AstroBigné seminars season 2021-2022

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28/06/2022

Mathieu Van der Swaelmen

Origin of the r-process: constraints from Eu, Mg and O in the Milky Way open clusters

Elements heavier than the iron nuclei are mostly produced by two different neutron-capture processes, the s- and the r-process, occurring in the final stage of a star's life. While the s-process is known to occur in the envelop of AGB stars, the nucleosynthetic sites of the r-process are still a matter of debate. Core-collapse supernovae and neutron-star mergers (especially after the multi-messenger observation of the the gravitational event GW170817) are both serious candidates as r-process sites but their respective contributions in the chemical evolution modelling of the Milky Way are heavily discussed by the community. To shed new light on this topic, we used the abundances of Eu, O and Mg obtained by the Gaia-ESO survey for the Milky Way field stars and open-clusters and compared them to chemical models to investigate different scenarios. We find that the Eu production in the Milky Way thin discs is dominated by core-collapse supernovae and that there is no strong evidence for a delayed production by neutron-star mergers. As a side-result, we find that the Mg production need a non-negligible contribution from type Ia supernovae to explain observational data.

21/06/2022

Rob van Holstein (ESO Santiago)

Expanding the polarimetric capabilities of SPHERE-IRDIS to characterize the formation environments of planets

The near-infrared linear-polarimetric imaging mode of the high-contrast imager SPHERE-IRDIS at the Very Large Telescope has proven to be very successful for the detection and characterization of planet-forming disks. In this talk, I will present our efforts to extend the polarimetric capabilities of SPHERE-IRDIS using the existing hardware. By taking advantage of the high polarimetric accuracy of the IRDAP pipeline, we detected for the first time near-infrared linear polarization of several known, directly imaged planetary mass companions. We also devised and tested an observing scheme to measure circular polarization with IRDIS. With this mode, we aim to measure for the first time circular polarization in planet-forming disks to characterize disk structures, scattering asymmetries, dust properties, and magnetic-field geometries, and to perhaps even shed light on the emergence of homochirality in biomolecules. Finally, we are currently developing a spectropolarimetric mode by combining the IRDIS long-slit spectroscopy (LSS) mode with polarimetry. We aim to use this mode to study the formation of planets and the origin of water on Earth by detecting water ice at solar-system scales in planet-forming disks, potentially revealing the water-ice sublimation line. Our efforts enable unique ways to characterize the formation environments of planets and explore new science cases and techniques for future high-contrast imaging polarimeters on the extremely large telescopes.

14/06/2022

Andrés Izquierdo Cartagena (ESO Garching)

Hunting kinematic planetary signatures through channel-map modelling

I will present recent work on the detection of gas substructure and localised velocity perturbations possibly driven by two unseen giant planets in the disc of HD 163296 as traced by 12CO. The study is performed using the Discminer channel-map modelling tool, which features a statistical technique to identify significant deviations from Keplerian rotation in both orbital radius and azimuth in the disc. The Discminer models are also well suited for studies of the gas properties and vertical structure of discs through the analysis of line profile attributes, from which we found that one of the planets in HD 163296 could also be triggering enhanced turbulent motions around its orbit. Finally, I will present preliminary results of applying the same techniques on high velocity resolution data of the discs around MWC 480 and AS 209.

07/06/2022

Cédric Plantet

Fine phasing of the Giant Magellan Telescope in an adaptive optics loop

The Giant Magellan Telescope Organization (GMTO) and the Adaptive Optics (AO) team of Arcetri have been collaborating in the last decade to design the Natural guide star Wavefront Sensor (NGWS) for the Natural Guide Star AO mode of the GMT. The GMT’s primary and deformable secondary mirror are each composed of 7 segments, and a critical task of the NGWS will be to keep these 7 segments in phase in addition to the AO correction. Simulations have shown that, in most cases, a classical AO system cannot achieve this task on its own. I will present the solution that was foreseen in the preliminary design and how we revisited this design in the current phase, for which the goal is to build a prototype of the NGWS and test it.

