Modelling gas clouds around black holes

Blackholes are found at the centre of something called ‘Active Galactic Nucleus’ or ‘AGN’ for short. An AGN is simply a compact region in the middle of a galaxy that is much brighter than the rest.

When we look at the energy released by AGN over the entire electromagnetic spectrum we see the energy increase and then quickly fall off just as it enters the ultra-violet section - it turns over! The graph of the distribution of energy over the electromagnetic spectrum is something called a Spectral Energy Distribution or SED for short.

The ‘turnover’ in the SED of the AGN happens much sooner than we expect, which is a big problem for researchers. It challenges our previous theories and is a problem that needs to be solved!

‘Coronal’ lines are unique types of emission lines created by super energetic photons coming from the black hole at the center of an Active Galactic Nucleus (AGN). They got the name ‘coronal’ because scientists first spotted them in the sun’s corona!

Coronal lines are incredibly helpful to scientists because each line originates from a specific location under unique conditions. By examining these lines - how prominent they are or which lines are seen - we can gain a detailed understanding of what's happening in the mysterious regions of space around black holes.

Iron coronal lines are among the most studied in astronomy, and we looked closely at two types: [FeVII] and [FeX]. The relationship between these lines is really important. It helps us figure out what's happening in the active areas around black holes, giving us clues about the space environment. This could even help us get a better understanding of what the SED of active galactic nuclei really looks like!

Moving on to the challenging part of the project (and believe me, it is quite the challenge!), most of my efforts are dedicated to experimenting with and testing various parameters and models. The goal is to craft a comprehensive model that accurately reflects the physical conditions observed in active galactic nuclei (AGNs). It's a demanding process, involving a lot of trial and error, but it's crucial for understanding these fascinating regions of space.

By varying parameters, we can explore how factors like the temperature of the black hole, the luminosity of the source, the distance, and the density of the surrounding gas cloud influence the production of these coronal lines. This approach helps us piece together how different environmental conditions affect the appearance and behavior of these lines in space.

Experimenting with various models, such as simulating the region with a single cloud or using multiple clouds, allows us to explore the diverse processes occurring in these regions. This approach helps us understand how different configurations and conditions contribute to the phenomena we observe.