投稿者: KatoRyo

Near-infrared Variability of (Ultra) luminous Infrared Galaxies

Speaker: Shun Hatano (NAOJ/SOKENDAI)

Abstract:

The origin of infrared emission in ULIRGs—starburst or AGN—remains uncertain. Compactness is key for differentiation, but infrared imaging is limited to resolutions of ~10–100 pc. In this study, we utilize NEOWISE time-domain data to examine near-infrared variability of ULRIGs. We identify multiple ULIRGs showing significant near-infrared variability, despite not being classified as AGN on the BPT diagram.

Gravitational waves from first star remnants

Speaker: Tomoya Kinugawa (Shinshu University)

Abstract:

We calculated binary evolutions of first stars (Pop III) and showed that the typical chirp mass of Pop III binary black holes is ∼30Msun with a total mass of ∼60Msun and the maximum mass of Pop III BBH is more massive than the limit mass of the pair-instability supernovae.
Our result, which predicted gravitational wave events like GW150914 and GW190521, can explain the origin of massive stellar binary black hole mergers.
In this talk, I will explain Pop III binary evolutions and the properties of Pop III binary black hole mergers.
There is a good chance to check indirectly the existence of Pop III massive stars by gravitational waves.

Numerical Challenges in Computational Astrochemistry

Speaker: Tommaso Grassi (Max Planck for Extraterrestrial Physics)

Abstract:

Astrophysical numerical models encounter substantial computational challenges when integrating complex, time-dependent chemistry with physical processes. To address these issues, I will present the use of autoencoders for the dimensionality reduction of chemical networks, enabling efficient solutions with standard ODE solvers while preserving key network features. Additionally, I will discuss the application of interpretable machine learning techniques to connect synthetic spectra with model parameters, facilitating the assessment of information retention in observational data.

The observer dependence of the Hubble parameter

Speaker: Jessica Santiago (LeCosPa)

Abstract:

Given the exponential growth on the upcoming supernovae data available, the possibilities of rigorously testing the cosmological principle becomes ever more real. One of the ways to do so is by measuring the multipole decomposition of the Hubble and deceleration parameters.

In this presentation, I will discuss the observational-theoretical approach, initially introduced by Kristian & Sachs, which allows for the interpretation of data in non-homogeneous and anisotropic universes. I will also explore the effects introduced by the relative motion between the observer and the matter frame, and show how the induced kinematic dipole can be disentangled from intrinsic anisotropies in the matter distributions. To conclude, I will show that the luminosity distance must be corrected depending on the chosen frame of the observer (z_cmb vs. z_hel).