Osservatorio Astronomico di Roma

colloquium - Stephane Courteau: Puzzles in Galaxy Structure
2023-06-15 11:30 - 12:30 (Europe/Rome) | Aula Gratton
Galaxies like our Milky Way can be described in terms of their structure,
dynamics, and stellar populations. Some robust correlations between
galaxy structural properties such as stellar mass, circular velocity, and
size display surprisingly small scatter over many orders of magnitude,
hinting at well-regulated galaxy formation processes. A major challenge
to understanding these scaling relations, their tight scatter, and ultimately
galaxy formation and evolution, is the elusive interplay between visible
and dark matter. Among others, the radial acceleration relation, concept
of “galaxy diversity”, intrinsic scatter in galaxy scaling relations, impact
of supermassive black hole on galaxies, and comparisons with numerical
simulations of galaxy formation are presented in this context.

colloquium - Gabriele Cescutti: First results of the MINCE survey
2023-06-20 11:30 - 12:30
The struggle to find the most metal port stars in our Galaxy has produced an important bias in the observations and the intermediate metal-poor stars (-2.5<[Fe/H]< -1.5)
have been frequently overlooked. The missing information has consequences for the precise study of the chemical enrichment of our Galaxy, in particular for
what concerns neutron capture elements. Measuring at intermediate metallicity neutron capture elements (MINCE) aims to cover this gap, gathering
high quality spectra (high signal to noise and high resolution) of several hundred bright and metal poor stars, manly from of our Galactic halo.
In this talk, I show the results of the first sample of 42 stellar spectra for 40 different stars with the abundances of the elements up to europium. I also present
the results for the hyperfine splitting effects in two metal-poor halo stars: the profiles of the barium lines in HD 4306 agree with an s-process composition whereas
those in HD 6268 have a different profile, most likely linked to the presence of an r-process isotopic pattern. Therefore, the lines of barium of HD 6268 and HD 4306
seem to confirm the expectation that both r-process events and s-process contribution by rotating massive stars have polluted the ancient halo of our Galaxy.

Colloquium - Kenneth Wong: An Independent Measurement of H0 from Lensed Quasars
2023-06-27 11:30 - 12:30
Strong gravitational lens systems with time delays between the multiple images are a powerful probe of cosmology, particularly of the Hubble constant (H0). This independent method is an important test of the recent tension between early-Universe and late-Universe measurements of H0. The TDCOSMO project has measured H0 from lensed quasars using deep Hubble Space Telescope and AO imaging, precise time delay measurements from dedicated monitoring observations, a measurement of the velocity dispersion of the lens galaxies, and a characterization of the mass distribution along the line of sight. Assuming well-motivated physical profiles for the lens galaxies, our latest results constrain H0 to be ~74 km/s/Mpc for a flat Lambda CDM cosmology, with a precision of ~2%. These results are consistent with independent determinations of H0 using type Ia supernovae calibrated by the distance ladder method, and are in >4-sigma tension with the results of Planck CMB measurements, hinting at possible new physics beyond the standard LCDM model and highlighting the importance of this independent probe. Relaxing our assumptions on the form of the lens galaxy mass profiles and only allowing kinematic constraints, we can constrain H0 to ~8% precision. Including information from external data sets can improve the precision to ~5%. Future observations to increase the sample size and control systematic uncertainties will be key to resolving the current tension in H0.

colloquium - Steven Finkelstein: Unveiling the Earliest Galaxies and Super-massive Black Holes with JWST
2023-07-04 11:30 - 12:30
Pushing the Hubble Space Telescope to its limits at the end of the last decade has allowed astronomers to view the tip of the cosmic iceberg at a time only 500 Myr after the Big Bang. While a few candidate galaxies were found, significant questions about the onset and evolution of the earliest galaxies persisted. The launch of JWST has opened up this epoch to direct and detailed observation by providing a significant leap in our ability to study the entire epoch of reionization due to its redder sensitivity and spectroscopic capabilities. The Cosmic Evolution Early Release Science (CEERS) and Next Generation Deep Extragalactic Exploratory Probe (NGDEEP) programs have enabled one of our first looks into this epoch, finding that galaxies at z > 9 are more abundant than predicted by most simulations. This hints at not only an early onset of galaxy formation, but that stars are forming differently at these early times (at higher efficiency and/or with different initial mass functions). The CEERS spectroscopic program has shown that photometric redshifts *work*, with a high fraction of spectroscopic confirmations, and only one (interesting, yet rare) case of contamination. These data have also significantly improve our ability to identify early growing supermassive black holes, showing that they appear (relatively) frequently at high-redshift, including a remarkable AGN at z=8.7. These observations pushing models of early black hole growth, implying that massive seeds and/or super-Eddington accretion are needed at early times.

