Invited speakers
Session 1June 6-7Margherita's work and legacy/Galactic archeology and formation of chemical elements
- P. Selvelli
- E. Caffau
- J. Gonzalez
- A. Skuladottir
- P. Molaro
- I. Vanni
- F. Z. Majidi
- G. Catanzaro
- S. Ferluga
- F. Thielemann
- A. Herrero
- L. Lombardo
- G. Costa
- F. Matteucci
- S. Bressan
- A. Mucciarelli
- E. Spitoni
- S. Taibi
- G. Bono
Title: Stellar spectroscopy, a tribute to Margherita Hack
Abstract: In my talk I will give a necessarily short overview of Margherita Hack’s most important research and scientific activities, which lasted more
than 60 years.
Stellar spectroscopy is the primary keyword to define the studies of MH,
further motivated by her collaboration with Otto Struve during her stay in
Berkeley. Her interests, however, covered a wide range of spectral regions,
from the far UV to the IR and the radio, and included topics as different
as Cepheids, the solar chromosphere, late type stars, the chemically
peculiar Ap stars, mass loss in early type stars, the problem of Lithium,
the galactic chemical evolution, the abundance of helium, stellar rotation,
stellar classification, and binary star evolution (including symbiotic
stars and her favorite systems: CH Cyg, Epsilon Aurigae, Beta Lyrae,
Upsilon Sgr, VV Cephei).
MH organized four international scientific meetings in Trieste (Colloquia
on Late Type Stars, on Supergiants Stars, on Mass Loss from Stars and
on High Resolution Spectrometry) and was very active in promoting
the development of, and participation in new scientific projects
(Copernicus, S59, IUE). She encouraged fruitful collaborations with international scientific institutions in France, Germany, Holland, Mexico and Turkey) and with researchers from (at that time) "developing"
countries, and took an important role in the growth of the Astrophysics Section of ISAS-SISSA in Trieste.
Her prolific activities as editor and writer resulted in the publication of
dozens of scientific and popular books, including two volumes on stellar
spectroscopy, the monumental NASA Monograph on CVS and Related Stars,
Modern Astrophysics: a memorial to Otto Struve, and, in Italian,
Esplorazioni Radioastronomiche, la Galassia e le sue popolazioni, la
Radioastronomia alla scoperta di un nuovo aspetto dell'Universo, L'Universo
violento della Radioastronomia.
Title: Searching for metal poor stars
Abstract: Metal-poor stars are fundamental objects to understand the formation and the chemical evolution of the universe.
Metal-poor (MP) stars and especially extremely metal-poor (EMP) stars hold in their atmospheres the fossil record of the chemical composition of the early phases of the Galactic evolution. The chemical analysis of such objects provides then important constraints on these early phases of the Universe.
Metal-poor stars are rare objects; to dig them out different techniques can be used and large amounts of data have to be processed.
We successfully selected EMP candidates by analysing the low-resolution spectra from the Sloan Digital Sky Survey (SDSS) and by combining broad-band photometry (SDSS or Gaia) to the Pristine narrow filter centred on the CaII-H and -K lines.
We also selected MP candidates from their kinematics.
During the ESO Large Programme TOPoS and the French-Italian GTO of the spectrograph X-Shooter, we could confirm a sample of EMP stars selected from the SDSS low-resolution spectra.
Thanks to low and high-resolution spectra acquired in the Pristine collaboration, we confirmed EMP candidates selected from the photometric selection.
The kinematical selection allowed us to conclude that the chemical pattern of the sample of stars with extreme kinematics with respect to the Sun is similar to the one of Galactic MP stars.
Title: Early phases of the Galaxy from the chemical imprint on iron-poor stars
Abstract: Low-mass extremely metal-poor stars must have formed from a mixture of material from the primordial nucleosynthesis and matter ejected from the first supernovae. Those stars are relics of the early epochs of the Milky Way, so their chemical composition, especially for those still on the main sequence, holds key information on the properties of the first stars and the early chemical enrichment of the Universe. We have been exploring large spectroscopic databases such as SDSS and LAMOST to search for such unique stars. We identified two extremely iron-poor dwarf stars J0815+4729 (Aguado et al. 2018a) and J0023+0307 (Aguado et al. 2018b) using the OSIRIS spectrograph at the 10.4m-GTC telescope in La Palma. We have also acquired high-resolution spectroscopy with UVES on the 8.2m-VLT telescope, and HIRES on the 10m-Keck telescope, to derive the detailed abundance pattern of these unique stars (Aguado et al. 2019; Gonzalez Hernandez et al. 2020), revealing e.g. the extreme CNO abundances in J0815+4729 with ratios [X/Fe] > 4. In addition, we were able to detect Li at the level of the lithium plateau in J0023+0307, whereas we were only able to provide an upper-limit on Li abundance, 0.7 dex below, in J0815+4729, shedding light on the cosmological lithium problem. We continue our searches of extremely iron-poor stars with new data taken at GTC and Keck. We will discuss these findings in the context of other stars with a metallicity of [Fe/H]<-5, and the prospects for searches using data from surveys such as WEAVE and DESI, and the upcoming data release 3 of the Gaia mission.
Abstract: Low-mass extremely metal-poor stars must have formed from a mixture of material from the primordial nucleosynthesis and matter ejected from the first supernovae. Those stars are relics of the early epochs of the Milky Way, so their chemical composition, especially for those still on the main sequence, holds key information on the properties of the first stars and the early chemical enrichment of the Universe. We have been exploring large spectroscopic databases such as SDSS and LAMOST to search for such unique stars. We identified two extremely iron-poor dwarf stars J0815+4729 (Aguado et al. 2018a) and J0023+0307 (Aguado et al. 2018b) using the OSIRIS spectrograph at the 10.4m-GTC telescope in La Palma. We have also acquired high-resolution spectroscopy with UVES on the 8.2m-VLT telescope, and HIRES on the 10m-Keck telescope, to derive the detailed abundance pattern of these unique stars (Aguado et al. 2019; Gonzalez Hernandez et al. 2020), revealing e.g. the extreme CNO abundances in J0815+4729 with ratios [X/Fe] > 4. In addition, we were able to detect Li at the level of the lithium plateau in J0023+0307, whereas we were only able to provide an upper-limit on Li abundance, 0.7 dex below, in J0815+4729, shedding light on the cosmological lithium problem. We continue our searches of extremely iron-poor stars with new data taken at GTC and Keck. We will discuss these findings in the context of other stars with a metallicity of [Fe/H]<-5, and the prospects for searches using data from surveys such as WEAVE and DESI, and the upcoming data release 3 of the Gaia mission.
Title: : Dwarf galaxies’ view of the heavy elements
Abstract: The origin of heavy elements such as europium (Eu) and gold (Au) remains a mystery, and the astrophysical site hosting the rapid neutron-capture process (r-process; high neutron flux) remains unclear to this day. With spectroscopic observations of individual stars in the Milky Way and the dwarf galaxy satellites, it becomes clear that (at least) two distinct r-process sites are needed to explain the data: a quick source with timescales comparable to core-collapse supernovae and a delayed source with characteristic timescales of a few ~Gyr, most probably originating in neutron star mergers. In this talk I will go over the data and the arguments leading to this result and show that only by looking at all the available data in many galaxies will we be able to solve the puzzle that is the r-process.
Abstract: The origin of heavy elements such as europium (Eu) and gold (Au) remains a mystery, and the astrophysical site hosting the rapid neutron-capture process (r-process; high neutron flux) remains unclear to this day. With spectroscopic observations of individual stars in the Milky Way and the dwarf galaxy satellites, it becomes clear that (at least) two distinct r-process sites are needed to explain the data: a quick source with timescales comparable to core-collapse supernovae and a delayed source with characteristic timescales of a few ~Gyr, most probably originating in neutron star mergers. In this talk I will go over the data and the arguments leading to this result and show that only by looking at all the available data in many galaxies will we be able to solve the puzzle that is the r-process.
Title: The problem of Lithium and the other Light Elements Deuterium, Beryllium and Boron
Abstract: Margherita Hack's first work on light elements dates back to 1963 with the discovery of Li-Excess in the magnetic star Coronae Borealis. The last one was released in 2004 when she was 82, and again on Li in peculiar stars, thus covering a time span of almost 40 years. Although this was not one of her major interests, it was a constant as it is shown by almost 30 works concentrated at the beginning and at the end of her scientific career. Following Hack’s works I will trace a brief history of our knowledge of the origin of light elements and will define today's picture.
Title: Galactic halo Metal-Poor stars: are they all imprinted by the first stars?
Abstract: Stellar archaeology allows us to give a glance at the early stages of star formation. The Galactic halo hosts the oldest and most metal-poor stars ever observed. Among them, two classes of stars have been identified: the Carbon-Enhanced Metal-Poor (CEMP-no, [C/F e] > 0.7, [Ba/F e] < 0) stars and the C-normal stars. C-enhanced halo stars show, one from each other, a big scatter in their chemical abundances, while C-normal halo stars do not. Does this mean that the birth environments of C-enhanced and C-normal stars have been imprinted by different stellar populations?
To address this question, we developed a simple chemical model for early metal enrichment and applied it to poorly star-forming mini-halos, which are believed to be the first star-forming objects. To account for the unknowns on the early cosmic star formation, we defined few free parameters and explored all the possible results varying them, including the initial mass function (IMF) of the first (PopIII) stars. We compared for the first time the resulting chemical abundances with metal-poor halo stars measurements of all the available elements.
We find that, for increasing explosion energy of low- and intermediate- mass PopIII stars (10M⊙ ≤ M∗ ≤ 100M⊙), the Fe abundance in the interstellar medium (ISM) of mini-halos increases and the [C/Fe] ratio decreases. Our results predict that the most Fe-poor and C-enhanced stars are born in mini-halos uniquely enriched by the least energetic PopIII stars SNe (E < 2 × 10^51erg). On the contrary, we find that the C-normal halo stars are predominantly imprinted by a subsequent generation of normal (PopII) stars exploding as core-collapse supernovae, which provide > 50% of the metal in their birth environments.
To address this question, we developed a simple chemical model for early metal enrichment and applied it to poorly star-forming mini-halos, which are believed to be the first star-forming objects. To account for the unknowns on the early cosmic star formation, we defined few free parameters and explored all the possible results varying them, including the initial mass function (IMF) of the first (PopIII) stars. We compared for the first time the resulting chemical abundances with metal-poor halo stars measurements of all the available elements.
We find that, for increasing explosion energy of low- and intermediate- mass PopIII stars (10M⊙ ≤ M∗ ≤ 100M⊙), the Fe abundance in the interstellar medium (ISM) of mini-halos increases and the [C/Fe] ratio decreases. Our results predict that the most Fe-poor and C-enhanced stars are born in mini-halos uniquely enriched by the least energetic PopIII stars SNe (E < 2 × 10^51erg). On the contrary, we find that the C-normal halo stars are predominantly imprinted by a subsequent generation of normal (PopII) stars exploding as core-collapse supernovae, which provide > 50% of the metal in their birth environments.
