The most extreme phase of black holes growth and feedback
2023-02-21 11:30 - 12:30 (Europe/Rome) | Aula Gratton
Deep surveys have revealed fully-grown supermassive black holes powering active galactic nuclei at very high redshifts, when the Universe was a few hundred Myr old, less than 10% of its current age. This challenges the theories of black holes growth, requiring long periods of high accretion, most likely above the Eddington limit. These objects will be difficult to study in detail, even with future advanced observatories. However, in the nearby Universe, there are several objects that shine beyond Eddington, can be studied in great detail and used as proxy for primordial black holes. In the supermassive regime we have some narrow line Seyfert 1 galaxies and tidal disruption events, whilst hundreds of stellar-mass black holes and neutron stars are known to power ultraluminous X-ray sources (ULXs). A common denominator to these stellar-mass and supermassive objects is the presence of extreme winds which confirm the predictions by theoretical models of super-Eddington accretion. These winds carry a huge amount of power owing to their mildly-relativistic speeds (~0.2c) and are able to significantly affect the surrounding medium and limit the amount of matter that can reach the central accretor. In this seminar I will discuss the state-of-art of super-Eddington accretion in different mass regimes and highlight future missions that will decisively boost this research field.

Connecting AGN and massive gas reservoir in protoclusters: the Chandra view of the Jackpot nebula at z=2
2023-02-28 11:30 - 12:30 | Aula Gratton
High-redshift, gas-rich galaxy protoclusters represent excellent laboratories
for investigating the effects of the environment on SMBH growth, nuclear
activity and onset of AGN feedback in overdense regions.
The detection of enormous (>200 kpc) Ly_alpha nebulae (ELANe) in some of these
systems, coupled with the presence of multiple AGN, has called for an extensive
follow-up observational campaign, including X-rays to properly census
the AGN population in these protocluster and, hence, determine their role in
powering ELANe.
In this talk, I will present an ongoing large Chandra program targeting some
high-redshift ELANe; in particular, I will focus on the properties of the
Jackpot nebula at z=2, showing four X-ray detected AGN in the inner part and
some additional AGN associated with Lyman alpha emitters on larger scales.
I will also report on the detection of diffuse X-ray emission in the inner
region of the nebula.

VVV Microlensing events as tracers of Galactic structure and kinematics
2023-03-07 11:30 - 12:30 | Aula Gratton
We report the discovery of ~1,000 microlensing events within an area covering 20.68 deg^2 between 2010 and 2015 in the zero-latitude region of the Galactic bulge using the VVV Survey near-IR data. We used the near-IR Color-Magnitude and Color-Color Diagram to analyze the extinction properties of the sample in the central region of the Galactic plane. We study the Einstein ring crossing time distribution as a strong dark mass indicator and study features of the Galactic structure. We found 20 distant microlensing events probably located in the far disk of the Galaxy. This is the first time a population of events has been discovered, allowing us to study the other side of the Milky Way. We also examine specific events, such as the long timescale events showing parallax that favor the presence of dark stellar remnants such as black holes and neutron stars, which are essential ingredients in our understanding of stellar evolution and mass distribution, galaxy evolution and structure, dark matter balance, etc.

colloquium - Sonia Fornasier: Latest results on 67P/Churyumov-Gerasimenko comet from the OSIRIS instrument onboard the ROSETTA mission
2023-03-21 11:30 - 12:30 | Aula Gratton
The Rosetta space mission of the European Space Agency Rosetta has observed comet 67P/Churyumov-Gerasimenko for about 2 years, delivering the lander Philae on the comet surface for the first time in the history of the space exploration. Ended in September 2016, the Rosetta/Philae mission, acquired an incredible amount of unique data of comet 67P, allowing the most detailed study ever attempted of a comet.
Rosetta had a large complement of scientific experiments including the OSIRIS imaging system which consists of a Wide Angle Camera (WAC) and a Narrow Angle Camera (NAC). More than 80000 images were acquired with the OSIRIS imaging system with spatial resolution ranging from several meters to a few centimeters per pixel during Rosetta’s descent to the comet in late September 2016. In particular, the high dynamics of the cameras detectors permitted to distinguish morphological structures on shadowed areas as well as frost layers, and to monitor at the same time the very dark surface, faint jets (with lifetimes shorter than a few minutes), and ices exposures.
An extensive catalogue of volatiles exposure was recently created permitting to investigate the link between composition, morphology and activity. It also indicates that ices exposures are typically sub-meter sized, information which is relevant for cometary models.
Detailed analysis of highly active regions revealed that the small lobe has different physical and mechanical properties than the big one and a lower volatile content, at least in its uppermost layers. These findings support the hypothesis that comet 67P originated from the merging of two distinct bodies in the early Solar System, as previously suggested by the geomorphological analyses of the comet terrains.
Finally, the reconstructed Philae orbit revealed that it had a second landing site located only 30 m apart from the final one. Philae stamped within a boulder for 25 cm depth, indicating that the cometary material is extremely soft and highly porous. This collision exposed the primordial water ice embedded within the boulder, providing an accurate measurement of the refractory to volatile ratio in comet 67P.