Quasars and the intergalactic medium at cosmic dawn
2023-09-20 14:30 - 15:30
High-redshift quasars provide direct probes to the formation of the earliest supermassive black holes, their connections to early galaxy formation, and the history of cosmic reionization. More than 200 quasars have now been discovered in the first billion years of the cosmic history, with the highest redshift currently at z=7.6, indicating that billion solar mass black holes have already fully formed merely half billion years after the first star formation in the universe. I will (1) review the current state of high-redshift quasar surveys and discoveries, as a result of the new generations of wide-field sky surveys and developments in data mining and machine learning; (2) discuss using high-redshift quasars as probes to the history of supermassive black hole growth in the early universe, using measurements of quasar luminosity function and black hole masses; (3) present the latest observations of the the co-evolution of early SMBH growth and galaxy formation, and the roles quasar played in early galaxy formation and structure formation; and (4) review the progress of using IGM absorption in quasar sightlines and properties of quasar proximity zones, which is unveiling a rapid and highly inhomogeneous reionization process at z~5.5 – 7.5. In particular, I will highlight new results from early JWST observations on early supermassive black hole growth, the environment of early quasars and the IGM and galaxy connection.

Colloquium - Riccardo La Placa: FRBs from neutron star magnetospheres: a unified model
2023-09-26 11:30 - 12:30
Fast Radio Bursts (FRBs) have, since their first detection, ranked among the most puzzling events in the sky owing to the extreme energies involved and the presence of both repeating and non-repeating sources: 15 years and thousands of bursts later, their emission mechanism still eludes us. I will present a new unified model for FRBs as magnetospheric events from neutron stars which naturally accounts for both types of behaviours, and show some predictions (and first applications) of the model on the expected energy and redshift distributions, both for the population at large and individual, well-studied sources.

Alessia Tortosa: Deep broad-band X-ray investigation of extreme accretion onto supermassive black holes
2023-10-10 11:30 - 12:30
Super-Eddington accretion periods are expected to be extremely important to explain the fast growth of the first supermassive black holes (SMBHs). While standard optically thick, geometrically thin accretion discs explain the observed spectral energy distribution (SED) of many AGN with low Eddington ratios, at higher accretion rates the disc becomes thin or slim and the nature of the accretion changes dramatically. Slim accretion disks are thought to have SEDs that are different from thick accretion disks, with strong anisotropy of the emitted radiation and a large fraction of the output carried out in the form of outflows and jets capable of controlling the growth and evolution of the host galaxy, and affecting the gas reservoir available for both star formation and SMBH accretion.
Among all accretion modes, accretion close or above the Eddington limit is still the least understood ones, and it is still largely debated what are the physical properties of the X-ray emitting plasma and of the accretion flow coming from the direct relativistic environment of the SMBH.
I will present the first systematic broad-band X-ray study of extreme accretion onto SMBHs of a sample of Hyper and Super Eddington accreting AGN with 1 < λEdd < 426. These sources belong to the Super-Eddington Accreting Massive Black Holes sample, which contains exclusively objects with black hole masses estimated via reverberation mapping. This analysis allowed us to investigate the properties of the X-ray corona and the behaviour of the reprocessed radiation in this regime of extreme accretion, as well as the structure of the iron complex and the properties of outflows.

colloquium Chris Sneden: Lithium-rich Red Giants: the helium and rotation connections
2023-10-17 11:30 - 12:30

Tiziana Macaluso, Francesco Poppi: Le prime osservazioni astronomiche in fotografia e le immagini conservate nell'archivio INAF-OAR. Studio a supporto del recupero conservativo.
2023-10-24 11:30 - 12:30
Le prime immagini astronomiche, conservate presso l’archivio INAF-OAR, sono tre dagherrotipi
ottenuti da Angelo Secchi nel 1851 presso l’Osservatorio del Collegio Romano, in occasione
dell’eclissi totale di Sole.
Nel 1857 fotografò anche le fasi lunari, acquisite con il telescopio equatoriale Merz. Queste
immagini rappresentano il primo atlante fotografico della Luna presentato il 28 agosto 1858
all’Académie des Sciences di Parigi, e poi all’Osservatorio londinese di Greenwich.
Successivamente, nel 1860 Angelo Secchi osservò e stampò su carta salata l’eclissi solare,
partecipando alla spedizione internazionale a Las Palmas de Gran Canaria. L’osservazione
dell’eclissi evidenziò le protuberanze solari e fu la prima prova della loro esistenza. Si dimostrò
anche che la corona appartiene al Sole e non alla Luna.
Queste pregevoli fotografie costituiscono anche le prime tecniche fotografiche delle origini,
nonché le prime osservazioni astronomiche per mezzo della fotografia.
Lo studio storico e le analisi diagnostiche di questi beni, utile a caratterizzare la natura dei
componenti e lo stato di degrado, arricchiranno le conoscenze sia in campo storico che scientifico,
e supporteranno il futuro restauro conservativo, che avverrà in collaborazione con corsi
universitari sul restauro e la conservazione di beni culturali.