Title: Characterizing Young Stellar Objects with VLT/X-Shooter
The focus of my talk will be the full characterization of the young stellar objects (YSOs) with VLT/X-Shooter; an intermediate-resolution, single-target spectrograph that covers a wide wavelength range (300-2500 nm), for stars as faint as ~ J = 15 mag. Analyzing this spectrum provides us with a wealth of information that directly sheds light on the chromospheric activity of the YSO candidates and their age, mass, effective temperature, spectral type as well as kinematic properties such as radial velocity and projected rotational velocity. Indirectly, it would also provide clues regarding whether there are disks or structures around the objects. However, although X-Shooter is a state-of-the-art spectrograph, depending on the nature of the objects, the spectroscopy of its targets can turn out to be challenging. Additionally, on occasions, the precision of the spectroscopy results is insufficient to fulfill specific scientific aims (such as confirming the wide companionship of stars or determining their membership in stellar associations). In this talk, I would like to address these challenges and drawbacks and what is expected from future spectrographs to fill in these gaps.
The focus of my talk will be the full characterization of the young stellar objects (YSOs) with VLT/X-Shooter; an intermediate-resolution, single-target spectrograph that covers a wide wavelength range (300-2500 nm), for stars as faint as ~ J = 15 mag. Analyzing this spectrum provides us with a wealth of information that directly sheds light on the chromospheric activity of the YSO candidates and their age, mass, effective temperature, spectral type as well as kinematic properties such as radial velocity and projected rotational velocity. Indirectly, it would also provide clues regarding whether there are disks or structures around the objects. However, although X-Shooter is a state-of-the-art spectrograph, depending on the nature of the objects, the spectroscopy of its targets can turn out to be challenging. Additionally, on occasions, the precision of the spectroscopy results is insufficient to fulfill specific scientific aims (such as confirming the wide companionship of stars or determining their membership in stellar associations). In this talk, I would like to address these challenges and drawbacks and what is expected from future spectrographs to fill in these gaps.
Title: Abundances and pulsations in Am stars
Abstract: Main-sequence chemically peculiar stars are objects that show anomalies in their chemical composition if compared to stars with the same effective temperature. Among them, the Am subgroup shows Ca II K-line too early for their hydrogen line types, while metallic lines appear too late, such that the spectral types inferred from the Ca II K- and metal lines differ by five or more spectral subclasses.
The radiative levitation and diffusive settling processes responsible for these abundance anomalies should also deplete helium from the region of the envelope that drives delta Scuti p-mode pulsations via the kappa mechanism. Therefore, these stars are not expected to pulsate in multiple radial and nonradial modes with periods of around 2 hours, characteristic of delta Scuti stars.
Nevertheless, there are cases in literature where Am stars are suspected to be pulsators. We started a series of spectroscopic observations of suspected and confirmed Am stars in order to derive atmosp
Title: Working with Margherita: the strange case of Epsilon Aurigae
Abstract: It is a pleasure for me to remind the long experience of personal friendship and scientific collaboration with Margherita Hack. She was an exceptional person, not only because of her well-known academic and scientific achievements, but also for her generosity and social commitment. During her entire life, her inseparable husband Aldo contributed to any aspect of Margherita’s activity, also writing books. Politics, athletics (when young), popular teaching, protection of animals, were among her passions. The common love for animals – particularly involving my wife – was at the base of our long friendship, as well as scientific collaboration. My scientific activity began at the University of Trieste after attending the Astronomy course by prof. Hack and later, when she was my Master supervisor at Sissa. That study was the beginning of a deep investigation about the eclipse of ε Aur, which is the only peculiar star visible to the naked eye. This phenomenon occurs every 27 years, and 1982-84 was just the right epoch to observe it, so my scientific research started with the photometric detection of a multi-ring eclipsing disk. In a similar way, the preceding eclipse occurred on 1955-57, at the beginning of Margherita’s scientific career; she discovered spectroscopically a hot companion star, when many authors previously suggested strange models for this unique naked-eye binary. In the past, the various objects composing the system of ε Aur – luminous F supergiant, eclipsing secondary (B star with surrounding disk) and envelope – could only be inferred and theoretically modelled. Recently, during the last 2009-11 eclipse, astronomers of the Chara Interferometer obtained stunning pictures, showing the dark disk which progressively transits in front of the bright F star! This is the final proof that, also in such case, Margherita was right.
Title: Sources of r-Process Abundances
Abstract: Various nucleosynthesis studies have shown that the rapid neutron capture r-process element abundances in very metal-poor (VMP) halo stars probably point to different origins. It has been known that an r-process can either be obtained in neutron-rich low Ye conditions or in high entropy environments. In this review we analyze with statistical methods the observational abundance patterns from trans-Fe elements up to the actinides and come to the conclusion that four to five categories of astrophysical events must have contributed. These include: (o) the ejection of Fe and trans-Fe elements Sr, Y, Zr (and continuing to slightly higher mass numbers), (i) and (ii) Fe and weak r-process contributions (including Eu in moderate to slightly larger but varying amounts), (iiia) and (iiib) strong r-process abundance patterns with no or negligible (in comparison to solar) Fe production, where IIIb shows a tendency for an actinide boost behavior.
When comparing these categories of events with presently existing nucleosynthesis predictions, we suggest to identify them (despite remaining uncertainties) with regular core-collapse supernovae, quark deconfinement supernovae, magnetorotational supernovae, neutron star mergers, and outflows from black hole accretion tori.
Title: The Spectroscopy of Massive Stars accross Ages
Abstract: In this talk we present the advances from the early times of stellar spectroscopy to our days in the field of massive stars, a human time scale. Together with always more realistic models, the improvements in data quality, wavelength coverage and multiplexing capabilities of the observations have revealed the strong links to other fields of Astrophysics and the high impact of these objects on our interpretation of the Universe, from our neighborhood to the early epochs, a cosmic time scale.
Title: CERES survey: stellar parameters and chemical abundances of selected elements
Abstract: High resolution studies of metal poor stars ([Fe/H]30), with extreme variations from r-rich to r-poor stars, typically in the region of lighter (Z<50) and actinide (88<Z<104) elements. Such abundance pattern variations could only occur: 1) if the physical condition vary during the r-process event, or 2) if multiple different astrophysical sites contribute to their formation.
The Chemical Evolution of r-process Elements in Stars (CERES) project aims at providing a homogeneous analysis of a sample of very metal poor stars ([Fe/H]<-1.5) to increase our knowledge of the physical conditions and formation sites of neutron capture elements. To achieve this goal, we relied on a sample of high-resolution, high signal-to-noise spectra obtained with ESO VLT/UVES.
In this talk I will present the stellar parameters and the chemical abundances of 18 elements lighter than Zr (Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, and Zr) for a sample of 52 giant stars. The homogeneity of the sample made it possible to highlight the presence of two Zn rich stars ([Zn/Fe]~0.7), one r-rich and the other r-poor.
We also discovered two stars with peculiar light n-capture abundance patterns: CES1237+1922 (BS 16085-0050), which is ~1 dex underabundant in Sr, Y, and Zr respect to the other stars in the sample, and CES2250-4057 (HE 2247-4113), which shows a ~1 dex overabundance of Sr respect to Y and Zr.
Abstract: High resolution studies of metal poor stars ([Fe/H]30), with extreme variations from r-rich to r-poor stars, typically in the region of lighter (Z<50) and actinide (88<Z<104) elements. Such abundance pattern variations could only occur: 1) if the physical condition vary during the r-process event, or 2) if multiple different astrophysical sites contribute to their formation.
The Chemical Evolution of r-process Elements in Stars (CERES) project aims at providing a homogeneous analysis of a sample of very metal poor stars ([Fe/H]<-1.5) to increase our knowledge of the physical conditions and formation sites of neutron capture elements. To achieve this goal, we relied on a sample of high-resolution, high signal-to-noise spectra obtained with ESO VLT/UVES.
In this talk I will present the stellar parameters and the chemical abundances of 18 elements lighter than Zr (Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, and Zr) for a sample of 52 giant stars. The homogeneity of the sample made it possible to highlight the presence of two Zn rich stars ([Zn/Fe]~0.7), one r-rich and the other r-poor.
We also discovered two stars with peculiar light n-capture abundance patterns: CES1237+1922 (BS 16085-0050), which is ~1 dex underabundant in Sr, Y, and Zr respect to the other stars in the sample, and CES2250-4057 (HE 2247-4113), which shows a ~1 dex overabundance of Sr respect to Y and Zr.
Title: Rotating stellar populations in NGC 1866
Abstract: Stellar rotation affects the evolution of stars in many ways and is a fundamental property that must be included in our stellar models to interpret better observations. In this talk, I will present the results of a comprehensive study of the young Large Magellanic Cloud cluster NGC 1866. We combined the analysis of the best studied Cepheids of the cluster with its very accurate color-magnitude diagram (CMD), obtained from the most recent HST photometry. Using a Bayesian method based on new PARSEC stellar evolutionary tracks and isochrones with rotation, we obtained a new estimate of the ages and initial rotation velocities of the cluster populations. Including the main effects of rotation in our models, such as the gravity darkening, let us reproduce the main characteristics of the cluster CMD (i.e., the extended main-sequence turn-off and the split of the main sequence). Our study reinforces the notion that some young clusters, such as NGC 1866, harbor rotating multiple populations.
Abstract: Stellar rotation affects the evolution of stars in many ways and is a fundamental property that must be included in our stellar models to interpret better observations. In this talk, I will present the results of a comprehensive study of the young Large Magellanic Cloud cluster NGC 1866. We combined the analysis of the best studied Cepheids of the cluster with its very accurate color-magnitude diagram (CMD), obtained from the most recent HST photometry. Using a Bayesian method based on new PARSEC stellar evolutionary tracks and isochrones with rotation, we obtained a new estimate of the ages and initial rotation velocities of the cluster populations. Including the main effects of rotation in our models, such as the gravity darkening, let us reproduce the main characteristics of the cluster CMD (i.e., the extended main-sequence turn-off and the split of the main sequence). Our study reinforces the notion that some young clusters, such as NGC 1866, harbor rotating multiple populations.
Title: Chemical evolution of the Milky Way
Abstract: Galactic archaeology allows us to reconstruct the history of formation and evolution of the Milky Way by means of comparison of model results with the abundances observed in stars and gas. I will review how to build a Galactic chemical evolution model for the Milky Way and discuss the main ingredients, such as stellar yields. Stellar yields are from core-collapse SNe, Type Ia SNe, novae and merging neutron stars. The most common models for the Milky Way will be described, in particular the so-called two-infall model and the parallel model. These different approaches produce different results which are then compared to the most recent observational data from large Galactic surveys, such Gaia-ESO and APOGEE. The bimodality of the [alpha/Fe] ratios at different Galactocentric distances will be discussed together with possible interpretations in terms of formation and evolution of the Milky Way.
