June 2025
June 9th
Speaker: Alessia Franchini (Università degli Studi di Milano)
Title: Gravitational wave sources in gaseous environments
Abstract: In this talk I will present our study of gravitational wave sources in gaseous environment. I will discuss the evolution of massive black hole binaries (MBHBs) and extreme mass ratio inspirals (EMRIs). Understanding the interaction of MBHBs with their gaseous environment is crucial since at sub-parsec scales the binary is too wide for gravitational wave emission to take over and to drive the two black holes to merge. The presence of a gaseous disc around sub-pc MBHBs can further trigger electromagnetic emission that can be detected by optical surveys (ZTF, VRO), therefore revealing the presence of hidden binaries. In this talk I will present our recent results on the evolution and emission signatures of MBHBs embedded in circumbinary discs. The second interesting class of gravitational wave sources are EMRIs, formed by small compact objects in-spiralling towards the massive black hole at the centre of galaxies. These EMRIs are impossible to detect before their in-spiral phase in absence of a gaseous environment. I will discuss how we can potentially detect EMRIs through soft X-ray flares in the light curves of tidal disruption events known as quasi periodic eruptions (QPEs).
May 2025
May 26th
Speaker: Ylva Gotberg (Institute of Science and Technology Austria)
Title: Stars stripped in binaries: from theory to observation
Abstract: A third of all massive stars are predicted to lose their hydrogen-rich envelope through mass transfer or common envelope ejection initiated by a binary companion star. As a result, the hot and compact helium core is exposed. These “stripped stars” are the direct progenitors of hydrogen-poor supernovae and merging binary neutron stars, but they are also so hot that they should boost the ionizing output from bursty star-forming galaxies. Despite their importance, stripped stars remained, until recently, observationally unconfirmed since their predicted existence over half a century ago. We found the first set of stripped stars by combining ultraviolet and optical photometry with follow-up spectroscopy in the Magellanic Clouds. By fitting their spectra with a new grid of models, we could measure stellar properties and thus confirm that the predictions from binary evolution models are broadly consistent with observed stripped stars.
May 12th
Speaker: Andrea Lapi (SISSA Trieste)
Title: Little Ado About Everything: ηCDM, a stochastic cosmology from structure formation
Abstract: I will present the ηCDM framework, a new cosmological model aimed to cure some drawbacks of the standard ΛCDM scenario, such as the origin of the accelerated expansion at late times, the cosmic tensions, and the violation of the cosmological principle due to the progressive development of inhomogeneous/anisotropic conditions in the late Universe via structure formation. To this purpose, the model adopts a statistical perspective envisaging a stochastic evolution of large-scale patches in the Universe, which is meant to render our ignorance on the complex processes leading to the formation of the cosmic web. The stochasticity among different patches is technically described via the diverse realizations of a multiplicative noise term (‘a little ado’) in the cosmological equations, and the overall background evolution of the Universe is then operationally defined as an average over the patch ensemble. I will highlight that the ensemble-averaged evolution in ηCDM can be described in terms of a spatially flat cosmology and of an ‘emergent’ dark energy with a time-dependent equation of state, able to originate the cosmic acceleration with the right timing and to solve the coincidence problem. I will showcase the extremely good performances of the ηCDM model in confronting the most recent supernova type-Ia, baryon acoustic oscillations and structure growth rate datasets. I will stress that ηCDM is able to alleviate simultaneously both the H0 and the fσ8 tensions. Finally, I will propose that the Linders’ diagnostic test may constitute a helpful tool to better distinguish ηCDM from the standard scenario in the near future via upcoming galaxy surveys at intermediate redshifts such as those being conducted by the Euclid mission.
April 2025
April 7th at 15:00 different time
Speaker: Luca Matra (Trinity College Dublin)
Title: Exocomets in the latest stages of planet formation
Abstract: Evidence for exocomets in extrasolar planetary systems has rapidly increased over the past decade, giving rise to the budding field of exocometary science. Exocomets are detected through the gas and dust they release as they collide and grind down within their natal belts (also known as debris disks), or as they sublimate once scattered inwards to the regions closest to their host star. Most detections are in young, 10 to a few 100 Myr-old systems that are undergoing the final stages of terrestrial planet formation. This opens the exciting possibility to study exocomets at the epoch of volatile delivery to the inner regions of planetary systems. In this talk, I will start by introducing exocometary belts and show some of the latest observational results on their structure and link with planets. I will then present the different lines of evidence for their exocometary nature from UV to mm wavelengths, both in the innermost and outer regions of planetary systems. Finally, I will focus on how detection of gas allows us to estimate abundances in young exocomets, and allow detail comparison with younger protoplanetary disks and Solar System comets – including the latest results from the ARKS ALMA Large Program.