colloquium Gregory Sloan: Carbon stars and dust in the Universe
2023-11-07 11:30 - 12:30
Intermediate-mass stars become carbon-rich in the final phases of their
lives as stars. As they die, carbon stars produce significant
quantities of carbon-rich dust, and they dominate the dust production in nearby
metal-poor galaxies like the Magellanic Clouds. Infrared spectroscopy
of carbon stars in these galaxies and our own reveals that (1) the
initial metallicity of a carbon star has little influence on how much
dust it will produce, and (2) the transition to strong pulsations in the
atmospheres of these stars leads to high rates of mass loss and dust
production, which will end the life of the star and eject most of its
mass back into its host galaxy. Stellar modeling shows that at lower
metallicity, stars evolve more quickly, and higher-mass stars can
become carbon stars. Carbon-rich dust has now been detected in
galaxies with redshifts up to 7, or only 800 million years after the
Big Bang. While carbon stars can evolve in this time, higher-mass
objects such as core-collapse supernovae or Wolf-Rayet stars are often
invoked as the likely source of that dust. Nonetheless, the available
evidence points to carbon stars as the most likely culprit.

colloquium - Richard de Grijs: Unveiling the complexities of massive star clusters
2023-11-13 11:30 - 12:30
Around the turn of the last century, star clusters of all kinds were considered ‘simple’ stellar populations. Over the past decades, this situation has changed dramatically. At the same time, star clusters are among the brightest stellar population components and, as such, they are visible out to much greater distances than individual stars, even the brightest, so that understanding the intricacies of star cluster composition and their evolution is imperative for understanding stellar populations and the evolution of galaxies as a whole. In this brief review of where the field has moved to in recent years, we place particular emphasis on the properties and importance of the effects of rapid stellar rotation, and the presence of multiplicity among the red-giant-branch populations in Magellanic Cloud star clusters with ages up to a few billion years.

colloquium - Davide Massari: Globular clusters as tracers of the Milky Way assembly history
2023-11-14 11:30 - 12:30
The combination of stellar proper motions measured by the Gaia mission with spectroscopic radial velocities has recently enabled the precise determination of the orbits of Milky Way stars and globular clusters. The information on their dynamics, coupled with existing chemical information, has allowed us to unravel many unknowns on their origin and evolution, as well as on the assembly history of the Milky Way itself. In this talk I will present the most recent results on this topic, focusing on how globular clusters can be superior tracers of the Milky Way build-up, and introducing a project, named CARMA, that aims at using globular cluster ages to characterise the most important merger events experienced by our Galaxy

colloquium - Mario Llerena: Probing the extreme ISM of extreme emission line galaxies at z~4-9
2023-11-21 11:30 - 12:30
Over the past decades, several studies have discovered a population of galaxies that undergo very strong star formation events. They are called extreme emission line galaxies (EELGs) and are characterized by typically high EWs which are driven by elevated specific star formation rates in low mass galaxies with subsolar metallicities and little dust. Such extreme systems are rare in the local universe, but the number density of EELGs increases with increasing redshift. Such starburst galaxies are currently presumed strongly to be the main drivers of Hydrogen reionization over 5.5 < z < 15, which serves to motivate many of the searches for high-z EELGs as well. I will present the physical properties of a sample of ~1000 EELGs at 4<z<9 photometrically-selected in the CEERS surveys using JWST/NIRCam and templates of local EELGs. Our results suggest they are metal-poor young starbursts with high ionization conditions which indicates they are strong LyC leakers candidates and ideal laboratories to NIRSpec follow-ups to study such extreme ISM conditions.

colloquium - Chiara Feruglio
2023-11-28 11:30 - 12:30

colloquium - Maria Lugaro
2023-12-05 11:30 - 12:30

colloquium - Giovanni Poggiali
2023-12-12 08:00 - 17:00

colloquium - Mauro Sereno
2023-12-12 11:30 - 12:30

Black hole accretion flows: from nearby stellar binaries to quasars at cosmic dawn
2024-01-09 11:30 - 12:30
I will review what we know about the emission from the accretion flow, starting with the stellar mass black holes in binary systems in our own galaxy. Scaling up to the supermassive black holes in active galaxies reveals both similarities and differences, and I will review what these might show about the nature of the accretion flow in quasars.

