Osservatorio Astronomico di Roma

colloquium Anita Zanella: The contribution of high-redshift star-forming regions to galaxy evolution
2022-01-25 11:30 - 12:30 (Europe/Rome)
Observations have shown that local galaxies have modest star formation rates and form the bulk of their stars in giant molecular clouds. In comparison, galaxies in the early Universe have high star formation rates and host large star-forming regions (dubbed “clumps”), 10 – 1000 times larger, brighter, and more massive than local giant molecular clouds. Interestingly, the formation phase of clumps has rarely been observed and their fate is highly uncertain. Are they born in-situ due to fragmentation of gas-rich disks or are they small satellite galaxies that merged with the host? Do they migrate inward and contribute to the formation of the galaxy bulge or are they rapidly disrupted by stellar feedback? Do they play a role in the mass assembly and structural evolution of the host galaxy? I will discuss our latest results derived from spatially-resolved HST, VLT/MUSE and ALMA datasets, as well as mock observations created from hydrodynamical simulations, which provide some answers to these open questions.

colloquium - Michele Fabrizio
2021-01-26 11:30 - 12:30

colloquium - Flavia Dell'Agli
2021-01-19 11:30 - 12:30

The X-ray rise of primeval titans: HYPerluminous quasars at the Epoch of ReionizatION (HYPERION)
2021-01-13 11:30 - 12:30
The outstanding mass growth of the Supermassive Black Holes powering
luminous quasars at the Epoch of Reionization (EoR, z > 6) is one of
the most debated open problems of modern extragalactic
astrophysics. These quasars are current targets of extensive
multiwavelength campaigns with todays flagship observatories, in order
to understand their properties. The limited sensitivity of current
X-ray observatories, however, has so far provided mostly low quality
spectra (< 10 − 15 counts; 0.5-10 keV) and therefore a poor
characterization of their nuclear properties. I will present HYPERION,
a 2.4 Ms Multi-Year Heritage XMM programme on the titans among z = 6 −
7.5 quasars (i.e. the most luminous/massive at their epoch) designed
to dramatically improve the X-ray data quality to 100 counts for a
sample of 15 sources. HYPERION will deliver unprecedented constraints
on their nuclear properties, accretion, ejection, disc/corona complex,
and, while perfectly complementing observations at other wavelengths,
will enable X-ray spectroscopic population studies at EoR to begin.

colloquium - Hans Van Winckel
2020-05-05 11:45 - 12:45 | Aula Gratton

colloquium - Suzanne Ramsey
2020-04-28 11:45 - 12:45 | Aula Gratton

colloquium - Giovanni Miniutti
2020-04-20 11:45 - 12:45 | Aula Gratton

colloquium - Matt Middleton
2020-04-07 11:45 - 12:45 | Aula Gratton

colloquium - Eleonora Fiorellino
2020-03-24 11:45 - 12:45 | Aula Gratton

colloquium - Brian Chaboyer
2020-03-17 11:45 - 12:45 | Aula Gratton

The role of starburst galaxies and mergers in the distant Universe
2020-03-10 11:45 - 12:45 | Aula Gratton
Starburst galaxies are the most luminous star-forming powered objects in the Universe. A long standing problem in galaxy evolution is to understand whether these systems are caused by merger events, or they are just gas rich galaxies undergoing stochastic accretion events. To properly characterize them, we need infrared data, given the huge dust attenuations affecting their UV and optical emission.
I will present a unique set of near-infrared rest-frame spectral observations of star-forming galaxies at redshift ~ 0.7, and show how these can be used to understand the dust properties and origin of starbursts. Furthermore, I will explain how additional multiwavelength information (from radio to X-rays) is crucial to trace the whole sequence of mergers, test the merger-AGN connection and the formation mechanism of passive galaxies. Finally, I will exploit high-resolution HST images to investigate the role of mergers on the origin of bright star-forming clumps in high-redshift galaxies. A complete study of near-infrared rest-frame lines will allow JWST to probe the physical properties (e.g., dust attenuation, metallicity) and the nature of the most dust-embedded systems up to the reionization epoch.

