Calendar

This study presents a statistical approach to accurately predict the effective temper-

atures of pre-main sequence stars, which are necessary for determining stellar ages

using the isochrone methodology and cutting-age starspots-dependent models. By

training a Neural Network model on high-quality spectroscopic temperatures from

the Gaia-ESO Survey as the response variable, and using photometric data from

Gaia DR3 and 2MASS catalogs as explanatory variables, we implemented a method-

ology to accurately derive the effective temperatures of much larger populations of

stars for which only photometric data are available. The model demonstrated robust

performance for low-mass stars with temperatures below 7 000 K, including young

stars, the primary focus of this work. Predicted temperatures were employed to con-

struct Hertzsprung-Russell diagrams and to predict stellar ages of different young

clusters and star forming regions through isochrone interpolation, achieving excellent

agreement with spectroscopic-based ages and literature values derived from model-

independent methods like lithium equivalent widths. The inclusion of starspot evolu-

tionary models improved the age predictions, providing a more accurate description

of stellar properties. Additionally, by applying this temperature–age framework to

a large, spatially complete sample of young stars in the solar neighbourhood, we in-

vestigate the recent star formation and how it relates to the structure of the Local

Bubble, thereby describing its role in influencing the local star-formation history.

Speaker: Alberto Traina (INAF-OAS Bologna)

Title: SMBHs growth in overdense environments: AGN enhancement in protoclusters with enormous Ly⍺ nebulae

Abstract: SMBHs are almost ubiquitous in galaxies’ nuclei in the local and in the high-redshift Universe. However, the formation and growth processes that lead to such massive objects in relatively short timescales are still unclear. A crucial role in accelerating their evolution may be played by the surrounding environment: large quantities of gas and higher merger rates are key to understand how their growth occurs. Protoclusters of galaxies, the precursors of today’s galaxy clusters, represent the perfect laboratories to investigate this effect at high redshift. The hunt for the SMBHs population in protoclusters and its characterization requires a multi-wavelength effort to obtain a complete census: in this perspective the X-rays represent the best channel to investigate the AGN activity, even in the most obscured conditions. In this talk, I will present recent deep (>200ks) Chandra observations targeting three protoclusters at z ~ 2-3, that host enormous Ly⍺ nebulae. I will discuss the spectral properties of the detected AGN as well as the effects of overdense environment on the growth of SMBHs. In particular, I will show the fraction of AGN and the X-ray luminosity functions of the protoclusters, which are significantly larger (1 – 2 dex!) than those of their local counterparts. I will present new results on how the enhancement of SMBHs in overdense environments (x10 larger than SMGs) suggests that protoclusters are indeed optimal sites for promoting their growth. Finally, I will show preliminary results on the growth of SMBHs in hydrodynamical cosmological simulations.