From high-mass X-ray binaries to ultraluminous X-ray sources: A (very personal!) journey through the realm of X-ray binaries
2024-01-16 08:00 - 17:00
X-ray binary systems are among the best astrophysical sources to study the processes of accretion of matter onto compact objects. Their broad phenomenology enables us to investigate distinct elements using a variety of analysis tools. In this talk, I will cover two main categories: high-mass X-ray binaries, represented by the archetypal Vela X-1, and ultraluminous and hyperluminous X-ray sources (ULXs and HLXs). For the first source, I will illustrate how high-resolution spectroscopy studies can help us investigate not only the compact object, but also the wind of the companion star. For the other classes, I will discuss an alternative method to determine the nature of the compact object in ULXs and I will present a population study of HLXs aiming at finding the best ULX-like candidates. This (very personal!) journey in the realm of X-ray binaries will also be a journey from sub- to super-Eddington accretion regimes.

Colloquium - Deimer Alvarez - Omega Centauri: a chemical perspective to understand its history
2024-01-23 11:30 - 12:30
Nowadays we know that Globular Clusters (GCs) are formed by multiple populations (MPs) with different light element abundances (C, N, O, Na, Mg, Al, Si, K) within the cluster stars, that are structured in well-defined patterns, such as the Na-O and Mg-Al anticorrelations. The evidence is interpreted as the signature of a self-enrichment process within the cluster, where a second population of stars was formed from material processed in the first population (or polluter) stars through the hot CNO cycle and its secondary NeNa and MgAl chains. A detailed study of these chemical anomalies is one of the paths to disentangle among the polluters proposed in the literature. In this sense, ω Centauri represents an ideal laboratory since this GC-like system exhibits magnified all the chemical anomalies usually observed in normal GCs. However, this system has a more complex history than a typical GC since it is probably the nuclear star cluster of a disrupted dwarf galaxy.
In this talk, through a chemical perspective I will show 1) how the outcomes of the MgAl chain can help to put more constraints on the nature of polluters responsible for the formation of MPs, and 2) what can we learn about the history of ω Centauri thanks to its metallicity distribution.

colloquium Francesco Carotenuto - Relativistic jets from black hole X-ray binaries: a MeerKAT view
2024-01-30 11:30 - 12:30
Black hole X-ray binaries (BH XRBs) can launch powerful outflows in the form of radio-emitting discrete jet ejecta, which are generally observed to be produced during bright outburst phases and to propagate at apparently superluminal speeds. However, little is known about the powering mechanism, the formation and composition of these jets, and studying them is important for understanding both their physics and their feedback on the surrounding environment. While discrete ejecta have been historically difficult to detect and to follow in their motion away from the central black hole, the MeerKAT radio-interferometer (precursor of the SKA) is now revolutionizing the field with its exceptional sensitivity at GHz frequencies. In this talk, I will present some of the most interesting advancements that we have obtained with MeerKAT observations of BH XRBs in the last five years, as part of the ThunderKAT collaboration. More in detail, I will present the MeerKAT detection of a number of new ejecta that we observed to interact with the interstellar medium (ISM) and to strongly decelerate at parsec scales far from the black hole. In this context, covering the deceleration phase is essential for the physical modelling of the jet kinematics, and I will discuss what is possible to learn from the application of these models on the jet physical parameters and on the properties of the environment surrounding BH XRBs.

colloquium Paolo Saracco - SHARP - A Near-IR Multi-mode Spectrograph conceived for the Multi-Conjugate adaptive optics module MORFEO@ELT
2024-02-06 11:30 - 17:00
The world’s largest aperture combined with state-of-the-art Adaptive Optics systems will enable the ELT to capture better data than the JWST in both sharpness and depth. Therefore, the spectrograph intended for the 2nd port of the Multi-Conjugate Adaptive Optics (MCAO) system MORFEO@ELT will be the most powerful instrument of the JWST era, revealing phenomena beyond the reach of others. SHARP (http://sharp.brera.inaf.it) is a near-IR (0.95-2.45 mu) spectrograph designed for the 2nd port of MORFEO@ELT, intended to be submitted in the upcoming ESO instrument call. Comprising a Multi-Object Spectrograph, NEXUS, and a multi-Integral Field Unit, VESPER, SHARP extends its wavelength range to ~2.45 μ. Coupled with MCAO-assisted observations, it delivers unprecedented high angular (~30 mas) and spectral resolution, outperforming NIRSpec@JWST (100 mas). MORFEO-SHARP will allow us to study the nearby and the early Universe in unprecedented detail, resolving the first galaxies and the star forming regions within galaxies far back in cosmic time, and providing spectra of individual nearby young stellar objects. This presentation introduces the scientific rationale behind SHARP, showcasing its features and inviting those interested to join the SHARP team.

