Exploring Sagittarius A* in gamma-rays with Fermi LAT Telescope

Detalhes bibliográficos
Autor(a) principal: Cafardo, Fabio Muffo
Data de Publicação: 2021
Tipo de documento: Tese
Idioma: eng
Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
Texto Completo: https://www.teses.usp.br/teses/disponiveis/14/14131/tde-10072021-074151/
Resumo: Sagittarius A*the supermassive black hole (SMBH) in the center of our galaxyhas been identified in most of the electromagnetic spectrum, from radio to X-rays. Diffuse gamma-ray emission has been observed around Sagittarius A* and a gamma-ray point source has been detected coinciding with the SMBH\'s position, although there is still no definitive association between the two. In this work, we have used ~11 years of Fermi Large Area Telescope (LAT) observations of the point source 4FGL J1745.6-2859 and performed a detailed analysis across four energy bands. Our goal is to elucidate the nature of the gamma-ray emission at the Galactic Center (GC) and whether it is associated with the SMBH. We find that the centroids of the emission approach Sagittarius A*\'s location as the energy increases and they are spatially associated with gas-rich regions in the GC. Assuming that the gamma-ray point source is located at the GC, we estimate a luminosity of 2.61 x 10E36 erg/s in the 100 MeV to 500 GeV energy range. This is consistent with Sagittarius A*\'s bolometric luminosity. Based on the point source properties, we ruled out several potential candidates for its nature and favor a cosmic ray origin accelerated byor in the vicinity ofthe SMBH. We also created light curves (LCs), with time bins as short as 15 days, in search of variability in the 4FGL J1745.6-2859 gamma-ray flux. In contrast with Sagittarius A*\'s flaring behavior in longer wavelengths, we detect that its gamma-ray flux distribution is compatible with a Gaussian, representative of a normal random process, hinting that the gamma-ray emission mechanism differs substantially from the low-energy regime. Finally, 4FGL J1745.6-2859\'s spectral energy distribution (SED) shows a pion-decay bump characteristic of gamma-ray hadronic emission. Its SED is also compatible with several hadronic models for Sagittarius A*\'s gamma-ray emission. Our results indicate that the point source at the GC is indeed the gamma-ray counterpart of Sagittarius A* in the GeV range. The characteristics of this emissionits spatial coincidence with gas reservoirs, energetics, lack of variability and SEDsuggest that hadronic processes are likely behind its origin.
id USP_c2b7f96ba0798083fc93e2d148dfca52
oai_identifier_str oai:teses.usp.br:tde-10072021-074151
network_acronym_str USP
network_name_str Biblioteca Digital de Teses e Dissertações da USP
repository_id_str 2721
spelling Exploring Sagittarius A* in gamma-rays with Fermi LAT TelescopeExplorando Sagitário A* em raios gama com o Telescópio Fermi LATblack holeburaco negrocentro da galáxiaFermi LATFermi LATGalactic Centergamma raysraios gamaSagitário A*Sagittarius A*Sagittarius A*the supermassive black hole (SMBH) in the center of our galaxyhas been identified in most of the electromagnetic spectrum, from radio to X-rays. Diffuse gamma-ray emission has been observed around Sagittarius A* and a gamma-ray point source has been detected coinciding with the SMBH\'s position, although there is still no definitive association between the two. In this work, we have used ~11 years of Fermi Large Area Telescope (LAT) observations of the point source 4FGL J1745.6-2859 and performed a detailed analysis across four energy bands. Our goal is to elucidate the nature of the gamma-ray emission at the Galactic Center (GC) and whether it is associated with the SMBH. We find that the centroids of the emission approach Sagittarius A*\'s location as the energy increases and they are spatially associated with gas-rich regions in the GC. Assuming that the gamma-ray point source is located at the GC, we estimate a luminosity of 2.61 x 10E36 erg/s in the 100 MeV to 500 GeV energy range. This is consistent with Sagittarius A*\'s bolometric luminosity. Based on the point source properties, we ruled out several potential candidates for its nature and favor a cosmic ray origin accelerated byor in the vicinity ofthe SMBH. We also created light curves (LCs), with time bins as short as 15 days, in search of variability in the 4FGL J1745.6-2859 gamma-ray flux. In contrast with Sagittarius A*\'s flaring behavior in longer wavelengths, we detect