RT info:eu-repo/semantics/masterThesis
T1 Dinámica de agujeros negros supermasivos
A1 Cervera Cortés, Mario
A2 Máster Universitario en Astrofísica
AB Black holes are one of the most intriguing objects that astrophysics is capable ofstudying, but they are not easy to detect. It is necessary for them to be surrounded by anaccretion disk in order for us to observe them. Each galaxy has a central supermassive blackhole with a mass on the order of several million times that of the Sun. When it starts accretingmatter, it becomes an Active Galactic Nucleus (AGN), which is classified based on its activitytype such as quasars, Seyfert galaxies, LINERs, and so on.In this project, we will analyze a population of AGN galaxies that exhibit a continuumenergy distribution dominated by the emission from the accretion disk surrounding the centralsupermassive black hole. The objective is to find a direct relationship between the mass of ablack hole and the temperature of the surrounding accretion disk.To establish the desired relationship, the emission of coronal lines [Si VI] and [Ne V]in these galaxies will be studied, and they will be normalized by dividing their fluxes by thebroad and narrow components of Brγ. Once these ratios are obtained, they will be comparedwith the mass of the central black hole in the galaxies to observe the trend they describe.The initial starting point is the publication by Prieto (2022), which we will aims tocontinue their research and expand it with a new population of galaxies, as well as with newrelationships that were inconclusive in that work. The data for the new galaxies is obtainedfrom the PARSEC project, taken with adaptive optics and in very high spatial resolution.Once the list of galaxies is obtained, the Seyfert nuclear activity classification will besearched to exclude those that do not meet the desired criteria. A data screening process isalso necessary, where galaxies with high levels of noise near the target lines will be eliminated,as well as those where the flux measurements are unclear.All the data, including MBH, [Si VI], [Ne V], Brγbroad and Brγnarrow fluxes, and Seyfertclassification of each galaxy, will be compiled into a single table. From this table, the valueswill be extracted and used to determine the desired relationships.The first relationship obtained in this study is the one found by Prieto (2022), whichrelates MBH and the [Si VI]/Brγbroad ratio in the galaxies of that publication. The goal is tovalidate the dual trend observed in their results by adding the rest of the galaxies and creatinganother graph for comparison. In the published study, they obtained a Pearson coefficient of-0.76, while our study yields a coefficient of -0.71, resulting in a slightly lower but equallyconsistent data correlation. Furthermore, by adding the new galaxies, the dual trend in theresults is still maintained. This study does not provide an explanation for the differentiationbetween the two groups of galaxies.2To continue, the normalizing factor for [Si VI] has been changed to Brγnarrow, and thewanted relationship has been explored in the same manner as before. This change was madebecause the research on which this study is based proposed the narrow component of Brγ asa potential improvement for the relationship between black hole mass and [Si VI]. This is dueto the coinciding formation region of these lines, which is not the case for Brγbroad. For thisrelationship, a correlation coefficient of -0.38 was obtained, significantly lower than when weuse the broad component. This discrepancy could be attributed to the possibility that some ofthe emission from Brγnarrow may be contaminated by circumnuclear star-forming regions thatemit in this spectral line.The next coronal line used in this study is [Ne V], and although it doesn't have thesame high ionization potential as [Si VI]. It was chosen because it has an advantage over theother: all the detectable [Ne V] emission will be in the form of gas and will be observable inthe spectrum, while with [Si VI], some of the emission will be blocked due to being in a solidform as a metal.In the relationship between MBH and the flux of [Ne V] normalized to Brγbroad, acorrelation coefficient of -0.61 is obtained, which is quite consistent, similar to the correlationobserved with the [Si VI] coronal line. When plotting these results, three galaxies wereidentified that did not follow the general trend of the rest. These outliers were marked and notconsidered in the regression analysis of the most galaxies. Further study of these galaxiesand the inclusion of more data points will be necessary to understand how this trend ismodified.Finally, the last relationship obtained is the trend of [Ne V] flux normalized to Brγnarrowwith MBH, resulting in two distinct trends again, with correlation coefficients of -0.84 and -0.78.Studying these two groups of galaxies, no definitive factor causing this significantdifferentiation between them has been identified. A potential solution for finding an explanationis to review the spectra of the [Ne V] flux in these galaxies and see if any data points exhibithigh levels of noise. Further analysis in this direction may provide insights into the observeddiscrepancy.In conclusion, the objectives initially set for this study have been achieved. It hassuccessfully contributed additional results to the research published by Prieto (2022) anddiscussed the findings presented therein. Trends have been established between each of theproposed data relationships, some showing stronger correlations than others, but all of themconsistent with an unique trend: an increase of the temperature of the accretion disc withdecreasing MBH. This confirmation is evidenced by observing that each of the obtained trendshas a negative slope.Thanks to this study, we have been able to gain a broader understanding of one of theleast known objects in the astrophysical landscape: black holes. Also, with this work we arecontributing to enlarge a bit the understanding of the accretion disc and its black hole at itscenter in the scientific community.
YR 2024
FD 2024
LK http://riull.ull.es/xmlui/handle/915/36849
UL http://riull.ull.es/xmlui/handle/915/36849
LA es
DS Repositorio institucional de la Universidad de La Laguna
RD 28-jun-2024