31/05/2022

Germano Sacco

The final data release of the Gaia-ESO Survey

The European Southern Observatory has just released the final catalogue of the Gaia-ESO survey. This catalogue has been derived from the observations of ~115,000 Galactic stars carried out with the multi-object spectrograph FLAMES at the VLT, during 340 nights distributed between the end of the 2011and the start of 2018. The catalogue contains radial and projected rotational velocities, stellar parameters and abundances of several elements for stars located in all the main components of the Milky Way and in a large sample of star clusters. It represents one of the best dataset to study the history of the Milky Way, the formation and evolution of star clusters, and all phases of stellar evolution. In this talk I will briefly describe the content of this catalogue, the work that has been done to build it, and some of the scientific results that have been obtained from the exploitation of these data, giving particular emphasis to the role of the Arcetri researchers in this ambitious project.

24/05/2022

Ana López-Sepulcre (Grenoble)

Organic molecules in protostars: searching for the building blocks of life pdf

The gas associated with the early stages of star formation contains traces of a large variety of molecular species, many of which are organic in nature. Interestingly, we observe a substantial chemical diversity among protostars, with some objects being enriched in what astrochemists label interstellar complex organic molecules (iCOMs), such as methyl formate (HCOOCH3) and formamide (NH2CHO), while others are overabundant in unsaturated carbon chains such as C4H. What is the cause of this diversity? And where should we place the proto-solar-system in this chemical context: was it rich in iCOMs, or in carbon chains, or in both? Thanks to the development of sensitive broadband (sub-)millimetre instrumentation, both in single-dish telescopes and interferometers such as those operated by IRAM, we are currently witnessing big steps forward in this area. At the same time, new observational challenges are arising which make us look to the future with hopeful eyes. I will summarise what we have learnt, in the past decade or so, about the molecular contents in solar-mass protostellar sources, and suggest a few guidelines to stimulate progress in the field.

17/05/2022

Armando Riccardi

ERIS at VLT: status of the commissioning pdf

ERIS is a new Adaptive Optics (AO) instrument installed at the Cassegrain focus of VLT-UT4 in February 2022 and led by a Consortium of Max-Planck Institut für Extraterrestrische Physik, UK-ATC, ETH-Zurich, NOVA-Leiden, ESO and INAF. ERIS hosts a new high-resolution coronographic camera (NIX) ranging from 1 to 5 microns and SPIFFIER, a refurbishment of the Integral Field Unit spectrograph currently installed in SINFONI, covering J, H and K bands. INAF has an important role in the project having the responsibility for the development, implementation and commissioning of the AO system (OAA), the Calibration Unit (OAAb) and the Instrument Software (OAPd). The FTEs spent on the project have been rewarded with 60 GTO nights for INAF. The talk presents the status of the Commissioning after the run held in April, focused on functionality, and the schedule for the Commissioning completion in September/October this year.

10/05/2022

Emanuele Nardini

Active Galactic Nuclei XIV: The Renaissance of Black Holes and Galaxies pdf

The 14th Italian national congress on Active Galactic Nuclei will be held in Firenze on May 23-27, hosted for the second time by the Arcetri INAF+UniFI research group. I will give a brief overview of how the meeting has evolved over the years, and briefly discuss the various logistics and administrative difficulties we had to face to organise an in-person event after two years of lockdown and virtual meetings.

03/05/2022

Fabian Scheuermann (Heidelberg University)

Planetary Nebula Luminosity Function distances for 19 galaxies observed by PHANGS–MUSE

We provide new planetary nebula luminosity function (PNLF) distances to 19 nearby spiral galaxies that were observed with VLT/MUSE by the PHANGS collaboration. Emission line ratios are used to separate planetary nebulae (PNe) from other bright [OIII] emitting sources like compact supernovae remnants (SNRs) or HII regions. While many studies have used narrowband imaging for this purpose, the detailed spectral line information provided by integral field unit (IFU) spectroscopy grants a more robust way of categorising different [OIII] emitters. We find generally good agreement with literature values from other methods. Using metallicity constraints that have also been derived from the same IFU data, we revisit the PNLF zero point calibration. Over a range of 8.34<12+log(O/H)<8.59 our sample is consistent with a constant zero point and yields M*=-4.542+0.103-0.059 mag, within 1σ of other literature values. MUSE pushes the limits of PNLF studies and makes galaxies beyond 20 Mpc accessible for this kind of analysis. This approach to the PNLF shows great promise for leveraging existing archival IFU data on nearby galaxies.