that its gamma-ray flux distribution is compatible with a Gaussian, representative of a normal random process, hinting that the gamma-ray emission mechanism differs substantially from the low-energy regime. Finally, 4FGL J1745.6-2859\'s spectral energy distribution (SED) shows a pion-decay bump characteristic of gamma-ray hadronic emission. Its SED is also compatible with several hadronic models for Sagittarius A*\'s gamma-ray emission. Our results indicate that the point source at the GC is indeed the gamma-ray counterpart of Sagittarius A* in the GeV range. The characteristics of this emissionits spatial coincidence with gas reservoirs, energetics, lack of variability and SEDsuggest that hadronic processes are likely behind its origin.Sagitário A* o buraco negro supermassivo no centro de nossa galáxia já foi identificado na maior parte do espectro eletromagnético, de rádio a raios X. Em raios gama, se observa emissão difusa ao redor de Sagitário A* e uma fonte pontual foi detectada coincidindo com a posição do buraco negro supermassivo, mas ainda não há uma associação definitiva entre eles. Neste trabalho, usamos ~11 anos de observações da fonte pontual 4FGL J1745.6-2859 pelo Fermi Large Area Telescope para realizar análises detalhadas em quatro bandas de energia. Nossa meta é elucidar a origem da emissão de raios gama do centro da galáxia e investigar sua possível associação com o buraco negro supermassivo. Nós identificamos que os centróides das emissões se aproximam de Sagitário A* em energias mais altas e que eles estão associados espacialmente à distribuição de gás no centro da galáxia. Supondo que a fonte pontual de raios gama encontra-se no centro da galáxia, estimamos sua luminosidade em 2,61 x 10E36 erg/s no intervalo de energia entre 100 MeV e 500 GeV. Este valor é consistente com a luminosidade bolométrica de Sagitário A*. Com base nas propriedades da fonte pontual, vários potenciais candidatos para esta emissão foram descartados, favorecendo uma interpretação em que os raios cósmicos são acelerados por ou próximos de Sagitário A*. Também elaboramos curvas de luz, com resolução temporal de 15 dias, em busca de variabilidade no fluxo de raios gama de 4FGL J1745.6-2859. Ao contrário do observado em comprimentos de onda mais longos, nós detectamos que a distribuição do seu fluxo de raios gama é compatível com uma Gaussiana, representativa de um processo aleatório normal, um indicativo de que o mecanismo de emissão de raios gama é distinto do regime de menores energias. Finalmente, a distribuição espectral de energia de 4FGL J1745.6-2859 apresenta um pion-decay bump\", característica de emissão de raios gama com origem hadrônica. Sua distribuição espectral de energia é, também, compatível com vários modelos hadrônicos para a emissão de raios gama de Sagitário A*. Nossos resultados indicam que a fonte pontual no centro da galáxia corresponde à contrapartida em raios gama de Sagitário A* em energias da ordem de GeV. As características desta emissão sua coincidência espacial com reservatórios de gás, sua energética, a falta de variabilidade e sua distribuição espectral de energia sugerem que processos hadrônicos estejam por trás de sua origem.Biblioteca Digitais de Teses e Dissertações da USPSilva, Rodrigo Nemmen daCafardo, Fabio Muffo2021-05-18info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesisapplication/pdfhttps://www.teses.usp.br/teses/disponiveis/14/14131/tde-10072021-074151/reponame:Biblioteca Digital de Teses e Dissertações da USPinstname:Universidade de São Paulo (USP)instacron:USPLiberar o conteúdo para acesso público.info:eu-repo/semantics/openAccesseng2021-07-19T17:32:03Zoai:teses.usp.br:tde-10072021-074151Biblioteca Digital de Teses e Dissertaçõeshttp://www.teses.usp.br/PUBhttp://www.teses.usp.br/cgi-bin/mtd2br.plvirginia@if.usp.br|| atendimento@aguia.usp.br||virginia@if.usp.bropendoar:27212021-07-19T17:32:03Biblioteca Digital de Teses e Dissertações da USP - Universidade de São Paulo (USP)false
dc.title.none.fl_str_mv Exploring Sagittarius A* in gamma-rays with Fermi LAT Telescope
Explorando Sagitário A* em raios gama com o Telescópio Fermi LAT
title Exploring Sagittarius A* in gamma-rays with Fermi LAT Telescope
spellingShingle Exploring Sagittarius A* in gamma-rays with Fermi LAT Telescope
Cafardo, Fabio Muffo
black hole
buraco negro
centro da galáxia
Fermi LAT
Fermi LAT
Galactic Center
gamma rays
raios gama
Sagitário A*
Sagittarius A*
title_short Exploring Sagittarius A* in gamma-rays with Fermi LAT Telescope