April 28th online seminar
Speaker: Alessia Ritacco (CNRS Grenoble)
Title: TBD
Abstract: TBD
March 2025
March 10th
Speaker: Heshou Zhang (Italian National Institute for astrophysics)
Title: A magnetized halo of the Milky Way from inner Galaxy outflows
Abstract: The large-scale structures such as Fermi Bubbles and eROSITA Bubbles provide a unique opportunity to study our Milky Way. However, the nature and origin of these large structures are still under debate. In this talk, I will present the identification of several kpc-scale magnetised structures based on their polarized radio emission and their gamma-ray counterparts, which can be interpreted as the radiation of relativistic electrons in the Galactic magnetic halo. These non-thermal structures extend far above and below the Galactic plane and are spatially coincident with the thermal X-ray emission from the eROSITA Bubbles. Multi-wavelength spectral energy distribution analyses have revealed that both thermal and non-thermal extended structures can be explained by Galactic outflows driven by the active star-forming regions located at 3 − 5 kpc from the Galactic Centre (Zhang, Ponti et al. 2024 Nature Astronomy, https://ui.adsabs.harvard.edu/abs/2024NatAs…8.1416Z/abstract ). These results reveal how X-ray-emitting and magnetised halos of spiral galaxies can be related to intense star formation activities.
March 24th
Speaker: Pasquale Serpico
Title: Primordial black hole formation from self-resonant preheating?
Abstract: TBD
February 2025
February 3rd
Speaker: Cristina Baglio INAF-OAB (Osservatorio Astronomico di Brera – Merate)
Title: Low mass X-ray binaries: an optical/NIR polarimetric view
Abstract: Low mass X-ray binaries are binary systems hosting a compact object (a stellar mass black hole or a neutron star) which accretes mass from a low-mass companion star through an accretion disc. These systems are perfect laboratories to study accretion mechanisms, and how these are coupled with ejections in the form of jets and/or winds. Optical and near-infrared (NIR) observations are of great importance, since at these frequencies, the companion star, accretion disc, the jet, the hot spot, the accretion disc wind and the hot accretion flow could be detected.
Carefully modeling the broad band spectral energy distribution of these systems can reveal sources of emission such as the disc and jet, but sometimes this is insufficient to disentangle all the components involved in the emission. Spectroscopic observations are an important tool in order to unambiguously detect the presence of discs or winds, thanks to the observation of specific features in the spectrum, like double-peaked emission lines and P-Cygni profiles. A very powerful tool is also offered by polarimetric observations, which, especially if combined with photometry or spectroscopy, can help to unveil unambiguously which physical processes are at play in the system, and can give important information about the geometry of the source.
Synchrotron radiation produced by collimated jets, Thomson scattering with free electrons in the accretion disc, scattering of the accretion disc’s radiation in the hot accretion flow located close to the inner radius of the disc are typically the main processes capable of producing linear polarization in X-ray binaries.
In this seminar I will present a review of the most recent and significant polarimetric measurements of these sources at optical/NIR frequencies. I will first focus on the polarization measurements aimed at detecting the emission of jets, showing how these can be crucial to probe the accretion/ejection coupling scenario proposed for these sources. I will also review how polarimetric observations can give important information on the geometry of the systems, and I will show how the contribution of jets to the emission of X-ray binaries can be constrained thanks to polarimetric observations.
February 10th
Speaker: Rebecca Nealon (University of Warwick)
Title: Warped discs as a pathway for planet formation
Abstract: The last decade of observations of protoplanetary discs have shown a wealth of substructure including rings, gaps and spiral arms. Perhaps most intriguingly these observations also revealed the importance of the 3D structure of discs, where some discs are observed to have orientations that change as a function of radius or may also be broken. These so called ‘warped discs’ have challenged our understanding of disc evolution, and recent work has shown that these discs form a significant fraction of the disc population. In this talk I will discuss the connection between warped discs and the onset of planet formation, a major open question in planetary science.