26/04/2022

Antonio Garufi

From 1978 to 2023: the "Protostars and Planets" conference series pdf

The "Protostars and Planets" are the ultimate conferences in the field of star and planet formation. Each chapter of the proceeding book is a compendium of the results obtained over the previous 6-7 years. The seventh edition will be held in one year in Japan. I tell the story of the first six editions and present the upcoming chapter on the "Near-IR view of planet-forming disks and protoplanets".

05/04/2022

Edvige Corbelli

Astronomia in pagella: alcune riflessioni al termine del primo ciclo pdf

L'astronomia viene inserita come materia curriculare ed interdisciplinare nel programma quinquennale del Liceo Scientifico attraverso un progetto sperimentale attivato al Gobetti-Volta. Oltre a presentare il progetto e gli strumenti utilizzati dai ricercatori di Arcetri per promuovere la cultura astronomica verso chi sceglie Il Potenziamento Astronomico, l'incontro vuole essere un momento di riflessione dopo i primi 5 anni. I primi ragazzi che hanno sperimentato questo percorso si avvicinano alla maturità: hanno sviluppato delle nuove competenze e migliorato l’apprendimento dei programmi di base? Come possiamo migliorare la nostra offerta? Quali sono gli ostacoli e le deviazioni di percorso di questa proposta didattica innovativa che affianca la nostra ricerca le infrastrutture ed i docenti della scuola?

29/03/2022

Olga Bayandina

From maser flares to accretion bursts pdf

The first initial stages of the evolution of massive young stellar objects (MYSOs) have long remained mysterious, since these stars are distant and originated deep in their parent clouds. A significant contribution to the development of the theory of the evolution of MYSOs has been made by the study of masers, whose flares have proven to be a powerful tool for detecting MYSOs going through episodic accretion bursts. In this talk I will discuss the activities of the Maser Monitoring Organization (M2O) - a global cooperative of maser monitoring programs, and the upcoming installation of high-frequency receivers on the INAF telescopes which will greatly assist us in studying accretion bursts in MYSOs.

22/03/2022

Antonino Marasco

Gas at the disc-halo interface of the Milky Way: evidence for a Galactic fountain with collimated outflows and diffuse inflows pdf

We model the spatial distribution and kinematics of the high- and intermediate- velocity clouds (HVCs and IVCs) observed in absorption towards a sample of 55 Galactic halo stars with accurate distance measurements. We employ a simple model of a thick disc whose main free parameters are the gas azimuthal, radial and vertical velocities, and apply it to the data by fully accounting for the distribution of the observed features in the distance-velocity space.
We find that at least two separate components are required to reproduce the data. A scenario where the HVCs and the IVCs are treated as distinct populations provides only a partial description of the observations. Instead, the data are better described by a combination of an inflow and outflow components, both characterised by rotation with speed comparable to that of the disc and vertical velocities of 50−100 km/s. Features associated with the inflow appear to be diffused across the sky, while those associated with the outflow are mostly confined within a bi-conic structure. Our findings indicate that the lower (|z|<10 kpc) Galactic halo is populated by a mixture of diffuse inflowing gas and collimated outflowing material, which are likely manifestations of a galaxy-wide gas cycle triggered by stellar feedback, that is, the galactic fountain.

15/03/2022

Simone Bianchi

Searching for anomalous microwave emission in nearby galaxies with SRT pdf

I will present the results of Sardinia Radio Telescope observations of four nearby spiral galaxies in the K band (18.6 and 24.6 GHz). The aim was to detect Anomalous Microwave Emission (AME), an elusive emission component seen in excess of thermal and synchrotron emission and presumably due to spinning dust grains. AME has been observed thus far in the Milky Way and only in a handful of other galaxies (most notably, M 31). We derived upper limits for the AME contribution in our targets, which are consistent with the few available detections, if a proper emissivity per dust mass is defined. We plan to put further constraints on AME in spiral galaxies, and study the largely unexplored mm-to-cm range of their Spectral Energy Distribution, with the high-frequency instrumentation which will become available at SRT from the next year.

08/03/2022

Asa Skuladottir (UniFI)

The 4DWARFS Community Survey in 4MOST pdf

Recently, our large spectroscopic survey 4DWARFS was awarded 520k fibre hours in 4MOST. I will talk about the aim and expected outcomes of 4DWARFS, which will target the Milky Way dwarf galaxies in the Southern hemisphere.

