Testing Hubble Tension Systematics with Cepheids, TRGB & JAGB
14/07/2025
The Hubble Tension refers to a >5 σ discrepancy between local and cosmological measurements of the Hubble constant (H0) and suggests the possibility of undiscovered early-universe physics or underestimated systematics. Probing the Hubble Tension necessitates intense scrutiny of the Cepheid-based distance scale, which currently provides the strongest constraints on local measurements of H0. One powerful approach to crosscheck systematics in the Hubble Space Telescope (HST) Cepheid section of the distance ladder is to develop and improve independent routes to measure distances to the same set of galaxies and H0, such as those using the tip of the red giant branch (TRGB) and J-region asymptotic giant branch (JAGB), or by adding an independent anchor. I will present a sub-2% Cepheid distance to M31, which prepares an additional anchor galaxy that can be used to construct the distance ladder once a high-precision geometric detached eclipsing binary observation
is feasible, as well as work improving standardization and calibration of the
TRGB, including a 2D maximum likelihood formalism enabling Milky Way
field star calibrations and contrast ratio standardization in the maser host
NGC 4258. I will also present recent James Webb Space Telescope (JWST) TRGB
distances to 8 hosts of 10 Type Ia supernovae (SNe Ia), later expanded to 25 hosts, which provides no evidence of a HST Cepheid systematic resolving the Hubble Tension, in addition to a H0 measurement using JWST observations of the JAGB with an expansion to 15 galaxies hosting 18 SNe Ia. While the JAGB remains promising as a tool that can crosscheck Cepheid systematics, non-uniform asymmetry in its luminosity function, caused in part by stellar contamination, presently limits the precision of this candle.
|
The Holographic Principle in de Sitter Space
08/07/2025
A great deal is known about quantum gravity in anti de Sitter space but almost nothing about the quantum theory of the more cosmologically relevant de Sitter space. I’ll explain recent developments in constructing holographic theories of de Sitter space and if there is time, the implications for cosmology.
|
Esplorare l'espansione dell'Universo con l'astronomia multi-messaggero
18/06/2025
Grazie alle sinergie tra gli esperimenti sulle onde gravitazionali (GW),
come LIGO/Virgo/KAGRA e osservazioni elettromagnetiche di
transienti e galassie, una varietà di nuove misurazioni cosmologiche
è diventato possibile di recente. Molte di queste misurazioni si basano su
l'uso degli eventi GW come "sirene standard". A seguito del rilevamento di
la prima controparte elettromagnetica di un evento GW, GW170817, la
è stata eseguita la prima misurazione della sirena standard "luminosa". Noi
continuare a cercare controparti ottiche per consentire una maggiore luminosità
analisi delle sirene con l'astronomia multimessaggera delle onde gravitazionali
DECam Survey (GW-MMADS), per il quale descriverò i nostri recenti risultati.
Misurazioni standard della sirena per eventi "oscuri", cioè senza un
controparte elettromagnetica confermata, può anche essere eseguita, utilizzando
correlazioni incrociate con i cataloghi di galassie o di nuclei galattici attivi. In
in questa conferenza mostrerò le nostre ultime misurazioni standard delle sirene e
previsioni e aspettative attuali per le rilevazioni multi-messaggero in
nei prossimi anni.
|
Chasing the Light: Shadowing, Collimation, and the Rapid Growth of Infant Black Holes
18/06/2025
Observations with the James Webb Space Telescope (JWST) have uncovered a substantial population of high-redshift broad-line active galactic nuclei (AGNs) characterized by moderate luminosities, weak X-ray emissions, and faint high-ionization lines, challenging conventional models of AGN activity. In this talk, I will propose that these sources are accreting at super-Eddington rates and discuss how such accretion flows, shaped by thick disk geometries and anisotropic radiation fields, may provide new insights into black hole growth in the early Universe.
|
New measurements of H0 and dark matter properties based on JWST observations of lensed quasars.
17/06/2025
I will present new cosmological measurements based on JWST observations of strong gravitationally lensed quasars. In the first part of the talk, I will show the results of a multi-year effort by the TDCOSMO collaboration to use gravitational time delays to infer the expansion history of the universe and thus the Hubble constant. This method is completely independent of the local distance ladder and the cosmic microwave background, and thus provides a new opportunity to understand whether the tension between the two arises from systematic uncertainties or may be indicative of new physics. In the second part of the talk, I will use new JWST-MIRI observations of strongly lensed quasars and to detect dark subhalos independent of their stellar content. This measurement tests a fundamental prediction of the cold dark matter model, i.e. that galaxies should be surrounded by large numbers of dark satellite subhalos. I will discuss the implications of this measurement in terms of fundamental properties of dark matter, such as free streaming length and self-interaction cross section.
|
IAU Office of Astronomy for Education Center Italy: cosa è, cosa fa, perché lo fa in quel modo
11/06/2025
Fondato nel marzo 2021, l’Office of Astronomy for Education Center Italy (I-OAE) è un ufficio internazionale della IAU, coordinato e finanziato da INAF. In collaborazione con altri Centri, finanziamo corsi di formazione per insegnanti in decine di paesi nel mondo e organizziamo un congresso internazionale annuale.