colloquium - Ester Marini
2020-03-03 11:45 - 12:45 | Aula Gratton

colloquium - Roberta Zanin
2020-02-28 11:45 - 12:45 | Aula Gratton

The interstellar medium at high redshift
2020-02-18 11:45 - 12:45 | Aula Gratton
The gaseous content of galaxies is one of the key ingredients of galaxy evolution: It fuels star formation and nuclear activity, and at the same time it is the main receiver of any feedback mechanism from these two processes. However, we have only very limited knowledge of the gas content and of its physical properties in galaxies beyond the local universe. As a result, no description of galaxy formation can be fully validated without a better understanding of 1) how much gas was available for star formation in different cosmic times; 2) how the star formation efficiency, i.e., the capability of a galaxy to form stars from a given amount of gas, evolve through cosmic history, and which are physical conditions that governed this evolution; 3) what was the interplay between the interstellar medium, star formation, and nuclear activity. These questions are particularly critical at the very high redshifts (z>6, when the universe was <1 Gyr old), where our census of galaxies is highly incomplete, especially at the high-mass end, and galaxies followed very different evolution according to the mass of their initial gas reservoir. In this talk I will present the results of various observational campaigns aimed at addressing these questions, in particular by capitalizing on the unprecedented capabilities offered by the Atacama Large Millimeter Array and the Northern Extended Millimeter Array. These findings will guide the next generation of simulations and theoretical models, thus marking a transformational step in our understanding of galaxy evolution.

The quest for observational evidence of the hierarchical formation process at the smallest galaxy scales
2020-02-11 11:45 - 12:45 | Aula Gratton
I will present our ongoing project devoted to the search and study of satellites, stellar streams, and substructures around dwarf galaxies. Deep, wide field imaging acquired with the Large Binocular Telescope and follow-up observations performed with the WFC3 on the Hubble Space Telescope provide evidence of multiple satellites associated with the very metal-poor star-forming dwarf galaxy DDO 68. This is a striking example of the few observed cases of hierarchical merging in action at the dwarf galaxy scales. To perform a systematic search of substructures around dwarf galaxies, we have started a Strategic Program at the LBT, named SSH (i.e. The Smallest Scales of Hierarchy Survey) to acquire deep, wide-field imaging of a sample of 45 late-type dwarf galaxies located within 10 Mpc. The survey, which is now close to completion, will provide one of the first systematic observational studies of the hierarchical formation process down to very small galaxy scales. In this talk I will introduce SSH and discuss the results obtained so far.

The X-ray universe at microarsec resolution: the power and promise of X-ray interferometry
2020-02-04 11:45 - 12:45 | OAR Monte Porzio Catone – aula Gratton, Via Frascati 33, Roma, RM, 00136, Italia
The spectacular image of a supermassive black hole `shadow’ taken by the Event Horizon Telescope last year highlights the potential of being able to resolve microarcsecond scale structures in astrophysical sources. Given the ~Angstrom scale of X-ray wavelengths, similar resolutions are theoretically possible with only a 1 m diameter telescope, which could be accommodated on a single spacecraft. Conventional X-ray imaging capability remains far from from this goal however.
In this talk I will explore the possibility, recently proposed to ESA’s Voyage 2050 program, of developing X-ray interferometry to break the resolution barrier in the X-rays, starting from X-ray fringes which have already been observed in the lab and examining what would be required for an X-ray interferometric space observatory, from the possibilities with single spacecraft to formation flyers which could push to sub-microarcsecond resolution. Such revolutionary observatories would enable detailed imaging-spectroscopy of stellar coronae and transiting exoplanets within ~100 pc, direct observation of X-ray binary orbits, supermassive black hole accretion flows and event horizons, and imaging of luminous transients and binary supermassive black holes across the observable universe.

3D magnetic structure, and brightening in sunspot penumbra
2020-01-28 11:45 - 12:45 | Aula Gratton
We analyzed spectropolarimetric data in the Fe I 617.3 nm and Ca II 854.2 nm lines of the sunspot in AR 12546 observed with the IBIS at the Dunn Solar Telescope on 20th May 2016 and co-temporal filtergrams by space-borne (Hinode, IRIS and SDO) instruments. The observed sunspot is one among the largest such features occurred over the last solar cycle. The IBIS data, taken under excellent seeing conditions that lasted more than three hours, were inverted with the NICOLE code, in order to retrieve the temperature, magnetic field, and plasma velocity of the studied sunspot as a function of optical depth and time. The umbral and penumbral regions are for the most part stable in the photosphere, while co-spatial chromospheric areas show waves in the umbra-penumbra boundary and intense brightening along penumbral filaments. We explored the origin of these chromospheric processes and their relation to changes in the 3D magnetic structure of the observed sunspot.

colloquium - Matteo Bachetti
2020-01-21 11:45 - 12:45 | Aula Gratton

The two-families scenario: what does it predict?
2020-01-14 11:45 - 12:45 | Aula Gratton
I will revisit the two-families scenario in which neutron stars coexist with strange quark stars, i.e. with compact objects made almost
entirely of deconfined quarks. I will outline the differences between this scenario and other schemes in which quark matter appears only at the center of compact stars and I will discuss how it compares with GW170817, GRB170817A, AT2017gfo and with the existing limits on masses and radii of compact stars.