01/03/2022

Jason Spyromilio (ESO)

ELT construction status

The current status of the ELT project shall be presented. The site activities have resumed following a shut down due to COVID. Manufacturing is continuing on the telescope components and lots of nice photographs shall be shown. The current state of the instrumentation projects shall be reviewed. Some discussion shall be presented on the challenges of the telescope control and what the user experience shall be like.

22/02/2022

Filippo Mannucci

Uncovering the missing population of dual AGNs with Gaia pdf

All cosmological models of structure formation predict the existence of a widespread population of dual supermassive black holes (SMBHs) in-spiraling inside their common host galaxy, eventually merging and giving rise to intense gravitational waves emission. These SMBHs are expected to accrete material from the host galaxy, triggering a pair of luminous active galactic nuclei (AGNs) separated by up to a few kpc. Identifying these systems is a difficult task and very few confirmed dual AGNs are currently known. We have developed a novel method that takes advantage of the unique capabilities of the Gaia satellite to obtain large and reliable samples of dual or lensed AGN candidates with sub-arcsec separations. Sampling separation down to 2 kpc at z>1, this technique allows us to probe the physical processes driving the inspiraling of the pairs of SMBH inside a single galaxy.

15/02/2022

David Aguado (UniFI)

The discovery of the most primitive system in the Milky Way pdf

The recent discovery of the C-19 stream has provided definitive proof that globular clusters with extremely low metallicities could exist. Thanks to the combined efforts of Pristine mapping and the innovative STREAMFINDER algorithm, the nature of this primitive system has been closely studied.

08/02/2022

Giovanna Caprio

Il repository istituzionale OA@INAF e l'Open Access: istruzioni per l'uso pdf

Il talk ha lo scopo di illustrare brevemente i motivi dell'istituzione del repository INAF, l'importanza dell'open access e i cambiamenti che questo sta apportando nel panorama della ricerca coinvolgendo editori, enti di ricerca, organi ministeriali e Commissione Europea. Allo stesso tempo sarà occasione per fare un breve ripasso delle modalità di sottomissione dei prodotti nel repository istituzionale, fornendo informazioni e suggerimenti utili in merito.

01/02/2022

Stefania Salvadori (UniFI)

Everything you always wanted to know about ERC grants but were afraid to ask pdf

Is there a trick to get an ERC grant? I do not think so, but in this talk I will tell you what I learnt from my experiences of both unsuccessful and successful grants application - including the ERC starting. While I will try to draw some general conclusions about specific issues, at the end of the talk I will demonstrate that the overall process is quite random. Hence, the key point is just *to apply*.

25/01/2022

Vladimiro Noce

The Instrument Control Unit of the ARIEL payload pdf

ARIEL (Atmospheric Remote-sensing Infrared Exoplanet Large-survey) is an ESA M-class mission (M4), part of the Cosmic Vision Program, whose launch is scheduled in 2029. Its operative life is planned in 3.5 years and it will be placed in a halo orbit around the L2 point.
From the scientific point of view, ARIEL will address key questions about exoplanets:
1. To perform research on the physical processes governing the planetary atmospheres
2. Investigate the composition of exoplanets
3. To study the planetary systems' formation and evolution
To accomplish its tasks, ARIEL will perform low-resolution transit spectroscopy and spectro-photometry of about one thousand exoplanetary atmospheres by means of two instruments:
1. FGS (Fine Guidance Sensor), that will contribute to spacecraft pointing precision as well
2. AIRS (ARIEL InfraRed Spectrometer) that will perform high-resolution spectroscopy between 1.95 and 7.8 µm.
The ICU (Instrument Control Unit) is an electronics box, part of the “warm” payload, composed of four boards: two Control & Data Processing Units (CDPU) and two Power Supply Units (PSU) that will implement a cold redundant scheme with cross strapping towards the two AIRS DCUs: the Detector Control Units that collect data from the CFEE (Cold Front-End Electronics). The ICU receives commands and the main power from the S/C service module. Commands are interpreted and delivered to the Payload exploiting an internal protocol. ICU also collects scientific and housekeeping data, compresses scientific telemetries by means of a lossless algorithm and, then, builds up the PUS (Packet Utilization Standard) packets that are transferred to the S/C on-board data handling system by means of SpaceWire links.
This talk will provide a very short overview of the ARIEL mission and the spacecraft as suitably designed for the science case. Then it will focus on the ICU design and how it evolved from earlier stages of the project up to the current status, prior to the Payload and Unit PDR (Preliminary Design Review).

