi-wavelength high resolution HST imaging. We found for this sample a mean fesc,rel=0.09±0.04 with no individual detections. We also observed a tentative correlation between the individual limits given in the LyC flux and the EW of the Lyα emission line. To better investigate this trend and other expected correlations with LyC properties of high redshift galaxies, we then analysed a much larger sample of more than 200 objects also from the VUDS survey. We found evidence that LyC is strongly related to a large Lyα EW and to the UV compactness, in agreement with theoretical expectations and observational studies at low redshift. In addition we found that galaxies with a small Lyα spatial extent have higher LyC flux compared to the rest of the population: such a correlation had never been analysed before and seems even stronger than the correlation with high Lyα EW and small UV effective radius.

Assemblea del Personale.
2018-02-27 | OAR Monte Porzio Catone – aula Gratton, Via Frascati 33, Roma, RM, 00136, Italia
RICERCATORI, TECNICI, AMMINISTRATIVI, PRECARI e STRUTTURATI DELL’ INAF – OAR

ASSEMBLEA DEL PERSONALE
Martedì 27 febbraio ore 10:00
INAF– Monte Porzio
Per discutere di:
1) Stabilizzazioni e Piano Fabbisogno Personale INAF 2018/2020;
2) Contrattazione integrativa;
3) Nuovo contratto Istruzione e Ricerca;
4)Elezioni RSU;

Saranno presenti all’ iniziativa :
Stefano Bernabei – Coordinatore nazionale C.d.E. INAF FLC-CGIL
Carlo Buttarelli – Coordinatore territoriale FLC – CGIL

Bright and dustiest stars in the JWST era: powerful tools to constrain the recent star formation history
2018-02-27 11:45 - 12:45, 2018-03-27 11:45 - 12:45 | Aula Gratton
With the advent of the JWST, the horizon of our knowledgies will be amazingly enlarged, providing an unprecedent look of a large volume of galaxies with a broad properties range. This will be possible in the IR domain where the extinction is low and bright cool evolved stars have their emission peak. This is the case of asymptotic giant branch stars (AGB), luminous objects and main dust producers for the galaxy. We present how the large release of AGB+dust evolutionary models developed in the last years, will enable a detailed study of these sources in different systems. The distribution of these objects in the IR colour-magnitude diagrams is a powerful instrument to determine the recent star formation history of the galaxy in detail.

An experiment in Astrobiology: exploring the climate parameter space of rocky planets
2018-03-06 11:45 - 12:45 | Aula Gratton
Astrobiology is a relatively new and fast-growing science, whose main
characteristic is to need expertises from different science fields.
I’ll show how the climate of a planet influences its abitability.
Astronomers from OATs, climatologists from CNR and experts in
databases from OATs joined their efforts to build a fast, simplified,
yet effective climate model and database for extra-solar planets. I
will describe
the model, its main feature, its validation, its application to a
specific exo-planet (Kepler 452b). I will then show how such a model
can be used to explore a huge parameter space and build a database
that can be used to characterize classes of habitable planets. I will
point out how this particular case is an good example of
High-Throughput Computing (HTC). Our database can also be used, e.g.,
as a tool to get a first estimate of the habitability of a newly
discovered rocky planet.
Then I will describe possible future developements of such a research
line, including the study of the effect of the biosphere itself on the
habitability.