colloquium - Giulia De Somma: The classical Cepheids modelling in the Gaia Era
2023-03-28 11:30 - 12:30 | Aula Gratton
Classical Cepheids are the most used primary distance indicators to calibrate
the cosmic distance ladder and reliable stellar population tracers. These stars
have been adopted to probe galactic evolution and star formation, thanks to
their intrinsic variability and the link between pulsation properties and
evolutionary parameters. A theoretical approach to the study of these objects
is crucial to interpret observed behaviors and fully exploiting the accuracy of
observed oscillation characteristics in terms of stellar properties and distances.
By using the Stellingwerf hydrodynamical code, we recently provided detailed
homogeneous nonlinear Classical Cepheid pulsation models. We take into
account variations of chemical composition, mass-luminosity (ML) relation, and
efficiency of super-adiabatic convection.
The predicted pulsation observables included the instability strips, multi-filter
light curves, and the corresponding mean magnitudes and colors.
We used these quantities to derive metal-dependent period-luminosity-color
(PLC) and period-Wesenheit (PW) relations. The latter were applied to a
sample of Gaia Early Data Release 3 (DR3) Galactic Cepheids. The inferred
theoretical parallaxes were tested against Gaia astrometric results. By
combining this pulsational scenario with updated stellar evolution
predictions and using the BASTI code, we derived new and accurate metal-
dependent Period-Age and Period-Age-Color relations, which were applied to
the same sample of Galactic Cepheids in the Gaia DR3 to constrain their age
distribution. These results are all discussed in view of the incoming SPECTRUM
project that will represent the first attempt to systematically compute
nonlinear convective pulsation models along stellar evolutionary tracks.

Colloquium - Gianluca Castignani: Processing of gas in galaxies within the cosmic web
2023-04-04 11:30 - 12:30 | Aula Gratton
Galaxies are distributed in a complex filamentary network of matter called the cosmic web. Several studies showed that galaxy properties can be influenced by their large scale environments: spiral galaxies may interact and merge into an elliptical galaxy, they can be stripped from their gas by ram pressure and see their star formation quenched, they can be harassed in small groups, even before entering into clusters. However, it remains debated which is the overall impact of the cosmic web in processing cold gas of galaxies, as they move through large-scale filaments around the clusters down to the densest regions of the cluster cores. To evaluate the degree of such processing it is essential to study the reservoirs of molecular gas as it is the raw material from which stars form. I will present the results of a large observational campaign, mainly exploiting IRAM millimeter facilities, with the goal of quantifying the processing of galaxies’ gas in the cosmic web and with cosmic time. I will discuss the degree of such processing in a variety of dense megaparsec-scale environments for: i) galaxies in the cosmological filaments around Virgo, the nearest cluster in the Universe, ii) galaxies in and around clusters at intermediate redshifts, iii) distant brightest cluster galaxies (BCGs) at the center of clusters. Finally, I will discuss the potential of such studies for next generation multi-wavelength facilities. Thousands of distant clusters and BCGs will be detected with Euclid, enabling an unprecedented leverage to constrain galaxy evolution in clusters.

colloquium - Eilat Glikman: Understanding the role of Quasar feedback and Radio emission in red Quasars
2023-04-18 11:30 - 12:30 | Aula Gratton
Observational evidence suggests that quasar activity plays an important role in regulating how
galaxies and their nuclear supermassive black holes grow and co-evolve, despite their
orders-of-magnitude difference in scale. In this talk, I will present a population of highly
luminous dust-reddened quasars that may be the key to understanding this co-evolution. Red
quasars are among the most intrinsically-luminous quasars in the Universe representing a
short-lived phase in the lifetime of a quasar, during which their energy output (feedback)
irrevocably impacts their host galaxy. Recent evidence has also shown that red quasars have
enhanced radio emission, possibly linking the formation of jets to the merger phenomenon or
exposing a different form of feedback in these systems, such as dusty radiation-driven winds.
Red quasars are thus ideal laboratories for addressing fundamental questions on the co-evolution
of black holes and their host galaxies as well as the physics of feedback. I will present
findings from several surveys that are uncovering this elusive population of quasars using
various selection methods across the electromagnetic spectrum to probe a broad range of redshift
and luminosity regimes.