Gamma-ray bursts under a new light: the TeV emission from GRB190114C seen by the MAGIC telescopes
2019-12-18 11:45 - 12:45 | Aula Gratton
Gamma-ray bursts (GRBs) are the most luminous sources of electromagnetic radiation known in the Universe. GRBs had been observed over a broad energy range from the radio band up to GeV gamma rays, but the TeV gamma-ray band had remained terra incognita for a long time. Thanks to the MAGIC telescopes, designed to catch the fast glimpses of the GRBs, the first ever clear detection in this band was achieved for GRB 190114C, a bright, long GRB. The TeV emission from GRB190114C belongs to a new energetic component, providing an energy output comparable at the one at lower energies. We will discuss the details of the observations by MAGIC and the accompanying multi-frequency measurements by more than 20 instruments, from radio to gamma- rays, and the inferences on the emission mechanisms. This historical, highly significant detection has followed an intriguing hint of TeV emission from GRB 160821B, a short GRB with an associated kilonova. This hint, if real, has potential multi-messenger implications on the detectability of gravitational wave alerts in high-energy gamma-rays.

Characterizing multi-phase gas outflows and their powering mechanism in nearby AGN
2019-12-10 11:45 - 12:45 | Aula Gratton
Active Galactic Nuclei are thought to play a crucial role in
the evolution of massive galaxies. In particular, fast outflows are
frequently observed in AGN covering various gas phases which may remove
a significant fraction of the gas content from the galaxies. I will
review the current state of research in this very active field of
ongoing research together with the advantages and disadvantages of
previous approaches. In particular, I will highlight the importance of
multi-wavelength observations to unravel the true multi-phase nature of
outflows by combining state-of-the-art observational facilities. In this
context I will present the first results from the ongoing Close AGN
Reference Survey (CARS), a multi-wavelength survey of 39 luminous
low-redshift unobscured AGN with extensive observations from VLT/MUSE,
ALMA, VLA, Chandra, SOFIA and many more. In addition, I will present the
multi-phase view of the famous ultra-luminous Quasar 3C273 where we
unlocked a few unknown secrets.

Acoustic oscillations and dynamo action in giants
2019-12-03 11:45 - 12:45 | Aula Gratton
The role of the magnetic field in determining the angular momentum transport in stellar interior is still an open issue. Acoustic oscillations are directly affected by the presence of a large-scale magnetic field but their study can provide fundamental information on the properties of the magnetic fields in solar-like stars. As an example the case of EK Eridani, a slowly rotating, overactive G8 giant, will be presented. Moreover the possibility to use asteroseismology to solve the long-lasting mystery on the origin of magnetic fields in Ap stars will be discussed.

LSST: an opportunity for the Italian Community
2019-11-26 11:45 - 12:45 | Aula Gratton
We review the current status of the LSST project, its expected performances, the key science goals and the involvment of the Italian Community

workshop Stamerra
2019-11-25 08:00 - 2019-11-28 17:00 | Aula Gratton

Lithium in the Universe: to Be or not to Be
2019-11-18 09:00 - 2019-11-22 18:00 | OAR Monte Porzio Catone – aula Gratton, Via Frascati 33, Roma, RM, 00136, Italia

Dal Sole a Sedna: una passeggiata per il sistema solare, e uno sguardo più in là
2019-11-15 16:00 - 17:00 | Aula Gratton
Dal 1959 ad oggi più di cento sonde spaziali hanno lasciato la Terra verso la Luna e lo spazio profondo. Queste appendici robotica dei nostri sensi hanno visitato tutti i pianeti e i principali satelliti del sistema solare, rivelando una straordinaria e inattesa varietà di forme e fenomeni. Ripercorrere vent’anni di scoperte sarà un tributo all’ingegno di quanti le hanno rese possibili. Grazie alle immagini più belle raccolte negli ultimi anni, la conferenza ripercorrerà le scoperte più significative nell’esplorazione del sistema solare, gettando infine uno sguardo ai pianeti delle stelle vicine. Forse tra questi ne esiste qualcuno che ospita la vita? Come trovarlo?