Drag and drift - decoupling of the dust and gas phases in astrophysical flows
2018-03-14 11:45 - 12:45
Simulating the dynamics of gas and dust in various astrophysical contexts is a topic of intense research. It includes simulations of the turbulent interstellar medium (ISM), active galactic nuclei (AGN), proto-planetary discs, and dusty stellar winds. I will focus on the ISM and dust-driven stellar winds, however, and only briefly mention a few other examples.
Using high-resolution (1024^3) simulations of homogeneous isothermal hydrodynamic turbulence, including a multi-disperse population of 10^7 dust grains imbedded in the gas, one may assess the efficiency of condensation, destruction and coagulation in molecular clouds. Due to hydrodynamic drag, large grains will decouple from a turbulent gas flow, while small grains will tend to follow the motions of the gas. Dust grains of various sizes will also cluster and increase the rate of grain-grain interaction. This may in turn lead to turbulence-driven coagulation and fragmentation.
In a stellar-wind context the decoupling between gas and dust is often called “drift”, which is referring to the fact that the two phases may develop different mean-flow velocities. In a spherically-symmetric setting, a mean-flow model of drift is fairly simple. But there are significant 3D effects, as well as instabilities, which we must take into account. For instance, dust grains of various sizes will cluster and increase the rate of grain-grain interaction. Moreover, due to spatial separation of dust and gas, condensation is likely less effective than in a velocity-coupled case. There are several implications for dust-driven stellar winds which arise from this. One is that the momentum-transfer efficiency (from dust to gas) of large grains may be low as they cluster where the gas is not; another is that the sublimation rate increases as grains are more exposed to the radiation field.

The science of HERMES: a constellation of nano-satellites for high energy astrophysics and fundamental physics
2018-04-10 11:45 - 12:45 | Aula Gratton
A distributed instrument, such that consisting of nano-satellites carrying simple X-ray detectors, can provide accurate (arcmin to arcsec) and prompt (within minutes) localisation of high energy transients, such as gamma ray bursts and the electromagnetic counterparts of gravitational wave events. In addition, once the position of the transient is computed, the signals registered by the different detectors can be realigned in time and added together to improve the statistics. This can allow the investigation of the temporal structure of transients down to a fraction of microsecond, providing crucial information on one hand on the physics of the transient inner engine, and, on the other hand, on the granular structure of space-time, through the study of light-travel effects.
The advantages of a distributed instrument based on nano-satellites are: a) modularity, which allows redundancies with the associated lower risks; b) the possibility to expand (and/or improve) the experiment with the time; c) low cost and quick development.

seminar by Filippo Ambrosino
2018-04-17 11:45 - 12:45 | Aula Gratton

seminar by Ambra Nanni
2018-04-24 11:45 - 12:45 | Aula Gratton

seminar by Antonio Frasca
2018-05-08 11:45 - 12:45 | Aula Gratton

Zooming into Dark Matter and primordial Star Formation with massive Lensing Clusters
2018-05-15 11:45 - 12:45 | Aula Gratton

seminar by Cristina Raimos Almeida
2018-06-12 11:45 - 12:45 | Aula Gratton

CTA: Scientific perspective and current status
2018-09-04 11:45 - 12:45 | Aula Gratton
The Cherenkov Telescope Array (CTA) is the major ground-based gamma-ray observatory planned for the next
decade and beyond. Consisting of two large atmospheric Cherenkov telescope arrays (one in the southern
hemisphere and one in the northern hemisphere), CTA will have superior energy and angular resolutions, a much
wider energy range, and up to an order of magnitude improvement in sensitivity, as compared to existing
instruments. The CTA science program will be rich and diverse, covering the major aspects of cosmic particle
acceleration, understanding extreme astrophysical environments, and probing physics frontiers beyond the
Standard Model. This talk will outline the scientific persective for CTA and will cover the most recent status of the project.

The planet formation seen through high-resolution images of protoplanetary disks
2018-09-11 11:45 - 12:45 | Aula Gratton
The high occurrence of exoplanets around solar-type stars suggests that planets form very efficiently in protoplanetary disks. Yet, numerical simulations and laboratory experiments show that the planet formation is a complicated process. The onset of optical/NIR and (sub-)mm surveys of young stars has been a game changer for our understanding of protoplanetary disks and planet formation. Thanks to the contributed effort of VLT/SPHERE, GPI, and ALMA we could resolve with unprecedented resolution several sub-structures at the disk surface and midplane from few to hundreds of au from the star. I show the method and the recent improvement of this type of observations and discuss the implications to the recurrent existence of these disk features.

SHARK-VIS: the upcoming high-resolution high-contrast visible imager for LBT
2018-09-18 11:45 - 12:45 | 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.