Title: Very massive stars and chemical evolution of extremely metal-poor galaxies
Abstract: In recent observations of extremely metal-poor low-mass starburst galaxies, almost solar Fe/O ratios are reported, despite N/O ratios that are instead consistent with their very low metallicity.
To interpret this peculiar chemical evolution path, we calculate new yields from very massive stars, for several rotation rates, and search for the IMF that best reproduces the observations. Our best models include a bi-modal IMF with an initial burst of rotating very massive stars.
We show that, almost solar Fe/O and normal N/O ratios at a very young starburst age, are a distinctive signature of an early enrichment produced by the presence of very massive stars dying as PISN.
Title: A relic from a past merger event in the Large Magellanic Cloud
Abstract: The galaxies populating our Universe have likely built up from the merger of smaller galaxies. The Milky Way is the result of this assembly process. Also smaller galaxies are expected to be built with the same architectural plan, only using smaller bricks. The amount of different metals in a star acts as a powerful DNA probe that allows us to trace the genealogy of each star and to distinguish those formed in other galaxies. We present the evidence that the LMC globular cluster NGC2005 exhibits a chemical composition clearly distinct from that of the other LMC clusters. In other words, its chemical DNA demonstrates that its parent galaxy was different from that of the other star clusters. With our study, we have shown for the first time that the process of hierarchical galaxy assembly took place also in a nearby small satellite of our own Milky Way, thus demonstrating that galaxies of every size are built following the same scheme.
Abstract: The galaxies populating our Universe have likely built up from the merger of smaller galaxies. The Milky Way is the result of this assembly process. Also smaller galaxies are expected to be built with the same architectural plan, only using smaller bricks. The amount of different metals in a star acts as a powerful DNA probe that allows us to trace the genealogy of each star and to distinguish those formed in other galaxies. We present the evidence that the LMC globular cluster NGC2005 exhibits a chemical composition clearly distinct from that of the other LMC clusters. In other words, its chemical DNA demonstrates that its parent galaxy was different from that of the other star clusters. With our study, we have shown for the first time that the process of hierarchical galaxy assembly took place also in a nearby small satellite of our own Milky Way, thus demonstrating that galaxies of every size are built following the same scheme.
Title: The [α/Fe] bimodality in the Milky Way disc with chemical evolution models
Abstract: The analysis of the data of diverse spectroscopic surveys such as Gaia-ESO, APOGEE, GALAH suggests the existence of a clear distinction between two sequences of disc stars at different Galactocentric distances in the [α/Fe] vs. [Fe/H] abundance ratio space: the so-called high-α sequence, classically associated to an old population of stars in the thick disc, and the low-α sequence, which mostly comprises relatively young stars in the thin disc. We present a multi-zone chemical evolution model designed for regions at different Galactocentric distances using measured chemical abundances from the APOGEE DR16 sample. In the outer disc (with radii R>6 kpc), the chemical dilution due to a late accretion event of gas with primordial chemical composition is the main driver of the [Mg/Fe] vs. [Fe/H] abundance pattern in the low-α sequence. In the inner disc, in the framework of the two-infall model, we confirm the presence of an enriched gas infall in the low-α phase as suggested by chemo-dynamical models. Our analysis based on the recent APOGEE DR16 data suggests a significant delay time, ranging from ∼3.0 to 4.7 Gyr, between the first and second gas infall events for all the analyzed Galactocentric regions, confirming the findings of previous works for the solar neighbourhood based on the APOKASC data. Recent results on the connection between the disc dichotomy signature in the vertical distribution of [Mg/Fe] abundance ratio and the delayed infall scenario in the solar neighbourhood will be also discussed. We will also test if the significant time delay between the two gas accretion episodes (which characterizes the two-infall model constrained by APOGEE data) will allow us to also produce Gaia/DR3 chemical abundances.
Abstract: The analysis of the data of diverse spectroscopic surveys such as Gaia-ESO, APOGEE, GALAH suggests the existence of a clear distinction between two sequences of disc stars at different Galactocentric distances in the [α/Fe] vs. [Fe/H] abundance ratio space: the so-called high-α sequence, classically associated to an old population of stars in the thick disc, and the low-α sequence, which mostly comprises relatively young stars in the thin disc. We present a multi-zone chemical evolution model designed for regions at different Galactocentric distances using measured chemical abundances from the APOGEE DR16 sample. In the outer disc (with radii R>6 kpc), the chemical dilution due to a late accretion event of gas with primordial chemical composition is the main driver of the [Mg/Fe] vs. [Fe/H] abundance pattern in the low-α sequence. In the inner disc, in the framework of the two-infall model, we confirm the presence of an enriched gas infall in the low-α phase as suggested by chemo-dynamical models. Our analysis based on the recent APOGEE DR16 data suggests a significant delay time, ranging from ∼3.0 to 4.7 Gyr, between the first and second gas infall events for all the analyzed Galactocentric regions, confirming the findings of previous works for the solar neighbourhood based on the APOKASC data. Recent results on the connection between the disc dichotomy signature in the vertical distribution of [Mg/Fe] abundance ratio and the delayed infall scenario in the solar neighbourhood will be also discussed. We will also test if the significant time delay between the two gas accretion episodes (which characterizes the two-infall model constrained by APOGEE data) will allow us to also produce Gaia/DR3 chemical abundances.
Title: The stellar metallicity gradients of Local Group dwarf galaxies
Abstract: To shed light on the different formation scenarios and the main mechanisms involved in the evolution of Local Group (LG) dwarf galaxies, detailed studies of their internal properties are needed. The stellar metal content of these galaxies can be in this respect a powerful observational parameter to obtain information on the mechanisms involved in their evolution. In particular, the inspection of their radial metallicity [Fe/H] profiles can provide important clues on the interplay between internal dynamics and star formation processes, as well as on possible external perturbations. We have explored correlations between the presence and strength of metallicity gradients in LG dwarf galaxies and their stellar mass, star formation history and environment, by performing a homogeneous analysis of literature spectroscopic [Fe/H] data of red giant stars. We were able to determine the radial metallicity profiles for 30 LG dwarf galaxies, providing the largest compilation to date of this type. The dwarf galaxies in our sample exhibit a range of metallicity gradient values when expressed as a function of their half-light radius (Rh). The majority of them have mild negative gradients (sample’s median value ~ -0.1 dex/Rh), with a few showing gradients as strong as -0.4 dex/Rh.
The analysed systems do not show any correlation between their gradients and their morphological types, nor with their distance from the Milky Way or M31. No correlations are found either with their stellar masses or star formation timescales. In particular, we do not find the linear relationship between a galaxy's metallicity gradient and its median age as shown in the literature for a set of simulated systems.
The high-mass systems in our sample with an extended star formation history (SFH), generally show flat metallicity profiles and significant stellar rotation. However, the mere presence of high angular momentum in the rest of our sample does not seem to guarantee a flatter gradient. Instead, the lower mass systems show mild negative gradients with little scatter, regardless of their stellar mass, dynamical state, and the length of their SFH. These results are in excellent agreement with several sets of simulations from the literature and analyzed using the same method as the observed LG dwarf galaxies. The strongest gradients in our observed sample are recovered in systems that likely experienced a major merger event in the past.
In general, the interplay between the multitude of factors that could drive the formation of metallicity gradients likely combine in complex ways to produce comparable strengths, regardless of stellar mass and SFH. The strongest indicator of steep gradients appears to be dwarf-dwarf merger events in a system's past. Taibi, S.; Battaglia, G.; Leaman, R.; Brooks, A.; Riggs, C.; Munshi, F.; Revaz, Y.; Jablonka, P.; submitted to A&A
Abstract: To shed light on the different formation scenarios and the main mechanisms involved in the evolution of Local Group (LG) dwarf galaxies, detailed studies of their internal properties are needed. The stellar metal content of these galaxies can be in this respect a powerful observational parameter to obtain information on the mechanisms involved in their evolution. In particular, the inspection of their radial metallicity [Fe/H] profiles can provide important clues on the interplay between internal dynamics and star formation processes, as well as on possible external perturbations. We have explored correlations between the presence and strength of metallicity gradients in LG dwarf galaxies and their stellar mass, star formation history and environment, by performing a homogeneous analysis of literature spectroscopic [Fe/H] data of red giant stars. We were able to determine the radial metallicity profiles for 30 LG dwarf galaxies, providing the largest compilation to date of this type. The dwarf galaxies in our sample exhibit a range of metallicity gradient values when expressed as a function of their half-light radius (Rh). The majority of them have mild negative gradients (sample’s median value ~ -0.1 dex/Rh), with a few showing gradients as strong as -0.4 dex/Rh.
The analysed systems do not show any correlation between their gradients and their morphological types, nor with their distance from the Milky Way or M31. No correlations are found either with their stellar masses or star formation timescales. In particular, we do not find the linear relationship between a galaxy's metallicity gradient and its median age as shown in the literature for a set of simulated systems.
The high-mass systems in our sample with an extended star formation history (SFH), generally show flat metallicity profiles and significant stellar rotation. However, the mere presence of high angular momentum in the rest of our sample does not seem to guarantee a flatter gradient. Instead, the lower mass systems show mild negative gradients with little scatter, regardless of their stellar mass, dynamical state, and the length of their SFH. These results are in excellent agreement with several sets of simulations from the literature and analyzed using the same method as the observed LG dwarf galaxies. The strongest gradients in our observed sample are recovered in systems that likely experienced a major merger event in the past.
In general, the interplay between the multitude of factors that could drive the formation of metallicity gradients likely combine in complex ways to produce comparable strengths, regardless of stellar mass and SFH. The strongest indicator of steep gradients appears to be dwarf-dwarf merger events in a system's past. Taibi, S.; Battaglia, G.; Leaman, R.; Brooks, A.; Riggs, C.; Munshi, F.; Revaz, Y.; Jablonka, P.; submitted to A&A
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Session 2 June 7-8Margherita’s work and legacy / Exoplanets discovery and characterization
- G. Micela
- K. Biazzo
- D. Queloz
- S. Raymond
- S. Benatti
- M. Messerotti
- A.Sozzetti
- S. Iglesias
- L. Silva
- G. Guilluy
Title: Stellar activity and exoplanets
Abstract: Star and planets are strictly inter-connected and the study of a planet cannot ignore the most accurate possible knowledge of the star.
In particular, the intrinsic variability of the star limits our ability to identify the planetary signal and modifies the energy input, particularly at high energies, received from the planet. In this talk, I will present how well planned observations and their accurate analysis can help in modelling the stellar activity to analyse the planetary spectrum. In particular, I will focus on very active stars showing the different information and synergies coming from photometric and low and high resolution spectra.