18/01/2022

Daria Dall'Olio (Chalmers + OAA)

"Magnetic fields inside out": a project to decipher the magnetic field role at the first stages of stellar birth pdf

A star is born from the collapse of a gigantic cloud made of gas and dust: these are the components of the interstellar medium, the material that occupies the space between stars. In the most dense regions of the cloud, the gas and the dust can condense and finally collapse under the action of gravity, generating a primordial star.
Magnetic fields are believed to be responsible of shaping the envelopes and the jet/disk systems, and circumstellar disks are the places where planets form and where the complex organic molecules, considered the building blocks of life, are stored. Despite their importance, it is not fully clear how the magnetic field acts at these stages, and thus more observations are needed to study its shape and strength. In this astrobigné I will shortly describe our "Magnetic fields inside out" project and I will give you a bite of our ideas on how we want to trace magnetic field morphology at different scales, by using a multi-wavelength and multi-scale approach and tools such as maser, dust and thermal line observations.

14/12/2021

Alessandro Marconi (UniFI/OAA)

ELT-HIRES, the high resolution spectrograph for the ELT pdf

HIRES is an optical-infrared High Resolution Spectrograph for the ELT which is expected to start construction phase in early 2022 to arrive at the telescope in early 2030. The HIRES project is carried out by an international consortium composed by 33 institutes from 13 countries of which INAF is the leading technical institute.
I will present an overview of the project, describing science cases and the baseline design. The top science cases of ELT-HIRES will be the detection of life signatures from exoplanet atmospheres, tests on the stability of Nature's fundamental couplings, and the direct detection of the cosmic acceleration. However, the science requirements of these science cases enable many other ground-breaking science cases. The baseline design, which allows to fulfil the top science cases, consists of a modular fibre-fed cross-dispersed echelle spectrograph providing a simultaneous range of 0.4-1.8 µm with a goal of 0.35-2.4 µm, at a resolution of 100,000 and with several observing modes. HIRES will be provided both in seeing- and diffraction-limited modes, the latter being characterised by a unique high resolution IFU, capable of a simultaneous wavelength coverage of 1-1.8 µm. Finally, I will conclude by presenting the future development of the project and the involvement of INAF and its community.

07/12/2021

Francesco Fontani

First survey of HCNH+ in high-mass star-forming cloud cores pdf

Most stars in the Galaxy, including the Sun, were born in high-mass star-forming regions. It is hence important to study the chemical processes in these regions to better understand the chemical heritage of both the Solar System and most stellar systems in the Galaxy. With the IRAM-30m telescope we searched for emission of the rare, but important, molecular ion HCNH+, towards 26 high-mass star-forming cloud cores. HCNH+ is thought to be crucial for the interstellar chemistry of nitriles, and it is also the most abundant molecular ion in Titan's atmosphere, but it was detected in a handful of star-forming regions before our study, and hence its chemistry was poorly known. We report the detection of HCNH+ in 16 out of 26 targets. We derive column densities and abundances w.r.t. H2 to provide constraints on chemical models. The targets are in different evolutionary stages, and hence allow us to investigate possible dependences of the molecular abundances with time and with changes in the physical properties. Our analysis indicates for the first time that the chemistry of HCNH+ is different in cold/early and warm/evolved cores, suggesting that this molecule could be used as a tool to discriminate between evolutionary phases.

23/11/2021

Fabio Giovanardi

How can CRAF protect radioastronomy? pdf

By its nature radio astronomy is a passive service, so it never causes interference to other radio users, but it is becoming increasingly difficult to protect radio astronomy operations from radio interference as spectrum usage increases for both terrestrial and space communications. In this talk, I will present an overview of the importance of Radio Committee on Radio Astronomy Frequencies (CRAF), and I will show some examples of how CRAF is currently active to protect radio astronomy service against possible interference of new technologies as the last standard for mobile communication 5G and the automotive radar technology.

16/11/2021

Luca Fini

What can you do with SymPy? pdf

SymPy is a Python package for symbolic mathematics. It deals with mathematical objects symbolically, just like anyone solving a system of equations by variable substitution. I will present an overview of an example of use to show some of the capabilities of the package.