February 17th
Speaker: Avishek Basu (University of Manchester)
Title: Long-term subtle emission changes and the interplay with Timing Noise in Pulsar Magnetosphere
Abstract: The average pulse profile of a pulse serves as its fingerprint and is unique to every pulsar. A wealth of information about the pulsar magnetosphere is derived from its profile shape. For the majority of the pulsars, the average shape remains invariant over time. However, for very few sources variations in the profile shape have been observed. Sometimes these changes are correlated with the changes in the rotation of the pulsar, which gives insight into the dynamic nature of the magnetosphere. The MeerKAT monitoring data accrued over the last few years on ~500 pulsars under the MeerTIME’s Thousand Pulsar Array (TPA) programme, has enabled the detection of subtle emission changes in seven sources not yet known to exhibit long-term profile evolution. These variations are theorised to originate from the magnetospheric state changes with associated current density variations. Precession could play a role, and emission heights could be affected. In this talk, I will briefly describe the techniques adopted to measure the subtle changes in the emission state of the pulsar both in the total intensity and polarization domain and discuss how they are connected to the rotational evolution of the neutron stars. Further, I will elucidate how these measurements have been used to derive the limits on the various measurable parameters such as changes in the emission height, impact parameter of the line of sight, and changes in the magnetospheric charge density.
February 24th AT 1:00 PM (instead of 1:30 PM)
Speaker: Nicoletta Krachmalnicoff (SISSA)
Title: The Present and Future of CMB Polarization Observations
Abstract:
Following the significant successes of the Planck space missions, we have entered a new era of Cosmic Microwave Background (CMB) observations, with experiments now focusing on precise measurements of the polarized signal. These measurements have the potential to shed light on many open questions in fundamental physics. A primary goal of current and future CMB experiments is the detection of the signature of primordial gravitational waves in the so-called B-mode polarization signal, which would provide unprecedented insight into the physics of the Inflationary epoch. In this talk, I will briefly introduce the physics of CMB polarization, review the current status of observations, and discuss how we are preparing to meet the numerous challenges posed by these measurements. I will highlight the importance of both ground-based and space-based observations, present preliminary maps from the Simons Observatory, and outline ongoing studies aimed at finalizing the design of the future LiteBIRD space mission.
January 2025
January 20th
Speaker: Simone Paradiso INAF-OAS (Bologna)
Title: Advancing cosmological data analysis: reducing biases and including model choice as a source of uncertainty
Abstract: In contemporary cosmology, precise data analysis is essential for understanding the universe’s most profound mysteries. Upcoming surveys will provide unprecedented high-precision data, offering new insights into “dark” aspects of the cosmological model, such as the nature and evolution of Dark Matter and Dark Energy. Yet, tensions within the standard ΛCDM model—such as discrepancies in the Universe’s expansion rate (Hubble tension) and the amplitude of clustering—underscore the need for innovative statistical techniques.This talk introduces two novel methods to address these challenges. Bayesian Model Averaging (BMA) provides a principled framework to incorporate model uncertainty as an additional source of error while enabling data-driven model selection. We demonstrate its application to the Hubble tension, exploring Early Dark Energy as an alternative to ΛCDM and analyzing the most prominent extensions of the standard model using the latest CMB, LSS and SNIa datasets. The second focus is on cosmological parameter biases in LSS analyses, particularly the projection effects arising when extending analyses to small-scale features. These biases stem from nuisance parameter priors, which can feedback into and distort linear-regime cosmological parameters. This talk presents an innovative solution: a reparameterization of nuisance parameters using non-linear transformations via Generalized Additive Models (GAMs), effectively mitigating projection effects. By leveraging well-established techniques from data-intensive fields, this talk demonstrates how these approaches unlock the full potential of cosmological datasets, advancing the cosmological model and overcoming longstanding limitations in standard analyses.
December 2024
December 16th
Speaker: Michele Moresco (Alma Mater Studiorum – Università di Bologna)
Title: Cosmology beyond standard probes: exploring new paths to constrain the expansion history of the Universe
Abstract: The measurement of the local expansion rate of the Universe, the Hubble constant, has recently triggered an important scientific debate. It has been found that this quantity, when measured with local probes, shows a 4-sigma tension with the one extrapolated from the analysis of the high-redshift Universe with Cosmic Microwave Background. This issue, often referred to as the ‘Hubble tension’, is now one of the hot topics in physics. Exploring new and complementary approaches to measuring how the Universe (and the structures therein) have evolved has, therefore, become fundamentally important. This will increase the accuracy of the measurements and keep systematic effects under control. In this talk, I will discuss different approaches and methods that can be pursued to obtain independent constraints on the Universe’s expansion rate, recently reviewed in Moresco et al. (2022). I will present how cosmic chronometers, the ages of the oldest star in the Universe, and gravitational waves can be exploited as cosmological probes and how they can provide fundamental information in modern cosmology in the future.