Title: Stellar characterization of exoplanet hosting stars within the GAPS (Global Architecture of Planetary System) program
Abstract: Exoplanetary properties depends on stellar properties: in order 'to know the planet' with precision and accuracy it is necessary 'to know the star' with precision and accuracy. Within the GAPS program, one of the aims is the accurate characterization of planet hosting stars. Here, we report recent results we obtained within GAPS thanks to the use of high-resolution GIARPS@TNG spectra. We characterized in a homogeneous and accurate way samples of planet hosting stars in terms of stellar properties, abundances of many elements, and kinematic parameters. Thanks to this kind of multidisciplinary approach, we also get insights into possible relation between stellar elemental abundances and position in the Galactic disk, possible relationships between stellar and planetary properties, and into the formation and migration history of the explored exoplanets. This study will be useful for future spectroscopic missions to go deeper in the understanding of the formation mechanisms of exoplanets.
Abstract: Exoplanetary properties depends on stellar properties: in order 'to know the planet' with precision and accuracy it is necessary 'to know the star' with precision and accuracy. Within the GAPS program, one of the aims is the accurate characterization of planet hosting stars. Here, we report recent results we obtained within GAPS thanks to the use of high-resolution GIARPS@TNG spectra. We characterized in a homogeneous and accurate way samples of planet hosting stars in terms of stellar properties, abundances of many elements, and kinematic parameters. Thanks to this kind of multidisciplinary approach, we also get insights into possible relation between stellar elemental abundances and position in the Galactic disk, possible relationships between stellar and planetary properties, and into the formation and migration history of the explored exoplanets. This study will be useful for future spectroscopic missions to go deeper in the understanding of the formation mechanisms of exoplanets.
Title: Exoplanets and life in the Universe
Abstract: The richness and diversity of planetary systems that have now been detected have modified our perspective on planet formation and our place in the Universe. They also represent an historical opportunity of perspectives and a compelling call to look for signs of life on these new worlds and to reflect on the origin of life in the Solar System. I will introduce the audience to the challenges and recent advances in this field, in the context of the new research centres set up at Cambridge and ETH-Z and how they address the origins of life on Earth and its prevalence in the Universe.
Title: Solar System formation in the context of Extra-Solar Planets
Abstract: The past decade of exoplanet observations has confirmed one of humanity's (and all teenagers') worst fears: we are weird. Even though Jupiter is the only Solar System planet likely to be detected with present-day technology, the Solar System is quantifiably unusual among exoplanet systems at the ~1% level. Instead, roughly half of main sequence stars host close-in "super-Earths", and ~10% have Jupiters on non-Jupiter-like, eccentric or close-in orbits. In this talk I will explore how the Solar System fits in a larger context by addressing key steps in planetary system formation. I will present models to explain the diversity of observed planetary systems (including super-Earth systems and giant exoplanets) and the mechanisms that create that diversity. While there is as yet no consensus on exactly how the Solar System formed, Jupiter is likely to have played a decisive role.
Title: Understanding the evolution of planetary systems with GAPS2
Abstract: The architecture of planetary systems evolves significantly with time, with several mechanisms acting on different timescales. Understanding their original configurations is easier when observing planetary systems at young ages (from few to few hundreds of Myr), with planets closer to their formation time and possibly also to their birth-sites. The blind detection of young planets is very challenging due to the intense stellar activity of their host stars, which can easily mask planet-induced signals in radial velocity (RV) time series. On the other hand, transit space missions are providing robust candidates to be followed-up with dedicated RV surveys. The “GAPS” (Global Architecture of Planetary Systems) project, that gathers a large part of the Italian community working on exoplanets, is currently performing such investigation by using the high resolution spectrographs mounted at the TNG. This work involves several aspects: we improved procedures to mitigate the impact of the stellar activity on the RV measurement, the validation of candidates, and the models of the planetary atmosphere evaporation due to the high-energy irradiation of the young stellar host. I will review the main results of our survey up to now, including the confirmation and the retraction of known planet candidates and the characterisation of young transiting companions, allowing us to unveil the still poorly known scenario of the formation and evolution of young close-in planets.
Abstract: The architecture of planetary systems evolves significantly with time, with several mechanisms acting on different timescales. Understanding their original configurations is easier when observing planetary systems at young ages (from few to few hundreds of Myr), with planets closer to their formation time and possibly also to their birth-sites. The blind detection of young planets is very challenging due to the intense stellar activity of their host stars, which can easily mask planet-induced signals in radial velocity (RV) time series. On the other hand, transit space missions are providing robust candidates to be followed-up with dedicated RV surveys. The “GAPS” (Global Architecture of Planetary Systems) project, that gathers a large part of the Italian community working on exoplanets, is currently performing such investigation by using the high resolution spectrographs mounted at the TNG. This work involves several aspects: we improved procedures to mitigate the impact of the stellar activity on the RV measurement, the validation of candidates, and the models of the planetary atmosphere evaporation due to the high-energy irradiation of the young stellar host. I will review the main results of our survey up to now, including the confirmation and the retraction of known planet candidates and the characterisation of young transiting companions, allowing us to unveil the still poorly known scenario of the formation and evolution of young close-in planets.
Title: Solar Radio Astronomy in Trieste Contributed to Avert a Nuclear War in 1967: An Ante Litteram Space Weather Application
Abstract: Solar radio astronomy was started in Trieste by Margherita Hack in the second half of the Sixties as an innovative and young field of research. In fact, Margherita Hack was interested in all innovative scientific observations, and, at that time, solar radio astronomy was a quite new discipline, as radio emissions were discovered in 1942 during the Second World War and systematic scientific observations started only in the second half of the Fifties.
In 2016, after the canonical 50-year time of non-disclosure according to military regulations, an interesting event was declassified and published in a scientific journal with the co-authoring of some of the protagonists. Hence, the science community could learn that the solar radio astronomical observations at 239 MHz carried out in May 1967 at the Trieste Astronomical Observatory helped to avert a nuclear war. This was an ante litteram Space Weather application relevant to the importance of Solar Radio Weather monitoring to detect potential radio frequency interferences to radio communications, which nowadays span HF communications, radars, GNSS receivers, and cellular communications.
In this work, we describe the solar radio event that was about to start a nuclear war by emphasising the role that the Trieste radio observations played to contribute to the correct scientific interpretation of the strong radio interferences suffered by the US BMEWS radars in 1967, i.e., that they were of natural origin and not due to a malicious action of an adversary. This event characterised the start of Solar Radio Weather operations in Trieste thanks to the open mind of Margherita Hack, and made it possible for the Trieste solar radio emission monitoring to gain a scientific and applied role that has been recognised worldwide.
Title: Planetary Systems Demographics: The view from High-Resolution Spectroscopy
Abstract: I will present an overview of the demographics of exoplanetary systems at short and intermediate orbital separations. I will focus on the results obtained with ultra-stable, high-resolution spectrographs capable of delivering (very) high-precision radial velocities, highlighting in particular the present and expected contributions to the field made by ongoing (e.g., HARPS-N/TNG, ESPRESSO/VLT) programs in which the Italian community plays key roles.
Title: Evidence for amino acids in the gas of the IC 348 star cluster of the Perseus
Abstract: Amino acids are building-blocks of proteins, basic constituents of all organisms and essential to life on Earth. They are present in carbonaceous chondrite meteorites and comets, but their origin is still unknown. Formation of amino acids in the interstellar medium is posible via specific gas-phase reactions in dark clouds, however sensitive radiosearches at millimeter wavelengths have not revealed their existence yet. The mid-IR vibrational spectra of amino acids provides an alternative path for their identification. We present Spitzer spectroscopic observations in the star-forming region IC 348 of the Perseus Molecular Cloud showing evidence for mid-IR bands of H2, OH, H2O, CO2, C2H2, C4H2, HC5N, C2H6, C6H2, C6H6, PAHs, fullerenes C60 and C70 and emission lines consistent with the most intense laboratory bands of the three aromatic amino acids, tyrosine, phenylalanine and tryptophan and the aliphatic amino acids isoleucine and glycine. Estimates of column densities give values 10-100 times higher for isoleucine and glycine than for the aromatic amino acids as in some meteorites. The strongest bands of each amino acid are also found in the combined spectrum of >30 interstellar locations in diverse star-forming regions supporting the suggestion that amino acids are widely spread in interstellar space. Future mid-IR searches for proteinogenic amino acids in protostars, protoplanetary disks and in the interstellar medium will be key to establish an exogenous origin of meteoritic amino acids and to understand how the prebiotic conditions for life were set in the early Earth.
Abstract: Amino acids are building-blocks of proteins, basic constituents of all organisms and essential to life on Earth. They are present in carbonaceous chondrite meteorites and comets, but their origin is still unknown. Formation of amino acids in the interstellar medium is posible via specific gas-phase reactions in dark clouds, however sensitive radiosearches at millimeter wavelengths have not revealed their existence yet. The mid-IR vibrational spectra of amino acids provides an alternative path for their identification. We present Spitzer spectroscopic observations in the star-forming region IC 348 of the Perseus Molecular Cloud showing evidence for mid-IR bands of H2, OH, H2O, CO2, C2H2, C4H2, HC5N, C2H6, C6H2, C6H6, PAHs, fullerenes C60 and C70 and emission lines consistent with the most intense laboratory bands of the three aromatic amino acids, tyrosine, phenylalanine and tryptophan and the aliphatic amino acids isoleucine and glycine. Estimates of column densities give values 10-100 times higher for isoleucine and glycine than for the aromatic amino acids as in some meteorites. The strongest bands of each amino acid are also found in the combined spectrum of >30 interstellar locations in diverse star-forming regions supporting the suggestion that amino acids are widely spread in interstellar space. Future mid-IR searches for proteinogenic amino acids in protostars, protoplanetary disks and in the interstellar medium will be key to establish an exogenous origin of meteoritic amino acids and to understand how the prebiotic conditions for life were set in the early Earth.
Title: Exploring exoplanetary habitability with climate models
Abstract: The quest for atmospheric spectral signatures that may witness biological activity in exoplanets is focussed on rocky planets. The best targets for future challenging spectroscopic observations will be selected among potentially habitable planets. Surface habitability can be quantified and explored with climate and planetary atmosphere models, according to different temperature-based criteria. The conceptual, modellistic, technological and interpretative complexity of the problem requires to develop a hierarchy of climate models, of their validation for non-Earth-like conditions, of a comprehensive exploration of observationally unconstrained parameters, and of different possible habitability definitions. I present the works we are performing at OAT in order to perform multi-parametric explorations of the habitability and corresponding observability of rocky exoplanets.
Abstract: The quest for atmospheric spectral signatures that may witness biological activity in exoplanets is focussed on rocky planets. The best targets for future challenging spectroscopic observations will be selected among potentially habitable planets. Surface habitability can be quantified and explored with climate and planetary atmosphere models, according to different temperature-based criteria. The conceptual, modellistic, technological and interpretative complexity of the problem requires to develop a hierarchy of climate models, of their validation for non-Earth-like conditions, of a comprehensive exploration of observationally unconstrained parameters, and of different possible habitability definitions. I present the works we are performing at OAT in order to perform multi-parametric explorations of the habitability and corresponding observability of rocky exoplanets.