I-OAE sostiene pratiche di insegnamento innovativo e inclusivo, con apprendimenti centrato sulla persona e la creazione di una comunità di pratica nel bacino del Mediterraneo.
Nei suoi primi anni di esistenza, I-OAE ha sviluppato una serie di processi collaborativi, a cui hanno partecipato rappresentanti di Albania, Cipro, Croazia, Egitto, Francia, Grecia, Israele, Italia, Marocco, Montenegro, Palestina, Portogallo, Slovenia, Siria, Spagna e Turchia. I-OAE coordina anche l’edizione internazionale di astroEDU, la piattaforma di attività didattiche peer-reviewed della IAU.
I-OAE è un ufficio aperto alla collaborazione di volontari che ne condividano valori e metodi.
|
Seeking the New World of Spin Zero - Fundamental mysteries of nature and cosmic microwave background (CMB) polarization
06/06/2025
Particle cosmology is a discipline seeking a fundamental understanding of the Universe based on particle physics. Five mysteries drive our research today: cosmic inflation, baryon asymmetry, neutrino properties, dark matter, and dark energy. Resolving any of the five mysteries will revolutionize our picture of the Universe. Numerous interesting theoretical hypotheses have been proposed to this end. Many require new scalar particles, such as inflatons, axions, supersymmetric particles, etc. They are essentially an attempt to expand the role of the vacuum. Since we have not yet found such spin-zero particles, we shall invent new eyes to make an experimental or observational breakthrough. To this end, the observation of CMB polarization is one of the keys today. In this seminar, I focus on research topics to which I have contributed, including observations of CMB polarization for studying inflatons and searches for light axion-like particles.
|
Origin of Lunar Water and its Role in Enabling Sustainable Solar System Exploration
21/05/2025
The presence of water on the Moon and in lunar samples has emerged as one of the most exciting discoveries in recent times. Multiple sources are believed to have contributed to the lunar water inventory. Understanding the origin of lunar water holds significance that transcends scientific, technological, and societal domains. The Moon is becoming a favourite target for both established and emerging space-faring nations as well as commercial entities. In addition to national pride and scientific curiosity, the resurgence in lunar exploration is driven by a growing recognition of the Moon as a technology testbed for exploring more distant bodies within the Solar System. In this talk, I will outline our pioneering research which contributed to the discovery of water on the Moon and is shaping a vision for the future, envisioning a sustainable human presence on the lunar surface, largely facilitated by the in-situ use of resources, including water.
|
The latest results from the Dark Energy Spectroscopic Instrument (DESI): Is the Standard Cosmological Model in Question?
19/05/2025
The Dark Energy Spectroscopic Instrument (DESI) has constructed the largest 3-dimensional map of the universe to date, using millions of galaxies and quasars from its first three years of observations. The way this map evolves across space and time is determined by the relative contributions of ordinary matter, neutrinos, and the enigmatic dark matter and dark energy. Surprisingly, when DESI’s new data are combined with other probes, the standard cosmological model struggles to provide a coherent picture of the universe’s evolution. A simple extension of the model, where the dark energy equation of state varies over time instead of remaining constant, appears to better align with the observations. I will present these latest DESI results and explore their implications and future prospects.
|
Vera Rubin Observatory's Legacy Survey of Space and Time: The greatest movie of all time
13/05/2025
The Legacy Survey of Space and Time (LSST), the first project at the new Vera C. Rubin Observatory, will be the most comprehensive optical astronomical sky survey ever undertaken. Starting this year, Rubin Observatory will obtain panoramic images covering the sky visible from its location in Chile every clear night for ten years. The resulting 60 petabytes of raw imaging data, essentially a digital color movie of the night sky, will include about 20 billion galaxies and a similar number of stars, and will be used for investigations ranging from cataloging potentially hazardous near-Earth asteroids to fundamental physics such as characterization of dark matter and dark energy. I will briefly describe scientific goals behind this project that drove its design, illustrate the progress of its ongoing construction, and finish with a discussion of data analysis challenges that need to be tackled to make the best use of the massive and complex LSST dataset.
|
|