The spectral parameters of BL Lacertae objects and their gamma-ray luminosity function

• Ano de defesa: 2025
• Autor(a) principal: Cordeiro, Giovanna Rocha
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: BL Lacertae; Fermi Large Area Telescope; função de luminosidade em raios gama; gamma-ray luminosity function
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/43/43134/tde-29052025-183220/

Blazars, a subclass of Active Galactic Nuclei (AGN), are among the most luminous and energetic objects in the Universe, powered by accretion onto supermassive black holes (SMBHs). In this work, we focus on the gamma-ray luminosity function (GLF) of BL Lacertae objects (BL Lacs), a type of blazar. We started by generating a synthetic catalog of BL Lacs sampling from the Luminosity-Dependent Density Evolution (LDDE) parameterization of the GLF, whose 12 parameters have been previously tuned to the Fermi Large Area Telescope (Fermi-LAT) first year data set. The sampling was performed by a Markov Chain Monte Carlo (MCMC) and included cosmological expansion effects. To assess the impact of instrumental effects on the reconstruction of the GLF, we performed a detailed simulation of a full sky Fermi-LAT survey. This simulation, along with the subsequent analysis, was conducted using the Fermi Science Tools (Fermitools), incorporating different diffuse background components (galactic and extragalactic) and flux cuts to evaluate biases in the reconstruction of the BL Lacs parametric power-law model. Our findings indicate that higher flux cuts and longer exposure times reduces the parameters statistical uncertainties, but do not eliminate completely systematic biases, and that the presence of the Galactic component strongly influences the reconstruction quality when the spectral distribution of this diffuse background is treated as a pure power-law. We have also explored the resolution limit on the determination of the BL Lacs GLF by reconstructing the posterior distributions of the LDDE parameters using an input catalog containing the total number of objects predicted by the model in the luminosity range 10^44 erg/s - 10^52 erg/s. We find that 6 of the parameters in this optimistic scenario are already hard to constrain. Future steps include incorporating detection efficiency, reconstructing parameters using real data from the Fermi Large Area Telescope, and leveraging the upcoming observations of the planned Cherenkov Telescope Array (CTA) extragalactic survey to improve the accuracy and precision of the GLF parameterization.