Title: The rich chemistry of three warm-giant planets
Abstract: High-resolution (HR) ground-based spectrographs have drastically improved the investigation of exoplanet atmospheres. In this scenario the near-infrared (0.9-2.45 µm) HR (R /sim 50000) spectrograph GIANO-B mounted at the Nasmyth-B focus of the Telescopio Nazionale Galileo (TNG) telescope is playing an important role. With the simultaneous detection of six molecules in the atmosphere of the Hot-Jupiter HD 209458b, we have recently demonstrated (Giacobbe+2021) that exoplanetary atmospheres can show a chemical richness previously unknown -as only a few molecules had been previously detected in an exoplanetary atmosphere. Thus, the question of whether the complexity of HD 209458b’s atmosphere is unique or other exo-atmospheres can also show such a rich molecular composition arises spontaneously. Here we report on transmission spectroscopy observations of three warm- giant planets, namely WASP-107b, WASP-69b, and WASP-80b, gathered within the GAPS large program aimed at detecting atomic and molecular species in exoplanet atmospheres and possibly constraining the planetary C/O ratio, which is thought to be linked to planet migration and formation mechanisms. We present the simultaneous detection of multiple molecules in the atmosphere of each of the investigated exoplanets -thus unveiling chemical richness also in warm Jupiters for the first time- and interpret the results in terms of possible scenarios of atmospheric composition (C/O ratio, metallicity). The analysis presented here, together with Giacobbe+ 2021, opens a new frontier in the characterization of exoplanetary atmospheres, and additional surprising discoveries are expected with both ground-based HR spectrographs, such as CRIRES+, SPIRou, and NIRPS, and the low-resolution (LR) spectrographs on board the JWST telescope.
Abstract: High-resolution (HR) ground-based spectrographs have drastically improved the investigation of exoplanet atmospheres. In this scenario the near-infrared (0.9-2.45 µm) HR (R /sim 50000) spectrograph GIANO-B mounted at the Nasmyth-B focus of the Telescopio Nazionale Galileo (TNG) telescope is playing an important role. With the simultaneous detection of six molecules in the atmosphere of the Hot-Jupiter HD 209458b, we have recently demonstrated (Giacobbe+2021) that exoplanetary atmospheres can show a chemical richness previously unknown -as only a few molecules had been previously detected in an exoplanetary atmosphere. Thus, the question of whether the complexity of HD 209458b’s atmosphere is unique or other exo-atmospheres can also show such a rich molecular composition arises spontaneously. Here we report on transmission spectroscopy observations of three warm- giant planets, namely WASP-107b, WASP-69b, and WASP-80b, gathered within the GAPS large program aimed at detecting atomic and molecular species in exoplanet atmospheres and possibly constraining the planetary C/O ratio, which is thought to be linked to planet migration and formation mechanisms. We present the simultaneous detection of multiple molecules in the atmosphere of each of the investigated exoplanets -thus unveiling chemical richness also in warm Jupiters for the first time- and interpret the results in terms of possible scenarios of atmospheric composition (C/O ratio, metallicity). The analysis presented here, together with Giacobbe+ 2021, opens a new frontier in the characterization of exoplanetary atmospheres, and additional surprising discoveries are expected with both ground-based HR spectrographs, such as CRIRES+, SPIRou, and NIRPS, and the low-resolution (LR) spectrographs on board the JWST telescope.
Session 3 June 8Tracing the baryons
Title: Illuminating the cosmic web and the circumgalactic medium with the help of quasars
Abstract: Our standard cosmological model predicts that most of the matter in the universe is distributed into a network of filaments - the Cosmic Web - in which galaxies form and evolve. Because most of this material is too diffuse to form stars, its direct detection in emission has remained elusive for several decades leaving fundamental questions still open, including: How are galaxies linked to each other? What are the morphological, physical and kinematical properties of the Cosmic Web and Circumgalactic gas on both large and small scales? How do they affect galaxy formation and evolution? During the last few years we have been able to start addressing these questions in a completely new way: i.e., by directly detecting intergalactic gas in emission thanks to “cosmic flashlights” such as quasars which can ionise and thus light-up through fluorescent emission cosmic gas over large volumes. Recent surveys exploiting the capabilities of new instruments such MUSE and KCWI are now providing a large statistical sample of three-dimensional images of rest-frame-UV line emission from “cold” gas haloes (and sometimes filaments) around galaxies, which are ubiquitously detected in the surrounding of quasars at all explored redshifts (2
Title: Unveiling the high redshift intergalactic medium with quasar absorption lines
Abstract: By charting the evolution of the early intergalactic medium, we can get an indirect view of the first galaxies. In this talk I will discuss some insights from simulations of the intergalactic medium at high redshift, focussing on simulations carefully calibrated to match results from observations of the Lyman-alpha forest. I will show how that by constructing synthetic absorption line spectra from the simulations, we can interpret observations of quasar absorption lines and learn about the high redshift Universe, such as pinpointing the timing of reionization, the enrichment of the intergalactic medium with metals and studying the growth of the first quasars.
Abstract: By charting the evolution of the early intergalactic medium, we can get an indirect view of the first galaxies. In this talk I will discuss some insights from simulations of the intergalactic medium at high redshift, focussing on simulations carefully calibrated to match results from observations of the Lyman-alpha forest. I will show how that by constructing synthetic absorption line spectra from the simulations, we can interpret observations of quasar absorption lines and learn about the high redshift Universe, such as pinpointing the timing of reionization, the enrichment of the intergalactic medium with metals and studying the growth of the first quasars.
Title: (Nearly) Three Decades of HIRES Spectroscopy at the Keck Telescope
Abstract: I will review three decades of scientific discoveries with the HIRES spectrograph on the W.M. Keck I Telescope with emphasis on the extragalactic universe. Highlights include constraints on big bang nucleosynthesis, the dark matter power spectrum, chemical enrichment of the universe, and galactic outflows. I will conclude with thoughts on the future of high resolution spectroscopy in the era of extremely large telescopes.
Title: The Baryon Cycle
Abstract: These are incredibly exciting times for extra-galactic astrophysics;
above all for studies of galaxy formation and growth of structure. New
observatories and advanced simulations are revolutionising our
understanding of the cycling of matter into, through, and out of
galaxies. In this talk I will provide an overview of the normal matter
in collapsed structures, their chemical make-up and dust content. I
will present fresh clues of the cosmic evolution of cold gas; revisit
the 20-year old "missing metals problem" and introduce new
calculations of the dust content of the Universe up to early
times. Together, these results provide an increasingly accurate
description of the baryon cycle which plays many crucial roles in
transforming the bare pristine Universe left after the Big Bang into
the rich and diverse Universe in which we live today.
Title: Completing HST's Legacy to Constrain the Epoch of Helium Reionization with HeII Lyman Alpha Absorption Spectroscopy
Abstract: Akin to neutral hydrogen, intergalactic singly ionized helium can be probed by Lyman alpha forest spectroscopy of rare UV-bright quasars at z~3. The advent of GALEX and HST/COS have revolutionized our view of HeII reionization, the final major phase transition of the intergalactic medium. Efficient surveys pioneered by my team densely sample the strongly fluctuating HeII absorption at 2.7<z3.5 sightlines observed to date show several Lyman alpha and beta transmission spikes that suggest HeII reionization was well underway by z=4. Their occurrence is in conflict with predictions from early radiative transfer simulations of a HeII reionization driven by bright quasars, and suggests a high space density of faint quasars at z>4 that may have a non-negligible contribution to hydrogen reionization. Moreover, due to the long HeII photoionization timescale in the intergalactic medium, the highly ionized HeII proximity zones of our discovered quasars enable the first precise measurements of the duration of individual quasar accretion episodes of up to ~30 Myr. The compiled legacy sample of more than 50 rare HeII-transparent quasars exemplifies HST's unique capability to secure science-grade UV spectra down to flux levels of ~1 microJansky (m_AB~24).
Abstract: Akin to neutral hydrogen, intergalactic singly ionized helium can be probed by Lyman alpha forest spectroscopy of rare UV-bright quasars at z~3. The advent of GALEX and HST/COS have revolutionized our view of HeII reionization, the final major phase transition of the intergalactic medium. Efficient surveys pioneered by my team densely sample the strongly fluctuating HeII absorption at 2.7<z3.5 sightlines observed to date show several Lyman alpha and beta transmission spikes that suggest HeII reionization was well underway by z=4. Their occurrence is in conflict with predictions from early radiative transfer simulations of a HeII reionization driven by bright quasars, and suggests a high space density of faint quasars at z>4 that may have a non-negligible contribution to hydrogen reionization. Moreover, due to the long HeII photoionization timescale in the intergalactic medium, the highly ionized HeII proximity zones of our discovered quasars enable the first precise measurements of the duration of individual quasar accretion episodes of up to ~30 Myr. The compiled legacy sample of more than 50 rare HeII-transparent quasars exemplifies HST's unique capability to secure science-grade UV spectra down to flux levels of ~1 microJansky (m_AB~24).
Title: Evidence for late hydrogen (5<z<6) and helium (2<z<4) reionization in large sample of quasar absorption spectra.
Abstract: The cosmic evolution of large-scale structures along with the astrophysical processes of galaxy formation and evolution leads to the (re)ionization of the low-density intergalactic medium (IGM). The changes in the thermal and ionization state of the IGM can be used to measure the reionization history. The current and future quasar absorption spectroscopic surveys are pivotal in constraining the hydrogen (z>5) and helium (2<z<4) reionization. However, the main challenges lie in modeling the reionization and understanding the observational systematics. In this talk, the speaker will discuss the modeling of reionization in the state-of-the-art cosmological hydrodynamical ({\sc gadget-3}) and radiative transfer ({\sc aton}) simulations. The speaker will show their recent measurements of the thermal state of the IGM from the optical (Keck HIRES, KODIAQ survey) and infrared (MIKE, Keck HIRES) observations of the Ly-alpha forest at 2<z<6. The implication of these measurements to reionization models, Galaxies/QSO properties and feedback processes will be discussed in the second part. Finally, the speaker will discuss the prospects of the space-based facility JWST and next-generation 30/40 m class optical telescopes TMT/E-ELT in measuring the reionization history at $2<z<6$.
Abstract: The cosmic evolution of large-scale structures along with the astrophysical processes of galaxy formation and evolution leads to the (re)ionization of the low-density intergalactic medium (IGM). The changes in the thermal and ionization state of the IGM can be used to measure the reionization history. The current and future quasar absorption spectroscopic surveys are pivotal in constraining the hydrogen (z>5) and helium (2<z<4) reionization. However, the main challenges lie in modeling the reionization and understanding the observational systematics. In this talk, the speaker will discuss the modeling of reionization in the state-of-the-art cosmological hydrodynamical ({\sc gadget-3}) and radiative transfer ({\sc aton}) simulations. The speaker will show their recent measurements of the thermal state of the IGM from the optical (Keck HIRES, KODIAQ survey) and infrared (MIKE, Keck HIRES) observations of the Ly-alpha forest at 2<z<6. The implication of these measurements to reionization models, Galaxies/QSO properties and feedback processes will be discussed in the second part. Finally, the speaker will discuss the prospects of the space-based facility JWST and next-generation 30/40 m class optical telescopes TMT/E-ELT in measuring the reionization history at $2<z<6$.