09/11/2021

Laura Colzi (CAB, Madrid)

The GUAPOS project: a comprehensive study of peptide-like bond molecules pdf

In this talk I will present the GUAPOS (G31.41+0.31 Unbiased ALMA sPectral Observational Survey) survey (PI: M. T. Beltrán). This is a sensitive spectral survey conducted with the ALMA (Atacama Large Millimeter/submillimetre Array) observatory towards the hot molecular core G31.41+0.31 (hereafter G31), covering the whole Band 3 (from 84 to 116 GHz), and with an angular resolution of 1.2" (about 4500 au). I will talk in details about one of the projects of the survey on peptide-like bond molecules. Among prebiotic molecules, those containing peptide bonds (NCO backbone) are of great interest because they can participate in the link of amino acids forming proteins. In particular, we searched for HNCO, HC(O)NH2, CH3NCO, CH3C(O)NH2, and CH3NHCHO towards G31, where these molecules have been observed together for the first time in the disk of our Galaxy, outside the Galactic Centre.
From the comparison with other sources, we find that molecular abundance ratios towards different sources are found to be consistent between them within one order of magnitude, regardless of the physical properties (e.g. different masses and luminosities), or the source position throughout the Galaxy. Correlations have also been found between the abundances of these molecules. These results suggest that all these species are formed on grain surfaces in early evolutionary stages of molecular clouds, and that they are subsequently released back to the gas-phase through thermal desorption or shock-triggered desorption.

02/11/2021

Seyma Mercimek

Visual storytelling: Raising awareness of scientific research using virtual reality pdf

In this talk, we are going to dive into virtual reality (VR) world in order to make a link between science and public. With developing technology, VR devices allow people to discover 3D data in a fully immersive fashion. In this way, as scientists, we can create a strong and direct connection with "current scientific data" to learn more about astronomy in Education and Public Outreach activities.
I am a phd student in the framework of the H2020 MSCA ITN Project AstroChemical Origins (https://aco-itn.oapd.inaf.it). One of the aims of this ITN project is to provide an astrochemical model in order to use with virtual reality tools (e.g mobile phones, oculus) and to bring it out at the end of the project. During the talk, I will also give several VR examples which can be useful for any scientific subject.

26/10/2021

Elena Pancino

The European COST actions and the COST-Gaia-MW opportunity pdf

I will briefly describe the European COST actions funding scheme, its goals, and how it works in practice. The COST actions are designed to foster collaboration and networking, and they are used to organize meetings, workshops, schools, and exchange visits. I will then describe the ongoing Gaia-Milky-Way COST action, of which I am one of the two Italian representatives in the Management Committee, and which is mainly devoted to the study of the Milky Way with Gaia and related research. However, I will describe how this can be considered an opportunity also for scientists from neighboring research fields in several ways, including projects that do not involve the Milky Way or Gaia at the moment, but that can have positive impact on the Gaia-MW research and community in an indirect way.

19/10/2021

Georgios Kyriakou

SKA1-Low: progress on SKALA4.1 antenna design and station deployment pdf

A long-awaited big step towards revolutionizing radioastronomy research, as a result of improving the sensitivity of the radio instruments, is the SKA (Square Kilometer Array) radiotelescope, which has recently gained the green light for construction. SKA will consist of two sites which will focus on radiation from different frequency bands.
The SKA1-Low project, which will be built in Western Australia, will enable science in the frequency range of 50MHz-350MHz and is the one which will study the 21cm Hydrogen line in high redshifts, going back to the Cosmic Dawn and Epoch of Reionization ages. In this talk, I will present the current status of SKA1-Low, and will focus on my work on the SKALA4.1 AL antenna design, the current model that has been selected by the SKA Organization and has been built as part of the Aperture Array Verification System 2.0 (AAVS2.0). Despite the design have passed all major evaluation criteria with respect to its performance, improvements could be made regarding its narrow-band gain smoothness. Due to the nature of a log-periodic antenna, discontinuities in the gain pattern have been observed, which could potentially severe the detection of the EoR 21cm cosmological signal. These so-called frequency glitches are due to simultaneous excitation of more than one dipole in the full 50MHz-350MHz frequency band of operation. Ways of mitigating the problem will be discussed, and a validation of the phenomenon by means of anechoic chamber measurements which agree with simulation findings will also be presented.