December 2nd
Speaker: Mattia Sormani (Università degli Studi dell’Insubria)
Title: The formation of nuclear rings in barred galaxies
Abstract: I will give an introduction to our theory for the formation of nuclear rings, which are remarkable gaseous structures commonly found at the centre of barred galaxies including our own Milky Way. The rotating external bar potential excites strong density waves near the inner Lindblad Resonance. The density waves remove angular momentum from the gas disc and transport the gas inwards. The accumulation of gas at the inner edge of the gap is the nuclear ring. The process has many similarities with the opening of gaps in protoplanetary disks driven by embedded planets & with the opening of gaps in planetary rings driven by satellites.
November 2024
November 18th –> moved to November 25th
Speaker: Marion Villenave (Università degli Studi di Milano)
Title: Observational constraints on dust concentration and planetesimal formation in protoplanetary disks
Abstract: To form giant planets during protoplanetary disk lifetime, small micron sized particles must grow rapidly to larger grains. A full understanding of that process requires a detailed characterization of the radial and vertical structure of the gas-rich disks associated with young pre-main sequence stars. This is because the level of dust concentration controls grain growth efficiency and planetesimal formation. Multi-wavelengths observations of protoplanetary disks, for example in the millimeter and near-infrared, allow to probe very different grain sizes that are differently affected by evolutionary mechanisms. Here, I will discuss observational constraints on dust accumulation in early and evolved disks, with a particular focus on recent constraints on vertical dust concentration using multi-wavelength observations from various instruments, such as ALMA, JWST, HST… The modeling of multi-wavelength observations of inclined disks allows to identify high density regions, favorable for grain growth and planet formation, and to study the efficiency of planet formation in protoplanetary disks.
November 4th
Speaker: Davide Bianchi (Università degli Studi di Milano)
Title: Measuring our expanding Universe: one year of DESI observations
Abstract: In its first year of observations the Dark Energy Spectroscopic Instrument (DESI) has built the largest map of galaxy redshifts to date, spanning the nearby universe to 11 billion light years. Accurate measurements of how galaxies distribute and cluster within this map allow us to trace the expansion history of the Universe to unprecedented precision and understand what role dark energy played in such process. In this talk I will present the first set of DESI cosmological results, coming from measurements of the baryonic acoustic oscillations (BAO) characteristic scale. (In the unlikely event that the results from “full shape” analysis will be released by the date of the talk I will include them in the presentation).
July 2024
July 5th
Double Seminar at 11:00AM in Aula Caldirola
Speaker: Ingunn Kathrine Wehus (U. of Oslo)
Title: Cosmoglobe DR2: Global analysis of the microwave and infrared sky
Abstract:
Two lessons learned from Planck was the importance of global analysis of instrumental, astrophysical and cosmological parameters as well as
the usefulness of joint analysis of multiple datasets for component separation purposes. These lessons has been further developed into a
coherent pipeline for global analysis of multiple datasets by BeyondPlanck and Cosmoglobe, which has been successfully applied to
joint end-to-end analysis of raw data from Planck LFI and WMAP. The recent Cosmoglobe Data Release 2 generalizes this to the infrared
spectrum, performing a reanalysis of the COBE-DIRBE raw data, supported by Planck HFI, WISE, Gaia and COBE-FIRAS. Expanding the upper frequency
range of the Cosmoglobe Sky Model from 1 to 240 THz requires a drastically altered thermal dust model, as well as adding models for
starlight, CII line emission and dynamical Zodical light emission. This global analysis leads to the strongest constraints on the cosmic
infrared background (CIB) spectrum from DIRBE published to date. I will give an introduction to global analysis before presenting our latest results.
Speaker: Hans Kristian Eriksen (U. of Oslo)
Title: Commander4 and OpenHFI — massively parallel end-to-end
Bayesian CMB analysis
Abstract:
I will present a recently funded Open Science ERC AdG program that aims to implement a single massively parallel end-to-end framework
called “Commander4” for the joint analysis of past, present and future CMB experiments. This framework will build on the existing Commander
code that was used by Planck for component separation, and subsequently generalized by the BeyondPlanck and Cosmoglobe projects
to derive new state-of-the-art frequency maps for Planck LFI, WMAP and DIRBE. However, the existing code only scales well up to O(10^2)
computing cores. Commander4 aims to improve this scaling to O(10^5) cores, as required for next-generation experiments such as Simons
Observatory and LiteBIRD. The first application of this new code, however, will be a re-analysis of the raw uncalibrated Planck HFI
time-ordered data. This work will be organized in a new collaboration called OpenHFI, as part of the larger Cosmoglobe effort. All
interested parties are warmly invited to join this work, both on the Commander4 framework itself and Planck HFI.