Title: First stars enriched gas in high-redshift absorbers
Abstract: The first stars were born from chemically pristine gas. They were likely massive and thus rapidly exploded as supernovae, enriching the surrounding gas with the first heavy elements. In the Local Group, the chemical signatures of the first stars were identified among low-mass, long-lived, very metal-poor ([Fe/H] < -2) stars, characterized by high abundances of carbon over iron ([C/Fe] > 0.7): the so-called carbon-enhanced metal-poor stars. Conversely, a similar carbon excess caused by first star pollution was not found in dense neutral gas traced by absorption systems. By means of cosmological models and hydrodynamical simulations I will first show why dense absorption systems are not the ideal environments to look for the signature of the first stellar generations. Then, I will present the detection of 15 very metal-poor, optically thick but relatively diffuse absorbers at redshift z~3-4, out of which 9 are carbon-enhanced. I will show that the abundance pattern of these systems (Lyman Limit and sub-DLA) reveals an overabundance with respect to Fe of all the analysed chemical elements (O, Mg, Al, Si). Moreover, their relative abundances show a distribution with respect to Fe that perfectly match those of very metal-poor stars. I will demonstrate that these absorbers have indeed been polluted by the first stellar generations, whose chemical signature survives in optically thick but relatively diffuse absorbers, not sufficiently dense to sustain further star formation.
Abstract: The first stars were born from chemically pristine gas. They were likely massive and thus rapidly exploded as supernovae, enriching the surrounding gas with the first heavy elements. In the Local Group, the chemical signatures of the first stars were identified among low-mass, long-lived, very metal-poor ([Fe/H] < -2) stars, characterized by high abundances of carbon over iron ([C/Fe] > 0.7): the so-called carbon-enhanced metal-poor stars. Conversely, a similar carbon excess caused by first star pollution was not found in dense neutral gas traced by absorption systems. By means of cosmological models and hydrodynamical simulations I will first show why dense absorption systems are not the ideal environments to look for the signature of the first stellar generations. Then, I will present the detection of 15 very metal-poor, optically thick but relatively diffuse absorbers at redshift z~3-4, out of which 9 are carbon-enhanced. I will show that the abundance pattern of these systems (Lyman Limit and sub-DLA) reveals an overabundance with respect to Fe of all the analysed chemical elements (O, Mg, Al, Si). Moreover, their relative abundances show a distribution with respect to Fe that perfectly match those of very metal-poor stars. I will demonstrate that these absorbers have indeed been polluted by the first stellar generations, whose chemical signature survives in optically thick but relatively diffuse absorbers, not sufficiently dense to sustain further star formation.
Session 4 June 8-9First Galaxies and their growth
Title: The first galaxies and reionization
Abstract: Two of the most outstanding issues in modern astrophysics are what reionized the Universe and when and how did the first objects form. The past decade has seen impressive progress in our understanding of these problematics and multi objects spectroscopy has played a key role since it has allowed us to securely identify and study galaxies up to the earliest epochs.
The Lyalpha line offers a powerful probe to study both reionization and the process of galaxy formation: it is an efficient tool for identifying young actively star forming galaxies and can provide a robust measure of how much neutral hydrogen is present in the environment of the galaxies, thus being a reionization test that complements the Gunn-Peterson trough observations in quasar spectra.
I will review the most recent observational results on high redshift galaxies, and the current constrains that we can place on the timeline of reionization. I will also present the first studies showing evidence that this process w
Title: Spectroscopy of high redshift galaxies in lensed fields
Abstract: Gravitational lensing acting as cosmic telescopes is allowing us to access high redshift galaxies at unprecedented small physical scales (< 100 parsec) and faint luminosity (Muv ~ -14), opening to the possibility of revealing the still elusive formation of globular clusters in the early Universe. Young stellar massive clusters are also the sites where O-type stars are mainly forged, making them key sources of (re-)ionizing radiation and stellar feedback, likely carving ionized tunnels in the host galaxy through which the Lyman continuum radiation (λ<912A) can escape into the intergalactic medium. Strong gravitational lensing boosts the spatial contrast allowing to definitely probe star forming complexes, ISM and stellar clusters with integral field spectroscopy up to the reionization epoch. Such a boosting i n the spatial contrast will also be key for the search of Population III stars.
Abstract: Gravitational lensing acting as cosmic telescopes is allowing us to access high redshift galaxies at unprecedented small physical scales (< 100 parsec) and faint luminosity (Muv ~ -14), opening to the possibility of revealing the still elusive formation of globular clusters in the early Universe. Young stellar massive clusters are also the sites where O-type stars are mainly forged, making them key sources of (re-)ionizing radiation and stellar feedback, likely carving ionized tunnels in the host galaxy through which the Lyman continuum radiation (λ<912A) can escape into the intergalactic medium. Strong gravitational lensing boosts the spatial contrast allowing to definitely probe star forming complexes, ISM and stellar clusters with integral field spectroscopy up to the reionization epoch. Such a boosting i n the spatial contrast will also be key for the search of Population III stars.
Title: The contribution of high-z AGNs to the Ionizing UV background
Abstract: One of the major challenges in observational cosmology is related to the redshift evolution of the hydrogen ionizing background in the Universe. It is a widespread opinion that hydrogen is mainly ionized by primeval star-forming galaxies, with a minor role of active galactic nuclei at high-z. In order to carry out an acid test of this scenario, it is fundamental to measure precisely the HI photo-ionization rate produced by active SMBHs, which critically depends on three important parameters: the luminosity density, the Lyman Continuum (LyC) escape fraction, and the mean free path of ionizing photons produced by bright QSOs and faint (M1450>-23) AGNs at high-z. A significant number of AGNs, selected by photometric redshifts, color, machine learning techniques, and X-ray information has been already confirmed in wide and deep fields, thanks to deep spectroscopic observations in the rest-frame UV. These observations are providing crucial information on the three main quantities (luminosity function, escape fraction, mean free path), which are fundamental to assess AGN's role in hydrogen Reionization. Based on the results of our spectroscopic campaigns at z>4, the derived space density of AGN is higher than previous estimates and this leads to an important contribution of the population to the IGM ionization, since their escape fraction and mean free path remain substantial even close to the epoch of Reionization. High-z AGNs can thus give a precise answer to the long sought question of the responsible for hydrogen Reionization.
Abstract: One of the major challenges in observational cosmology is related to the redshift evolution of the hydrogen ionizing background in the Universe. It is a widespread opinion that hydrogen is mainly ionized by primeval star-forming galaxies, with a minor role of active galactic nuclei at high-z. In order to carry out an acid test of this scenario, it is fundamental to measure precisely the HI photo-ionization rate produced by active SMBHs, which critically depends on three important parameters: the luminosity density, the Lyman Continuum (LyC) escape fraction, and the mean free path of ionizing photons produced by bright QSOs and faint (M1450>-23) AGNs at high-z. A significant number of AGNs, selected by photometric redshifts, color, machine learning techniques, and X-ray information has been already confirmed in wide and deep fields, thanks to deep spectroscopic observations in the rest-frame UV. These observations are providing crucial information on the three main quantities (luminosity function, escape fraction, mean free path), which are fundamental to assess AGN's role in hydrogen Reionization. Based on the results of our spectroscopic campaigns at z>4, the derived space density of AGN is higher than previous estimates and this leads to an important contribution of the population to the IGM ionization, since their escape fraction and mean free path remain substantial even close to the epoch of Reionization. High-z AGNs can thus give a precise answer to the long sought question of the responsible for hydrogen Reionization.
Title: X-shooter reveals the suppression of black-hole growth by strong outflows at redshifts 5.8-6.6
Abstract: In this talk I will present new results, to appear in a forthcoming Nature paper, on strong black-hole outflows in quasars at the epoch of Reionization. These objects are ideal targets to investigate the early growth phases of super-massive black-holes (SMBHs) and to understand when and how SMBH feedback started influencing the growth of the host-galaxies, leading toward the symbiotic growth observed in the local Universe. To this purpose, I will show results based on the ESO/VLT large program XQR-30, the Ultimate X-shooter Legacy Survey of Quasars at the Reionization epoch, finding that about half of z≥6 quasars reveal powerful winds, as traced by broad blu-shifted absorption line (BAL) throughs in their spectra. The BAL quasar fraction at z≥6 is 2-3 times higher than in lower redshift quasars. XQR-30 BAL quasars also exhibit extreme outflow velocities, rarely observed at lower-z. These outflows inject large energy amounts into the galaxy interstellar medium and may slow down the black-hole growth by hampering nuclear gas accretion.
Abstract: In this talk I will present new results, to appear in a forthcoming Nature paper, on strong black-hole outflows in quasars at the epoch of Reionization. These objects are ideal targets to investigate the early growth phases of super-massive black-holes (SMBHs) and to understand when and how SMBH feedback started influencing the growth of the host-galaxies, leading toward the symbiotic growth observed in the local Universe. To this purpose, I will show results based on the ESO/VLT large program XQR-30, the Ultimate X-shooter Legacy Survey of Quasars at the Reionization epoch, finding that about half of z≥6 quasars reveal powerful winds, as traced by broad blu-shifted absorption line (BAL) throughs in their spectra. The BAL quasar fraction at z≥6 is 2-3 times higher than in lower redshift quasars. XQR-30 BAL quasars also exhibit extreme outflow velocities, rarely observed at lower-z. These outflows inject large energy amounts into the galaxy interstellar medium and may slow down the black-hole growth by hampering nuclear gas accretion.
Title: The Final Frontier: Galaxies at the Epoch of Reionization with JWST
Abstract: In recent years, HST observations of blank fields enabled us to detect galaxies as far as z~11. However, very little is known about those galaxies from imaging, and they are mostly the most luminous representatives. Clusters of galaxies, when used as cosmic telescopes, can greatly simplify the task of obtaining spectra of normal galaxies at high redshifts. I will present results from HST and Keck spectroscopic surveys with the largest spectroscopic sample of ordinary high-redshift galaxies to date. In the future, several large surveys are planned with JWST with the main goal of identifying and studying the star formation of galaxies at z > 7. I will conclude by identifying new puzzles facing these surveys.
Title: Galaxy and structure formation before the cosmic noon. The perspective from galaxy spectroscopic surveys.
