Tirthankar Choudhury (NCRA, Pune)
Cosmic Neutral Hydrogen: A Probe of the First Stars in our Universe
Friday, April 5th, 2024, 11:30am – Aula D (old SISSA building) & streaming
Abstract. Detecting the signatures of the very first stars in our Universe offers a promising avenue for understanding cosmic evolution. These stars leave their imprint on the large-scale distribution of cosmological hydrogen through the process of reionization, driven by the photoionization of hydrogen atoms by ultraviolet photons. The evolution of reionization serves as a valuable tool not only for investigating the properties of galaxies in the early Universe, but also for constraining cosmological models. In this presentation, we provide an overview of ongoing and upcoming observational probes for studying reionization, alongside recent advancements in theoretical modelling. Furthermore, we outline future prospects for detecting the signatures of the first stars utilizing cutting-edge telescopes such as the SKA, highlighting interesting findings from our research group.
Contact: Matteo Viel
Video – Tirthankar Choudhury’s webpage
José Manuel Carmona (University of Zaragoza)
QGMM network: theoretical and experimental challenges and opportunities for research in quantum gravity phenomenology
Friday, January 19th, 2024, 11:30am – Aula D (old SISSA building) & streaming
Abstract. The experimental search of non-conventional effects predicted by bottom-up approaches and theoretical models of quantum gravity is a quite recent field of research. Generically, it requires to consider probes of very high-energy and amplification mechanisms, conditions which are fulfilled by the propagation of the cosmic messengers. Advances in multi-messenger astronomy during the last decade has driven progress in the field, but a number of theoretical and experimental challenges still lie ahead. In order to tackle them, collaboration between theorists experts in the phenomenology of quantum gravity models and the various experimental communities involved in the detection of the cosmic messengers (high-energy gamma rays and neutrinos, ultra high-energy cosmic rays, and gravitational waves) is essential. Such collaboration has effectively started with the establishment of the QGMM network, born from the community joined together within the recently finished COST Action CA18108 “Quantum gravity phenomenology in the multi-messenger approach”. In this colloquium we will describe some of the challenges identified within this network and an outlook of the opportunities that future exploration may offer for the advancement of the field of quantum gravity phenomenology.
Contact: Stefano Liberati
Video – Slides – José Carmona’s Webpage
Avery Meiksin (University of Edinburgh)
Revealing the Dark Ages in 21-cm radiation
Friday, December 1st, 2023, 11:30am – Aula D (old SISSA building) & streaming
Abstract. After primordial hydrogen and helium from the Big Bang recombined when the Universe was a few hundred thousand years old, the Universe remained dark for another half billion years until Cosmic Dawn, when the first radiation sources appeared. While the individual sources were too dim to detect directly, they may be revealed indirectly through a 21-cm signal produced by their impact on neutral intergalactic hydrogen, including driving the last major phase change in cosmological baryons from neutral to ionized during the Epoch of Reionization. The discovery of the 21-cm signal is now a primary science goal for a new generation of radio telescopes. I will discuss the physical origin of the signal, what it may tell us about the first radiation sources and the progress made to date toward its detection.
Contact: Matteo Viel
Video – Webpage
Anna Bonaldi (Manchester University)
The Square Kilometre Array Observatory: current status and science preparatory activities
Friday, November 10th, 2023, 2:00pm – Aula D (old SISSA building) & streaming
Abstract. The Square Kilometre Array (SKA, www.skao.int), currently under construction, will be the world’s largest radio observatory once completed. It will consist of one radio telescope operating in the 50-350 MHz frequency range (SKA-Low, Western Australia) and another one operating in the 350 MHz-15 GHz range (SKA-Mid, South Africa). I will describe the SKA’s science drivers and give an update on the current construction activities, with a focus on the Italian contributions. I will describe the Observatory’s timeline and access policy. I will finally describe the current science preparatory activities, in particular the SKA science data challenges.
Contact: Tommaso Ronconi
Video
Francesca Matteucci (Università di Trieste)
Galactic archaeology: a natural history of the Milky Way
Friday, October 13th, 2023, 11:30pm – Aula D (old SISSA building) & streaming
Abstract. Galactic archaeology allows us to reconstruct the history of star formation and evolution of galaxies by means of chemical abundances. Most of the attention is paid to the Milky Way for which we have now the largest amount of observational data. In the last years, in fact, large stellar spectroscopic surveys of the Milky Way have allowed us to compare theoretical chemical evolution models to data and infer important constraints on the history of our Galaxy. I will first explain how to build detailed chemical models and discuss the main necessary ingredients I will then review and interpret the highlights in the chemical evolution of the Milky Way, such as the observed bi-modality in the [alpha/Fe] ratios in the stars of the thick and think disc, the different stellar populations inhabiting the bulge, the abundance gradients along the thin disc and their evolution with time. I will also discuss the formation of neutron capture elements, such as Europium, by merging neutron stars and supernovae core-collapse. The possibility that the stellar Galactic halo was formed by stars accreted from dwarf satellites will be also discussed by means of specific chemical clocks. The Lithium cosmological problem, which involves Galactic halo stars, will be finally presented.