June 2024
June 10th
Speaker: Piero Madau (UCSC and Milano Bicocca)
Title: Reionizing the Universe: A Brief History of Baryons and the Cosmic Web
Abstract:
The “forest” of hydrogen and helium Lyman-alpha absorption lines observed in the
spectra of distant quasars encodes information on the physics of structure formation,
the nature of the dark matter, and the temperature and ionization state of baryons in the
Universe. In this talk I will describe the multiple steps needed to connect flux
fluctuations in quasar spectra to physical parameters, present an unprecedented suite
of thousands of high-resolution hydrodynamical simulations of structure formation with
different gas thermal histories along with different free-streaming lengths of (warm)
dark matter particles, and use it to perform a statistical comparison of mock spectra with the
observed 1D flux power spectrum and other data.
June 7th
Speaker: Michele Pizzardo (Saint Mary’s University, Halifax)
Title: The growth of clusters with IllustrisTNG
Abstract: Galaxy clusters are massive bound systems. Their virialized core extending to ~ 1-2 Mpc, accretes matter from the outer region that extends for ~ 5-10 Mpc. We use the radial velocity profile of galaxies drawn from IllustrisTNG clusters with M200>10^14 Msun and 0.01<=z<=1.04 to explore cluster growth. We locate distinct dynamical regions and estimate mass accretion rate (MAR). The MAR is correlated with cluster mass and redshift. The typical MAR ~ 10^4-10^5 Msun/yr. Dense spectroscopy of real clusters infall region will soon be a platform for applying and testing these model results.
June 3rd
Speaker: Mariachiara Rossetti (INAF IASF-Milano)
Title: Building on the Planck legacy: the CHEX-MATE project on galaxy clusters
Abstract: The Cluster Heritage project with XMM-Newton – Mass Assembly and Thermodynamics at the Endpoint of structure formation (CHEX-MATE) is a Multi-year Heritage programme to obtain uniform XMM observations of a complete Planck-selected sample of 118 galaxy clusters. The scientific goal of the projects include the reconstruction of the main thermodynamic quantities of the ICM and the accurate measurement of the total mass for a large representative sample of galaxy clusters. The observations have been recently concluded and the analysis, in which the IASF-Milan group has a leading role, is ongoing.
I will present the goals of the project and some preliminary results, focusing in particular on the temperature profiles, which are a key ingredient for deriving the total mass through the hydrostatic equilibrium equation.
May 2024
May 27th
Speaker: Mattia Sormani (Universita’ dell’Insubria)
Title: TBD
Abstract: TBD
May 21th
Speaker: Matteo Cataneo (Bonn)
Title: TBD
Abstract: TBD
May 20th
Speaker: Stefano Gariazzo (Madrid/Universita’ di Torino)
Title: TBD
Abstract: TBD
May 6th
Speaker: Sabrina Realini (University of Groningen)
Title: Developing ALMA’s future at NOVA
Abstract:
In this talk, I will provide an overview of the current, and currently foreseen, development activities at the NOVA Sub-mm Instrumentation Group (University of Groningen), mostly in the light of the ALMA 2030 Development Roadmap, but also for future ground-based telescopes. The group is involved in fundamental R&D spanning from solid-state quantum detector physics to optics design and instrumentation concepts, as well as in the series production of instrumentation.
Among the main activities, there is an ESO-cofunded study on the feasibility of upgrading the existing ALMA Band 9 (600-720 GHz) receivers to sideband-separating operation, with a bandwidth four times as wide as the current ALMA bands. Additionally, following the successful installation and testing of the ALMA Band 2 (67-116 GHz) pre-production receivers, our group is advancing into the production phase of a full set of receivers, one for each ALMA antenna.
In addition to these efforts, developments include a 210-275 GHz mixer (Band 6) primarily for LLAMA in Argentina and front-end optics design for the African Millimeter Telescope in Namibia.