Abstract: Galaxy evolution is affected in many ways by the environment in which galaxies reside. In the local universe we do see the result of this environment-driven evolution, however galaxies are affected by the surrounding environment all along their life-time, during which they might also experience different kinds of environments, as dark matter structures build up. For this reason, it is particularly interesting to isolate the on-set of environmental effects at high redshift, and find how everything begins. To robustly parameterise environment, spectroscopic redshifts are especially needed, but they are more and more difficult to collect at higher and higher redshift. Fortunately, the future is bright in this respect, as there are new facilities that will allow us to collect deep galaxy spectroscopic samples on large areas. I will show how well we can study environment in recently collected high z (z>2) spectroscopic samples, and a few highlights of what we can expect from future high-z spectroscopic surveys.
Abstract: Galaxy evolution is affected in many ways by the environment in which galaxies reside. In the local universe we do see the result of this environment-driven evolution, however galaxies are affected by the surrounding environment all along their life-time, during which they might also experience different kinds of environments, as dark matter structures build up. For this reason, it is particularly interesting to isolate the on-set of environmental effects at high redshift, and find how everything begins. To robustly parameterise environment, spectroscopic redshifts are especially needed, but they are more and more difficult to collect at higher and higher redshift. Fortunately, the future is bright in this respect, as there are new facilities that will allow us to collect deep galaxy spectroscopic samples on large areas. I will show how well we can study environment in recently collected high z (z>2) spectroscopic samples, and a few highlights of what we can expect from future high-z spectroscopic surveys.
Title: Investigating clusters assembly history: the case of AS1063
Abstract: The processes responsible for galaxy evolution in different environments as a function of galaxy mass remain heavily debated. Rich galaxy clusters are ideal laboratories in which to distinguish the role of environmental versus mass quenching because they consist of a full range of galaxies and environments. Using the CLASH-VLT survey, we assembled an unprecedentedly large sample of 1234 spectroscopically confirmed members in Abell S1063. Thanks to these data, we investigated the cluster environmental and dynamical effects on galaxy evolution by analysing the projected phase-space diagram and the orbits as a function of galaxy spectral properties. By comparing data with simulations we also constrained the accretion redshift of galaxies with different spectral types. The performed analysis shows that extensive spectroscopic information on large samples of cluster members, extending well beyond the virial radius, allows new insights to be obtained on the assembly history of cluster galaxies in relation to their star formation histories via direct comparison of observed (projected) phase-space diagrams with those derived from cosmological simulations.
Abstract: The processes responsible for galaxy evolution in different environments as a function of galaxy mass remain heavily debated. Rich galaxy clusters are ideal laboratories in which to distinguish the role of environmental versus mass quenching because they consist of a full range of galaxies and environments. Using the CLASH-VLT survey, we assembled an unprecedentedly large sample of 1234 spectroscopically confirmed members in Abell S1063. Thanks to these data, we investigated the cluster environmental and dynamical effects on galaxy evolution by analysing the projected phase-space diagram and the orbits as a function of galaxy spectral properties. By comparing data with simulations we also constrained the accretion redshift of galaxies with different spectral types. The performed analysis shows that extensive spectroscopic information on large samples of cluster members, extending well beyond the virial radius, allows new insights to be obtained on the assembly history of cluster galaxies in relation to their star formation histories via direct comparison of observed (projected) phase-space diagrams with those derived from cosmological simulations.
Title: Integral field spectroscopy allows us to distinguish among the different physical mechanisms affecting galaxies in the different Environments
Abstract: Galaxies inhabit a wide range of environments and therefore are affected by different physical mechanisms. GAs Stripping Phenomena in galaxies (GASP) is a program aimed at studying gas removal processes in ~100 nearby galaxies in different environments, using observations at different wavelengths (X, UV, optical, sub-mm, radio).
The core of the program is an integral-field spectroscopic survey with MUSE at the VLT, that allows to study the spatially resolved properties of galaxies. I will show how spatially resolved maps combined with the knowledge of the hosting environment are very powerful for classifying galaxies by physical process. I will discuss the multitude of mechanisms that can affect galaxies in isolation, groups and filaments, clusters. I will show how a single group can host galaxies undergoing many different processes, such as starvation, ram pressure stripping and gas accretion. I will also show how filaments can assist gas cooling and increase the star formation in the densest regions in the circumgalactic gas of the galaxies flowing through them.
I will then show examples of galaxy-galaxy interactions, mergers, and cosmic web stripping. I will present how the vast majority of cluster galaxies are affected only by ram pressure stripping and how this impacts on cluster galaxy evolution. I will emphasise the successes and limitations of a visual optical selection in identifying the processes that deplete galaxies of their gas content and probes the power of IFU data in pinning down the acting mechanism. Future facilities will allow to perform similar analyses at higher redshifts.
Abstract: Galaxies inhabit a wide range of environments and therefore are affected by different physical mechanisms. GAs Stripping Phenomena in galaxies (GASP) is a program aimed at studying gas removal processes in ~100 nearby galaxies in different environments, using observations at different wavelengths (X, UV, optical, sub-mm, radio).
The core of the program is an integral-field spectroscopic survey with MUSE at the VLT, that allows to study the spatially resolved properties of galaxies. I will show how spatially resolved maps combined with the knowledge of the hosting environment are very powerful for classifying galaxies by physical process. I will discuss the multitude of mechanisms that can affect galaxies in isolation, groups and filaments, clusters. I will show how a single group can host galaxies undergoing many different processes, such as starvation, ram pressure stripping and gas accretion. I will also show how filaments can assist gas cooling and increase the star formation in the densest regions in the circumgalactic gas of the galaxies flowing through them.
I will then show examples of galaxy-galaxy interactions, mergers, and cosmic web stripping. I will present how the vast majority of cluster galaxies are affected only by ram pressure stripping and how this impacts on cluster galaxy evolution. I will emphasise the successes and limitations of a visual optical selection in identifying the processes that deplete galaxies of their gas content and probes the power of IFU data in pinning down the acting mechanism. Future facilities will allow to perform similar analyses at higher redshifts.
Session 5 June 9Cosmology and fundamental physics
Title: Spectrographs and spectroscopy for the Sandage Test
Abstract: The redshift drift is a small, dynamic change in the redshift of objects following the Hubble flow. Its measurement provides a direct, real-time, model-independent mapping of the expansion rate of the Universe.
It is fundamentally different from other cosmological probes: instead of mapping our (present-day) past light-cone, directly compares different past light-cones. Being independent of any assumptions on gravity, geometry or clustering, it directly tests the pillars of the ΛCDM paradigm. Recent theoretical studies have uncovered unique synergies with other cosmological probes, including the characterization of the physical properties of dark energy.
At the time of the original proposal by Sandage (1962) the expected change in the redshift of objects at cosmological distances appeared to be exceedingly small for reasonable observing times and beyond technological capabilities.
In the last decades progress in the spectrographs (e.g. ESPRESSO), in the collecting area of telescopes and in the samples of cosmic beacons, enabled by new datasets and new machine-learning-based selections, have drastically changed the situation, bringing the Redshift Drift Grail within reach. As a consequence, this measurement is a flagship objective of the Extremely Large Telescope (ELT), specifically of its high-resolution spectrograph, ANDES (see talk by A. Marconi).
Title: The Lyman-alpha forest as a cosmological probe
Abstract: I will review the use of the Lyman-alpha forest as a probe of cosmology and fundamental physics.
In particular I will focus on the following aspects: nature of dark matter, measurements of neutrino masses, dynamics and geometry of the Universe. I will also present some new results on the low-z Lyman-alpha forest.
Title: Building the high-redshift Hubble Diagram with quasars
Abstract: In recent years, quasars have been shown to be reliable standardizable candles, thanks to the non-linear relation between their X-rays and ultraviolet luminosity. Quasars are also very numerous and they are found at all the observed redshifts: this allows us to investigate the expansion rate of the Universe and the cosmological parameters in a previously almost untested redshift range (z∼2-7). In this talk, I will firstly discuss the reliability of the luminosities relation; then I will show how detailed optical/UV and X-rays spectroscopic analysis can be used (i) to obtain more precise distance estimates, especially at high redshift, and (ii) to derive information about the physical process behind the luminosities relation. Finally, I will discuss the implementation of quasars together with Supernovae Ia in the Hubble diagram, the Hubble Diagram parametric and non-parametric fit, and the presence of a strong tension (>4σ) with a standard flat ΛCDM model at high redshift.
Abstract: In recent years, quasars have been shown to be reliable standardizable candles, thanks to the non-linear relation between their X-rays and ultraviolet luminosity. Quasars are also very numerous and they are found at all the observed redshifts: this allows us to investigate the expansion rate of the Universe and the cosmological parameters in a previously almost untested redshift range (z∼2-7). In this talk, I will firstly discuss the reliability of the luminosities relation; then I will show how detailed optical/UV and X-rays spectroscopic analysis can be used (i) to obtain more precise distance estimates, especially at high redshift, and (ii) to derive information about the physical process behind the luminosities relation. Finally, I will discuss the implementation of quasars together with Supernovae Ia in the Hubble diagram, the Hubble Diagram parametric and non-parametric fit, and the presence of a strong tension (>4σ) with a standard flat ΛCDM model at high redshift.
Title: Understanding cosmology with slitless spectroscopy
Abstract: The Euclid satellite will survey most of the visible extragalactic sky, collecting a spectroscopic sample of ~30 million H-alpha emitting galaxies in the redshift range from 0.9 to 1.8. Spectroscopy will be taken in slitless mode, similar to what happens with Hubble Space Telescope. The resulting spectroscopic sample will be remarkably different from ground-based surveys like BOSS or VIPERS, where a parent photometric sample is very carefully defined and spectra are taken with fibers in a targeted spectroscopy campaign. I will illustrate the expected characteristics of the spectroscopic survey, and the current effort to characterize the sample and mitigate its predicted (or unpredicted) systematics.
Abstract: The Euclid satellite will survey most of the visible extragalactic sky, collecting a spectroscopic sample of ~30 million H-alpha emitting galaxies in the redshift range from 0.9 to 1.8. Spectroscopy will be taken in slitless mode, similar to what happens with Hubble Space Telescope. The resulting spectroscopic sample will be remarkably different from ground-based surveys like BOSS or VIPERS, where a parent photometric sample is very carefully defined and spectra are taken with fibers in a targeted spectroscopy campaign. I will illustrate the expected characteristics of the spectroscopic survey, and the current effort to characterize the sample and mitigate its predicted (or unpredicted) systematics.
A new era of fundamental constant measurements at high redshift
Abstract: I will talk about new astronomical measurements of the fine structure constant using ESPRESSO and HARPS, instruments designed for extremely precise spectroscopic measurements. Both are equipped with a Laser Frequency Comb technology that allows removing previously dominant systematic effects, thus reaching precision of 1 part per million or better in measuring any departure of fine structure constant from its terrestrial value. A new advanced tool using Artificial Intelligence algorithms, AI-VPFIT, was developed to aid the analysis. AI-VPFIT provides robust and objective measurements free from human bias and allows us to explore the impact of model non-uniqueness for the first time. I will present our most recent results, including a new high-precision result using a single atomic species, FeI, that eliminates certain potential systematics that may afflict analyses involving several species simultaneously.
