The South African astronomer became the fifth graduate of the program taught by the Institute of Astrophysical Studies of the Diego Portales University last Tuesday, December 19th.
01/15/2024
“Exploring [CII] Haloes and Quasar Environments in and near the Epoch of Reionization”, is the title of Trystan Lambert’s thesis, whose supervising professors were Roberto Assef and Manuel Aravena, and whose objective was to study the Universe when it was only 10% of its current age, close to a period called “the epoch of reionization.”
It is to this field of research that the doctoral thesis of Trystan Lambert contributes, who became the fifth graduate of the program taught by the Institute of Astrophysical Studies of the Diego Portales University.
Lambert’s work, who also holds a bachelor’s and master’s degree in Astronomy and Astrophysics (both from the University of Cape Town), was composed of two parts. The first was the study of the interstellar medium, (material found between the stars in a galaxy), in a “normal” galaxy at this time.
“By normal, it refers to a relatively common galaxy, and this is interesting because, being so far away, it is much easier to study giant and extremely bright galaxies, but those are so atypical that they do not allow us to draw general conclusions. A normal galaxy, on the other hand, is much less bright and therefore more difficult to study, but much more representative of what common galaxies at that time are really like. These observations were made with ALMA,” explains Professor Assef.
The second part, meanwhile, consisted of studying the environment of an extreme object at this time. Specifically, what is called “a luminous quasar,” which corresponds to a galaxy with a supermassive black hole that is accreting gas, making this object extremely luminous. What is logical, and supported by theory, is that these galaxies should exist in the center of extremely dense regions of the Universe, such that there is a lot of gas to fuel these processes. This implies that there should be many galaxies nearby.
“However, the searches that have been carried out have given mixed results, concluding that they actually live in dense regions, with some studies concluding that they live in regions that are below the average density of the Universe,” comments the professor. And he adds, “In this work, Trystan used observations with the DECam instrument on an object chosen under very specific criteria that allow not only to give a more definitive answer, but also potentially understand why there is so much variance between other studies.”
Asked “what was most challenging about this research?”, Trystan says that “due to the COVID pandemic, much of this work was done remotely and largely in isolation. Apart from this, I used instruments and telescopes that I had not used before, in particular ALMA”.
Regarding the first part of the thesis, he indicates that “our work consists of a single galaxy and it is difficult to reach robust general conclusions with a single piece of data, so I believe that, with these new observations”, in reference to the CRISTAL program of the ALMA observatory in which a number of UDP researchers participate, “in the coming years we will begin to understand how common these [CII] halos are in the early Universe, and more importantly, begin to determine what physical mechanisms are responsible for them,” he elaborates.
Regarding quasar environments at the time of reionization, “the tension in the research field, due to the wide variety of results around different objects, by different equipment, and with different techniques, could be explained by our work and future work could begin to elucidate these problems,” concludes the new Doctor in Astrophysics.
After defending his thesis, Trystan Lambert is the fifth graduate of the UDP Doctorate in Astrophysics, after Danielle De Brito Silva, who successfully defended her thesis on December 11; Ana Posses, who obtained the degree at the beginning of December; Dejene Zewdie, who got it in October; and Kriti Gupta – first graduate – in May last year.