12/10/2021

Emanuele Nardini

BBQ astrophysics: accretion, feedback, and cosmology with Bright Blue Quasars pdf

Thanks to the intrinsic tightness and non-linearity of the relation between their UV and X-ray luminosities, in the last few years quasars have been elevated to the rank of promising (if not reliable) cosmological probes. I will discuss some of the most recent results we have obtained on a unique sample of 30 hyper-luminous quasars at z~3, which demonstrate that maximising the cosmological value of quasars is inevitably connected to addressing the most compelling questions on SMBH accretion physics, with implications also in the fields of AGN feedback and galaxy evolution.

05/10/2021

Victor M. Rivilla (CAB, Madrid)

Molecular precursors of the RNA-world in the interstellar medium pdf

The question of the origin of Life has intrigued human beings for centuries. We still do not understand how simple molecules combine together to form large molecules essential for living organisms. Recent prebiotic experiments, based on the RNA-world hypothesis for the origin of Life, have suggested that the three basic macromolecular systems (nucleic acids, proteins and lipids) could have formed from relatively simple precursors. The detection of some of these molecules in space, thanks to the unprecedented capabilities of current astronomical ground-based and space facilities, has opened a new window for Astrobiology from the Astronomical point of view.
A deep understanding of the chemical reservoir of the different phases of star formation, including molecular clouds, star-forming regions, protoplanetary disks, protoSolar nebula analogs and Solar System bodies (planets, meteorites and comets), is crucial to understand how Life could have appeared starting from simple molecular precursors.
In this talk I will present an overview of the most recent results of my project COOL (Cosmic Origins Of Life), which is devoted to the search in space of key molecular precursors of the RNA-world. Using data from ultradeep spectra surveys carried out with the Yebes 40m and IRAM 30m telescopes and the ALMA interferometer, and from measurements of the ESA Rosetta space mission, our works have revealed the presence of more than 10 new molecules in the interstellar medium and in the comet 67P/Churyumov-Gerasimenko, which are direct precursors of nucleic acids (e.g. NH2OH or HOCH2CN), proteins (e.g. CH3NCO or C2H5NCO), and lipids (e.g. NH2CH2CH2OH). This amazing chemical complexity, which might be only the tip of the iceberg, means that interstellar chemistry offers an extremely rich feedstock for triggering prebiotic chemistry.

28/09/2021

Marta De Simone (Grenoble)

Unveiling hot corinos nature at cm wavelengths pdf

Hot corinos, central planet-forming regions of Solar-like protostars enriched in interstellar complex organic molecules (iCOMs), are the likely analogues of the early Solar System. Deceivingly, after almost 20 years of hunting, only about twenty hot corinos are known. Surprisingly, many of them are binaries with the two components showing different millimeter molecular spectra. There are two possible explanations for why hot corinos are so difficult to find and why the millimeter spectra of coeval objects are so different: 1) the dust is so optically thick that hides the molecular lines; 2) the different observed spectra reflect an intrinsic chemical diversity probably due to the different composition of the grain mantles, formed in the prestellar phase.
In order to verify these two possibilities, centimeter observations are the key as i) we can observe iCOMs at wavelengths where the dust opacity is negligible, and ii) we can simultaneously observe two major grain mantle components, methanol (CH3OH, also the simplest iCOMs) and ammonia (NH3). Pilot projects performed using JVLA observations of CH3OH and NH3 toward a sample of objects in Perseus, demonstrated that indeed dust hides the hot corino with the largest dust content, that ices can be different, and that abundances derived at sub-mm regimes can be severely underestimated. This studies pave the way to new facilities in the cm range, such as the New Generation Very Large Array (ngVLA) and the Square Kilometre Array (SKA) that are the perfect facility capable to overcome the current limits, thanks to their high sensitivity and high angular resolution. Indeed, they will allow to observe more complex iCOMs with abundances lower than the CH3OH one (of at least few order of magnitude) at small angular scales (<10 au) fully sampling the planet-forming hot corinos region.