Session 6 June 8 - June 9Breakthrough science enabled by future spectrographs / Margherita and Society
Title: The future of UV spectroscopy: the CUBES spectrograph
Abstract: Accessing the UV band from Earth has always been a demanding task for the observers. However, it is an observing window rich of diagnostics for many categories of astrophysical sources. CUBES (Cassegrain U-Band Efficient Spectrograph) is the forthcoming ESO VLT spectrograph to be installed at one Cassegrain focus of the Very Large Telescope. This instrument will cover with high efficiency the UV ground-based region (300 - 400 nm) with intermediate resolution (about 20000). In spite of the future advent of extremely large telescopes, the combination of CUBES+VLT will provide for years the most efficient UV spectrographs available for astronomers. We here want to describe the project and its main scientific goals.
Title: Spectroscopy with JWST: an unprecedented leap forward
Abstract: The James Webb Space Telescope is offering a far wider variety of spectroscopic observing modes than its predecessor, the Hubble Space Telescope, and with a sensitivity orders of magnitude higher than any other past and current facility.
I will give an overview of Webb's impressive spectroscopic capabilities and illustrate a variety of outstanding science cases that astronomers will be able to pursue by using this cutting-edge observatory.
I will also give an overview of some of the main science programmes that will be conducted already Cycle 1 by emphaising their legacy value for the astronomical community.
Title: La statua di Margherita
Abstract: La prima statua dedicata a una donna scienziata. E chi meglio di lei puo' rappresentare l'immaginario di tutta Italia? Sara' pronta per il suo centesimo compleanno.
Sembra incredibile ma in Italia, paese dell'arte, invasa da statue di ogni genere e forma, le statue di donne "vere" si contano sulle dita di una mano. Ci sono statue femminili che rappresentano sante, oppure le virtu' o anche l'Europa, per dire. Ma proprio quella signora li', quella che e' esistita veramente, che ha fatto questo e quello, no. Ad accorgersene e' il comune di Milano che realizza nel 2021 la statua a Cristina Trivulzio di Belgioioso. E segue a ruota con la prima statua di donna scienziata, donata dalla Fondazione Deloitte in seguito a un bando per il bozzetto che coinvolge alcune artiste italiane e internazionali. La statua scelta sara' realizzata entro giugno e inaugurata il 12 giugno 2022, in occasione del centenario.
Ho imparato tutte queste cose in fretta, coinvolta proprio nel processo di scelta del bozzetto di statua da realizzare, e vorrei condividere con voi il racconto di Margherita Hack come vista attraverso gli occhi di queste artiste.
Title: The Inaf avatar Martina Tremenda: a free and professional maverick
Abstract: Come raccontare le nostre scoperte ai più piccoli senza essere accademici, ma con la libertà e la sfrontatezza richiesta? Come mettere in scena il concetto di libertà di pensiero, alla base di qualsiasi ricerca scientifica?
L’Istituto Nazionale di Astrofisica ci ha provato con la creazione del personaggio di Martina Tremenda, che dialoga con bambini e bambine di 6-10 anni. Martina Tremenda è una ragazzina di 12 anni, figlia di Pippi Calzelunghe (Astrid Lindgren) e Giovannino Perdigiorno (Gianni Rodari). E sotto molti aspetti, possiamo considerarla anche nipotina di Margherita Hack. Seguendo la sua curiosità, rompe in modo naturale gli stereotipi di genere: si costruisce un’astronave a pedali ed esplora l’universo, discutendone anche animatamente con Eu-genio, l’Intelligenza Artificiale di bordo.
Martina Tremenda è diventata prima la protagonista di un libro edito da Scienza Express, Astrokids – avventure escoperte nello spazio, poi uno spettacolo teatrale Martina Tremenda nello spazio, che è stato realizzato attraverso un processo di scrittura collettiva, condiviso da scienziati e professionisti del settore teatrale. Il processo ha coinvolto 5 fra astrofisici e astrofisiche, un regista, una vice-regista e un’attrice. La scrittura è stata preceduta da due brainstorming a Milano (11-12 luglio 2017) e Padova (13 settembre 2017).
Dal 2019, Martina Tremenda firma anche una rubrica di news astronomiche sulla testata Focus Junior (tiratura mensile: 80mila copie). A oggi, ha pubblicato circa 40 news e la collaborazione è in corso.
In questi mesi, infine, Martina diviene la protagonista di un podcast in 12 puntate, con il medesimo target, che sarà reso disponibile gratuitamente su piattaforma (al tempo della sottomissione non sappiamo esattamente i tempi della pubblicazione).
I temi affrontati raccolgono l’attenzione sollevata dai media e permettono ai bambini di consolidare quel che hanno letto o sentito oppure di rivedere il proprio pensiero in modo critico: l’esplorazione dello spazio, i pianeti extrasolari, gli alieni, i buchi neri.
In ciascuno contributo, facciamo convergere tecniche tradizionali e digitali. I 4 protagonisti dello spettacolo, per esempio, sono realizzati ciascuno in modo diverso: Martina Tremenda è interpretata dal vivo dall’attrice professionista Debora Mancini; l’Intelligenza Artificiale è una retroproiezione pre-registrata interpretata dallo scrittore Roberto Piumini. Il topo Amleto, un topo quantistico, è realizzato con un burattino, mentre Lucilla, una bambina di luce, in computer graphics. Allo spettacolo segue un incontro con un’astrofisica o astrofisico. I risultati sono lusinghieri: 21 repliche in 12 mesi (fermati dalla chiusura dei teatri), oltre 5mila bambini dai 6 ai 10 anni coinvolti.
Session 7 June 9-10Breakthrough science enabled by future spectrographs
- A. Cimatti
- S. Hinkley
- G. Cresci
- C. Neiner
- G. Tinetti
- A. Vallenari
- S. Campana
- S. Piranomonte
- M. Cirasuolo
- A. Marconi
- L. Tasca
- T. Schmidt
Title: The role of Euclid spectroscopic surveys in cosmology and galaxy evolution
Abstract: Euclid was selected in the framework of "Cosmic Vision 2015-2025" as a M-class mission and will be launched in 2023. Euclid is a cosmological survey mission based on a 1.2 m diameter telescope. It will cover 15,000 deg^2 (Wide Survey) with visible (broad-band red filter) plus near-infrared imaging (Y,J,H filters), and with near-infrared spectroscopy in the 1.25-1.85 micron spectral range. In addition, the Deep Survey will observe in imaging (optical and near-infrared) 40 deg^2 going deeper by 2 magnitudes than the Wide Survey, and additional spectroscopy will also be done at 0.92-1.35 micron for further studies on galaxy formation and evolution. Euclid will provide high-quality images and optical/near-IR photometry for more than 2 billion galaxies, as well as redshifts and spectra for tens of million galaxies out to redshift around 2 and beyond. The revolutionary power of Euclid relies on the combination of different, independent and complementary probes capable to address the key questions of cosmology (dark energy, modified gravity, relations between luminous and dark matter): weak gravitational lensing, baryonic acoustic oscillations, redshift-space distorsions, galaxy clusters, and cross-correlations with the CMB (Laureijs et al. 2011). The legacy value of the Euclid dataset will be immense for a wide range of science cases. In particular, Euclid will place tight constraints on galaxy formation and evolution with unprecedented statistics. Last but not least, the Deep Survey will allow us to shed light on the first phases of galaxy and massive black hole formation in the young Universe during the first billion years after the Big Bang.
The presentation will focus on the key role of Euclid spectroscopic surveys and the synergies with other facilities in the next decade.
Title: Spectroscopy of Exoplanetary Systems with JWST and Beyond
Abstract: The direct characterization of exoplanetary systems with high contrast imaging is among the highest priorities for the broader exoplanet community. As large space missions will be necessary for detecting and characterizing exo-Earth twins, developing the techniques and technology for direct imaging of exoplanets is a driving focus for the community. For the first time, JWST will directly observe extrasolar planets over their full luminous range, and deliver detailed spectroscopy revealing much more precise chemical abundances and atmospheric conditions. In this talk, I will describe some of the first observations that will be obtained with JWST, focussing on our Early Release Science Program that will utilize all four JWST instruments to carry out early characterisation of planetary mass companions at wavelengths beyond 10 microns. Ours will be among the first-ever observations of bona fide exoplanets at these wavelengths, and will be crucial test cases for atmospheric models that have mostly focussed on the visible and near-infrared. Further, our program will demonstrate the degree to which atmospheric abundances can be obtained from JWST spectroscopy, possibly providing clues to the planet formation process. I will also discuss how this program fits into the broader ground-based context of exoplanet characterization using state-of-the-art instruments such as GRAVITY at the Very Large Telescope Interferometer.
Title: UV spectropolarimetry: a new tool for breakthrough science
Abstract: Several space mission projects for high-resolution spectropolarimeters covering a wide range of UV wavelengths are currently in preparation. From technological and scientific demonstration on the French CASSTOR nanosatellite to Pollux onboard the future large LUVOIR-like NASA flagship mission, through the NASA MIDEX Polstar and ESA M7 Arago mission proposals, a whole range of science cases become accessible. I will present these mission projects, their main science goals, and the timeline of the UV spectropolarimetry roadmap for astrophysics.
Title: TBD
Title: Son of X-Shooter: the transient hunter
Abstract: The SOXS (Son Of X-Shooter) is a single object, wide-band (350-2000 nm) spectrograph, built by an international consortium for the 3.6-m ESO New Technology Telescope at the La Silla Observatory. The consortium is focused on a clear scientific goal: the spectrograph will observe all kinds of transient and variable sources discovered by different surveys with a highly flexible schedule, updated daily, based on the Target of Opportunity concept. It will provide a key spectroscopic partner to any kind of imaging survey, becoming one of the premier transient follow-up instruments in the Southern hemisphere. SOXS will study a mixture of transients encompassing all distance scales and branches of astronomy, including fast alerts (such as gamma-ray bursts and gravitational waves), mid-term alerts (such as supernovae and X-ray transients), and fixed-time events (such as the close-by passage of a minor planet or exoplanets).
Title: From VLT to ELT
Abstract: I will present how current and new facilities at the Very Large Telescope are
tackling some key issues in galaxy formation and evolution. In particular I will present some
new results obtained with KMOS and the potential of the new multi-object
spectrograph MOONS.
Finally I will put these results in the context of the forthcoming European Extremely Large Telescope.
The ELT is now under construction and with its 39-metre primary mirror it will be the largest
optical/near-IR telescope in the world. I will present an overview of the ELT Programme,
focusing on the latest status of the telescope, its instrumentation and the scientific synergies.
Title: ANDES: the high resolution spectrograph for the European Extremely Large Telescope
Abstract: ANDES (ex HIRES) is an optical-infrared high resolution spectrograph for the ELT which is expected to start construction in 2022 to arrive at the telescope in 2030. The ANDES project is carried out by an international consortium composed of 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 ANDESwill 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. ANDES 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.
Title: TBD