March 2024
March 11th
Speaker: Anze Slosar (Brookhaven National Laboratory)
Title: LuSEE-Night: a Pathfinder Radio Telescope on the Far Side of the Moon
Abstract:
LuSEE-Night is a novel collaborative effort between NASA and
DOE aiming to land a path-finder radio telescope on the far side of the
Moon. The instrument consists of 4 monopole antennas and will observe
the radio sky between 0.1Mhz and 50MHz. This observational band is
largely inaccessible from the Earth due to ionosphere and radio
interference, but offers potentially transformational information about
the early universe. LuSEE-Night will demonstrate a novel in-orbit
calibration technique. It is manifested to launch on the Firefly Blue
Ghost Mission 2 in December 2025 and land in early 2026. I will
describe the science, the instrument and challenges associated with such
aggressive delivery schedule.
February 2024
Febraury 27th
Speaker: Julien Lesgourgues (Aachen)
Title: Testing Dark Matter properties with cosmological surveys
Abstract: From the particle physics point of view, there is a wide range of plausible particle dark matter candidates. Some of them can impact cosmological observations through their velocity distribution, life time, annihilation cross-section or scattering properties. I will review the potential of current and forthcoming CMB and large scale structure experiments to detect such smoking guns, with a focus on Dark Matter models that affect fluctuations on relatively large scales in the universe, in the linear or mildly non-linear regime.
December 2023
December 18th
Speaker: Martina Gerbino, Universita’ di Ferrara
Title: The left hand of lightness: how we get to understand neutrinos (and other particles) by hunting for the most ancient light in the Universe
Abstract
The intersection of the cosmic and neutrino frontiers is a rich field where much discovery space still remains. Cosmology is an independent window to the physics of light relics – active neutrinos and other light massive particles that may populate the cosmological plasma – and allows to probe their behaviour over cosmological times and scales, something unachievable via terrestrial laboratory searches. In this talk I will discuss how observations of the cosmic microwave background radiation can be used to constrain the properties of neutrinos and other light relics. In the final part, I will focus on “new physics” scenarios (e.g. beyond-standard-model properties, axion-like particles….). I will further discuss detection prospects from forthcoming cosmological observations.
December 11th
Speaker: Alberto Sesana, Universita’ di Milano Bicocca
Title: TBD
December 4th
Speaker: Blake Sherwin, Cambridge DAMTP
Title: Do we understand cosmic structure growth? Insights from new CMB lensing measurements with the Atacama Cosmology Telescope
Abstract
One of the most powerful tests of our cosmological model is to verify the predicted growth of large-scale structure with time. Intriguingly, many recent measurements have reported small discrepancies in such tests of structure growth (“the S8 tension”), which could hint at systematic errors or even new physics. Motivated by this puzzling situation, I will present new determinations of cosmic structure growth using CMB gravitational lensing measurements from the Atacama Cosmology Telescope (ACT). These ACT DR6 CMB lensing measurements allow us to directly map the dark matter distribution in projection out to high redshifts; new cross-correlations of CMB lensing with unWISE galaxies also allow us to probe the matter tomographically. I will discuss the implications of our lensing results for the validity of our standard cosmological model as well as for key cosmological parameters such as the neutrino mass and Hubble constant.
November 2023
November 13th
Speaker: ChangHoon Hahn, Princeton University
Title: ML x Cosmology with 50 Million Galaxies
Abstract:
The 3D spatial distribution of galaxies encodes key cosmological information that can be used to probe the nature of dark energy and measure the sum of neutrino masses. The next generation of galaxy surveys, such as the Dark Energy Spectroscopic Instrument (DESI) and the Prime Focus Spectrograph (PFS), will observe 50 million galaxies over unprecedented cosmic volumes and produce the most precise measurements of galaxy clustering across 10 billion years of cosmic history. In my talk, I will present how we can leverage machine learning (ML) to go beyond current analyses and extract the full cosmological information of these galaxy surveys. In particular, I will present SimBIG, a framework for analyzing galaxy clustering using ML-based simulation-based inference. I will show the latest results from applying SimBIG to SDSS-III: BOSS observations and demonstrate that we can more than double the precision of current analyses. Lastly, I will present the status of the DESI and PFS surveys and how I will apply SimBIG to them to produce the leading constraints on dark energy and the sum of neutrino masses.
November 20th
Speaker: Marianna Annunziatella , (Centro de Astrobiología (INTA-CSIC), Departamento de Astrofísica, Madrid, Spain
Title: First results from the MIRI Deep Imaging Survey (MIDIS)
Abstract:
In this seminar, I will give an overview of the first-year results from the Mid-Infrared Instrument (MIRI) Deep Imaging Survey, a deep JWST/MIRI survey of the Hubble Ultra Deep Field (HUDF) field conducted by the MIRI European Consortium GTO program (Prog. ID 1283, PI: G. Östlin). While MIRI was observing the HUDF with the F560W filter during ~60 hrs in MIDIS, parallel data were also being acquired by the Near Infrared Imager and Slitless Spectrograph (NIRISS) and Near Infrared Camera (NIRCam) instruments. I will focus on the results obtained on high redshift galaxies (e.g. the estimate of the ultraviolet luminosity function and of the cosmic star formation rate density at 8 < z < 13), and on the detailed analysis of intermediate redshift galaxies (e.g. lyman-alpha emitters at z~4).
