Unless otherwise noted, the Astrophysics Seminars take place on Monday, usually every other week, at 1:30pm in Aula Caldirola.
June 2024
June 10th
Speaker: Piero Madau (UCSC and Milano Bicocca)
Title: TBD
Abstract: TBD
May 2024
May 27th
Speaker: Mattia Sormani (Universita’ dell’Insubria)
Title: TBD
Abstract: TBD
May 6th
Speaker: Sabrina Realini
Title: TBD
Abstract: TBD
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