About Me
Hello there! Iām Alessandro, a postdoc at Eureka Scientific and a Laboratory Associate at Yale University. I specialize in the study and evolution of active galactic nuclei (AGN) across various large-area surveys. My work involves several key projects focused on high-luminosity, heavily obscured AGN, both at high redshifts and in nearby galaxies. My expertise spans X-ray spectral/photometric analysis, AGN/galaxy SED fitting, multi-wavelength AGN counterpart matching, and the management of large catalogs and databases. I also have a deep love for statistics, which plays a crucial role in my research.
Research
Explore my main research projects focused on active galactic nuclei (AGN) studies across various surveys and methodologies.
BASS High-L and obscured AGN in comparison with high-z Universe
We studied 21 of the most luminous and obscured AGN in the BASS survey. Our spectral analysis revealed that around half of them may experience intense activity, with radiation from the central black hole likely clearing out the obscuring material. Moreover, we compared our results with high-z obscured AGN, finding discrepancies in [NeV]λ3426 emission, raising critical questions about the nature of these objects.
Ultra-Fast Inflows?
The detection of an absorption feature in two separate NuSTAR observations of the obscured AGN ESP 39607 suggests the presence of an ultra-fast inflow (UFI) with a velocity of 15ā20% the speed of light. We explore the physical mechanisms behind this phenomenon, including failed winds and non-standard chaotic accretion models.
Stripe 82X Survey
We have conducted a population study of X-ray AGN up to high redshift in the Stripe 82X survey, where we characterized AGN properties. In particular, we traced the obscured AGN fraction and found that it increases with redshift across all luminosity regimes covered by our survey. We also constructed an X-ray luminosity function that remains valid at high luminosities and is publicly available for download (see below).
Our XLF Tools:
Stripe 82-XL Survey
Built from archival Chandra and XMM data, Stripe 82-XL increases the area and depth of its predecessor, making an important contribution to X-ray surveys towards lower fluxes and larger area.
X-ray Redshift for AXIS Probe
We applied the method of Peca et al. (2021) to estimate reliable redshifts using X-ray spectra from the AXIS probe, focusing on obscured AGN in the planned surveys.
AGN Database (AGN-DB)
The AGN-Database aims to be the largest repository of all discovered AGN, at all redshifts and wavelengths (radio to X-rays).
J1030 Chandra Deep Field
Developed a method to derive reliable redshift estimates for obscured AGN using X-ray spectra alone, applicable to deep X-ray surveys. The method is particularly usefull when spectroscopic and photometric redshift are not available and/or well constrained.