title_full Exploring Sagittarius A* in gamma-rays with Fermi LAT Telescope
title_fullStr Exploring Sagittarius A* in gamma-rays with Fermi LAT Telescope
title_full_unstemmed Exploring Sagittarius A* in gamma-rays with Fermi LAT Telescope
title_sort Exploring Sagittarius A* in gamma-rays with Fermi LAT Telescope
author Cafardo, Fabio Muffo
author_facet Cafardo, Fabio Muffo
author_role author
dc.contributor.none.fl_str_mv Silva, Rodrigo Nemmen da
dc.contributor.author.fl_str_mv Cafardo, Fabio Muffo
dc.subject.por.fl_str_mv black hole
buraco negro
centro da galáxia
Fermi LAT
Fermi LAT
Galactic Center
gamma rays
raios gama
Sagitário A*
Sagittarius A*
topic black hole
buraco negro
centro da galáxia
Fermi LAT
Fermi LAT
Galactic Center
gamma rays
raios gama
Sagitário A*
Sagittarius A*
description Sagittarius A*the supermassive black hole (SMBH) in the center of our galaxyhas been identified in most of the electromagnetic spectrum, from radio to X-rays. Diffuse gamma-ray emission has been observed around Sagittarius A* and a gamma-ray point source has been detected coinciding with the SMBH\'s position, although there is still no definitive association between the two. In this work, we have used ~11 years of Fermi Large Area Telescope (LAT) observations of the point source 4FGL J1745.6-2859 and performed a detailed analysis across four energy bands. Our goal is to elucidate the nature of the gamma-ray emission at the Galactic Center (GC) and whether it is associated with the SMBH. We find that the centroids of the emission approach Sagittarius A*\'s location as the energy increases and they are spatially associated with gas-rich regions in the GC. Assuming that the gamma-ray point source is located at the GC, we estimate a luminosity of 2.61 x 10E36 erg/s in the 100 MeV to 500 GeV energy range. This is consistent with Sagittarius A*\'s bolometric luminosity. Based on the point source properties, we ruled out several potential candidates for its nature and favor a cosmic ray origin accelerated byor in the vicinity ofthe SMBH. We also created light curves (LCs), with time bins as short as 15 days, in search of variability in the 4FGL J1745.6-2859 gamma-ray flux. In contrast with Sagittarius A*\'s flaring behavior in longer wavelengths, we detect that its gamma-ray flux distribution is compatible with a Gaussian, representative of a normal random process, hinting that the gamma-ray emission mechanism differs substantially from the low-energy regime. Finally, 4FGL J1745.6-2859\'s spectral energy distribution (SED) shows a pion-decay bump characteristic of gamma-ray hadronic emission. Its SED is also compatible with several hadronic models for Sagittarius A*\'s gamma-ray emission. Our results indicate that the point source at the GC is indeed the gamma-ray counterpart of Sagittarius A* in the GeV range. The characteristics of this emissionits spatial coincidence with gas reservoirs, energetics, lack of variability and SEDsuggest that hadronic processes are likely behind its origin.
publishDate 2021
dc.date.none.fl_str_mv 2021-05-18
dc.type.status.fl_str_mv info:eu-repo/semantics/publishedVersion
dc.type.driver.fl_str_mv info:eu-repo/semantics/doctoralThesis
format doctoralThesis
status_str publishedVersion
dc.identifier.uri.fl_str_mv https://www.teses.usp.br/teses/disponiveis/14/14131/tde-10072021-074151/
url https://www.teses.usp.br/teses/disponiveis/14/14131/tde-10072021-074151/
dc.language.iso.fl_str_mv eng
language eng
dc.relation.none.fl_str_mv
dc.rights.driver.fl_str_mv Liberar o conteúdo para acesso público.
info:eu-repo/semantics/openAccess
rights_invalid_str_mv Liberar o conteúdo para acesso público.
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
dc.coverage.none.fl_str_mv
dc.publisher.none.fl_str_mv Biblioteca Digitais de Teses e Dissertações da USP
publisher.none.fl_str_mv Biblioteca Digitais de Teses e Dissertações da USP
dc.source.none.fl_str_mv
reponame:Biblioteca Digital de Teses e Dissertações da USP
instname:Universidade de São Paulo (USP)
instacron:USP
instname_str Universidade de São Paulo (USP)
instacron_str USP
institution USP
reponame_str Biblioteca Digital de Teses e Dissertações da USP
collection Biblioteca Digital de Teses e Dissertações da USP
repository.name.fl_str_mv Biblioteca Digital de Teses e Dissertações da USP - Universidade de São Paulo (USP)
repository.mail.fl_str_mv virginia@if.usp.br|| atendimento@aguia.usp.br||virginia@if.usp.br
_version_ 1809090584818745344