November 27th
Speaker: Miguel Vioque, UniMi/ESO
Title: Intermediate and high-mass forming stars (Herbigs) and why we should care about them
Abstract:
Intermediate and high-mass forming stars (aka Herbig stars, ~1.5 to 20 Msun YSOs) are currently of great importance for the star and the planet formation fields, and for studies on protoplanetary disk dynamics and evolution. Historically, the study of the general properties of intermediate and high-mass forming stars has been limited by the lack of a well-defined sample. In addition, only few and mostly serendipitously discovered sources were known. However, this has recently changed thanks to the homogeneous discovery of many new stars of the class. In this talk, I provide a summary of my research on Herbig stars and describe our current knowledge of this population of objects. After a brief historical review on how Herbig stars were first identified, I describe their observational characteristics, and what we know about their protoplanetary disks and accretion mechanisms. In addition, I report the Gaia-based clustering properties of Herbig stars and analyze the correlation of this group of stars with large-scale Galactic structure.
April 2023
April 3rd
Speaker: Jose Luis Bernal, Max Planck Institute for Astrophysics and Cantabria Institute of Physics
Title: Cosmic optical background, blazars, and line-intensity mapping view for multi-electronvolt axion-like particle dark matter
Abstract:
Axions and axion-like particles (ALPs) are a natural dark-matter candidate that involves a self-interaction that modifies small-scale clustering, as well as a coupling with photons that causes photon-axion oscillations in the presence of magnetic fields and triggers axion decay into photons. With a viable mass range spanning more than 40 orders of magnitude, the phenomenology of this dark matter model is extremely rich. However, the multi-electronvolt range is very hard to probe. Recently, this range of ALP masses has become very relevant, because their decay may contribute to the 4 sigma excess measured in the cosmic optical background. Therefore, finding new and more sensitive avenues to probe ALPs in this mass range is of utmost importance.
In this talk I will review this measurement and the significance of the excess, and discuss two novel probes of the axion-photon coupling for multi-electronvolt ALPs. First, I will report very recent constraints from the attenuation of the flux of gamma-rays from distant blazers, which improve current sensitivities by up to more than one order of magnitude. Afterwards, I will discuss the promising prospects of detecting directly the products of ALP decays with line-intensity mapping surveys, using the strategies I developed to extract the signal from the line-intensity maps.
March 2023
March 27th
Speaker: Leonardo Testi, University of Bologna
Title: The dawn of planetary systems
Abstract: Planetary systems are found to be a very common outcome of the star formation process, but the diversity of planetary architectures is stunning. The analysis of the Solar System as we know it today provide detailed insights on its formation history. One of the major questions in the field of planet formation is how widespread these conditions and history are. In this talk I will try to address this question based on what we have been and are learning about planet formation based on the study of protoplanetary disks in nearby star forming regions. I will discuss the constraints on the evolution of solids and volatiles in protoplanetary disks and compare these with what we think were the conditions in the young Solar System. I will also try to highlight the major open questions in the field and where we hope to make progress in the near future.
February 2023
February 27th
Speaker: Matteo Brogi, University of Torino
Title: Exoplanet atmospheres at high spectral resolution
Abstract: High-resolution spectroscopy (HRS) from the ground has become a great complement to space observations to study the composition and physical properties of exoplanets. Thanks to the ability to resolve molecular bands into individual lines and to measure their Doppler shift, it is particularly effective at detecting species and the orbital motion of exoplanets. I will show the working principles of the methodology and I will review recent highlights, among which the simultaneous detection of 6 molecular species and the measurement of elemental abundances (C/O ratio, metallicity) at precisions comparable to early JWST results. Future instrumental development, in particular the upcoming high-resolution spectrographs at the ELT, promise to extend the method to probe the atmospheres of terrestrial temperate exoplanets, and ultimately look for species potentially associated with biological activity.