JAC colloquium - Andrea Miglio
2024-02-14 11:30 - 12:30

Colloquium Letizia Stanghellini - Advances in stellar and galactic evolution with the population of planetary nebula progenitors from the APOGEE DR17 survey
2024-02-20 11:30 - 12:30
Planetary nebulae (PNe) are the ejected gas and dust shells of Asymptotic Giant Branch (AGB) stars, which represent the late life of low- and intermediate-mass stars (LIMS). With the advent of the APOGEE DR17 survey, there is a purpose in comparing Red Giants (RGs) and PNe abundances to disclose their similarities and differences since such a comparison has been rarely, and not recently, done in the Milky Way. While we expect similarities in most of the alpha-element distributions across the two populations, given their limited evolution in LIMS, differences in Fe and S abundances allow us to determine their depletion due to grain condensation in post-AGB phases. Differences in N and C between PNe and their progenitors set new limits to their production in the late stages of LIMS evolution. Finally, we use radial metallicity gradients from RGs and PNe and Gaia-calibrated distances to constrain galaxy evolution in the framework of the current chemical evolution models.

colloquium - Andres Gurpide
2024-02-27 11:30 - 12:30

colloquium - Alice Borghese: The zoo of isolated neutron stars
2024-03-12 11:30 - 12:30
Neutron stars have shown diverse characteristics, leading us to classify them into different classes. In this talk, I will focus on the observational properties of isolated neutron stars: from magnetars, the strongest magnets we know of, to central compact objects, the so-called anti-magnetars, stopping by the rotation-powered pulsars and X-ray dim isolated neutron stars. Moreover, I will show you how some sources have exhibited features straddling those of different groups. I will then finish with some considerations on possible evolutionary links between neutron star families.

Colloquium Antonella Barucci - The JAXA sample return MMX (Martian Moon eXploration) mission
2024-03-12 11:30 - 12:30
The JAXA MMX mission will be launched in 2026 to Martian system to carry out three years observations of the Martian moons, and to bring back to Earth in 2031 samples (>10 g) from Phobos. The spacecraft will arrive at Mars system in 2027, injected into Phobos co-orbit, to observe Phobos and monitor Mars’ atmosphere. Deimos will be also explored by several fly-bys.
The mission is devoted to study the origin of Martian moons, to enlarge the knowledge of the Martian system and to assess the possibility of Martian life,.
The major goals of the mission are to decipher the origins of the Martian moons and constrain processes for planetary formation and material transport in the region connecting the inner and outer Solar System. From the Martian moon Phobos, MMX will investigate the transport of water and organic materials across the Solar System and explore how life and habitable environments were created. The mission will clarify the driving mechanism of the transition of the Mars-moon system and add new knowledge to the evolution history of Mars.
An imager spectrometer MIRS (MMX Infrared Spectrometer) has been requested to our team at LESIA-Paris Observatory to accomplish several of the science objective of the mission.
The status of art of the mission will be presented.

colloquium - Srefano Camera
2024-03-19 11:30 - 12:30

colloquium Mikako Matsuura - Dust and molecules in dying stars
2024-03-26 11:30 - 12:30
There is a large debate about how dust grains have been accumulated in the interstellar medium (ISM) of galaxies. One of the major sources of dust grains into the ISM is evolved stars, such as AGB stars, red supergiants and supernovae (SNe). On the other hand, fast-expanding SN blast waves could be so efficient that theoretical models predict that almost entire ISM dust grains ejected by stars can be wiped off by SN explosion. There are still uncertainties in dust evolution in the ISM. We present several results about studies of AGB stars, planetary nebulae (PNe) and SNe in my talk. The first part is GAIA studies of AGB stars, showing the distribution of local dust output from AGB stars. The second part is studies of dust in PN, using JWST, indicating the final re-processing of dust grains before they are integrated into the ISM. Finally, JWST observations capture how dust grains are destroyed by SN blast waves in Supernova 1987A.

colloquium - Giovanni Cresci
2024-04-23 11:30 - 12:30