Lithium in the local Volume
2019-11-14 11:45 - 12:45 | Aula Gratton
We present our recent study on the chemical evolution of lithium in the thin disc of the Milky Way.
We found that the best agreement with the observed Li abundances in the thin disc is obtained
considering novae as the main source of lithium. We assumed a delay time of ≈1 Gyr for nova
production and an effective 7Li yield of 1.8(± 0.6)×10−5 Msun over the whole nova lifetime.
The possibility to check our detailed assumptions on lithium production on other stellar systems, such
as the satellites of our Milky Way, is seriously hampered by their distance from us. In these systems
dwarf stars (where the original lithium can be measured) are too faint to detect lithium lines.
However, thanks to the Gaia mission, it was recently possible to disentangle the stars of a disrupted
dwarf galaxy in the Galactic halo (called Enceladus or Galactic sausage). Adopting a chemical evolution
model able to match the chemical enrichment in alpha elements and the metallicity distribution function
of Enceladus, we present our prediction for the lithium abundance of the stars of this disrupted galaxy.

The ultraluminous X-ray pulsar NGC 5907 ULX-1 and its nebula
2019-11-08 11:45 - 12:45 | Aula Gratton
Ultraluminous X-ray pulsars are accretion-powered pulsars whose X-ray
luminosity, if isotropic, largely exceeds their Eddington limit. Only a handful
are known to date and NGC 5907 ULX-1, distant 17 Mpc from us, is the most luminous of them,
at 1e41 erg/s 500 times its Eddington limit. We constrained through
pulsar timing its orbit and spin behavior, estimating a 5d orbital period and a spin-up
time <40 yr. We detected an extended X-ray feature surrounding the source: likely a young and
powerful bubble driven by the wind from the accreting pulsar system. The nebula
has been powered at ~1e41 erg/s for ~70 kyr proving that a highly super-Eddington
regime can be sustained for much longer than the spin-up time of the pulsar.
I will present the current status of the observations and understanding of this system
and the prospects to solve the still open problems it raises.

The impact of AGB stars on the life of stellar systems
2019-11-05 11:45 - 12:45 | Aula Gratton
During the latest phases of their lives, low-intermediate mass stars (M<8Msun) evolve through the Asymptotic Giant branch (AGB) phase. Although very rapid, the AGB phase represents a crucial step for the chemical evolution of the system where these stars form. The reason is that AGB stars undergo an advanced nucleosynthesis and experiment dredge-up events, while they progressively lose the majority of their mass through stellar winds. Furthermore, the low temperature and high densisty of their stellar winds prove extremely favourable conditions for dust condensation in the circumstellar envelopes. All the reprocessed gas and dust lost by the AGB stars enrich the insterstellar medium of the host system. Detailed modelling of these complex physical processes are essential to reconstruct the impact that these stars had on the history of formation and chemical evolution of stellar clusters and galaxies. In this talk I will present how the latest generation of AGB+dust evolutionary models has been recently used to this scope in different environments: from globular clusters, to unveil the origine of multiple populations, to Local Group dwarf galaxies, to infer star formation history and dust production rate.

Post-AGB stars as tracers of the origin of elements in the Universe
2019-10-29 11:45 - 12:45 | Aula Gratton
The chemical evolution of galaxies is governed by the chemical yields from stars, especially from Asymptotic Giant Branch (AGB) stars. This underlines the importance of understanding how AGB stars produce their elements by obtaining accurate stellar nucleosynthetic yields. Although AGB nucleosynthesis has general validity, critical uncertainties (such as the treatment of convective-driven mixing processes and mass loss) exist in current stellar models. Observations from Post-Asymptotic Giant Branch (post-AGB) stars serve as excellent tools to confront predictions from a dedicated suite of stellar models, quantify the strongest discrepancies, and eliminate crucial uncertainties that hamper stellar modelling. Our recent studies of post-AGB stars have shown an intriguing chemical diversity that ranges from stars that are extremely enriched in carbon and s-process elements to the discovery of the first post-AGB star with no traces of carbon nor s-process elements. Additionally, our studies have also shown that AGB nucleosynthesis is significantly affected by a binary companion. These results reflect the complexity that surrounds the element production in AGB stars. In this talk, I will present the intriguing chemical diversity observed in post-AGB stars and its implications on element/isotope production in AGB stars and stellar nucleosynthetic yields.