OAR student's day
2023-05-09 | Aula Gratton

JAC Colloquium: Bertrand Lamasle
2023-05-17 14:30 - 15:30 | Aula Gratton

colloquium - Alessandra De Rosa: The quest for dual and binary supermassive black holes
2023-05-23 11:30 - 12:30 | Aula Gratton
Hierarchical models of galaxy formation predict that galaxy mergers represent a key transitional stage of rapid SMBH growth; however, the lack of a census of AGN pairs over cosmic time prevents us from firmly connecting AGN triggering and merging processes.
The quest for pairs of SMBHs at the dawn of the multi-messenger era is compelling. These systems represent the natural precursor to coalescing SMBHs that are among the loudest sources of gravitational waves. Detecting dual AGN – active SMBHs at projected separations larger than several parsecs – and binary AGN – active SMBHs bound in a Keplerian binary – is an observational challenge.
The talk will review the observational efforts, across the electromagnetic spectrum, on the detection and study of dual and binary SMBHs and will reflect on broader implications of these findings when considering the current simulations of merging BH.

colloquium - Michele Perna: First results from the JWST GTO programme 'Galaxy Assembly with NIRSpec IFS’ (GA-NIFS): The gaseous environment and ISM properties of quasars at z = 3-7
2023-05-30 11:30 - 12:30 | Aula Gratton
The JWST/NIRSpec GTO programme ‘Galaxy Assembly with NIRSpec IFS’ (GA-NIFS) is an ambitious project aimed at characterising the internal structure of >40 distant galaxies and active galactic nuclei (AGN) and quasars (QSOs) at z=3-9, and, therefore, to investigate the primary physical processes driving galaxy evolution across cosmic time. In this talk I will present an overview of the very first results obtained from a subsample of QSOs, as well as the analysis and the knowledge on optimising the QSO-host decomposition in NIRSpec IFS data (Perna et al. 2023, Marshall et al. 2023, Übler et al. 2023).
I will discuss the interacting environment of two QSOs at z~6.8 and one at z~5.5, as well as the ultra-dense environment of a dual AGN at z~3.3. I will also present their interstellar medium properties, in terms of dynamical conditions, ionisation, metallicity, and outflows energetics. In particular, I will discuss the limitations of classical emission line diagnostics to distinguish between AGN and star formation ionisation source, and the relation between black hole masses and host galaxy properties in the context of other recent JWST results on high-z QSOs.

colloquium - Shuowen Jin: Massive galaxies and clusters in the making: Multi-wavelength study of optically-dark SMGs and galaxy overdensities at z>2.5
2023-06-06 11:30 - 12:30
Recent studies have revealed an important population of submillimeter galaxies (SMGs) that dropped out in deep optical surveys, however their nature is still largely unknown. On the other hand, high-z protoclusters are often suspected to be forming the local massive clusters, while the evolutionary path is still elusive. Thus discovering more SMGs and galaxy overdensities towards high redshift are key to pushing our understanding of the formation of massive galaxies and structures. Here I report recent discoveries and study on the two topics from our team, including (1) spectroscopic confirmation of a sample of optically-dark SMGs at z~4–6 using ALMA, NOEMA and JWST; (2) detailed insight into a z=2.58 HST-dark SMG by synergy of JWST and ALMA data; (3) discovery of protoclusters and compact galaxy groups at z~3–5 using NOEMA, ALMA and JWST. We found that most of the optically-dark SMGs have optically thick dust in FIR, and they consist of s significant fraction of star-forming galaxies at z~4. By comparison with simulations, we revealed that low-mass and compact galaxy groups most likely merge into single massive galaxies at lower-z, i.e., “proto-massive galaxy”, while only the most massive protoclusters are likely to evolve to local clusters.

colloquium - Stephane Courteau: Puzzles in Galaxy Structure
2023-06-15 11:30 - 12:30 | 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 | Aula Gratton
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 | Aula Gratton
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 | Aula Gratton
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 | Aula Gratton
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 | Aula Gratton
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 | Aula Gratton
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 | Aula Gratton

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 | Aula Gratton
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 | Aula Gratton
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 | Aula Gratton
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 | Aula Gratton
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 | Aula Gratton
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 | Aula Gratton

colloquium - Maria Lugaro
2023-12-05 11:30 - 12:30 | Aula Gratton

colloquium - Giovanni Poggiali
2023-12-12 08:00 - 17:00 | Aula Gratton

colloquium - Mauro Sereno
2023-12-12 11:30 - 12:30 | Aula Gratton

Black hole accretion flows: from nearby stellar binaries to quasars at cosmic dawn
2024-01-09 11:30 - 12:30 | Aula Gratton
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.
