Niebla Models Extragalactic Background Light, Enabling Detailed Analysis of Very High-Energy Gamma Ray Absorption

The faint glow of the Extragalactic Background Light, a pervasive field of photons stretching from visible to infrared wavelengths, presents a significant challenge to astronomers studying distant, high-energy gamma rays. Sara Porras-Bedmar from Universität Hamburg and Manuel Meyer from University of Southern Denmark, along with their colleagues, now address this problem with a new open-source code called niebla. This software accurately models the absorption of gamma rays by the Extragalactic Background Light, allowing researchers to account for this effect when analysing observations of very high-energy sources. By offering a fully customizable approach and incorporating various models of dust reemission, niebla enables detailed investigations into the nature of this elusive background light and promises to refine our understanding of the universe’s most energetic phenomena, ultimately allowing astronomers to distinguish between competing theories about the origin and evolution of cosmic dust.

Understanding the EBL is crucial for interpreting high-energy observations and studying the evolution of the universe. Researchers created new models to estimate the intensity of the EBL at different wavelengths and distances, and then compared these models to existing frameworks to refine our understanding of this diffuse light field. The team validated their models using data from the active galactic nucleus, Markarian 501. Accurately modelling the EBL requires careful consideration of various contributing factors, including the history of star formation, the absorption of light by dust, and the evolution of these processes over cosmic time. By comparing their model to established frameworks, the scientists highlighted key differences and similarities, improving the precision of EBL estimations. This code calculates the EBL by tracing the history of light emission from stars and other sources, accounting for the absorption and re-emission of light by dust. This forward-folding approach calculates the EBL intensity from fundamental principles, modelling the sources of radiation and tracking their evolution over cosmic time. Niebla allows researchers to explore how different models of dust re-emission affect observations of very high-energy gamma rays, offering a means to distinguish between these models and refine our understanding of the EBL itself.

Researchers calculated the EBL intensity by integrating the emissivity of source populations over time and distance, utilizing established parameters to account for the expansion of the universe. They modelled the evolution of stellar populations, considering both metallicity and star formation rates, to accurately determine their contribution to the EBL at different epochs. To validate niebla, the team simulated a high-energy observation of the blazar Markarian 501, demonstrating the model’s ability to constrain cosmic dust properties and distinguish between different dust re-emission prescriptions. This code calculates the EBL by modelling the sources of radiation and their evolution over time, allowing for fully customizable inputs and detailed analysis of EBL opacities. The core of niebla calculates the total EBL emissivity by summing contributions from various sources, beginning with stellar populations. The code models a simple stellar population, a group of stars born from a single gas cloud, and calculates its luminosity based on age, metallicity, and the cosmic star formation rate density. Additionally, the model accounts for contributions from intra-halo light, light emitted by stripped stars, and even the potential decay of axion-like dark matter into photons. To validate niebla, the team simulated a Very High Energy (VHE) observation of the blazar Markarian 501, demonstrating the sensitivity of the VHE spectrum to the EBL opacity, confirming the code’s ability to model complex interactions and provide a framework for constraining cosmic dust properties.