February 13th
Speaker: Marco Castellano, INAF-OAR
Title: A new and unexpected view of the high-redshift universe with JWST
Abstract: JWST is transforming our understanding of the high-redshift universe and of the epoch of cosmic dawn. In this talk, I will present the capabilities of JWST instruments for investigating the high-redshift universe and an overview of the most recent results obtained from cycle 1 programs and public surveys. In particular, I will focus on the results from the GLASS-JWST survey that has provided the deepest NIRCam images collected by the ERSprograms. The first set of GLASS-JWST NIRCam observations led to the discovery of two robust photometric candidates at z~10.5 and z~12.2, that have been both found to have a possible counterpart in ALMA follow-up observations. The discovery of these two objects in a relatively small volume, together with independent analysis from other surveys, points to a number density of bright galaxies at z>9 which is significantly larger than predicted by theoretical models, and could possibly even be in tension with the standard cosmological scenario. A subsequent analysis of NIRCam observations including GLASS and other programs targeting the foreground cluster Abell 2744 led to the discovery of 7 bright objects at z>9 providing further evidence of an unexpected high density of bright galaxies 300-500 Myr after the Big Bang, and hinting at the presence of an overdensity in the field.
January 2023
January 16th
Speaker: Davide Gerosa, University of Milano-Bicocca
Title: TBD
November 2022
November 28th
Speaker: Stefano Facchini, University of Milan
Title: Unveiling the infancy of planetary systems
November 14th
Speaker: Pietro Bergamini, University of Milan
Title: Strong lensing by galaxy clusters in the light of the new observational facilities
Abstract: Over the last decade, strong gravitational lensing has become the most powerful technique to study the mass density distribution of dark matter in the inner regions of galaxy clusters, from their central brightest galaxies down to about a third of their virial radii. This remarkable progress in cluster lens modeling has been mainly possible thanks to dedicated, extensive imaging and spectroscopic surveys, carried out in the cores of a sizable sample of massive galaxy clusters. In particular, by combining the multiband imaging capabilities of the Hubble Space Telescope (HST) with the Very Large Telescope VIMOS and MUSE spectroscopic data, we have moved from lens models counting just a few tens of multiple images with photometric redshifts to a new generation of high-precision strong lensing models exploiting several hundreds of spectroscopically confirmed multiple images and cluster member galaxies. An even larger growth (from hundreds to possibly thousands of multiple images) is expected now, with the advent of new observational facilities, among which stand out the James Webb Space Telescope (JWST) and the Euclid satellite. By using the JWST in combination with the magnification power of the cluster gravitational lenses, we are now discovering the first stellar complexes at z>10. These sources, the progenitors of the galaxies in the local Universe, may play an important role in the re-ionization of the Universe. I will present our latest strong lensing models for the galaxy clusters MACS J0416.1-2403 and Abell 2744 that are currently used as the reference models for the JWST observations. A comparison between our models and other published models of the same clusters demonstrates that ours are better suited to accurately reproducing the positions, shapes and fluxes of the observed multiply-imaged sources. Thus, other than to robustly characterize the total mass distribution of the cluster, our models can provide accurate and precise magnification maps that are crucial to studying the intrinsic physical properties of the faint, high-redshift sources magnified by the lens clusters. The methodology we have started developing in these years and its future refinements are timely, since a very large number of strong cluster lenses will soon be discovered by the large-area surveys, such as LSST (Large Synoptic Survey Telescope) and Euclid. In the final part of my talk, I will present a novel python code that, starting from HST observations in different bands, is able to produce simulated Euclid images of galaxy clusters in the H, J, Y, and RIZ photometric filters. These simulated images, which are realistic and accurately reproduce the complexity of observed galaxy clusters, can already be used to test the robustness of cluster strong lensing models based on Euclid data only.
November 7th
Speaker: Azadeh Moradinezhad-Dizgah, University of Geneva
Title: Cosmology and astrophysics with intensity mapping beyond 21cm: forecast and modelling
Abstract: Line intensity mapping (LIM) is emerging as a powerful technique to map the cosmic large-scale structure. Measurement of spatial fluctuations in the intensity of spectral lines together with their observed frequency provide a spectroscopic three-dimensional map of the structure over a wide range of scales and redshifts. Considering several emission lines (including rotational lines of carbon monoxide, fine structure line of ionized carbon, and oxygen lines), in the first part of the talk, I will discuss the prospects of future ground- and space-based mm-wavelength LIM surveys in constraining fundamental physics and astrophysics. In particular, I will present forecasts showing the potential of LIM in probing primordial non-Gaussianity, properties of neutrinos and light relics, and possible modifications to gravity. Furthermore, I will discuss the possibility of probing formation channels of binary compact objects taking advantage of the synerg