21/09/2021

Giulia Pagnini (UniFI)

First stars chemical signatures into the Galactic bulge pdf

The standard ΛCDM model of the early Universe predicts that the first stars formed out of gas of primordial composition, within the first few hundred million years after the Big Bang. The chemical fingerprints of these early generations could be retained within the photospheres of old, low-mass, metal- poor second-generation stars observed in the Local Group. A significant fraction of these objects are stars called Carbon-Enhanced Metal-Poor (CEMP), characterized by an overabundance of carbon with respect to iron, [C/Fe] > 0.7. These have been observed in large quantities in the Galactic halo and in the Ultra- Faint Dwarf galaxies (UFDs). Interestingly, although the Milky Way bulge is predicted to host the oldest stars, the dearth of CEMP stars here is particularly striking, since only one CEMP star has been found. In my Master Thesis, I explored the possible reasons of this anomaly. I initially performed a statistical analysis on the observations of metal-poor stars in the different regions of the Local Group. Then I focused on theoretical predictions derived from the ΛCDM cosmological model, through the combination of an N-body simulation and a semi-analytical model, and the use of analytical calculations. My analysis shows that the scarcity of CEMP stars in the Galactic bulge is not due to the low statistics of metal-poor stars within it, but is the result of a different formation process of this region. In fact, by comparing my results with the observed sample of metal-poor stars in the Galactic bulge, I have been able to indirectly prove the existence of very massive first stars which, exploding as high-energetic pair instability supernovae, partially washed out the high [C/Fe] values caused by less energetic faint supernovae.

 

Andrea Saccardi (UniFI)

Chasing the signatures of the first stars in high redshift Lyman Limit Systems pdf

The first generation of stars, i.e. the so-called Population III (PopIII) stars, played a fundamental role in the cosmic history. They marked the end of the cosmic "Dark Ages", transforming the early Universe from its initial state of simplicity, a homogeneous and neutral "metal free" gas made by hydrogen (H) and helium (He) only, into one of ever increasing complexity. Under- standing the role of PopIII stars in early metal enrichment is thus crucial, since they represent the sources of the first chemical elements heavier than H and He. The key chemical signatures of massive first stars, 10M⊙ < MPopIII < 60M⊙, which exploded as faint supernovae with mixing and fallback, have been identified in present-day second-generation stars (e.g. Salvadori et al. 2015), which are ancient Carbon-Enhanced, [C/Fe] > 0.7, and Metal-Poor, [Fe/H] < −2, i.e. the so-called CEMP stars. Can the chemical signature of the first stars be found also in high redshift gaseous environments? The detection of gas exhibiting similar abundance patterns as CEMP stars would open a new window to investigate the impact of the first stars in the early Universe and to study the unknown properties of the first stars. To address this question I analysed the homogeneous and high quality sample of spectra from the XQ-100 Legacy Survey (Lopez et al. 2016), which observed 100 sight-lines of quasars in the redshift range z ∼ 3.5 − 4.5 with the X-SHOOTER Spectrograph on the Very Large Telescope (VLT). I performed a detailed study of metal-absorption lines and neutral hydro- gen Lyman transitions, through the Voigt fit of the absorption features in the quasar spectra. I identified 39 Lyman Limit Systems (LLS) and Sub-Damped Lyman Alpha Systems (Sub-DLA), defined as gaseous environments in the neutral hydrogen column density range 17.0 < log(NHI/cm−2) < 20.3. Considering ionization corrections and neglecting dust depletion, I determined their metallicity distribution function and the abundance ratios [X/Fe] of different chemical elements, such as O, Mg, Al, and Si. For the first time I found 15 very metal-poor, [Fe/H] < −2, absorption systems, 7 of which are carbon enhanced, [C/Fe] > 0.7. By comparing the chemical abundances of LLSs/Sub-DLAs with those of the ancient stars in the Milky Way halo and in Local Group dwarf galaxies, I observed that the abundance ratios [X/Fe] as a function of [Fe/H] of LLSs/Sub-DLAs cover the same abundances range of ancient metal-poor stars. The abundance pattern of the carbon-enhanced, [C/Fe] > 0.7, metal-poor, [Fe/H] < −2, absorption systems revealed an overabundance for all the analysed chemical elements, in agreement with the abundance pattern of CEMP stars. The discovery of a gaseous, high redshift, counterpart to CEMP stars represents an important breakthrough, since it implies that the gas was likely imprinted by the first stars. Indeed, the exclusion of a contamination of the gas environments by the wind of asymptotic giant branch (AGB) stars allowed me to robustly claim that the newly discovered carbon-enhanced metal-poor absorbers are consistent with a PopIII star enrichment: zero-metallicity faint supernovae.

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